Question

Consider the raft foundation shown in Figure Q1 Dense soil ?-320 c-0 Raft Foundation q 700kPa 8m -o 8m Dense soil ?=32° c- 0 sa 18kN/m Plan Section Figure Q1 Compute 5 marks] [5 marks i. Change in Stress in the centre of raft at a depth of 5m from ground. ii. Allowable Bearing capacity.

Answer 1

For raft foundation we have to consider trapezondal stenessdisribution with slope 1: 2 i)delta s = q times A /13^2 = 700 times 64/13 times 13= 265.084pa ii) According tenzaghi ultimate bearing capacity = CN_C + qN_q + 1/2 gamma B N gamma now c = 0 for straight pie =32^degree Nq = 28.52 N gamma = 26.87 q = gamma D _f = 1B times 2e 3c kn/m^2 now here we have to make water correction factor 0.5(1 + 2/B) here Z = depends of watch table from the base = 0 therefore R = 0.5 therefore q_u = 36.times 28.52 + 1/2 times 18 times 8times 26.87 times R q_u = 1994.04 KN/m^2.