week 8 tut - selected is 0.8 meter. The soil is uniform...

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Answers to Tutorial questions 2 1 As shown in the sketch, a group of seven piles is arranged in a circle. All the piles are floating concrete piles with a diameter of 1.2m and cast in place with 12 meters imbedded into sand. No water exists within the layer. The sand has a total weight of 20 kN/m 3 . Suppose the efficiency of the pile group is 75%, determine the bearing capacity of the pile group. The results of standard penetration tests on the sand are listed below. Using the empirical expression N 2 f s = and kPa 400N D L 0N 4 f b = for the estimation of the bearing capacity of the pile group in sand. Results of standard penetration tests Soil depth z (m) 0.2 3 6 8 11.5 N Standard penetration resist. 8 15 18 20 23 2. As shown in the Figure, a 2X2 pile group is driven 12 meters into a deep soft clay foundation. The diameter of the pile
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Unformatted text preview: selected is 0.8 meter. The soil is uniform with sat = 20 kN/M 3 . The undrained shear strength of the soil at the surface is 20 kPa and increases with depth by 3 kPa per meter. Calculate the ultimate bearing capacity on the pile foundation. 3. Estimate the load allowed for a pile group with four identical piles (see the sketch). The diameter of the piles are 0.75m and they are 8m driven into soil. A safety factor of 3 is required. The profile of the soil is shown in the sketch. The undrained shear strength for clay is 40 kPa at z=3m (at the top of the clay layer) and increases with clay depth by 3kPa per meter. The standard penetration resistance for the sand layer at the top is N=5 and at z=2.5m N=18. D g = 8m W=3 m B=4 m P u sand 3m clay 5m pile D=0.75m L=8m W=2.5 m B=3 m...
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