不同加载应力路径下饱和砂土力学特性试验研究

通过全球数字系统(global digital system, GDS)动三轴测试系统,对砂土进行了常规三轴压缩试验和偏压固结下的等p(平均应力)、等σ_3(围压)、等σ_1(围压)等不同应力路径的试验。通过对所有的实验结果进行了对比分析,研究了砂土材料在不同应力路径下的应力-应变、变形特性、强度特性。试验研究结果表明,等压应力路径试验中试样都是先体积收缩随后出现体积膨胀现象,这与高围压下砂土的剪胀性变化情况不一样;偏压固结试验中,整个加载阶段前期表现为应变硬化,但是后期的软化现象不是很明显,这与等压固结试验应变硬化-软化现象略有不同。虽然常规三轴和偏压固结下的σ_3等试验采用的是两种不同的固结方式,但是达到的峰值强度基本上是一样的,说明固结方式对于试样的强度没有太大的影响。偏压固结试验中,不同的应力路径达到峰值强度时所对应的轴向应变是不同的,而且峰值强度也不一样,说明不同的应力路径会对砂土的强度造成影响,同时也说明了砂土力学特性对于应力路径的依赖性。

Experimental Study on the Mechanical Characteristics of Saturated Sandy Soil Under Different Loading Stress Paths

Through the GDS dynamic triaxial test system, the conventional triaxial compression tests of sand were performed, and a series of tests of constant p, constant , constant under biased consolidation were performed.The stress-strain, deformation characteristics and strength characteristics of sandy materials under different stress paths are studied by comparing and analyzing all the experimental results.The experimental results show that in the isobaric stress path test, the sample shrinks first and then expands, which is different from the change of the dilatancy of sand under high confining pressure.In bias consolidation test, strain hardening occurs in the early stage of loading, but the softening phenomenon was not obvious in the later stage, which was slightly different from the strain hardening-softening phenomenon in isobaric consolidation test.Although the conventional triaxial and biased consolidation constant P tests adopt two different consolidation modes, the peak strength was basically the same, indicating that the consolidation mode has little effect on the strength of the specimen.In bias consolidation tests, the corresponding axial strain and peak strength are different when different stress paths reach the peak strength.It showed that different stress paths would affect the strength of sand, and it also shows that the mechanical properties of sand depend on stress paths.