密实度不同时格栅–砂土界面循环剪切及其后直剪特性

Cyclic and post-cyclic direct shear behaviors of geogrid-sand interface with different soil densities

为研究密实度不同时格栅–砂土界面在经历循环剪切及其后的表现,采用大型直剪仪进行了一系列大型单调直剪试验、循环直剪试验和循环后单调直剪试验。并将单调直剪试验与循环后单调直剪试验的结果进行对比分析。结果表明:单调直剪试验中,随着砂土密实度的增加筋土界面抗剪强度增加,剪切体胀现象变的明显;格栅–密砂界面发生循环剪切软化现象,土样在循环剪切过程当中整体上发生剪缩,且砂土密实度越大经历相同循环次数时的剪缩量越小;循环后单调直剪试验中,3种砂土密实度界面抗剪强度发展曲线都为软化型,在直剪过程中都发生自始至终的剪胀;遭受循环剪切后密砂–格栅界面抗剪强度发生了退化。

In order to investigate the cyclic and post-cyclic shear behaviors of geogrid-sand interface with different soil densities, a series of large-scale monotonic direct shear tests, cyclic direct shear tests and post-cyclic monotonic direct shear tests are performed using a large-scale direct shear device. Comparison and analysis are made between the results from monotonic direct shear tests and post-cyclic monotonic direct shear tests. The results show that the interface shear strength increases with soil density, and more evident dilatancy is observed with higher soil density in the monotonic direct shear tests. The degradation of cyclic shear stress is observed in the geogrid-dense sand interface, the soil tends to be contracted when suffering from cyclic shear, and the volume contraction increases with soil density. The interface shear strength tends to be strain softening, and the soil exhibits dilatancy throughout the tests in the post-direct shear tests with different soil densities. The degradation of the post-cyclic shear is observed in the dense sand-geogrid interface.