22z, m σv, kPa u, kPa σ'v, kPa σ'h, kPa τ, kPa At the soil surface 0 0 0 0 0 0 At the water table 5 95 0 95 47.5 23.17 At the base of the pile 25 475 196.2 278.8 139.4 67.99 The surface area of the upper 5m of the pile is (π×0.3)m ×5m = 4.71m2, and the average shear stress over this area is 23.17kPa ÷2 = 11.59kPa. The surface area of the lower 20m of the pile is (π×0.3)m ×9m = 18.85m2, and the average shear stress over this area is (23.17kPa + 67.99kPa) ÷2 = 45.58kPa. Thus the overall frictional resistance is (4.71m2×11.59kPa) + (18.85m2×45.58kPa) = 914kNQ2.6 The depth of the friction uplift pile described in main text Example 2.4 is increased to 20m, where the undrained shear strength of the clay is 40 kPa. Calculate the short- and long-term uplift resistance of the 20m pile. Q2.6 Solution The total shear resistance of the clay/pile interface is given by
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