Question

A laboratory consolidation test was performed on a specimen from the middle of the clay layer shown below, with the test results tabulated below. Determine pc, OCR, Cr field, and Ce field; include plots and supporting calculations. Pay attention to the units of stress ks Q-50 kips/ft 0.25 0.8869 0.5 0.8848 10.8768 2 0.8637 4 0.8364 80.7767 16 0.6796 80.6857 4 0.6948 2 0.7070 10.7212 0.7161 0.7079 0.6970 16 0.6600 0.5331 64 0.3766 B- 10 ft Sand oat-120 PC 10 ft Clay aat- 105 PC 0.9 ф,-23° 15 ft e,

Answer 1

From the plot it was noted Preconsolidation pressure P_c = 7.6 Ksf C_r = 0.0364, C_c = 0.492 load on clay at centre of strata = 120 times 10 + 105 times 15/2 + 50/10 times 1000 sigma = 7775 Psf = 7.775 Ksf OCR = P_c/sigma = 76/7.77 = 0.978 overburden stress sigma_0 = 120 times 10 + 105 times 15/2 = 2775 Pst = 2.775 Ksf therefore Settlement S = S_1 + S_2 = Cr/1 + rho_0 H log (P_c/rho_0) + C_c/1 + rho H log(sigma/P_c) = 0.0364/1 + 0.887 (15) log(7.6/2.775) + 0.492/1 + 0.81 15 log(7.77/7.6) = 0.1266 + 0.039 = 0.169ft = 2 inch