Madhav

STUDIES ON DRAINAGE CHARACTERISTICS OF GSB MIXES USING DRIP SOFTWARE A DESSERTATION REPORT SUBMITTED IN PARTIAL FULFILLMENT OF REQUIREMENTS FOR THE AWARD OF THE DEGREE OF MASTER OF ENGINEERING -CIVIL (MAJOR: HIGHWAY ENGINEERING) By MADHAV.M.P. IV Semester M.E., (Civil)

Under The Guidance Of

Dr. L.MANJESH Assistant Professor Faculty of Civil Engineering Bangalore University Bangalore-560056

FACULTY OF CIVIL ENGINEERING UNIVERSITY VISVESVARAYA COLLEGE OF ENGINEERING BANGALORE UNIVERSITY, BANGALORE-560 056 2009

1

SYNOPSIS Granular Sub-base (GSB) is an intermediate layer between subgrade and base course. This layer functions as a stress-transmitting medium to spread the surface wheel loads and as a drainage layer for the pavement to avoid excess wetting and weakening of subgrade. Various materials and techniques are used for the construction of GSB. The granular material for sub-base shall preferably be natural and locally available or blended to attain the required properties from locally available materials. To design GSB mixes, locally available soils were collected from different rural roads of Karnataka. The soil samples taken for GSB mixes were having liquid limit greater than 25 and plastic limit greater than 6, which do not meet the specified limits for sub-base. To achieve the specified consistency limits, the soil samples were blended with quarry dust. After arriving at the optimum proportion with quarry dust, the soil samples were mixed with the aggregates and gravel at different proportions to achieve required gradation as per IRC: SP: 20-2002. The laboratory investigations include Grain size analysis, determination of Consistency limits, Compaction tests and CBR tests for locally available soils and GSB mixes. From the test results, it was observed that for GSB mixes the dry density and CBR value increased when compared to the unblended soil samples. Comparative studies have been carried out to observe the improvement in gradation of GSB mixes using gravel and aggregates To investigate the drainage capacity of GSB mixes in pavement design and to develop design charts for drainage capacities of GSB layers, the permeability tests were carried out in the laboratory. The drainage analysis of GSB based on available analytical models was carried out using DRIP (Drainage Requirements in Pavements) software. Analytical results indicate that for a particular design thickness and permeability of GSB, the parameters such as pavement width and rainfall intensity significantly influence the drainage capacity. The limited permeability studies indicated the Grade-III GSB material specified in IRC: SP: 20-2002 will not function as an effective drainage layer for rural road construction. Hence it is recommended to consider the granular sub-base material with permeability of 250 m/day for the construction of drainage layer.

2

ACKNOWLEDGEMENTS It is immense pleasure to thanks DR.L.MANJESH, Assistant Professor of Civil Engineering, U.V.C.E., who spared no pains in extending his helping hand and for invaluable guidance during the course of this Seminar work, be it with suggestions or guidance. I express my sincere thanks to, Dr. M.S.AMARNATH, Professor of Civil Engineering, Civil Engineering Department, for his guidance and suggestions. I express my sincere thanks to, Dr. G.SURESH, Civil Engineering Department, for his suggestions to complete this work. I express my sincere thanks to, Sri. H.A.VIJAYKUMAR, Lecturer of Civil Engineering, Civil Engineering Department, for his suggestions to complete this work. I express my sincere thanks to, Dr.S.GANGADHAR, Asst. Professor of Civil Engineering Department, for his suggestions to complete this work. I express my sincere thanks to, K.C.MANJUNATH, Research Scholar in Civil Engineering department, for his suggestions to complete this work. I am thankful to my Classmates and my Juniors, for their help and cooperation extended throughout the experimental work. I express my thanks to all non-teaching staff of the Highway Engineering laboratory for their help during the laboratory studies. Finally, all appreciation for this seminar work is due to those mentioned above, faults, if any are mine. MADHAV.M.P.

3

CONTENTS CHAPTER 1 INTRODUCTION

1

1.1 General

1

1.2 Pavement Structure

1

1.3 Components of Flexible Pavements

2

1.3.1 Surface Course

2

1.3.2 Base Course

2

1.3.3 Sub-base Course 2 1.4 Need for Granular Sub-Base (GSB) and Drainage Layer

3

1.5 Requirements of GSB as Per IRC: SP 20-2002

3

1.6 Need for Use of Locally Available Materials

5

1.7 Features of DRIP Software

5

1.8 Objectives of the Present Study

6

CHAPTER-2 LITERATURE REVIEW

7

2.1 Field Measurement of Granular Base Drainage Characteristics

7

2.2 Comparison of Pavement Drainage Systems

7

2.3 Locating the Drainage Layer for Bituminous Pavements in Indiana

8

2.4 Asphalt Overlay and Subsurface Drainage of Broken and Seated Concrete Pavement

9

2.5 Effective Approach to Improve Pavement Drainage Layers

9

2.6 Design Charts for Drainage Capacities of Granular Sub-bases

10

2.7 Road Drainage

10

2.8 DRIP Software for Drainage Design

13

2.8.1 Depth of Flow (Steady-state flow)

14

2.8.2 Time-to-drain (Unsteady-state flow)

15

2.9 Permeability

16

2.9.1 Darcy’s Law

16

2.9.2 Coefficient of Permeability for common soil types

16

CHAPTER-3 PRESENT INVESTIGATIONS

18

3.1

18

Selection of the Test Stretches for Soil Sampling

4

3.2

Materials Used for GSB Mix Design

18

3.2.1 Gravel

18

3.2.2 Aggregate

18

3.2.3 Quarry Dust

20

3.2.4 Locally Available Soil

20

3.3 Tests on GSB materials

20

3.3.1 Gravel

20

3.3.2 Aggregates

20

3.3.3 Gravel

20

3.3.4 Locally available soils

21

3.4 Proportioning of materials for GSB Mixes

21

3.4.1 Proportioning of materials for GSB Mix-I

21

3.4.2 Proportioning of materials for GSB Mix-II

21

3.5 Tests on GSB mix

22

3.6 Drainage Estimation using DRIP software

22

3.6.1 Roadway Geometry

23

3.6.2 Sieve Analysis

24

3.6.3 Inflow

25

3.6.4 Permeable Base Design

26

CHAPTER-4 RESULTS AND DISCUSSIONS

27

4.1 Laboratory test results for GSB materials

27

4.1.1 Gravel

27

4.1.2 Aggregates

27

4.1.3 Quarry Dust

28

4.1.4 Locally available soils

29

4.2 Properties of GSB mixes

32

4.2.1 Gradation

32

4.2.2 Tests on GSB mixes

37

4.3 Parameters for Sub-base Drainage Analysis

40

4.4 Estimation of Inflow

40

4.5 Drainage capacity of GSB

41

CHAPTER-5 5

CONCLUSIONS AND RECOMMENDATIONS

51

Conclusions

51

Recommendations

52

CHAPTER-6 SCOPE FOR FURTHER STUDY

53

REFERENCES

54

6

LIST OF TABLES Table 1.1 Gradation requirements for Coarse Graded Granular Sub-Base

4

Table 1.2 Gradation requirements for Close Graded Granular Sub-Base

4

Table 2.1 Coefficient of Permeability for common soil types

17

Table 2.2 Degree of Permeability

17

Table 3.1 List of Selected Rural Roads for Sub-grade soil sampling

19

Table 4.1 Particle size distribution and Consistency limits of Gravel sample from Hoskote.

27

Table 4.2 Test Results of Coarse Aggregates

28

Table 4.3 Particle size distribution of Quarry Dust.

28

Table 4.4 Percentage Gravel, Sand, Silt & Clay fractions and Atterberg limits.

29

Table 4.5 Particle size distribution of Sub-grade soil samples.

30

Table 4.6 OMC, MDD. CBR and Permeability values of Sub-grade soil samples. 31 Table 4.7 Sieve analysis and proportioning of Mix-I for Stretch 1

32

Table 4.8 Sieve analysis and proportioning of Mix-I for Stretch 2

33

Table 4.9 Sieve analysis and proportioning of Mix-I for Stretch 3

33

Table 4.10 Sieve analysis and proportioning of Mix-I for Stretch 4

33

Table 4.11 Sieve analysis and proportioning of Mix-I for Stretch 5

33

Table 4.12 Sieve analysis and proportioning of Mix-I for Stretch 6

34

Table 4.13 Sieve analysis and proportioning of Mix-I for Stretch 7

34

Table 4.14 Sieve analysis and proportioning of Mix-I for Stretch 8

34

Table 4.15 Sieve analysis and proportioning of Mix-I for Stretch 9

34

Table 4.16 Sieve analysis and proportioning of Mix-I for Stretch 10

35

Table 4.17 Sieve analysis and proportioning of Mix-II for Stretch 1

35

Table 4.18 Sieve analysis and proportioning of Mix-II for Stretch 2

35

Table 4.19 Sieve analysis and proportioning of Mix-II for Stretch 3

35

Table 4.20 Sieve analysis and proportioning of Mix-II for Stretch 4

36

Table 4.21 Sieve analysis and proportioning of Mix-II for Stretch 5

36

Table 4.22 Sieve analysis and proportioning of Mix-II for Stretch 6

36

Table 4.23 Sieve analysis and proportioning of Mix-II for Stretch 7

36

Table 4.24 Sieve analysis and proportioning of Mix-II for Stretch 8

37

Table 4.25 Sieve analysis and proportioning of Mix-II for Stretch 9

37

Table 4.26 Sieve analysis and proportioning of Mix-II for Stretch 10

37 7

4.2.2 Test results for GSB mixes

37

Table 4.27 OMC, MDD. CBR and Permeability values of GSB Mix-I.

38

Table 4.28 OMC, MDD. CBR and Permeability values of GSB Mix-II.

