被动围压条件下非饱和黏土动态压缩性能试验研究

Experimental study on dynamic compression performance of unsaturated clay under passive confining pressure condition

为揭示软黏土的应变率效应及建立动态响应参数及其影响因素的定量关系,设计并开展了被动围压条件下的非饱和黏土霍普金森压杆(split Hopkinson pressure bar, SHPB)动态压缩试验,分析了应变率效应、冲击次数、含水率变化对软黏土动态力学特性的影响。试验结果表明:非饱和黏土的动弹性模量与动应力峰值具有显著的应变率效应;当试样的应变率处于255~587 s^(-1)范围内时,动态响应参数与应变率在双对数坐标系下表现出良好的线性拟合关系,且线性拟合曲线的斜率k反映了动力响应参数随应变率变化的敏感程度;含水率对软黏土应变率敏感性影响较大,其中,35%含水率试样动力响应参数的率敏感性最为显著,而39%含水率试样动力响应的率敏感性最差;此外,动力响应参数表现出随冲击次数的增加呈幂函数增长,冲击气压与试样含水率均对重复冲击载荷下的软黏土动力响应有较大影响。

Here,to reveal the strain rate effect of soft clay and establish a quantitative relation between dynamic response parameters and their influencing factors,SHPB dynamic compression tests of unsaturated clay under passive confining pressure condition were designed and conducted.Effects of strain rate effect,impact frequency and moisture content changes on dynamic mechanical properties of soft clay were analyzed.The experimental results showed that dynamic elastic modulus and dynamic stress peak values of unsaturated clay have significant strain rate effect;when specimen strain rate is within the range of 255~587 s^(-1),there is a good linear fitting relation between dynamic response parameters and strain rate in double-logarithmic coordinate system,and slope k of linear fitting curve reflects the sensitivity of dynamic response parameters to changes in strain rate;moisture content has a larger impact on strain rate sensitivity of soft clay,the rate sensitivity of dynamic response parameters of 35%moisture content specimen is the most significant,while the rate sensitivity of dynamic response of 39%moisture content specimen is the worst;in addition,dynamic response parameters have a power function growing with increase in impact frequency,both impact pressure and specimen moisture content have a larger impact on dynamic response of soft clay under repeated impact load.