沉积环境对软土物理及力学特性的影响

Influence of deposit environment on physical and mechanical properties of soft soil

在分析杭嘉湖平原全新世海侵软土层成因的基础上,取全新世时期河口湾、低盐沼泽和潮坪—泻湖三种不同沉积环境中形成的软土,结合室内土工试验,对软土物理性质和力学指标与成因环境进行了相关性分析。研究结果表明:河口湾在沉积过程中多处于较激烈的水动力环境中,粉粒含量较多导致其含水量和孔隙比均较小,内摩擦角相对较大;低盐沼泽环境沉积软土层较薄,其渗透固结路径短,使得含水量和压缩性也相对较低,内摩擦角一般;而潮坪—泻湖环境则相对安静和低能,沉积物以细颗粒物质为主,含水量、孔隙比和压缩性均是三种环境中最大的,其内摩擦角较小。杭嘉湖平原全新世海侵软土层压缩系数与压缩模量呈较好的幂数函数关系。

On the basis of analysis the genesis of soft soil in the area of Hangzhou-Jiaxing-Huzhou plain during Holocene transgression of sea, then different soil samples from different deposit environments named estuary, low-salt marsh and tidal-lagoon are taken, and the correlation between physical, mechanical properties and formation mechanism is analysed combined with the indoor test. The results show that during the deposition process, the estuary was in a competitive hydrodynamic environment, resulting in higher silt content, considerably smaller moisture content and porosity, while with relatively large internal friction angle. Soil deposition from low-salt marsh was always thinner, accompanied by short consolidation path, low moisture content and smaller compressibility, and the internal friction angle was middle. Tidal-lagoon environment is relatively quiet and low-energy, in which the sediments always build up by fine particle matter, and its water content, void ratio and compression were the largest of the three conditions but its internal friction angle was the lowest. Compression factor and modulus was much fit to a power function for the soft soil aggraded during Holocene transgression of area in Hangzhou-Jiaxing-Huzhou plain area.