盐度对海洋黏土力学特性影响与扰动预固结试验

Influence of salinity on mechanical properties of marine clay andpre-consolidation test of disturbance

海洋黏土与陆域一般黏土相比,其孔隙水具有一定的含盐量,孔隙水含盐量会影响其力学特性,因此试验中在制样饱和时不宜改变其孔隙水的含盐量。对饱和度较低的海洋黏土,需制备与海洋土中孔隙水含盐量一致的水样,然后再进行真空法饱和;对饱和度大于92%的海洋黏土样,建议采用反压力法饱和。由于海洋黏土在取样、运样和样品存贮过程中受扰动影响,试验时不排水强度降低50%甚至更多。基于扰动样不排水强度的SHANSEP法开展室内扰动模拟的试验研究,对通过预固结法减少扰动导致的试验偏差作进一步的探讨。试验结果表明:预固结应力的选取与土样的扰动方式和扰动程度相关,针对我国现有的岩土勘察技术,预固结应力选取较国外标准的折减系数(75%~80%)要低得多。因此如何合理地选取预固结应力,需要不断地积累工程经验,并经工程检验后进一步推广应用。

Compared with the general clay in continent,marine clay has certain amount of salt in pore water.The salt content of pore water in marine clay can affect its mechanical properties,so it is not appropriate to change the salt content of pore water when preparing a saturated sample.For marine clay with low saturation,salt water containing the same salt content as the pore water in the marine soil must be prepared and then clay samples could be saturated by vacuum method.For marine clay samples with saturation greater than 92%,it is best to use a back-pressure method to saturate the sample.In the process of sampling,sample is susceptible to disturbance during transportation,sampling and storage,so its undrained strength decreases by 50%or more.Based on the SHANSEP method of undrained strength of the disturbance sample,the experimental study on reducing clay disturbance induced test error by the pre-consolidation method was discussed.The results show that the determination of pre-consolidation stress is related to the disturbance mode and degree of soil samples.For existing geotechnical investigation technology in China,the selection of pre-consolidation stress is often much lower than the reduction coefficient(75%~80%)of foreign standards.How to reasonably select the pre-consolidation stress needs to accumulate engineering experience continuously and engineering inspection.