38

Table 4.29 Permeability, Time to Drain 50% water, Minimum thickness

required

for GSB Mix-I for different intensity of rainfall

43

Table 4.30 Permeability, Time to drain 50% water for minimum GSB thickness (0.10m) for GSB Mix-I

45

Table 4.31 Permeability, Time to Drain 50% water, Minimum thickness required for GSB Mix-II for different intensity of rainfall

46

Table 4.32 Permeability, Time to drain 50% water for minimum GSB thickness (0.10m) for GSB Mix-II

48

Table 4.33 Minimum thickness of Drainage Layer (GSB) required for Different Intensity of Rainfall

49

8

LIST OF FIGURES Figure 1.1 Components of Flexible Pavement

3

Figure 4.1 Dry Density v/s Moisture content for Subgrade Soil Samples

31

Figure 4.2 Dry Density v/s Moisture content for GSB Mix-I

39

Figure 4.3 Dry Density v/s Moisture content for GSB Mix-II

39

Figure 4.4 Permeability v/s Minimum GSB thickness for GSB Mix-I

44

Figure 4.5 Permeability v/s Time to drain 50% water for GSB Mix-I

44

Figure 4.6 Permeability v/s Time to drain 50% water for 0.10 thick layer of GSB Mix-I

45

Figure 4.7 Permeability v/s Minimum GSB thickness for GSB Mix-II

47

Figure 4.8 Permeability v/s Time to drain 50% water for GSB Mix -II

47

Figure 4.9 Permeability v/s Time to drain 50% water for 0.10 thick layer of GSB Mix-II Figure 4.10 Permeability v/s Minimum GSB thickness

48 50

9

LIST OF COMMONLY USED TERMS GSB

-

Granular Sub-Base

CBR -

California Bearing Ratio

OMC -

Optimum Moisture Content

MDD -

Maximum Dry Density

DPR

-

Detailed Project Report

k

-

Coefficient of permeability

DRIP -

Drainage Requirements in Pavements

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CHAPTER 1

INTRODUCTION General Water plays havoc with all structures and is equally true in a highway. It is not sufficient merely to provide the road with the surfacing, the water must be collected and removed from the roadway to ditches or soakways at a safe distance from the road foundation to prevent surface water reaching the sub-soil and thus lowering its bearing strength. The geographical features vary greatly in India. Similarly, the rainfall is meager, moderate and heavy at different places. Thus the road drainage problems are sure to differ from place to place. Drainage is one of the most important factors in pavement design. One misconception is that good drainage is not required if the thickness design is based on saturated conditions. This concept may have true during the old days when the traffic loading and volume were small. As the weight and number of axle loads increase, water may cause more damage to pavements, such as pumping and degradation of paving materials, other than the loss of shear strength. Theoretically, an internal drainage system is not required if the infiltration into the pavement is smaller than the drainage capacity of the base, sub-base and subgrade. Because the infiltration and drainage capacity vary a great deal and are difficult to estimate, it is suggested that drainage layers be used for all important pavements. Pavement Structure One of the main structural elements involved in road construction is the pavement. A pavement is designed to support the wheel loads imposed on it from traffic moving over it. Additional stresses are also imposed by changes in the environment. It should be strong enough to resist the stresses imposed on it and it should be thick enough to distribute the external loads on the subgrade. Based on the structural behavior, pavements are generally classified into two categories, Flexible Pavements and Rigid Pavements Flexible pavements are those, which on the whole have low or negligible flexural strength and are rather flexible in their structural action under the loads. A typical flexible pavement consists of base course, sub- base course and surface course 11

Rigid pavements are those which posses flexural strength or flexural rigidity. The rigid pavement is based on slab action and is capable of transmitting the wheel load stresses through a wider area. A typical rigid pavement consists of base course and a cement concrete slab. 1.3 Components of Flexible Pavements In order to take maximum advantage, material layers are usually arranged in order of descending load bearing capacity with the highest load bearing capacity material (and most expensive) on the top and the lowest load bearing capacity material (and least expensive) on the bottom. A typical flexible pavement structure (Figure 1.1) consists of: 1.3.1 Surface course. The layer will be in contact with traffic loads. It provides characteristics such as friction, smoothness, noise control, rut resistance and drainage. In addition, it prevents entrance of surface water into the underlying base, subbase and subgrade. This top structural layer of material is sometimes subdivided into two layers: the wearing course (top) and intermediate/binder course (bottom). 1.3.2 Base course. The layer immediately beneath the surface course. It provides additional load distribution and contributes to drainage and frost resistance. Base courses are usually constructed out of aggregate or HMA. 1.3.3 Sub-base course. The layer between the base course and subgrade. It functions primarily as structural support but it can also (i) minimize the intrusion of fines from the subgrade into the pavement structure, (ii) improve drainage and (iii) minimize frost action damage. The subbase generally consists of lower quality materials than the base course but better than the subgrade soils.

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Figure 1.1 Components of Flexible Pavement

1.4 Need for Granular Sub-Base (GSB) and Drainage Layer Granular Sub-base is an intermediate layer between subgrade and base course. This layer functions as a stress-transmitting medium to spread the surface wheel loads and as a drainage layer for the pavement to avoid excess wetting and weakening of subgrade. Various materials and techniques are used for the construction of GSB. The granular material for sub-base shall preferably be natural and locally available or blended to attain the required properties from locally available materials. 1.5 Requirements of GSB as per IRC: SP 20-2002 The materials to be used for GSB should be natural sand, moorum, gravel, crushed stone, crushed slag, granulated slag etc. The materials used should be free from organic or deleterious materials. The material passing 425 micron sieve when tested according to IS: 2720 (Part 5)-1985 should have liquid limit and plasticity index of not more than 25 and 6 respectively. The material with the CBR greater than 15% can be used for GSB construction. The gradation requirements for coarse graded and close graded Granular Sub-bases are given in Table 1.1 and Table 1.2

Table 1.1 Gradation requirements for Coarse Graded Granular Sub-Base IS SIEVE (mm)

% by weight passing the IS sieve 13

Grading I

Grading II

Grading III

75.0

100

-

-

53.0

-

100

-

26.5

55-75

50-80

100

4.75

10-30

15-35

25-45

2.36

-

-

-

0.425

-

-

-

0.075

<10

<10

<10

CBR values

30

25

20

Table 1.2 Gradation requirements for Close Graded Granular Sub-Base IS SIEVE (mm)

% by weight passing the IS sieve Grading I

Grading II

Grading III

75.0

100

-

-

53.0

80-100

100

-

26.5

55-90

70-100

100

9.50

35-65

50-80

65-95

4.75

25-55

40-65

50-80

2.36

20-40

30-50

40-65

0.425

10-25

15-25

20-35

0.075

3-10

3-10

3-10

CBR values

30

25

20

14

1.6 Need for use of locally available materials India is a vast country with divergent environmental conditions in different areas ranging from mountainous terrain to plain terrain and from deserts to coastal and water logged areas. Also there exists a wide range in the subgrade soil types, rainfall, traffic patterns and availability of various construction materials. Since specifications for rural road construction depend on the type of terrain and other environmental conditions, certain low-cost alternative specifications maximizing the use of local materials have been tried out on full scale on a large number of low volume roads for different sets of conditions as under plain areas of Indo-Gangetic plains, black cotton soil areas, high rainfall areas, water logged areas, hilly areas and desert areas Low grade marginal materials like moorum, kankar, dhandla, laterite etc where available within economic leads, should be made use of in pavement construction to the maximum extent feasible. The material may occur in a graded form or as discrete blocks or admixtured with soil. There is a variety of waste materials which, if available close to the construction site of a rural road project, can be utilized to advantage. The various waste materials that can be incorporated in rural road works are Flyash in road embankments, lime-flyash stabilized soil, lime-flyash bound macadam, Iron and steel slag in lieu of stone aggregates in WBM, rice husk ash in lime-rice husk ash concrete, recycled concrete aggregates in cement concrete, in water-bound macadam (WBM), other waste materials like quarry waste etc 1.7 Features of DRIP Software Following are the features of DRIP software •

Performs drainage designs for flexible and rigid pavements and retrofit edge drains.

•

Calculates the time-to-drain and depth-of-flow in the drainage layer.

•

Performs separator layer and geotextile designs.

•

Performs edge drain and geocomposite fin-drain designs.

•

Converts input and output from SI to English units, or vice versa.

15

Objectives of the Present Study The laboratory investigations on strength and drainage characteristics of GSB mixes designed using locally available material have been carried out with the following objectives. 1. To determine the gradation, consistency limits, OMC, MDD, CBR and

Permeability values for the soil samples collected from selected rural roads of Karnataka. 2. To determine physical properties and gradation for quarry dust, gravel and stone

aggregate. 3. To design Grade-III Granular Sub Base mixes using locally available soil, stone

aggregates, gravel and stone dust. 4. To determine strength and permeability characteristics of designed Granular Sub

Base mixes and to compare results. 5. To determine drainage characteristics of designed Granular Sub Base mixes and to compare results. 6. To analyze the drainage characteristics of GSB mixes using DRIP 2.0 software

and to develop design charts for drainage capacities of GSB layers.

16

CHAPTER-2

LITERATURE REVIEW 2.1 Field Measurement of Granular Base Drainage Characteristics (1) Knowledge of the in-situ drainage characteristics of pavement base and coarse sub-grade materials at an early stage of the design process, allows the pavement designer to avoid many design-related problems. The use of a device to measure the in-situ drain ability of base and sub-grade materials during construction would help ensure that base and sub-grade layers are capable of removing infiltrated water from the pavement system at a rate adequate to prevent accelerated pavement deterioration. The results of this project will include: 1. A user's manual for two devices that can be used for measuring the in-situ drainage characteristics of aggregate base and granular sub-grade materials. 2. Recommendations regarding "action limits" on the drain ability characteristics of the aggregate base, granular, and select granular materials used by Mn/DOT. 3. Computerized database of the in-situ drainage characteristics of the various base and granular sub-grade materials used by Mn/DOT. 2.2 Comparison of Pavement Drainage Systems (2) Pavement drainage systems have become a common addition to construction and reconstruction plans. Several types of transverse and longitudinal drains that vary in shape, size, and cost are often included in designs, although little is known about their performance. The drainage characteristics and pavement performance of four drainage systems under jointed Portland cement concrete pavement are described and evaluated. Included are the Minnesota Department of Transportation (Mn/DOT) standard densegraded base, two dense-graded base sections incorporating traverse drains placed under the transverse joints, and permeable asphalt-stabilized base-a design that reflects current Mn/DOT drainable-base thinking. All sections contain longitudinal edge drains. Experiment variables include drainage flows, percent of rainfall drained, time to drain, base and sub grade moisture content, and pavement and joint durability. Two primary conclusions were reached. First, although all systems appear capable of removing drainable water from the pavement base, the permeable asphalt-stabilized base usually drained the most water within 2 hr after rainfall ended, while providing the driest 17

