Principles of Foundation Engineering
9th Edition
ISBN: 9780357684832
Author: Das
Publisher: Cengage Learning US
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Chapter 14, Problem 14.5P
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Find the total load on pile raft
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A group of piles are arranged as shown in the figure. The piles are square in section with sides equal to 400 mm and has a spacing of 1.80 m on centers. One pile has a total length of 18 m. Unit weight of clay is 19.7 kN/m3 and has a cohesion of 90 kPa. Ground water table is located at depth of 20 m below the ground surface. Adhesion factor is 0.90. Determine the ultimate load – bearing capacity of the group of piles considering the piles acting individually.
2. For the group of piles shown in Figure 2, determine the safe length of piles.
Q2: The plan of a group piles is shown below. Assume that the piles are embedded
in a saturated homogeneous clay having a 7sa= 19.24 kN/m, C=41.2 kN/m?
.Given: diameter of piles (D) = 305 mm, center-to-center spacing of piles 762
mm, and length of piles = 13.7 m. Find the allowable load-carrying capacity of the
pile group. Use FS = 3.
P
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Principles of Foundation Engineering
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- Figure P12.36 shows a 3 5 pile group consisting of 15 concrete piles of 400 mm diameter and 12 m in length. What would be the maximum load that can be allowed on the mat with a factor of safety of 3? The piles have a center-to-center spacing of 1200 mm.arrow_forwardDesign a reinforced concrete footing supported on piles. The column is 600 mm square and exerts a factored load of 800 kN on the footing. The allowable bearing capacity of each pile is 95 kN. Use f = 28 MPa, fy = 414 MPa. The arrangement of piles is shown in the figure. 450 850 850 450 450 850 + 850 ++ 450arrow_forwardA nine-pile group composed of 0.30 m diameter pipe piles is embedded 15 m in clay soil with conditions indicated by the sketch. 1. Det the total capacity if piles act individually 2. Find the total capacity if piles act as a group 3. Det the design load if factor of safety is 3. C = 42.81 kpa a = 0.85 6m C = 57.46 kpa a = 0.75 6m C = 95.76 kpa a = 0.5 Nc = 8 3m 0.75m 1-8 0.75m 上tt 0.75m 0.75marrow_forward
- Question 3 A nine-pile group arranged in a square pattern is used as a foundation for a column in sand. Piles are 300 mm in diameter and placed at a spacing of 900 mm in each direction. What will be the settlement of pile group, if the settlement of single pile is 5 mm ?arrow_forwardA 400 mm diameter, 10 m long piles are used as foundation for a column in uniform deposit of clay (cu = 600 kN/m2). The spacing between pile is 300 mm. There are 9 piles in the group arranged in a square pattern. Determine the group efficiency assuming adhesion factor 0.4arrow_forward5. a. Why do we sometimes need pile foundations for a substructure? b. Discuss the various installations methods for piles in caving and/or squeezing soils in deep foundations. c. A concrete pile is 15m long and has 406 mm diameter circular cross section. The pile is fully embedded in sand, for which the unit weight y =18 kN/m³ and the frictional angle o = 30°. Calculate the ultimate point load Qp. i. ii. Determine the total frictional resistance Qs. iii. Determine the total ultimate load of the pile. A concrete pile 500 mm by 500 mm square cross section is embedded in a saturated clay. The length of the embedment is 16m. The undrained cohesion, Cu of clay is 40 kN/m?, and the unit weight of the clay is 20 kN/m². Use a factor of safety of 5 to determine the allowable load the pile can carry. d.arrow_forward
- In Hiley’s formula for driven piles i.e. R=E/(s+0.5c), why is a coefficient of 0.5 applied for the term elastic deformation of piles and soil?arrow_forwardA group of 9 friction piles are arranged in a square grid maintaining equal spacing is all direction. Each piles is of diameter 300 mm and length 7 m. Assume that the soil is cohesionless with effective friction angle = 32°. What is the centre to centre spacing of the piles (in m) for the piles group efficiency of 60%? 100arrow_forwardThe pile group shown consists of 12 friction piles each 0.3 m diameter. Each pile is driven clay layer with different unconfined compressive strength. Unit weight of the clayey soil is 18.18 KN/m^3. Bearing capacity factor Nc = 9. Factor of safety is 3.0.1. Compute the allowable load of the pile group considering that the piles act individually. a. 2650 kNb. 2370 kNc. 2460 kNd. 3360 kN2. Compute the allowable load of the pile group based on block failure. a. 2650 kNb. 2370 kNc. 2460 kNd. 3360 kN3. Compute the maximum center- to- center spacing of piles to achieve 100% efficiency. *a. 627 mmb. 860 mmc. 800 mmd. 560 mmarrow_forward
- 2. Consider a group of 450 mm x 450 mm reinforced concrete piles were driven into thick loose sand layer with the average unit weight and internal friction angle of 16 kN/m3 and 30°, respectively. Estimate the group pile capacity with the arrangement as shown in Figure Q2 if the length of pile embedment is 30 m assuming ground water table is far below the ground surface. Use 8 = 0.80 and K = 1.5Ko. 3B 3B 3B 1 3 3.5B b 'P 9. 10 11 a 3.5B 2 4 1.5B 1.5B 1.5B 1.5B 1.5B 1.5B Figure Q2arrow_forwardThe plan of a group pile is shown in the Figure below. Assume that the piles are embedded in a saturated homogeneous clay having a c, = 86 kN/m?. Given: diameter of piles (D) = 316 mm, center-to-center spacing of piles d = 790 mm, and length of piles = 20 m. Find the allowable load-carrying capacity of the pile group. Use FS = 3. (pa 100 kPa) Qu1) = n,n: [94,0(2) +Ea'pc,AL| Q.e) = L,B,CN+E2(L, + B, )e,AL u(p) 'c If Qu(1) < Qu@), then Q, = Qu)7 Number of piles in group: n,×n2 D 7 =1– 7, (n, – 1) + n, (n, – 1)+ vZ (n – 1)(n, – 1)| adn,n, Table 11.10 Variation of a (interpo- lated values based on Terzaghi, Peck and Mesri, 1996) LJB, = 1 8 Cu 7 Pa < 0.1 0.2 1.00 6 0.92 0.3 0.82 0.4 0.74 0.6 0.62 4 T 0.8 0.54 3 4 5 1.0 0.48arrow_forwardThe section of a 4 x 4 group pile in a layered saturated clay is shown in Figure P 9.29. The piles are square in cross section (356 mm x 356 mm). The center-to-center spacing (d) of the piles is 1 m. Determine the allowable load bearing capacity of the pile group. Use FS = 3 and Table 9.10.arrow_forward
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