间歇振动荷载致黏土刚度软化试验研究

Experimental Study on Stiffness Softening of Clay under Intermittent Vibration Loads

研究目的:黏土在间歇动载作用下的刚度软化是黏土重要的动力特性之一,同时土体在间歇期会发生内部结构的调整,从而对土体的力学性质产生影响。为探究间歇动载作用下黏土刚度的变化特性,采用共振柱试验系统,对南昌地区粉质黏土在间歇振动荷载作用下的模量软化及恢复进行研究。试验中详细地研究了荷载幅值、含水率、围压等因素对土体模量变化的影响,并引入土体模量演化模型,对土体软化和恢复的关键影响因素进行分析。研究结论:(1)随施加动载幅值的逐渐增加,土体模量软化程度也显著增强;含水率对土体软化指数的影响与其对干密度影响相似;(2)增大围压能够提高土体的抗软化能力,有利于减小土体在间歇性动载下所产生的变形;(3)黏土在间歇动载作用下的软化和恢复可以统一由所引入的理论模型进行描述,证实了所引入的理论模型的适用性;(4)尽管本文是针对区域性土进行的研究,但是采用的分析方法、使用的模型及相应的结论可以推广至其他地区黏土相关性质的研究。

Research purposes:The stiffness softening of clay under intermittent dynamic load is one of the important dynamic characteristics of clay.At the same time,the internal structure of clay will be adjusted in the intermittent period,which will affect the mechanical properties of soil.In order to investigate the variation characteristics of clay stiffness under intermittent dynamic load,the modulus softening and recovery of silty clay in Nanchang area under intermittent vibration load were studied by using resonance column test system.The influences of load amplitude,water content,confining pressure and other factors on the soil modulus were studied in detail,and the soil modulus evolution model was introduced to analyze the key influencing factors of soil softening and recovery.Research conclusions:(1)The softening degree of soil modulus increases significantly with the increase of dynamic load amplitude.The effect of water content on soil softening index is similar to that on dry density.(2)Increasing confining pressure can improve the softening resistance of soil and reduce the deformation of soil under intermittent dynamic load.(3)It is found that the softening and recovering of clay under intermittent dynamic load can be described by the introduced theoretical model,which confirms the applicability of the introduced theoretical model.(4)Although the study in this paper is for regional soils,the analytical methods,models used and corresponding conclusions can be generalized to the study of clay-related properties in other areas.