Question

C5 A concrete pile 450 mm in diameter and 15 m long is driven into a clay. The undrained strength of the soil varies linearly with depth such that cu-0.22 Ơ'z Determine the allowable pile load capacity. The factor of safety required is 2 and Vsat- 17 kN/m3. Groundwater is at the surface.

Answer 1

Length of the pile, L = 15m Diameter of the pile, D = 0.45m f mid dot o middot s = 2 gamma sat = 17 KN/M^3 Given that underined strength of soil c_u varies depth such that c_u = 0.22 sigma Z Since water table is at surface level gamma = gamma_sat -gamma_w = 17 - 9.81 = 7.19 KN/m^3 there fore c_u = 0.22 times gamma z times Z {sigma = gamma Z} 0.22 times (gamma_sat - gamma_w) Z^2 = 1.5818 Z^2 which varies with depth there fore integrating implies integral^15_0 1.5818 Z^2 dZ sigma c_u = [1.5818 Z^3/3}^15_0 = 1779.525 KN/M^2 \r\n c_u = 1779.525/15 = 118.635 KN/M^2 where c_u = Avg mid dot chorision over depth of pile Unit cohension at the base of pile, C_u C_u = 1.5818 times Z^2 at 15m, Cu = 1.5818 times 15^2 cu = 355.905 KN/M^2 ultimate load on pile is given by Q = c_u N_c A_6 + alpha C_u A_s Where A_6 =