复杂应力路径下饱和粉土孔压与变形试验研究

Experimental study on excess pore pressure and deformation of saturated silt under complex stress paths

为了研究均等固结条件下复杂应力路径(循环应力比CSR和循环加载幅值比δ)对饱和粉土孔压和变形的影响,利用GDS空心圆柱扭剪仪,开展了轴向-扭转耦合循环加载的重塑饱和粉土不排水试验。采用累积广义剪应变γg来描述粉土在复杂应力路径下的变形,并以γg=5%为液化破坏标准。研究表明:(1)未液化粉土γg的发展趋势可以通过修正Monismith模型较好地表示,模型得到的预测值与测量值的误差大致在10%以内。(2)当CSR≤0. 05时,CSR和δ对于粉土γg随孔压比ru增大而增大的影响不明显,此时粉土γg几乎不发展且ru远小于1. 0。(3)粉土在不同应力路径下的临界循环应力比CSRth有所不同,当δ=1时,0. 05 <CSRth≤0. 065;δ=2时,0. 065 <CSRth≤0. 08;δ=4时,试验粉土均不会液化。

In order to study the influences of complex stress paths (cyclic stress ratio CSR and cyclic loading amplitude ratio δ)on the excess pore pressure and deformation of saturated silt under isotropic consolidation conditions. Using the GDS hollow cylinder apparatus,a series of undrained tests are performed on the remolded saturated silt under combined axial-torsional cyclic loading.The accumulative generalized shear strain γg is used to describe the deformation of the silt under complex stress paths,and take Yg =5%as the liquefaction triggering criteria.The test results show that:(1)The development trend of γg can be well expressed through the correct Monismith model in the non-liquefaction silt,and the deviation between the predicted values and the measured values is within 10%. (2)When CSR≤0.05,the influence of CSR and δon the increase of excess pore pressure ratio ru and γg is not obvious.At this time,γs is almost not developed and ru was far less than 1.0 of silt.(3)The threshold cyclic stress ratios CSRth are different under different stress paths,when δ=1,0.05<CSRth≤0.065and δ=2,0.065< CSRth 40.08,but silt will not liquefy when δ=4in this experimental study.