A PRACTICAL METHOD FOR OBTAINING CORRECTION FACTOR OF LIQUEFACTION RESISTANCE FOR MEMBRANE PENETRATION

抄録

In order to obtain practically a correction factor of the liquefaction resistance of saturated soils for the reduction of membrane penetration during cyclic triaxial test, LR_m, the relationships between LR_m and uniformity coefficient U_c are investigated. Here LR_m={(σ_d/2 σ'₃₀)_nc-(σ_d/2 σ'₃₀)_c}/(σ_d/2 σ'₃₀)_nc×100, in which (σ_d/2 σ'₃₀)_nc and (σ_d/2 σ'₃0)_c denote the stress ratios before and after the correction for the reduction of membrane penetration, respectively. Samples used are two kinds of sands and two kinds of decomposed granite soils, having uniformity coefficients of l.68, 1.83, 6.40, and 28.92 respectively. Membranes are three kinds of latex rubber ones with thicknesses of O.18mm, O.25mm, and O.60mm respectively. From the tests it was found that our correction method (Ohara and Yamamoto, 1981, 1982) is valid, and LR_m increases with the value of logarithm of U_c for the cases when the number of cycles required to cause liquefaction N_L is in the region of 10∼50. In the case, for example, of N_L=10, the values of LR_m are 8%, 16%, and 28% respectively for U_c= 2, 5, and 25. Furthermore, it was found that the strength effect of membrane on the liquefaction resistance of the soils can be ignored.