冲击荷载下软土的动力响应及结合水变化试验研究

通过SPAX-2000动静真三轴测试系统,研究了饱和软黏土在冲击荷载作用下的应力、应变、孔隙水压力等指标的变化特征。同时,通过差热分析法和理论计算,对比了试验前后软土中结合水含量大小。研究表明,土中结合水含量及其变化对土的物理性质和力学行为有重要影响。试验前后饱和软黏土中结合水含量变化较大,水性转化现象明显,土体固结作用显著,并且冲击荷载作用下土中水性转化、弱结合水排出与动力排水固结程度有因果联系。在一定试验条件组合下,存在饱和冲击能,此时能激发土中结合水转化为自由水量最多;伴随孔隙压力的消散和土体的固结,土的抗剪强度提高、压缩性减小,土体成为超固结土。该研究能揭示软基加固的微观机理,可为静动力排水固结法设计提供理论依据。

Experiment Study on Dynamic Response and Variation of Bound Water of Soft Clay under Impact Loading

Through tme-triaxial testing system of Static-dynamic Spax-2000,the dynamic response characteristics of saturated soft clay under impact loading were analyzed,including dynamic stress,pore water pressure,axial strain.Meanwhile,bound water content of saturated soft clay was obtained by thermal gravimetric analysis and theoretical calculation method before and after triaxial experiments.The research shows that bound water content and its variation have important influence on the physical properties and mechanical behavior of soil.Drainage consolidation of saturated soft clay was obvious and variation of bound water content was large under triaxial impact loading.There is causal relationship between some weakly bound water removed and saturated soft clay dynamic drainage consolidation.In certain test condition,there is a saturated impact energy,which can transform the most bound water to free water.With the dissipation of pore pressure and drainage consolidation,shear strength increased,the compressibility decreased,the soil became over consolidated soil.This study is helpful for understanding of mircomechanism of soft ground reinforcement,and it can provide theoretical basis for design of static-dynamic drainage consolidation method.