制样方法对粉土力学特性及孔隙特征的影响

Influence of the compaction procedure on mechanical behaviors and pore characteristics of silts

以郑州粉土为研究对象,分别采用静力压实法和动力击实法制取试样,并进行三轴剪切试验与压汞试验测定其力学特性和孔隙分布曲线,研究制样条件对粉土力学特性及孔隙结构分布的影响。结果表明:制样方法及制样含水率对土样应力–应变曲线形态的影响和围压有关。动力击实样应力–应变关系由低围压和低含水率下的应变软化型向较大围压和较大含水率下的应变硬化型过渡,而静力压实样则始终呈应变硬化特性。2种制样方法所得试样的剪切强度和黏聚力均在最优含水率时最大,但对于相同的制样含水率,击实样剪切强度和黏聚力均高于压实样,而制样方法对粉土残余黏聚力的影响可忽略。另外,制样条件对土样的内摩擦角和残余内摩擦角影响均很小。压汞试验表明,与击实样相比,压实样的孔径分布曲线整体呈向右平移趋势,峰值孔径及分布密度增大,且团粒内较大孔隙含量较多。这一定程度上可以解释静力压实样和动力击实样力学性状的演化规律。

Taking Zhengzhou silt as the research object,the samples were prepared by static and dynamic compaction methods,and a series of triaxial shear tests and mercury injection tests were carried out to study the influence of different sample preparation conditions on mechanical behaviours and pore structure distribution of silt.The results show that the influence of the sample preparation method and the water content on the stress and strain relationship depends on the confining pressure.The stress and strain relationship of dynamic compaction samples transfers from the strain softening type with lower confining pressure and lower water content to the strain hardening type with larger confining pressure and larger water content,while the relationship of static compaction samples is always the strain hardening type.The shear strength and the cohesion of the samples obtained by the two sample preparation methods reach the maximums at the optimal moisture content.The shear strength and the cohesion of the dynamic compacted samples are higher than those of the static compacted samples for the case of the same water content,while the sample preparation method has no obvious influence on the residual cohesion of silty soil.Mercury injection test results indicate that,compared with the dynamic compaction samples,the pore diameter distribution curve of the static compaction samples shifts to the right as a whole,the peak pore diameter and distribution density increase and the larger pore content is more.The research results can explain the evolution law of the mechanical property of the static and dynamic compaction samples to some extent.