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# Examination Question of SUB STRUCTURE DESIGN - Jntuk/GDMM ENNGG.COLLEGE - GDMM , Nandigama - 2017

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#### Examination Question of SUB STRUCTURE DESIGN - Jntuk/GDMM ENNGG.COLLEGE - GDMM , Nandigama - 2017 / 4

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Code No: I8705/R16 M.Tech. I Semester Regular Examinations, January-2017 SUB-STRUCTURE DESIGN (Common to SE and SD) Time: 3 hours Max. Marks: 60 Answer any FIVE Questions All Questions Carry Equal Marks 1. a b List out and explain the Design Considerations of Open Drive Samplers How soil samples are classified based on the amount of disturbance in sampling? 6 6 2. a b Explain about the cleaning of bore holes. Why it is required? Why the preservation of Soil samples is required? What are the important precautions to be taken against what? 6 6 3. a What are the criteria for deciding the depth of foundations? Write brief critical notes on tolerable settlements for buildings A footing, 2 m square, is founded at a depth of 1.5 m in a sand deposit, for which the corrected value of N is 27. The water table is at a depth of 2 m from the surface. Determine the net allowable bearing pressure, if the permissible settlement is 40 mm and a factor of safety of 3 is desired against shear failure. Use Teng’s Solution. 6 b 4. A square footing of 1.5 x 1.5 m in dimension resting on sand at 1.5 m depth. The horizontal force is 0.1 times to the vertical force. Ground slope is 100 and base tilt is 100. Unit weight of the sand 17.4 kN/m3, c = 0 and φ = 300. The water table at great depth. Using Vesic, Compute the Ultimate Bearing Capacity of the footing. For φ = 300 Vesic bearing capacity factors are  Nc = 30.13, Nq = 18.4 and Nγ = 22.4 Shape factors Sc = 1 + 6 12 Nq B B B Sq = 1 + tan φ and S r = 1− 0.4 L Nc L L Depth factors dc = 1.0 + 0.4 k, dq = 1 + 2 tanφ(1-sinφ)k and dγ = 1.0; where k = D/B for D/B ≤ 1 and k = tan-1(D/B) for D/B > 1 (rad)    Inclination factors, iq = 1 −  H  V + A f ca cot φ  m   H  iγ = 1 −  V + A f ca cot φ    m +1 where m = 2+ B/L 1+ B / L H is parallel to B. Base factors: bc = 1-η/147, bq = bγ = (1-ηtanφ)2 Ground factors: gc = 1-β/147 and gq =gγ = (1-tanβ)2. 5. a b What are the conditions under which combined footings are used? When is a trapezoidal combined footing preferred to as rectangular one? Explain how it is proportioned. 1 of 2 WWW.MANARESULTS.CO.IN |''|'|''|''|''|'|''| 6 6

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Code No: I8705/R16 6. a b Write note on pile groups, their load carrying capacity and efficiency. A pile group consisting of 9 piles is arranged in 3 rows with 3 piles in each row. Diameter of each pile is 40 cm and spacing is 1.2 m. Length of pile is 10 m. The piles are driven completely in clayey soil having unconfined compressive strength of 100 kN/m2. The piles are designed as frictional. Determine the capacity of pile group 6 6 7. a Explain the basic difference in the bearing capacity computation of shallow and deep foundations. How are skin friction and point resistance of a pile computed? A square pile 25 cm size penetrates into soft clay with unit cohesion of 75 kN/m2 for a depth of 18 m and rests on stiff soil. Determine the capacity of the pile by skin friction. Assume an adhesion factor of 0.75. 6 Explain the circumstances under which a strap footing is used. What are the general considerations in the choice of the foundation type? How is the depth of the foundation determined? 4 8 b 8. a b ***** 2 of 2 WWW.MANARESULTS.CO.IN |''|'|''|''|''|'|''| 6

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Code No: I8705/R16 M. Tech. I Semester Regular/Supple Examinations, Jan/Feb-2018 SUB-STRUCTURE DESIGN Common to Structural Engineering (87) and Structural Design (85) Time: 3 Hours Max. Marks: 60 Answer any FIVE Questions All Questions Carry Equal Marks 1. a What is soil exploration and what is the need for carrying it? What might happen if soil exploration is not carried out/ carried out half-heartedly? b What is a borelog report? 8M 2. a Discuss the type of samples? b What kind of care is to be exercised for preservation, labeling and shipment of soil samples? 6M 6M 3. a Explain the procedure to determine the bearing capacity of stratified soils? b A 1.8m square column is founded at a depth of 1.8m in sand, for which the corrected N-value is 24. The water table is at a depth of 2.7m. Determine the net allowable bearing pressure for a permissible settlement of 40mm and a factor of safety of 3 against shear failure. 6M 6M 4. a Discuss the types of shallow foundations and the criteria to choose any one of these? b Explain the IS procedure to design raft foundations? 6M 6M 5. Explain the cyclic pile load test? 12M 6. Proportion a strap footing for the following data: Allowable pressures: (i) 150 kPa for (DL + reduced LL) (ii) 225 kPa for (DL + LL) 12M Column loads DL LL Column A 540kN 400kN Column B 690kN 810kN Proportion the footing for uniform pressure under (DL + reduced LL). Distance c/c of columns = 5.4 m Projection beyond column A not to exceed 0.5m. DL + reduced LL for column A = 740kN DL + reduced LL for column B = 1095kN 1 of 2 WWW.MANARESULTS.CO.IN |'''|||||''|'''||||| 4M

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Code No: I8705/R16 7. Write a note on the two popular geophysical methods? 12M 8. A group of piles with pile diameter 30cm is subjected to a load of 2500kN as shown in the figure below. Estimate the consolidation settlement. 12M For Layer I : above WT, γ = 16kN/m3 below WT, γ = 20kN/m3 For Layer II : γsat = 21kN/m3, Cc =0.26, e0 =0.75 For Layer III : γsat = 23kN/m3, Cc =0.22, e0 =0.60 Use a load dispersion of 1 horizontal : 2 vertical ***** 2 of 2 WWW.MANARESULTS.CO.IN |'''|||||''|'''|||||