围压路径对冻结粉质砂土变形行为及强度的影响研究

目前关于冻土的室内三轴压缩试验研究多采用恒围压下的轴向加载方法，而实际工程中的受压土体基本处于围压、轴压同时发生变化的情况。以冻结粉质砂土为研究对象，进行了变围压和恒围压下的三轴剪切测试。根据试后试样变形情况，给出了试样面积的统一修正公式，研究结果表明：当含水量较小时，围压路径对应力-应变曲线的初始段和最终段没有显见影响，但在应力-应变曲线中间段，变围压下的应力-应变曲线明显在相应的恒围压曲线之下，且初始围压越小，曲线位置越低。当含水量不低于饱和值时，围压路径和含冰量共同影响着应力-应变曲线的发展趋势，且变围压曲线的最终段基本都在相应的恒围压曲线之上，中间段变化特点与含冰量和初始围压有关。围压路径对强度随围压变化趋势的影响跟含水量大小有关。当含水量较小时，两种围压路径下的强度值比较接近；当含水量不低于饱和值时，恒围压下的强度值低于相应变围压下的强度值。

A study of the effect of confining pressure path on strength and deformation of frozen silty sand

At present triaxial compressive tests in laboratory are usually conducted by axial loading method with a constant confining pressure.However,the soil in the practical engineering is often in a stress status that the confining pressure coincides with axial loading.According to the practical consideration,triaxial shear tests for frozen silty sand were carried out under different confining pressure paths.Bases on the deformation of the tested sample,the modified formula of the sample section is proposed,and then the data was processed.The results show that the confining pressure path has little influence on the initial and final segments of stress-strain curve when the water content is small,and at the middle section of stress-strain curve,the curve of varying confining pressure is lower than that of constant confining pressure,and the smaller the initial confining pressure is,the lower the curve position is.When the water content equals or exceeds the saturation value,the combination of confining pressure path and ice content controls the trend of stress-strain curve;the final section of stress-strain curve is higher under the varying confining pressure than that under the constant confining pressure,and the features of middle segment are related to ice content and initial confining pressure.The confining pressure path has insignificant effect on the relation between strength and confining pressure.When the water content is small,the strength values of the two confining pressure paths are close each other;when the water content is high,the strength of constant confining pressure is less than that under varying confining pressure.