pavement foundation and the least early pavement distress. Second, sealing the longitudinal and transverse joints temporarily reduced all rain inflow. After about 2 wk inflow resumed, although the joint sealants appeared to be intact. 2.3 Locating the Drainage Layer for Bituminous Pavements in Indiana (3) Pavement subsurface drainage and its effect on pavement performance has been a subject of interest since the 18th and 19th centuries. Without doubt the detrimental effect of heavy wheel loads on pavements with saturated base material is a significant factor. The consequence of subsurface water on pavement performance includes premature rutting, cracking, faulting, and increased roughness, all of which lead to a decrease in serviceability. This research study involves the evaluation of the drainage performance of three section configurations. The sections were built with a difference in the filter as well as the drainage layer. Indiana #5D, and #53 impermeable layers were used as a filter. Indiana #2 and #5C base were used as drainage layer. The study was carried out by field instrumentation, laboratory testing, field data collection, and numerical modeling. The main objective of this study is to evaluate the sub-drainage performance of three pavement sections adopted by the Indiana Department of Transportation (INDOT). Instruments were installed to monitor the air and pavement temperature, frost penetration, and pavement moisture conditions, and time and duration of rainfall and pavement outflow volumes. Sub-grade and asphalt core samples were obtained from the field. Tests were performed on these samples to determine their hydraulic conductivity characteristics. It was found that the permeability of the #5C drainage base layer material was higher than the #2 base by approximately 10 times. Since most of the water source in the pavement was the surface infiltration, the filter layer plays a key role in controlling the moisture migration from the pavement into the sub-grade. The section with the #5D HMA impermeable layer showed the lowest moisture migration into the sub-grade. The #5C base had the tendency to retain less water than the #2 base, making the stripping potential less of a problem. Contamination of the trench material from the #53 aggregate fines appears to have occurred, and therefore, section1 (#5D filter layer). In addition, the outlet pipe inlet capacity was found to be low. Frost penetration was found to be about 1.0 m. This result compared well with empirical methods. From the field temperature measurements, the SHRP coldest surface pavement temperature was evaluated and found in good agreement. A large amount of data was obtained about pavement and sub-grade material hydraulic characteristics. The finite element analysis showed good simulation of 18

the actual pavement surface conditions. A simulation of cracked surface pavement showed a full saturation condition of the pavement layers. 2.4 Asphalt Overlay and Subsurface Drainage of Broken and Seated Concrete Pavement (4) This research was conducted to study subsurface drainage issues surrounding an asphalt overlay. The type of pavement that was examined in this study was a Superpave overlay on top of a Broken and Seated Jointed Reinforced Concrete Pavement ~B&S JRCP!. A finite-element model of the pavement was developed and a number of numerical analyses were performed to evaluate the movement of water in the pavement. The pavement drainage modeling was conducted using the SEEP/W 2002 in GEOSLOPE program. A steady-state saturated flow analysis was used to obtain the flow path of the infiltrated water and flux quantity through the cross-sectional area in the pavement. This analysis was done for the pavement models with different layer arrangements and different drainage practices. The findings of this research revealed that high water permeability in the asphalt base and Superpave surface layers contributed to water flow into the pavement. This infiltration of water into the pavement structure is a serious issue that must be addressed in pavement drainage design. The broken and seated layer functions as an efficient drainage layer. 2.5 Effective Approach to Improve Pavement Drainage Layers (5) The objective of this study was twofold: quantify the benefits of a specially designed geocomposite membrane of low modulus polyvinyl chloride - PVC layer sandwiched between two nonwoven geotextiles to act as a moisture barrier in flexible pavement systems; and quantitatively measures the moisture content of unbound granular materials nondestructively. The geocomposite membrane was installed over half the length of a pavement test section at the Virginia Smart Road, while the other half of the test section consisted of the same design without the interlayer system. Air-coupled ground penetrating radar - GPR system with 1 GHz center frequency was used to monitor and detect the presence of moisture within the pavement system over different periods of time corresponding to different levels of water accumulation. Results of GPR data analysis indicated that the use of the geocomposite membrane reduced water infiltration to the aggregate base layer by as much as 30% when measurements were performed after rain. It was also found that the moisture content underneath the interlayer 19

was almost constant and therefore independent of the amount of rainwater, which is the primary source of moisture in pavement systems that have a low water table. The impact of moisture in the granular layers was

investigated using the results of a

deflection monitoring program. The results indicate that the area with the geocomposite membrane always showed less deflection than the area without the interlayer. The study recommends that any pavement drainage layer must be backed by an impermeable interface, given that the water table is low. 2.6 Design Charts for Drainage Capacities of Granular Sub-bases (6) The studies were carried out at NIIT, Surathkal to investigate the significance of drainage capacity of GSB in pavement design and to develop design charts for drainage capacities of GSB layers. The permeability and porosities of Grading-III GSB mixes were used in the drainage capacity analyses. The drainage analyses of GSB based on available analytical models were carried out using DRIP software. Analytical results now that for a particular design thickness and permeability of GSB, the parameters such as pavement width and rainfall intensity significantly influences on the drainage capacity. Hence it is recommended to consider these parameters in the design of GSB thickness, in addition to the strength and traffic parameters. 2.7 Road Drainage (7) Water plays havoc with all structures and is equally true in a Highway. It is not sufficient merely to provide the road with the surfacing, the water must be collected and removed from the roadway to ditches or soakways at a safe distance from the road foundation to prevent surface water reaching the sub-soil and thus lowering its bearing strength. The geographical features vary greatly in our country. Similarly, the rainfall is meager, moderate and heavy at different places. Thus the road drainage problems are sure to differ from place to place. Adequate drainage is one of the important fundamental factors governing the stability, load carrying capacity and life of a roadway. It involves a multiplicity of factors which increase the complexity of the problem and diffuses its various facts. The problem of road drainage could be divided in two principal parts, viz. surface water drainage and sub-surface water drainage. Under the surface water drainage the period of frequency of floods, design of various drainage structures like culverts and inlet gutters, prevention of erosion, roadside channels, dykes, median drainage, cross-slopes and side-slopes, catch drains, longitudinal gradients, etc. has to be taken into account The sub-surface aspect 20

would require consideration of items like under drain for seepage water, beeding and backfill materials for under drainage, measures against freezing, sub-soil and branch drains and interceptor and French drains. Drainage facilities are necessary to prevent flooding of the road and weakening of the sub-grade soil and the road pavements will be different for various classes of roads. The method of drainage employed on rural roads is dependent on the amount of traffic using the road, the drainage characteristics of the sub-grade soil, and the topography. The general aim is to remove surface water and to keep the water taken at a depth below road level sufficient to avoid weakening of the sub-grade soil. More elaborate arrangements will be necessary in case of arterial roads carrying heavy traffic. The drainage of roads in city areas, because of the limitation of land width and also due to presence of foot paths, dividing islands and other road facilities pose problems of different kinds and co-operation of many agencies including public will be needed to solve them. The drainage problem in plains may not be as difficult as in hilly and high altitude areas. In plains, proper camber on road surfaces and berms and construction of side drains should normally provide for adequate drainage. When water table is high, use of sand blanket as a capillary cut-off, French Drains and deep side drains should be made besides keeping the embankment high so that sub-grade is sufficiently above the ground water. The slopes of road embankment should be made gentler 1:3 or 1:4. In addition to the transverse fall to remove the surface water, it is necessary to have some longitudinal fall, particularly at the edge channels, for the same purpose. The greater concentration of water at the edges of the road makes a lower slope acceptable, as flat as 1 on 200. On a kerbed road, it is preferable that the longitudinal gradient of the road should be no flatter than 1 on 200. Where this is not possible, it is necessary to ‘summit’ the channel to introduce crests and valleys with this minimum slope between. Such a device is rather unsightly, but is more acceptable at the edge of a shoulder. If a kerb is used, only the channel should be ‘summitted’, and the kerb kept to a uniform line. Berms constructed to proper design on both sides of road could also check the traveling of water towards the road. Grass-lined channels would also be useful. If water channels run parallel to a road, cross-drainage should receive special attention. Digging of deep borrows pits on road sides should also be avoided as accumulated water affects sub-grade besides marring the aesthetics of the road. In hilly areas, there is need to provide catch-water drains, catch 21

pits, side drains, cross drains, scuppers and sometimes valley side drains. The hill sides also require protection in the shape of turffing, planting of trees, construction of breasts, retaining walls, etc. The side wall should also be built sufficiently wide so that there is no over-flow of water. In high altitude regions, cross-drainage is very important and snow-sheds would be useful when road passes through glacier locations. Realizing the importance of the subject, the Indian Roads Congress published a booklet containing some of the practices on road drainage in various countries and later a Panel Discussion was arranged during its Nainital Session in September 1967. Arising out of this Panel Discussion, a subcommittee was set up to draft a Code of Practice on this subject for the benefit of practicing engineers. While a Code of Practice will provide answers to many of the problems about road drainage being faced by the Highway Engineers, much will depend upon the ingenuity and skill. If the Highway Engineers builds a road to a proper design keeping in view the problems of drainage of sub-surface and the surface levels, he may not have to face the drainage problem later on, on the other hand any lack of care to these heavy loads or the heavy rains. It is, therefore, but proper that great emphasis should be laid on the drainage aspect while designing and building highways. While all this looks so simple, it has to be remembered that proper data of rainfall, soil condition, and sub-surface water level should be collected by the Highway Engineers before undertaking any road project. Drainage facilities in the existing roads should also be surveyed with a view to improving them where considered necessary. Highways built to a proper design with an inbuilt road drainage system will last longer, avoid extra maintenance costs and above all provide all weather routes for free flow of road traffic and also prove economical in the long run. The maintenance aspect is equally important and should not be lost sight of. Routine cleaning and repair of drainage facilities are also important and, therefore, proper and adequate arrangement should be made for these also.

