Rr410101 Foundation Engineering

RR

Code No: RR410101

IV B.Tech I Semester(RR) Supplementary Examinations, December 2009 FOUNDATION ENGINEERING (Civil Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) Differentiate between disturbed, undisturbed and non-representative samples. Also discuss the uses to which such soil samples can be put to, respectively. (b) Explain and discuss the various factors that helps to decide the number and depth of bore holes required for subsoil exploration. [8+8] 2. (a) What are the different factors of safety used in the analysis of infinite slopes? Define them. (b) Describe the procedure for determining the factor of safety of a finite slope using the standard method of slices. [8+8] 3. (a) Explain the similarities and differences between the Coulomb and the Rankine classical theories of earth pressure. (b) A vertical wall 6m high supports a cohesive soil with c= 20kPa and phi= 100 . The unit weight of the soil is 18.62kN/m3 . Compute the depth of tension cracks and the active thrust behind the retaining wall before the formation of tension cracks and after their formation. [8+8] 4. (a) Why retaining walls are usually designed for active earth pressure?

[4]

(b) A trapezoidal masonry retaining wall 1m wide at top and 3m wide at bottom is 4m high. The vertical face of the wall is retaining a soil (γ= 18 kN/m3 and φ =300 ) at a surcharge angle of 200 with the horizontal. Check the stability of retaining wall against sliding, overturning and for ‘No tension condition’. The safe bearing capacity of the soil is 100 kN/m2 . [12] 5. (a) Discuss the various types of foundations and their selection with respect to different situations. [10] (b) Distinguish clearly between ‘local shear failure’ and ‘general shear failure’.

[6]

6. (a) What are the different methods by which bearing capacity at a place is determined? Briefly describe the methods [10] (b) Discuss the limitations of SPT. Explain the various corrections that are required to be applied to the observed value of N. [6] 7. (a) What is negative skin friction? Why it occurs in soils? Discuss clearly. (b) Write a note on dynamic pile formulae.

[8+8]

8. (a) Discuss about pile load tests. (b) A group of 12 piles each having a diameter of 500mm and 30 metres long supports a column. The piles are arranged in 3 rows and spaced at 1.25 metres c/c. The properties of the foundation soil (clay) are as follows:-Unit weight = 11 kN/m3 , Unconfined compressive strength = 100 kN/m2 .Determine the capacity of the pile group. [8+8] ?????