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Rr410102 Foundation Engineering

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Code No: RR410102 Set No. 1 IV B.Tech I Semester Supplementary Examinations, February 2007 FOUNDATION ENGINEERING (Civil Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) Describe open excavation methods of exploration. What are their advantages and disadvantages? (b) What is a bore log? Give a typical example. [8+8] 2. (a) Discuss the various factors of safety used in the stability analysis of slopes. Show that the factor of safet
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  Code No: RR410102 Set No. 1 IV B.Tech I Semester Supplementary Examinations, February 2007FOUNDATION ENGINEERING(Civil Engineering)Time: 3 hours Max Marks: 80Answer any FIVE QuestionsAll Questions carry equal marks ⋆ ⋆ ⋆ ⋆ ⋆ 1. (a) Describe open excavation methods of exploration. What are their advantagesand disadvantages?(b) What is a bore log? Give a typical example. [8+8]2. (a) Discuss the various factors of safety used in the stability analysis of slopes.Show that the factor of safety with respect to cohesion gives the same conceptas that of factor of safety with respect to height.(b) Find the critical height of a slope of infinite extent having a slope of 30 0 .The slope is made of stiff clay having cohesion of 20 kN/m 2 , angle of internalfriction of 20 0 , void ratio of 0.7 and specific gravity of 2.7. Consider thefollowing cases for the analysis. [8+8]i. the soil is dryii. the water seeps parallel to the surface of slopeiii. the slope is submerged3. (a) Compare Rankine’s and Coulomb’s theory of earth pressure.(b) A 5m high rigid retaining wall has to retain a backfill of dry, cohesionless soilhaving the following properties:- φ = 30 0 , void ratio, e= 0.74, G= 2.68Plot the distribution of Rankine lateral earth pressure on the wall and deter-mine the magnitude and point of application of the resultant thrust. [8+8]4. (a) Explain how you will determine active pressure by Culmann’s graphical methodfor cohesionless soil without surcharge line load.(b) What are the stability requirements of a retaining wall? [8+8]5. (a) How is a deep foundation different from a shallow foundation? [4](b) Discuss five important factors affecting bearing capacity of sands. [6](c) Compute the safe bearing capacity of a continuous footing 2.0 m wide andresting on a clayey sand at a depth of 1.5 m if c = 16 kN/ m 2 , φ = 25 0 , γ  sat =19 kN/ m 3 , N  c = 25, N  q = 12.5, N  γ  = 10 and F.S.=3.0. [6]6. (a) The results of a plate load test on a sandy stratum are shown in Table. Thesize of the plate used is 30 cm 30 cm. determine the size of a square footing for1 of 2  Code No: RR410102 Set No. 1 a column carrying a load of 1800 kN with a maximum permissible settlementof 50mm. [6]Load intensity ( kN/m 2 ) 0 100 200 300 400 500 600 700Settlement (mm) 0 4 5.5 9 12.5 19 28 63(b) Discuss the tolerable settlements of various structures. [10]7. (a) Discuss different methods for the installation of piles. [8](b) A timber pile is being driven with a drop hammer weighing 20kN and havinga free fall of 1m. The total penetration of the pile in the last five blows is30mm. Determine the load carrying capacity of the pile using EngineeringNews Record formula. [4](c) What are the different circumstances under which a pile foundation is used?[4]8. (a) Discuss about pile load tests.(b) A group of 12 piles each having a diameter of 500mm and 30 metres longsupports a column. The piles are arranged in 3 rows and spaced at 1.25 metresc/c. The properties of the foundation soil (clay) are as follows:-Unit weight= 11 kN/ m 3 , Unconfined compressive strength = 100 kN/ m 2 .Determine thecapacity of the pile group. [8+8] ⋆ ⋆ ⋆ ⋆ ⋆ 2 of 2  Code No: RR410102 Set No. 2 IV B.Tech I Semester Supplementary Examinations, February 2007FOUNDATION ENGINEERING(Civil Engineering)Time: 3 hours Max Marks: 80Answer any FIVE QuestionsAll Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) Discuss with neat sketches any two boring methods used in soil exploration.[10](b) What is a bore log? Give a typical example. [6]2. (a) Define the various factors of safety used in the analysis of stability of slopes.(b) An infinite slope in a sandy soil (with angle of friction of 40 0 ) has a slope of 300. What is the factor of safety? If there is seepage what will happen to theabove factors of safety? [8+8]3. (a) What are the various types of earth pressures? Give field example for eachtype.[ 8 ](b) A 10m high retaining wall with smooth vertical back supports a horizontalbackfill ( φ = 33 0 , c= 25kPa, Density above water table 15kN/ m 3 and belowwater table 18kN/ m 3 ). The water table is at a depth of 3m below the surfaceof the backfill. The backfill supports a surcharge of 10kPa. Determine themagnitude and line of action of passive earth pressure. [8] 4. Describe Culmann’s graphical method of finding earth pressure and explain theclassical theory of earth pressure on which this procedure is based. Explain howsurcharge will affect earth pressure in active and passive states. [16]5. (a) Explain what is meant by ‘safe bearing capacity’ of soil. Indicate how thebearing capacity shallow footing in a given soil can be calculated from thestrength characteristics of the soil. [6](b) Distinguish clearly between ‘local shear failure’ and ‘general shear failure’ inrelation to design of foundations in sands. Where would you expect each of them to occur? What corrections you would incorporate in Terzaghi’s bearingcapacity equation to workout bearing capacity when foundation does not failby general shear but fails by local shear? [10]6. (a) Describe the procedure of determining the safe bearing capacity based on thestandard penetration test.(b) A 1.8 m square column is founded at a depth of 1.8 m in sand, for which thecorrected N- value is 24. The water table is at a depth of 2.7 m. Determinethe net allowable bearing pressure for a permissible settlement of 40mm anda factor of safety of 3 against shear failure. [8+8]1 of 2  Code No: RR410102 Set No. 2 7. (a) State the situations where pile foundations are preferred to over other types.[4](b) State the advantages and disadvantages between cast-in-situ piles and pre-castpile.[6](c) Using a drop hammer of 20 kN capacity and the height of drop being 4m. Theaverage penetration over the last 5 blows was 10mm. Determine the allowableload on the pile using Engineering News formula. [6]8. (a) Discuss about pile load tests.(b) A group of 12 piles each having a diameter of 500mm and 30 metres longsupports a column. The piles are arranged in 3 rows and spaced at 1.25 metresc/c. The properties of the foundation soil (clay) are as follows:-Unit weight= 11 kN/ m 3 , Unconfined compressive strength = 100 kN/ m 2 .Determine thecapacity of the pile group. [8+8] ⋆⋆⋆⋆⋆ 2 of 2
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