2.8 DRIP Software for Drainage Design (8) Moisture-related pavement distresses have long been recognized as a primary contributor to premature failures and accelerated pavement deterioration. The Federal Highway Administration (FHWA) provides design guidance for drainage in its manual 22

numbered FHWA-TS-80-224, “Highway Subdrainage Design.” Under a study known as Demonstration Project No. 87, or simply “Demo 87,” the FHWA Pavement Division developed a comprehensive effort to provide design guidance for handling water that infiltrated into the pavement structure from the surface. That study resulted in the production of the Participant Notebook for Demonstration Project No. 87. Engineers needed a concise and user-friendly microcomputer program that replicates the subsurface drainage design procedures in the Participant’s Workbook for Demonstration Project No. 87. Also, because of the increasing use of the SI unit system, there was a need for the program to incorporate both SI and pound-inch (U.S. Customary) units. In response to these needs, Applied Research Associates, Inc., developed a microcomputer program titled “Drainage Requirements in Pavements (DRIP) Version 1.0” under a contract from the FHWA (contract No. DTFH61-95-C-00008). Robert Baumgardner of the FHWA supplied technical control for the project. The ARA principal investigator was Walter Barker, and development of the computer program was led by Tim Wyatt, Jim Hall served as program manager. The program was delivered to the FHWA in September 1997. In 1998, a new National Highway Institute course (NHI Course No. 131026) titled “Pavement Subsurface Drainage Design” was developed to further improve the guidance on pavement subsurface drainage design, construction, and maintenance. DRIP Version 1.0 was completely integrated into this course to perform hydraulic design computations. The program has since been used in the industry and has received excellent reviews. However, several valuable suggestions were made by DRIP users to further improve the program. The suggestions mainly pertained to improving design input screen graphics, variable plot displays and outputs, and the user’s manual. Certain key drainage calculations and plotting options were also suggested to enhance DRIP’s technical capabilities. In addition, there was a need to upgrade the program to be compatible with the computing environments prevalent today. To make these program modifications, the FHWA entered into a contract (FHWA Contract No. DTFH61-00-F00199) with the ERES Division of ARA. Mr. Robert Baumgardner and Mr. Bing Wong of the FHWA supplied the technical control for the project. The ERES principal investigator was Jim Hall, and Gregg Larson implemented the program modifications. Jagannath Mallela of ERES served as the project manager. Under this contract, the

23

microcomputer program “Drainage Requirements In Pavements (DRIP) Version 2.0” and a revised user’s guide were developed. This program was developed for subsurface design for highway pavements. The most significant changes in DRIP 2.0 are related toprogram usability—interface improvements, improved help, refined analysis, and easy program output access. Most of the analysis routines developed in the original version of DRIP were retained. The program performs the following key functions: •

Performs drainage designs for flexible and rigid pavements and retrofit edgedrains.

•

Calculates the time-to-drain and depth-of-flow in the drainage layer.

•

Performs separator layer and geotextile designs.

•

Performs edgedrain and geocomposite fin-drain designs.

•

Converts input and output from SI to English units, or vice versa.

2.8.1 Depth of Flow (Steady-state flow) In this concept, permeable bases are designed to have a steady-stat flow (q d) equal or greater than the inflow (qi) from the design rainfall. Generally Moulton’s equation, as presented below are used If,

(S2 – 4q / k) < 0 then

If,

(S2 – 4q / k) > 0 then

If,

(S2 – 4q / k) = 0 then

2.8.2 Time-to-drain (Unsteady-state flow) In this approach, the specific time (t) taken for specific degree of discharge through the drainage path of the permeable base is computed. The t-value is used to evaluate the drainage quality of the permeable base. In the present investigation, the specific time for 50 % discharge (t50) was computed using the following equations, developed by Casagrande and Shannon. 24

Where, S = Slope Sf = slope factor = H/LS H = thickness of granular layer H1 = depth of water at the upper end of flow path L = width of granular layer

Lr = Length of drainage k= permeability ne =effective porosity of granular material t50 = time for 50% discharge T50 = time factor for 50% drainage qi = rate of uniform flow

2.9 Permeability The soil can be considered as a porous medium and the interconnected voids allow water to flow through it. Water can flow from points of high energy to points of low energy. The permeability k is used to quantify this property. Coarse grained soils have larger voids and higher permeability. The fine grained soils have smaller voids and lower permeability. Many geotechnical engineering problems are related to the soil permeability such as •

Rate of consolidation

•

Stability of slopes, embankments and retaining walls

•

Pumping water for underground construction

•

Quantity of safety of an earthern dam

2.9.1 Darcy’s Law Darcy (1856) proposed that average flow velocity through soils is proportional to hydraulic gradient (based on the experimental observation) V = k Δh / L = ki Where k is a proportional coefficient and is called coefficient of permeability (hydraulic conductivity). The unit of k is length /time. Darcy’s law is valid for all soils if the flow is laminar (Reynolds number < 1). Fluid through soils finer than coarse gravel is laminar. That is, the small pore and low flow speed can warrant a laminar flow in sand, silt and clay. The Darcy’s law will be valid for those soils. For every coarse sands, gravels and boulders, the pore size is large

25

and the flow speed is high, so the turbulent flow may occur and the Darcy’s law is no longer valid. 2.9.2 Coefficient of Permeability for common soil types The following characteristics can influence hydraulic conductivity of soils •

Particle size

•

Void ratio

•

Composition

•

Fabric (structure)

•

Degree of saturation

•

The wholeness (homogeneity, layering, fissuring, etc.)

The coefficient of permeability values for common soils are tabulated in the Table 2.1 and degree of permeability in the Table 2.2

Table 2.1 Coefficient of Permeability for common soil types Soil type

k (cm/sec)

Clean gravel

>1.0

Clean sand, clean sand and gravel mixtures

1.0 to 10-3

Fine sand, silts, mixtures comprising sands, silts and clays

10-3 to 10-7 <10-7

Homogenous clay

The permeability of soils exhibits a great range of values, in order of ten. For a soil having a homogenous fabric, the permeability depends on the fine particles than on the large. A small percentage of fines can clog pores of an otherwise coarse material and results in lower hydraulic conductivity Table 2.2 Degree of permeability Degree of Permeability

Value of k (cm/sec)

High

Over 10-1

Medium

10-1 to 10-3 26

Low

10-3 to 10-5

Very low

10-5 to 10-7

Practically impermeable

Less than 10-7

27

CHAPTER-3

PRESENT INVESTIGATIONS 3.1 Selection of the Test Stretches for Soil Sampling To study the drainage characteristics of the subgrade soil samples, newly constructed rural roads were selected. The roads which were one year old or less than one year were grouped under newly constructed roads. A list of forty newly constructed roads was obtained from Karnataka Rural Road Development Agency (KRRDA), Bangalore. The Detailed Project Report (DPR) for each of the newly constructed road was collected and details regarding year of construction, pavement thickness, rainfall data and soil investigation reports were obtained. Based on the preliminary studies and details given in Detailed Project Report (DPR), only 10 road stretches were selected for collecting soil samples. The roads selected have been widely distributed in Karnataka covering different soil types, traffic and environmental condition. The list of the road stretches selected for sub-grade soil sampling has been given in Table 3.1. The details regarding year of construction, sub-grade CBR, rainfall and crust thickness of selected roads has been obtained from DPRs and presented in the Table 3.1. 3.2 Materials Used for GSB Mix Design 3.2.1 Gravel In the present study, gravel was collected from a quarry near Hoskote. Test conducted on Gravel are Grain size distribution and Atterberg limits. Gravel was used to design GSB mix. 3.2.2 Aggregate The aggregate is the basic material for any road construction. It forms the greater part of the body of the road. It is called upon to bear the main stresses occurring in the road and top surfaces resists wear from surface abrasion. In the present study, aggregate passing 20mm sieve was collected from M/s Kaveri asphalt, Bangalore. These aggregates were used to design GSB mix. Table 3.1 List of Selected Rural Roads for Sub-grade soil sampling Sample No

Name of the Road

Name of the Block

Year of

Data as per DPR SubCrust details,

Rainfall,

28

Construction

grade CBR, %

mm PMC

Stretch 1

H B Road To Karaki

Hosanagara

Sep-05

6.8

Stretch 2

Shanuboganahalli To T-16

Arakalagudu

Jul-07

4

WBM II =75

Stretch 4

Stretch 5

K D Road to Narasipura

Sagara

May-05

6.7

WBM II =75

Bailur - Nayarbettu Road

Karkala

NH-17@ 255.30 KM to Bijur

Kundapura

Jan-08

4

WBM II = 75

Stretch 7

Stretch 8

Stretch 9

Stretch 10

Kambliganahalli to NH-4

2000

= 175 = 20

WBM III=75

2000

WBM II =75 PMC = 20

Jan-07

4

WBM III=75 WBM II =75 GSB PMC

Stretch 6

1800

= 200 = 20

WBM III= 75 GSB PMC

2000

= 50 = 20

WBM III=75 GSB PMC

Stretch 3

= 20

WBM III=75 GSB PMC

mm/Year

Hoskote

Sep-06

2

CTR Road to Doddacheemanahalli

Devanahalli

M K Road To Kothavinahalli

Maddur

Jul-06

7

= 200 = 20

WBM III =75 WBM II =75 GSB PMC

2350

650

=160 = 20

WBM III=75

740

WBM II =75 PMC = 20

Jun-05

6

WBM III=75 WBM II =75 SG PMC

M.G.Road -Manjilnagara

Srinivasapura

NH-13 To Borenahalli

Holalkere

2007

6

1100

= 210 = 20

WBM III=75

500

WBM II =75 PMC = 20

Jul-05

8

WBM III=75 WBM II =75 GSB

600

= 75

29

3.2.3 Quarry Dust The quarry dust used for the work was collected from local quarry. Quarry dust was collected from M/s Kaveri asphalt, Bangalore. This quarry dust was used to design GSB mix. 3.2.4 Locally Available Soil The locally available soil samples were obtained from selected rural roads. For this purpose trenches were cut open near the pavement edges. Then from each trench a minimum of 20kgs of soil samples were obtained and collected in neat water proof bags. The bags were numbered and labeled for easy identification. Soil samples were collected in small sealed covers for determining of field moisture. Then the samples were transported to the laboratory to carry out further laboratory investigations. 3.3 Tests on GSB materials 3.3.1 Gravel In the present study, the soil samples which were collected from quarry were subjected to the following laboratory test, i) Particle size distribution and ii) Atterberg limits. Grain size analysis was carried out based on IS: 2720 (part 4)-1985 and Atterberg limit test was carried out based on IS: 2720 (part 5)-1985 3.3.2 Aggregates In the present study, aggregate collected from local quarry was subjected to the following laboratory tests, i) Specific gravity ii) Water absorption iii) Aggregate crushing value and iv) Aggregate impact value. Water absorption was carried out based on IS: 2386 (part-3), Soundness test was carried out based on IS: 383 and Impact value was carried out based on IS: 2386(part-4). 3.3.3 Quarry Dust In the present study, quarry dust collected from local quarry was subjected to Sieve Analysis. Grain size analysis was carried out based on IS: 2720 (part 4)-1985.

