南海荔湾深水重塑沉积物的静、动力特性

Static and cyclic behaviors of remoulded deepwater sediments of Liwan in South China Sea

通过大量试验,对重塑后的南海荔湾深水浅层沉积物的静、动力特性进行了研究,得出以下结论:该深水沉积物的液限与塑性指数高,含水率高,天然容重小;其渗透系数比世界其他深水浅层沉积物渗透系数大1-2个数量级,为2.59×10-7cm/s;此类沉积物属高压缩性、中高灵敏的软土,其固结系数约为1.54×10-3cm2/s;依据k0固结不排水三轴压缩试验确定的MohrCoulomb强度参数预测k0固结不排水三轴拉伸强度,预测结果明显小于试验结果;低频循环荷载作用下,该沉积物的不排水循环强度变化规律与一般饱和软粘土的变化规律一致;地震荷载作用下,尽管它不会发生震动液化,但土层中会产生显著的震动累积孔隙水压力,且破坏时的震动累积孔隙水压力将达到上覆有效压力的90%,这表明地震荷载作用下此种深水沉积物的强度弱化与基础震陷可能是比较明显的。

Static and cyclic behaviors of the remoulded deepwater sediments of Liwan in South China Sea were studied by a lot of tests. Following conclusions were obtained The water content, the liquid limit and the plastic index of the sediments were high but its unit weight was low. Its permeability coefficient was 2.59í10-7cm/s and 1-2 magnitude order larger than that of deepwater sediments in other areas of the world. It was the soft sediments with high compression and medium to high sensitivity and its consolidated coefficient was about 1.54í10-3 cm/s. If the undrained triaxial extension strength was predicted under k0 consolidated condition using Mohr-Coulomb parameters determined based on undrained triaxial compression test results under k0 consolidated condition,the predicted results were obviously less than test results. The variation of undrained cyclic strength was the same as that of general saturated soft clays under cyclic loads with low frequency. Although liquefaction did not occur for the soft sediments under earthquake loads, the cyclic accumulative pore water pressure in the stratum would be significant and it might develop to the level of about 90% of the effective overburden pressure when the sediment was failure, which showed that strength degradation of the sediment and seismic settlement of foundation might be obvious under seismic loads.