细粒含量对饱和砂土静态液化失稳特性影响的三轴试验研究

Study on the Effect of Fine Particle Content on Static Liquefaction Instability of Saturated Silty Sands by Triaxial Tests

通过开展三轴固结不排水剪切试验,研究了初始相对密实度、黏土掺量及固结方式对含细粒砂土静态液化特性的影响。纯丰浦砂试验结果表明,中密和密实试样的应力应变关系呈持续应变硬化特性,孔压先增加后减小到负值,只有在极松散(密实度D_(r)=5%)情况才出现持续的应变软化。掺入一定量上海黏土的丰浦砂试样试验结果表明,在细粒含量不高条件下,细粒含量增加导致砂土更易发生应变软化。基于试验结果以及计算得到的二阶功变化情况,获得了砂土静态液化失稳触发点对应的应力比。该应力比随试样初始密实度增大而增大,随细粒含量增加而减小,说明砂土越松散、细颗粒含量越高越易触发静态液化失稳。

The effects of initial relative density,fine particle content and consolidation mode on static liquefaction of sand were studied by using consolidated undrained triaxial shear test.For pure Toyoura sand,the stress-strain relationship of medium dense and dense samples shows continuous strain hardening characteristic,and the pore pressure first increases and then decreases to negative values.The continuously strain softening occurs only in the very loose sample(D_(r)=5%).The results indicate that when the content of fine particles is low,the sand is more prone to strain softening.Based on the test results and the calculated second-order work,the stress ratio corresponding to the triggering point of static liquefaction instability of sand is obtained.The stress ratio increases with the increase of initial compactness and decreases with the increase of finegrained content,indicating that loose specimen with a high fine-grain content is apt to trigger static liquefaction instability.