30

3.3.4 Locally Available Soil In the present study, the soil samples which were collected from different sources were subjected to the following laboratory test. i) Particle size distribution ii) Atterberg limits iii) Compaction Test iv) California Bearing Ratio Test and v) Permeability Test. Grain size analysis was carried out based on IS: 2720 (part 4)-1985, Atterberg limit test was carried out based on IS: 2720 (part 5)-1985, Light compaction test was carried out based on IS: 2720 (part 17)-1980, CBR test was carried out based on IS: 2720 (part 16)-1979 and Falling head permeability test was carried out based on IS: 2720 (part 17)-1986. 3.4 Proportioning of Materials for GSB Mixes 3.4.1 Proportioning of Materials for GSB Mix-I The GSB mix was prepared using 20 mm down size aggregates, gravel, locally available soil and quarry dust. Aggregates were added to achieve CBR requirements and quarry dust was added to achieve the desired consistency limits as per IRC: SP-20-2002. Different percentage of dust was mixed with the soil and consistency limits were determined. From the results it was observed that quarry dust by 5% of weight of soil was good enough to reduce the liquid limit to less than 25 and plasticity index less than 6. But to satisfy gradation requirements quarry dust in the range of 7% to 10% by weight of soil was added. The sieve analysis was carried out for aggregates, gravel, locally available soils and quarry dust. Based on the results of sieve analysis, gradation was fixed using Trial and Error method. The Sieve analysis and proportioning of materials for GSB Mix-I are shown in Table 4.6 to 4.15 3.4.2 Proportioning of Materials for GSB Mix-II The GSB mix was prepared using 20 mm down size aggregates, locally available soil and quarry dust. Aggregates were added to achieve CBR requirements and quarry dust was added to achieve the desired consistency limits as per IRC: SP-20-2002. Different percentage of dust was mixed with the soil and consistency limits were determined. From the results it was observed that quarry dust by 5% of weight of soil was good enough to reduce the liquid limit to less than 25 and plasticity index less than 6. But to satisfy gradation requirements quarry dust in the range of 7% to 10% by weight of soil was added. The sieve analysis was carried out for aggregates, locally available soils and quarry dust. Based on the sieve analysis, gradation was fixed using Trial and 31

Error method. The Sieve analysis and proportioning of materials for GSB Mix-II are shown in Table 4.16 to Table 4.25. 3.5 Tests on GSB mix The tests conducted on GSB mixes were compaction test (heavy compaction), CBR test and permeability test. To determine density-moisture relationship, IS heavy compaction test was conducted. To determine CBR value of GSB mixes, tests were conducted for soaked (4 days) condition. The constant-head permeability test is conducted to find out the change in permeability values of the GSB mixes. The results of the compaction test, CBR test and permeability test for GSB Mix-I and GSB Mix-II are shown in Table 4.26 and Table 4.27 respectively. The plots for Dry Density v/s Moisture content for GSB Mix-I and Mix-II are shown in Fig 4.3 and 4.5 respectively. 3.6 Drainage Estimation using DRIP software This program was developed for subsurface design for highway pavements. The most significant changes in DRIP 2.0 are related to program usability—interface improvements, improved help, refined analysis, and easy program output access. The program performs the following key functions: •

Performs drainage designs for flexible and rigid pavements and retrofit edgedrains.

•

Calculates the time-to-drain and depth-of-flow in the drainage layer.

•

Performs separator layer and geotextile designs.

•

Performs edgedrain and geocomposite fin-drain designs.

•

Converts input and output from SI to English units, or vice versa.

32

3.6.1 Roadway Geometry Using this program feature, the user can compute the length and slope of the true drainage path based on the longitudinal and transverse grade of the roadway, as well as the width of the underlying base material. The user can perform these calculations for the two common roadway cross-sections commonly encountered—crowned and super elevated (uniform slope) sections.

33

3.6.2 Sieve Analysis The effective grain sizes (Dx), total and effective porosities, coefficient of uniformity and gradation, and coefficient of permeability can be computed for any userentered gradation using this program feature. Plots of the gradations on semi-log and FHWA power 45 templates can also be obtained from this program screen.

34

3.6.3 Inflow The amount of moisture infiltrating the pavement structure from rainfall and melt water can be computed using this program option. The surface infiltration calculations can be performed using two different approaches—the Infiltration Ratio approach and the Crack Infiltration approach. Melt water computations can be performed for a variety of soil types and pavement cross-section depths.

35

3.6.4 Permeable Base Design The program offers two permeable base design options—depth-of-flow and timeto-drain. These methods allow the user to design an open-graded base that can handle the inflow entering the pavement structure.

36

CHAPTER-4

RESULTS AND DISCUSSIONS 4.1 Laboratory test results for GSB materials 4.1.1 Gravel Wet sieve analysis of gravel and Atterberg limits tests for gravel was carried out to determine the grain size distribution and consistency limits. The results are shown in Table 4.1 Table 4.1 Particle size distribution and Consistency limits of Gravel sample from Hoskote. Grain size distribution Sample

Gravel from Hoskote Quarry

Sieve size, in mm

% Passing

20.00

100.00

10.00

88.50

4.750

75.68

2.360

66.42

1.180

61.30

0.600

51.36

0.425

44.52

0.300

38.12

0.150

27.28

0.075

21.22

Consistency limits LL

PL

PI

NON-PLASTIC

4.1.2 Aggregates Tests on aggregates have been carried out to determine the aggregate impact value, crushing strength, Los Angles Abrasion value and specific gravity. The test results are presented in Table 4.2. These results indicate suitability of the aggregates for construction of GSB.

37

Table 4.2 Test Results of Coarse Aggregates Sl no

Tests on Aggregates

Test results

As per MORT&H IV revision- 2001 Specifications

1

Aggregate Crushing value

28.5%

---

2

Los Angeles Abrasion value

27.6%

Max 35%

3

Aggregate Impact value

24.3%

Max 27%

4

Water absorption (%)

0.681

Max 2%

5

Specific Gravity

2.60

2.5-3.0

4.1.3 Quarry Dust The Sieve analysis of Quarry dust sample was carried out to determine the grain size distribution. The results are tabulated in Table 4.3 Table 4.3 Particle size distribution of Quarry Dust.

Sample

Quarry dust from M/s Kaveri Asphalt, Bangalore.

Sieve size, in mm

% Passing

20.00

100.00

10.00

100.00

4.75

97.46

2.36

87.40

1.18

73.34

0.60

47.30

0.43

36.34

0.30

28.68

0.15

18.26

0.08

9.46

4.1.4 Locally Available Soils 38

The laboratory investigations have been carried out on sub-grade soil samples collected from selected rural roads in Karnataka. Wet sieve analysis, consistency limits, Standard Proctor compaction test, CBR and permeability tests were carried out and results have been recorded.. Results for percentage gravel, sand, silt & clay fractions and Atterberg limits are tabulated in Table 4.4. Particle size distribution for soil samples are given in Table 4.5. Results for compaction test, CBR test and permeability test are shown in Table 4.6. Dry density v/s moisture content for all the soil samples are shown in Figure 4.1. Table 4.4 Percentage Gravel, Sand, Silt & Clay fractions and Atterberg limits.

Stretch No

Gravel

Sand

Silt and Clay

Liquid Limit %

Plastic Limit %

Plasticity Index

1

0.00

64.14

35.86

27.20

NP

NP

2

14.62

48.58

36.80

26.80

18.25

9.0

3

40.86

29.94

29.20

40.80

29.86

11.0

4

26.50

48.32

25.18

34.00

25.89

8.0

5

43.50

28.70

27.80

38.00

27.78

10.0

6

3.38

40.96

55.66

35.20

25.00

10.0

7

0.68

80.48

18.84

0.00

NP

NP

8

19.94

62.54

17.52

0.00

NP

NP

9

3.02

49.60

47.38

38.60

25.00

14.0

10

8.50

47.25

44.25

46.60

36.79

10.0

39

Table 4.5 Particle size distribution of Sub-grade soil samples. SIEVE SIZE

Percent Passing Sample 1

Sample 2

Sample 3

Sample 4

Sample 5

Sample 6

Sample 7

Sample 8

Sample 9

Sample 10

20 mm

100.00

100.00

78.02

100.00

97.10

100.00

100.00

100.00

100.00

100.00

10 mm

100.00

90.64

70.98

94.66

79.94

100.00

99.46

91.60

100.00

98.52

4.75

100.00

85.38

59.14

73.50

56.50

96.62

99.32

80.06

96.98

91.50

2.36

99.72

81.08

45.02

52.78

45.20

94.38

98.34

68.74

76.50

76.60

1.18

99.34

76.08

38.90

43.58

40.28

92.84

93.46

62.32

63.76

68.02

600 µ

92.80

66.06

34.94

35.98

36.38

85.00

76.98

51.96

56.78

58.64

425µ

83.28

59.94

33.72

32.66

34.28

78.20

66.86

45.08

54.42

55.22

300 µ

72.26

54.20

32.76

30.34

32.48

70.98

54.18

38.24

52.70

52.86

150 µ

48.86

43.66

31.12

26.90

29.76

61.24

30.48

24.86

49.68

48.30

75 µ

35.86

36.80

29.20

25.18

27.80

55.66

18.84

17.52

47.38

44.25

Table 4.6 OMC, MDD. CBR and Permeability values of Sub-grade soil samples. Standard Proctor Compaction test Stretch No

