Foundation: Session 9 - 10

Course : CIVL6080-Construction Methods & Heavy Equipment Effective Period : September 2017

Foundation Session 9 - 10

Acknowledgement

These slides have been adapted from: Peurifoy, R.L., Schexnayder, C.J., Shapira, A., & Schmitt, R. (2010). Construction Planning, Equipment, and Methods. 07. McGraw Hill. New York. ISBN: 978-0073401126.

Chapter 22

Learning Objectives

• Students are able to apply which foundation is suitable in a specific civil engineering project based on the specification of the project

Outline • • • • • • •

Introduction Shallow foundation Deep foundation Classification of piles Hammers Types of pile hammers Positioning piles during driving

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Introduction

A foundation is a sub -structure that transfers loads from upper-structure to the earth without causing : - shear failure at the soil, and - excessive foundation’s settlement Foundations are generally broken into two categories: shallow foundations and deep foundations. Bina Nusantara University

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Shallow Foundations

Shallow foundations are usually placed within a depth D beneath the ground surface less than the minimum width B of the foundation. Shallow foundations consist of

spread and continuous footings, wall footings and mats. Bina Nusantara University

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Types of Shallow Foundations

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Deep Foundations

6m

60 m

Deep foundations can be as short as or as long as or more and may consist of driven piles, drilled shafts or stone columns. Deep foundations may be designed to carry

superstructure loads through poor soil (loose sands, soft clays, and collapsible materials) into competent bearing materials.

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Classification of Piles

Piles can be classified on the basis of either their use or the materials from which they are made. On the basis of use, there are two major classifications: (1) sheet and (2) load bearing. Bina Nusantara University

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Sheet Pile • Sheet piles are used primarily to create a rigid barrier for earth and water. • Typical uses include cutoff walls under dams, and for cofferdams, bulkheads, and trenching • Timber sheet piles, prestressed concrete sheet piles & steel sheet piles

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Load Bearing Piles

Load-bearing piles, as the name implies, are used primarily to transmit structural loads

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Pile Type • Timber Pile :

• Concrete Pile :

• Steel Pile : • Composite Pile :

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- treated with preservative - untreated - Precast-prestressed - Cast-in-place with shells - Augered cast-in-place - H section - Steel pipe - Concrete and steel - Plastic with steel pipe core

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Timber Pile Timber piles are

made from the trunks

of trees. Such piles are available in most sections of the country and the world. Ordinary lengths are

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15 to 45 ft

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Concrete Pile • Concrete piles may be either precast or cast-in-place • Precast piles  prestressed / post tensioned • Cast in place  augered cast in place pile & temporary/permanent casing cast in place pile

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Steel Pile • Load-bearing steel piles can be H sections, hollow box or tubular sections, or pipes. • Suitable for piles driven to great depth

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Composite Pile Several types of composite piles are available. These are usually developed and offered to meet the demands of special situations. Two of the most common situations that cause problems, when conventional piles are used, are hard driving conditions and warm marine environments.

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Bored Pile

Bored pile is another type of reinforced concrete pile which is used to support high building which has heavy vertical load. Bored pile is a cast-in-place concrete pile where the bored piles have to be cast on construction site, while other concrete piles like Spun Pile and Reinforced Concrete Square Pile are precast concrete pile which they’re cast in the factory.

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Bored Pile • Normally bored piling has be to carried on those tall buildings or massive industrial complexes, which require foundations which can bear the load of thousands of tons, most probably in unstable or difficult soil conditions. • Bored piling is cast by using bored piling machine which has specially designed drilling tools, buckets and grabs, it’s used to remove the soil and rock. • Normally it can be drilling into 50metres depth of soil. The advantage of bored piling is its’ drilling method, little vibration and lower noise level.