Optimum Moisture Content, %

Maximum Dry Density, g/cc

CBR, %

Permeability, m/day

1

12.9

1.950

7.00

0.048

2

12.4

1.876

6.00

0.043

3

13.9

1.880

9.00

0.077

4

13.1

1.950

10.00

0.044

5

16.4

1.895

9.00

0.036

6

12.2

1.736

6.00

0.053

7

12.1

1.890

3.00

0.043

8

10.0

1.876

8.00

0.056

9

12.3

1.689

6.00

0.030

10

13.8

1.780

7.00

0.046

2.00 1.95 S tretc h 1

1.90

S tretc h 2 S tretc h 3

Dry Density g/cc

1.85

S tretc h 4 S tretc h 5

1.80

S tretc h 6 S tretc h 7

1.75

S tretc h 8 S tretc h 9

1.70

S tretc h 10

1.65 1.60 6.00

8 .0 0

10.00

12.00

14.0 0

16.00

18.00

20.00

M o istu re C o n te n t %

Figure 4.1 Dry Density v/s Moisture Content for Subgrade Soil Samples

41

It is observed from test results of sieve analysis the percentage of gravel, sand and silt and clay together varies from 0% to 43.50%, 29.94% to 80.48% and 17.52% to 55.66% respectively, from test results of Standard Proctor Compaction test, the optimum moisture content and maximum dry density for different subgrade soil samples ranges from 10 % to 16.4 % and 1.689 g/cc to 1.950 g/cc respectively. From test results of CBR test, the CBR values varies from 3.0% to 10% and from test results of permeability test, the permeability values varies from 0.036 m/day to 0.077 m/day for soil samples collected from different stretches.. 4.2 Properties of GSB mixes 4.2.1 Gradation The GSB mixes were prepared using aggregates, gravel, locally available soil and quarry dust. Aggregates were added in order to in achieve CBR requirements and quarry dust was added in order to achieve the desired consistency limits as per IRC: SP-202002. Different percentage of dust was mixed with the soil and consistency limits tests were conducted and from the results it was observed that 5% of dust by dry weight of soil was good enough to reduce the liquid limit to less than 25 and plasticity index less than 6. But for gradation requirements more percentage of dust was added. The proportion for Mix-I with subgrade soil, stone aggregate, gravel and stone dust and Proportion for Mix-II with soil, stone aggregate and stone dust are shown in Table 4.7 to Table 4.26.. Table 4.7 Sieve analysis and proportioning of Mix-I for Stretch 1 Percentage Passing IS Sieve size, mm

Soil (A)

Aggregate (B)

Gravel ( C)

Dust (D)

Mixture A:B:C:D 10:60:20:1 0

26.5 4.75 0.075

100.00 100.00 35.86

100.00 0.00 0.00

100 75.68 21.22

100.00 97.46 9.46

100 35 9

Required Gradation for Coarse GSB III as per IRC : SP :202002 100 25-45 <10

42

Table 4.8 Sieve analysis and proportioning of Mix-I for Stretch 2 Percentage Passing IS Sieve size, mm

Soil (A)

Aggregate (B)

Gravel ( C)

Dust (D)

Mixture A:B:C:D 11:58:21:1 0

26.5 4.75 0.075

100.00 85.38 36.80

100.00 0.00 0.00

100 75.68 21.22

100.00 97.46 9.46

100 35 9

Required Gradation for Coarse GSB III as per IRC : SP :202002 100 25-45 <10

Table 4.9 Sieve analysis and proportioning of Mix-I for Stretch 3 Percentage Passing IS Sieve size, mm 26.5 4.75 0.075

Soil (A)

Aggregate (B)

Gravel ( C)

Dust (D)

Mixture A:B:C:D 11:58:21:1 0

100.00 59.14 29.20

100.00 0.00 0.00

100 75.68 21.22

100.00 97.46 9.46

100 35 9

Required Gradation for Coarse GSB III as per IRC : SP :202002 100 25-45 <10

Table 4.10 Sieve analysis and proportioning of Mix-I for Stretch 4 Percentage Passing IS Sieve size, mm 26.5 4.75 0.075

Soil (A)

Aggregate (B)

Gravel ( C)

Dust (D)

Mixture A:B:C:D 11:58:21:1 0

100.00 73.50 25.18

100.00 0.00 0.00

100 75.68 21.22

100.00 97.46 9.46

100 35 9

Required Gradation for Coarse GSB III as per IRC : SP :202002 100 25-45 <10

Table 4.11 Sieve analysis and proportioning of Mix-I for Stretch 5 Percentage Passing IS Sieve size, mm 26.5 4.75 0.075

Soil (A)

Aggregate (B)

Gravel ( C)

Dust (D)

Mixture A:B:C:D 11:58:21:1 0

100.00 56.50 27.80

100.00 0.00 0.00

100 75.68 21.22

100.00 97.46 9.46

100 33 9

Required Gradation for Coarse GSB III as per IRC : SP :202002 100 25-45 <10

43

Table 4.12 Sieve analysis and proportioning of Mix-I for Stretch 6 Percentage Passing IS Sieve size, mm

Soil (A)

Aggregate (B)

Gravel ( C)

Dust (D)

Mixture A:B:C:D 11:58:21:1 0

26.5 4.75 0.075

100.00 96.62 55.66

100.00 0.00 0.00

100 75.68 21.22

100.00 97.46 9.46

100 35 10

Required Gradation for Coarse GSB III as per IRC : SP :202002 100 25-45 <10

Table 4.13 Sieve analysis and proportioning of Mix-I for Stretch 7 Percentage Passing IS Sieve size, mm 26.5 4.75 0.075

Soil (A)

Aggregate (B)

Gravel ( C)

Dust (D)

Mixture A:B:C:D 11:58:21:10

100.00 99.32 18.84

100.00 0.00 0.00

100 75.68 21.22

100.00 97.46 9.46

100 35 7

Required Gradation for Coarse GSB III as per IRC : SP :202002 100 25-45 <10

Table 4.14 Sieve analysis and proportioning of Mix-I for Stretch 8 Percentage Passing IS Sieve size, mm 26.5 4.75 0.075

Soil (A)

Aggregate (B)

Gravel ( C)

Dust (D)

Mixture A:B:C:D 11:58:21:1 0

100.00 80.06 17.52

100.00 0.00 0.00

100 75.68 21.22

100.00 97.46 9.46

100 35 7

Required Gradation for Coarse GSB III as per IRC : SP :202002 100 25-45 <10

Table 4.15 Sieve analysis and proportioning of Mix-I for Stretch 9 Percentage Passing IS Sieve size, mm 26.5 4.75 0.075

Soil (A)

Aggregate (B)

Gravel ( C)

Dust (D)

Mixture A:B:C:D 11:58:21:1 0

100.00 96.98 47.38

100.00 0.00 0.00

100 75.68 21.22

100.00 97.46 9.46

100 34 9

Required Gradation for Coarse GSB III as per IRC : SP :202002 100 25-45 <10

44

Table 4.16 Sieve analysis and proportioning of Mix-I for Stretch 10 Percentage Passing IS Sieve size, mm 26.5 4.75 0.075

Soil (A)

Aggregate (B)

Gravel ( C)

Dust (D)

Mixture A:B:C:D 11:58:21:1 0

100.00 91.50 44.25

100.00 0.00 0.00

100 75.68 21.22

100.00 97.46 9.46

100 34 9

Required Gradation for Coarse GSB III as per IRC : SP :202002 100 25-45 <10

Table 4.17 Sieve analysis and proportioning of Mix-II for Stretch 1 IS Sieve size, mm 26.5 4.75 0.075

Percentage Passing Soil (A)

Aggregate (B)

Dust ( C)

Mixture A:B:C 25:65:10

100.00 100.00 35.86

100.00 0.00 0.00

100.00 97.46 9.46

100 35 10

Required Gradation for Coarse GSB III as per IRC : SP :202002 100 25-45 <10

Table 4.18 Sieve analysis and proportioning of Mix-II for Stretch 2 Percentage Passing IS Sieve size, mm 26.5 4.75 0.075

Soil (A) 100.00 85.38 36.80

Aggregate (B)

Dust ( C)

Mixture A:B:C 25:65:10

100.00 0.00 0.00

100.00 97.46 9.46

100 31 10

Required Gradation for Coarse GSB III as per IRC : SP :202002 100 25-45 <10

Table 4.19 Sieve analysis and proportioning of Mix-II for Stretch 3 IS Sieve size, mm 26.5 4.75 0.075

Percentage Passing Soil (A)

Aggregate (B)

Dust ( C)

Mixture A:B:C 32:58:10

100.00 59.14 29.20

100.00 0.00 0.00

100.00 97.46 9.46

100 29 10

Required Gradation for Coarse GSB III as per IRC : SP :202002 100 25-45 <10

Table 4.20 Sieve analysis and proportioning of Mix-II for Stretch 4 IS

Percentage Passing 45

Sieve size, mm

Soil (A)

26.5 4.75 0.075

100.00 73.50 25.18

Aggregate (B)

Dust ( C)

Mixture A:B:C 33:57:10

100.00 0.00 0.00

100.00 97.46 9.46

100 34 9

Required Gradation for Coarse GSB III as per IRC : SP :202002 100 25-45 <10

Table 4.21 Sieve analysis and proportioning of Mix-II for Stretch 5 Percentage Passing IS Sieve size, mm 26.5 4.75 0.075

Soil (A) 100.00 56.50 27.80

Aggregate (B)

Dust ( C)

Mixture A:B:C 33:57:10

100.00 0.00 0.00

100.00 97.46 9.46

100 28 10

Required Gradation for Coarse GSB III as per IRC : SP :202002 100 25-45 <10

Table 4.22 Sieve analysis and proportioning of Mix-II for Stretch 6 Percentage Passing IS Sieve size, mm 26.5 4.75 0.075

Soil (A) 100.00 96.62 55.66

Aggregate (B)

Dust ( C)

Mixture A:B:C 16:72:12

100.00 0.00 0.00

100.00 97.46 9.46

100 27 10

Required Gradation for Coarse GSB III as per IRC : SP :202002 100 25-45 <10

Table 4.23 Sieve analysis and proportioning of Mix-II for Stretch 7 Percentage Passing IS Sieve size, mm 26.5 4.75 0.075

Soil (A) 100.00 99.32 18.84

Aggregate (B)

Dust ( C)

Mixture A:B:C 26:64:10

100.00 0.00 0.00

100.00 97.46 9.46

100 36 6

Required Gradation for Coarse GSB III as per IRC : SP :202002 100 25-45 <10

Table 4.24 Sieve analysis and proportioning of Mix-II for Stretch 8 IS

Percentage Passing 46

Sieve size, mm

Soil (A)

Aggregate (B)

Dust ( C)

Mixture A:B:C 31:59:10

26.5 4.75 0.075

100.00 80.06 17.52

100.00 0.00 0.00

100.00 97.46 9.46

100 35 6

Required Gradation for Coarse GSB III as per IRC : SP :202002 100 25-45 <10

Table 4.25 Sieve analysis and proportioning of Mix-II for Stretch 9 Percentage Passing IS Sieve size, mm

Soil (A)

26.5 4.75 0.075

100.00 96.98 47.38

Aggregate (B)

Dust ( C)

Mixture A:B:C 20:70:10

100.00 0.00 0.00

100.00 97.46 9.46

100 29 10

Required Gradation for Coarse GSB III as per IRC : SP :202002 100 25-45 <10

Table 4.26 Sieve analysis and proportioning of Mix-II for Stretch 10 Percentage Passing

IS Sieve size, mm 26.5 4.75 0.075

Soil (A)

Aggregate (B)

Dust ( C)

Mixture A:B:C 21:69:10

100.00 91.50 44.25

100.00 0.00 0.00

100.00 97.46 9.46

100 29 10

Required Gradation for Coarse GSB III as per IRC : SP :202002 100 25-45 <10

4.2.2 Test results for GSB mixes The tests conducted on GSB mixes were compaction test (heavy compaction), CBR test and permeability test. To determine density-moisture relationship, IS heavy compaction test was conducted. To determine CBR value of GSB mixes, tests were conducted for soaked (4 days) condition. The constant-head permeability test was conducted to find out the permeability values of the GSB mixes. The results of the compaction test, CBR test and permeability test for GSB Mix-I and GSB Mix-II are shown in Table 4.27 and Table 4.28 respectively. The plots for Dry Density v/s Moisture content for GSB Mix-I and GSB Mix-II are shown in Fig 4.2 and Fig 4.3. Table 4.27 OMC, MDD. CBR and Permeability values of GSB Mix-I. Stretch

Modified Compaction test

CBR, % 47

No

Optimum Moisture Content, %

Maximum Dry Density, g/cc

Permeability m/day

1

7.10

2.060

36

1.68

2

8.10

2.020

24

1.59

3

9.10

2.100

37

1.20

4

9.00

2.090

35

1.35

5

8.60

2.030

38

1.27

6

8.00

2.020

34

2.47

7

7.10

2.040

33

3.08

8

8.10

2.000

24

2.50

9

8.30

2.010

28

2.07

10

6.80

2.020

30

2.24

Table 4.28 OMC, MDD. CBR and Permeability values of GSB Mix-II. Modified Compaction test Stretch No

Optimum Moisture Content, %

Maximum Dry Density, g/cc

CBR, %

Permeability m/day

1

5.10

2.170

44

3.56

2

6.30

2.120

30

3.08

3

7.50

2.220

46

3.92

4

7.30

2.190

44

2.04

5

6.80

2.140

47

1.89

6

4.90

2.120

41

3.14

7

6.00

2.100

38

2.22

8

5.20

2.080

27

2.78

9 2.10

5.90

2.090

32

10

5.00

2.130

39

Dry Density g/cc

2.05

3.24

Stretch 2 Stretch 3 Stretch 4

2.00

Stretch 5 Stretch 6

1.95

Stretch 7 Stretch 8

1.90 1.85 0.00

2.97 Stretch 1

Stretch 9 Stretch 10

48 2.00

4.00

6.00

8.00

Penetration mm

10.00

12.00

14.00

Figure 4.2 Dry Density v/s Moisture Content for GSB Mix-I

2.25

Stretch 1

Dry Density g/cc

2.20

Stretch 2

2.15

Stretch 3

2.10

Stretch 4 Stretch 5

2.05

Stretch 6

2.00

Stretch 7

1.95

Stretch 8 Stretch 9

1.90 1.85 0.00

Stretch 10 2.00

4.00

6.00

8.00

10.00

Pene tration mm

Figure 4.3 Dry Density v/s Moisture Content for GSB Mix-II

It is observed from the test results that the designed GSB mixes I and II were non plastic for all subgrade soil samples. The OMC value for the designed GSB mixes I and II varies from 6.8% to 9.1% and 4.9 % to 7.5 % respectively. The MDD value for GSB mixes I and II varies from 2.000 g/cc to 2.090 g/cc and 2.080 g/cc to 2.220 g/cc. The CBR value for GSB mixes I and II varies from 24 % to 38% and 27 % to 47 % 49

respectively. The Permeability value for GSB mixes I and II varies from 1.20 m/day to 3.08 m/day and 1.89 m/day to 3.56 m/day respectively for both the mixes. 4.3 Parameters for Sub-base Drainage Analysis The sub-base drainage analysis was made using DRIP 2.0 software. The parameters considered for analysis in DRIP software were intensity of rainfall (intensity of rainfall for Karnataka state varies from 40 mm/hr to 120 mm/hr) and road geometry (pavement width, shoulder width and cross slope). Gradation of GSB mixes and physical properties of GSB mixes (effective porosity and permeability) were also considered. 4.4 Estimation of Inflow The major sources of inflow are surface infiltration, groundwater seepage and melt water from ice. In the present study, it was assumed that the subgrade neither contributes to inflow nor allows for infiltration of water. Also, prevailing climatic conditions for Karnataka state doesn’t support frost formation in soils, melt water was not considered as a source of inflow. The only source of inflow is due to infiltration of rainwater. This is computed by two methods, i.

Infiltration-ratio method

ii.

Crack-infiltration method Due to non-availability of information of pavement infiltration tests, this

approach was not considered. Therefore only infiltration-ratio method was adopted to compute the inflow for different rainfall intensities and pavement width (3.75m). An infiltration ratio of 0.415 was assumed for asphalt pavements. Drainage capacity of GSB The main requirement of any drainage layer or permeable base is that is should drain the inflow quickly and safely. Therefore, the design capacity should have a greater outflow rate than inflow rate. The drainage layer has to satisfy two design requirements; i) The steady-state flow (depth-of-flow) capacity must be greater than the inflow rate ii)The unsteady-state capacity must be such that water can be drained quickly after precipitation. The present analysis is based on the assumption of saturated flow condition. Thus, the drainage capacity is a function of material property, length of drainage layer, depth of permeable layer, effective slope of the drainage layer and rate of flow. 50

In the first phase of the study, the minimum GSB thickness required to achieve design drainage capacity was computed based on the steady-state flow capacity (depth -of -flow approach using DRIP software). The results are given in the Table 4.28 and Table 4.30. Two graphs (log-log scale) were plotted with permeability on x-axis and computed minimum GSB thickness on y-axis. The Fig 4.7 and Fig 4.9 shows the design thickness curves. That is, minimum GSB thickness versus permeability values of the GSB material for pavement width of 3.75 m. These thickness curves were plotted for different intensities of rainfall (40 mm/hr to 120 mm/hr). In the second phase of the study, the drainage capacity of GSB was determined based on the unsteady-flow (time-to-drain) approach. The capacity is decided by considering the design criteria corresponding to the time required for 50% drainage (t50). The relationship derived by Casagrande and Shannon (DRIP software) were used to compute t50 of GSB mixes. The results are shown in the Table 4.28 and Table 4.30. Two graphs (log-log scale) were plotted with permeability on X-axis and computed duration to drain 50% water on Y-axis. The Fig 4.8 and Fig 4.10 shows the design thickness curves that is duration to drain 50% water versus permeability values of the GSB material for pavement width of 3.75m for calculated GSB thickness. These curves were plotted for different intensities of rainfall (40 mm/hr to 120 mm/hr). From the results it was observed that the time required to drain 50% of water for GSB Mix-I and MIX-II varied within the range of 2.64 hrs to 6.85 hrs and 1.42 hrs to 5.75 hrs. The minimum thickness of GSB required varies from 1.28m to 3.57m and 1.13m to 2.91m for Mix I and Mix II respectively Two graphs (log-log scale) were plotted with permeability on X-axis and duration to drain 50% water on y-axis. The results are given in the Table 4.29 and Table 4.31. The Fig 4.11 and Fig 4.12 shows the design thickness curves; that is duration to drain 50% water versus permeability values of the GSB material for pavement width 3.75m and GSB thickness, H=0.10m, It was observed from the results that the time required to drain 50% of water varies from 40.18 hrs to 68.85 hrs and 14.21 hrs to 44.41 hrs and it is also observed that the time required to drain 50% of water will be same for any intensity of rainfall. A graph (log-log scale) was plotted with permeability values (0.10 m/day to 1000 m/day) in X-axis and calculated minimum GSB thickness (varies from 0.04m to 13 m) in Y-axis. The results are tabulated in the Table 4.32. The Fig 4.13 shows the design 51

thickness curves that is minimum GSB thickness versus permeability values of the GSB material for pavement width of 3.75m. These thickness curves were plotted for different intensities of rainfall (40 mm/hr to 120 mm/hr). From the results it is observed that for a GSB mix with lesser permeability value, the required thickness of GSB will be more.

52

Table 4.29 Permeability, Time to Drain 50% water, calculated Minimum thickness required for GSB Mix-I for different intensity of rainfall Rainfall Intensity For 40mm/hr rainfall

For 60mm/hr rainfall

For 80mm/hr rainfall

For 100mm/hr rainfall

For 120mm/hr rainfall

Stretch No

Permeability m/day

Time to Drain 50% water, t50, hrs

Minimum thickness required, Hmin, m

Time to Drain 50% water, t50, hrs

Minimum thickness required, Hmin, m

Time to Drain 50% water, t50, hrs

Minimum thickness required, Hmin, m

Time to Drain 50% water, t50, hrs

Minimum thickness required, Hmin, m

Time to Drain 50% water, t50, hrs

Minimum thickness required, Hmin, m

1

1.68

5.63

1.76

4.63

2.17

4.04

2.51

3.63

2.82

3.32

3.09

2

1.59

6.15

1.81

5.06

2.23

4.41

2.58

3.96

2.90

3.63

3.18

3

1.20

6.22

2.09

5.12

2.57

4.46

2.98

4.01

3.34

3.67

3.67

4

1.35

5.98

1.97

4.93

2.42

4.29

2.81

3.85

3.15

3.53

3.46

5

1.27

6.85

2.03

5.64

2.50

4.91

2.90

4.41

3.25

4.04

3.57

6

2.47

4.45

1.44

3.67

1.77

3.20

2.06

2.88

2.31

2.64

2.54

7

3.08

4.98

1.28

4.11

1.58

3.58

1.84

3.22

2.06

2.95

2.26

8

2.50

5.93

1.43

4.89

1.76

4.26

2.05

3.83

2.30

3.51

2.52

9

2.07

5.46

1.57

4.50

1.94

3.92

2.26

3.52

2.53

3.23

2.78

10

2.24

5.24

1.51

4.24

1.87

3.69

2.17

3.32

2.43

3.04

2.67 53

Figure 4.4 Permeability v/s Minimum GSB thickness for GSB Mix-I

Figure 4.5 Permeability v/s Time to drain 50% water for GSB Mix-I

54

Table 4.30 Permeability, Time to drain 50% water for minimum GSB thickness (0.10m) for GSB Mix-I

Stretch No

Minimum GSB thickness, m

Permeability m/day

Time to Drain 50% water, t50

1

1.68

49.49

2

1.59

55.43

3

1.20

64.29

4

1.35

58.42

1.27

68.85

2.47

32.62

7

3.08

32.84

8

2.50

43.20

9

2.07

43.48

10

2.24

40.18

5 6

0.10

Figure 4.6 Permeability v/s Time to drain 50% water for 0.10 thick layer of GSB Mix-I