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Bored Pile Method

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Bored Pile Method

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Bored Pile Method

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Bored Pile Method

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Bored Pile Method

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Pile Hammers

• Variable subsurface conditions can dictate the use of different pile hammers. • The function of a pile hammer is to furnish the energy required to drive a pile Bina Nusantara University

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Type of Pile Hammers • • • • • • •

Drop Single-acting steam or compressed air Double-acting steam or compressed air Differential-acting steam or compressed air Diesel Hydraulic - impact and drivers Vibratory drivers

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Drop Hammer •

• • • • •

A drop hammer is a heavy metal weight that is lifted by a hoist line, then released and allowed to fall onto the top of the pile. Because of the high dynamic forces, a pile cap is positioned between the hammer and the pile head. Pile cap serves to uniformly distribute the blow to the pile head and as a shock absorber. Hammer weight = 0.5 – 2 times pile weight Max drop height = 15 ft for timber pile, 8 ft for concrete pile Suitable for use in remote project and for project where time of completion is not an important factor  4-8 blows/minute

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Single – acting Hammer • These hammers rely

solely on

gravity acting on the striking weight to achieve their driving energy. • The a freely falling weight, called a

“ram” that is lifted by steam or

compressed air • Drop height = 1 – 5 ft • 40 – 60 blows/minute • Hammer weight ≈ weight of pile

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Double – acting Hammer • With double-acting hammers, the striking ram is

driven by compressed air or steam both when rising and when falling. • Thus, with a given weight of ram, it is possible to attain a desired amount of energy per blow with a shorter stroke than with a longer single-acting hammer

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Differential – acting Hammer • A differential-acting air is a modified single-acting hammer in that the air or steam pressure used to lift the ram is not exhausted at the end of the upward stroke but is valved over the piston to accelerate the ram on the downstroke • Can drive a pile in 1 ½ time required by the same size single acting hammer

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Diesel Hammer • A diesel pile-driving hammer is a self-contained driving unit that does not require an external source of energy such as an air compressor or steam boiler. • The downstroke of the ram compresses air and fuel to ignition heat and the resulting explosion drives the pile downward and the ram upward to repeat its stroke. • Open-end diesel hammer  40 – 55 blows/minute • Closed-end diesel hammer  75 – 85 blows/minute • Performs well in cohesive or very dense soil layer • Normal soil condition  ratio of ram weight to weight of pile plus cap = 1:2 – 1.5:1 • May not operate well into soft ground

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Diesel Hammer 1. Raise the piston to start. 2. Injection of diesel fuel and compression. 3. Impact and explosion. 4. Exhaust ports exposed and gases escape. 5. Draws fresh air through the exhaust ports.

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Hydraulic – Impact Hammers • • •

•

There is a trend toward the use of hydraulic hammers. A hydraulic hammer operates on the differential pressure of hydraulic fluid instead of compressed air or steam. Develop 140 tons of pressing or extracting force, are compact, make minimal noise, and cause little vibration Suitable for areas where there is restricted overhead space, piles can be driven in short length Type of hydraulic-impact hammer: – Hydraulic drop hammer – Double acting hydraulic hammer  50 – 60 blows/minute

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Positioning Piles During Driving • When driving piles, it is necessary to have a method that will position the pile in the proper location with the required alignment or batter and that will support the pile during driving.

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Positioning Piles During Driving • Fixed leads have a pivot point at the crane’s boom top and a brace at their bottom that attaches to the crane. • Fixed leads offer good control of the pile position and keep the pile in correct alignment with the hammer so that eccentric impacts are minimized.

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Positioning Piles During Driving • Swing leads  leads that are not attached at their bottom to the crane or driving platform • The leads and hammer are held by separate lines from the crane. • Allowing the driving rig to position a pile at a further location • However it is more difficult to position the pile accurately and to maintain vertical alignment during driving

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Positioning Piles During Driving • Many times a template is used to support and hold the pile in the proper position during driving. • Templates are usually constructed from steel pipe or beams and may have several levels of framing to support long piles or piles on a batter.

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Handling Piles • Care must be exercised to prevent damage to the pile from flexural stresses.

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References

• Peurifoy, R.L., Schexnayder, C.J., Shapira, A., & Schmitt, R. (2010). Construction Planning, Equipment, and Methods. 07. McGraw Hill. New York. ISBN: 9780073401126. Chapter 22.