55

Table 4.31 Permeability, Time to Drain 50% water, calculated Minimum thickness required for GSB Mix-II for different intensity of rainfall Rainfall Intensity For 40mm/hr rainfall

For 60mm/hr rainfall

For 80mm/hr rainfall

For 100mm/hr rainfall

For 120mm/hr rainfall

Stretch no

Permeability m/day

Time to Drain 50% water, t50, hrs

Minimum thickness required, Hmin, m

Time to Drain 50% water, t50, hrs

Minimum thickness required, Hmin, m

Time to Drain 50% water, t50, hrs

Minimum thickness required, Hmin, m

Time to Drain 50% water, t50, hrs

Minimum thickness required, Hmin, m

Time to Drain 50% water, t50, hrs

Minimum thickness required, Hmin, m

1

3.56

2.81

1.18

2.32

1.46

2.00

1.70

1.80

1.91

1.67

2.10

2

3.08

3.38

1.28

2.78

1.58

2.43

1.84

2.18

2.06

2.00

2.26

3

3.92

2.42

1.13

1.99

1.39

1.74

1.62

1.56

1.82

1.43

2.00

4

2.04

4.03

1.59

3.32

1.96

2.90

2.27

2.60

2.55

2.38

2.80

5

1.89

4.20

1.65

3.46

2.04

3.01

2.36

2.71

2.65

2.48

2.91

6

3.14

3.34

1.27

2.76

1.57

2.40

1.82

2.16

2.04

1.98

2.24

7

2.22

5.75

1.52

4.75

1.87

4.14

2.18

3.72

2.44

3.41

2.67

8

2.78

5.34

1.35

4.41

1.67

3.84

1.94

3.45

2.17

3.16

2.39

9

2.97

3.13

1.13

2.58

1.40

2.25

1.62

2.02

1.82

1.85

2.00

10

3.24

3.16

1.24

2.61

1.54

2.28

1.79

2.05

2.01

1.87

2.21 56

Figure 4.7 Permeability v/s Minimum GSB thickness for GSB Mix-II

Figure 4.8 Permeability v/s Time to drain 50% water for GSB Mix -II

57

Table 4.32 Permeability, time to drain 50% water for minimum GSB thickness (0.10m) for GSB Mix-II

Stretch No

Minimum GSB thickness, m

Permeability m/day

Time to Drain 50% water, t50

1

3.56

17.34

2

3.08

22.27

3

3.92

14.21

4

2.04

32.36

1.89

34.92

3.14

21.84

7

2.22

44.41

8

2.78

37.00

9

2.97

19.56

10

3.24

20.37

5 6

0.10

Figure 4.9 Permeability v/s Time to drain 50% water for 0.10 thick layer of GSB Mix-II

58

Table 4.33 Minimum thickness of Drainage Layer (GSB) required for Different Intensity of Rainfall Minimum GSB thickness, m Intensity of Rainfall Permeability m/day

0.1 1 2 3 4 5 6 7 8 9 10 20 30 40 50 60 70 80 90 100 200 300 400 500 600 700 800 900 1000

40 mm/hr rainfall

60 mm/hr rainfall

80 mm/hr rainfall

100 mm/hr rainfall

120 mm/hr rainfall

7.41 2.30 1.60 1.30 1.11 0.99 0.90 0.83 0.77 0.72 0.68 0.46 0.37 0.31 0.27 0.25 0.22 0.21 0.19 0.18 0.11 0.09 0.07 0.06 0.05 0.05 0.04 0.04 0.04

9.09 2.83 1.98 1.60 1.38 1.23 1.11 1.03 0.96 0.90 0.85 0.58 0.46 0.39 0.35 0.31 0.28 0.26 0.25 0.23 0.15 0.11 0.09 0.08 0.07 0.06 0.06 0.05 0.05

10.51 3.28 2.30 1.86 1.60 1.43 1.30 1.20 1.11 1.05 0.99 0.68 0.54 0.46 0.41 0.37 0.34 0.31 0.29 0.27 0.18 0.14 0.11 0.10 0.09 0.08 0.07 0.07 0.06

11.76 3.67 2.57 2.09 1.80 1.60 1.46 1.34 1.25 1.18 1.11 0.77 0.62 0.53 0.46 0.42 0.38 0.36 0.33 0.31 0.21 0.16 0.13 0.11 0.10 0.09 0.08 0.08 0.07

12.89 4.03 2.83 2.30 1.98 1.76 1.60 1.48 1.38 1.30 1.23 0.85 0.68 0.58 0.51 0.46 0.43 0.39 0.37 0.35 0.23 0.18 0.15 0.13 0.11 0.10 0.09 0.09 0.08

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Figure 4.10 Permeability v/s Minimum GSB thickness

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CHAPTER-5

CONCLUSIONS AND RECOMMENDATIONS Conclusions 1. The laboratory investigations of the soil samples collected from the rural roads covering different regions of Karnataka have indicated that, three soil samples were non-plastic and remaining seven samples were having liquid limit greater than 25 and plasticity index greater than 6. Hence, majority of soil samples needed blending with quarry dust to bring down the consistency limits so as to make them suitable for GSB mixes. 2. The CBR values for soil samples for GSB mixes were in the range of 3% to 10%. But the minimum CBR value of GSB Grade III material should not be less than 15% as per IRC: SP: 20-2002. Hence all the soil samples were blended with gravel and aggregate to increase the CBR value of the mixes to greater than 15%. 3. Two GSB mixes were designed: Mix-I by blending soil samples with quarry dust, aggregates and locally available gravel, Mix-II by blending soil samples with quarry dust and aggregates only. Both the GSB mixes satisfies the requirements of gradation, CBR and consistency limits specified in IRC: SP: 20-2002 for rural road construction. 4. The permeability tests carried out in the laboratory for GSB Mix-I and Mix-II indicated ‘k’ value in the range of 1.20 m/day to 3.08 m/day and 1.89 m/day to 3.92 m/day respectively. The permeability values for both the mixes indicate poor drainage potential of GSB mixes. 5. The thickness of drainage layer computed using DRIP software is in the range of from 1.13 m to 3.57 m. The higher thickness of GSB layer from drainage considerations is mainly due to poor drainage characteristics of GSB mixes 6. Time to drain 50% of water from saturated drainage layer was computed for GSB Mix-I and Mix-II. The time required for 50% drainage of water was found to be in the range of 1.42 hrs to 5.75 hrs for designed GSB thickness and quality of drainage can be classified as good.

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7. In rural road construction 0.10 m of Grade III GSB layer is treated as drainage layer. The drainage analysis using DRIP software clearly indicates the thickness used in practice is inadequate. 8. 0.10m thick GSB layer can effectively perform as a drainage layer for rural roads, only when permeability values of such mixes are equal to or greater than 250m/day. In such cases, the GSB layer has to be separated from subgrade by a inverted filter or a geotextile separator to prevent subgrade intrusion. Recommendations Indian Road Congress Special Publications, IRC: SP: 20-2002 has specified the requirements of material to be used in GSB constructions in terms of only gradation, CBR and consistency limits. Since GSB is also used as drainage layer in rural road construction, it is absolutely necessary to incorporate permeability parameters in the specifications for rural road construction.

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CHAPTER-6

SCOPE FOR FURTHER STUDY 1. To design suitable GSB mixes for rural roads can satisfactorily perform as drainage layer, with a mix layer thickness of 0.10m. 2. To conduct field studies on GSB mixes, in order to determine the field permeability values and drainage potential of GSB mixes.

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REFERENCES 1. Vaughan Voller., “Field Measurement of Granular Base Drainage Characteristics” Intelligent Transportation Systems, 2007. 2. Hagen m. G., Cochran G. R.” Comparison of Pavement Drainage Systems” Transportation research record, January 1996. 3. Hassan H., and White T., “Locating the Drainage Layer for Bituminous Pavements in Indiana”, Transportation Research Program, January 1996.. 4. Kamyar C. Mahboub., Yinhui Liu and David L. Allen, “Asphalt Overlay and Subsurface Drainage of Broken and Seated Concrete Pavement”, Journal of Transportation Engineering, August 2005. 5. Imad L. Al-Qadi, Samer Lahouar, Amara Loulizi, Mostafa A. Elseifi, and John A. Wilkes, “ Effective Approach to Improve Pavement Drainage Layers”, Journal of Transportation Engineering, Sept/Oct 2004. 6. Suresha.S.N., Ravishankar.A.U., and Varghese George, “Design Charts for Drainage Capacities of Granular Sub-bases”, Journal of the Indian Road Congress, JanuaryMarch 2009. 7. Indian Highways, “Road Drainage”, VOL 3, July 1975. 8. NCHRP., “Guide for Mechanistic-Empirical Design of New and Rehabilitated Pavement Structures”, Transportation Research Board, Washington, D.C., February 2001. 9. Satyapriya Behera., “Strength and Permeability Characteristics of Granular Sub-base Developed Using Locally Available Materials”, Dept. of Civil Engineering, NITK, Surathkal, July 2005. 10. IS: 1888-1982,”Method of Load Tests on Soils”. 11. IS: 2720(part-13)-1985,”Method to test for soils: Direct Shear Test”. 12. IS: 2720(part-16)-1979,”Method to test for soils: Laboratory determination of CBR”. 64

13. IS: 2720(part-17)-1986,”Method to test for soils: Laboratory determination of permeability”. 14. IS: 2720(part-2)-1973,”Method to test for soils: Determination of Water Content”. 15. IS: 2720(part-3)-1973,”Method to test for soils: Determination of Specific Gravity”. 16. IS: 2720(part-36)-1987,”Method to test for soils: Laboratory Determination of permeability of granular soils (constant head)”. 17. IS: 2720(part-4)-1985,”Method to test for soils: Grain Size Analysis”. 18. IS: 2720(part-7)-1973,”Method to test for soils: Determination of Water content-Dry Density Relation using Light Compaction”. 19. IS: 2720(part-8)-1973,”Method of test for soils: Determination of Water content-Dry Density Relation using Heavy Compaction”. 20. IS: 383-1970,”Specification for coarser and fine aggregates from natural source for concrete”. 21. Khanna. S.K. and Justo.C.E.G (1984),”Highway Engineering”, Nem Chand and Bros, Roorkee Sixth Edition.

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