K0固结软黏土的应变率效应研究

在已建立的K0固结软土弹黏塑性本构模型基础上,推导了一维先期固结压力和三轴不排水抗剪强度的计算式,并着重分析了应变率对两者的影响,分别用各自的应变率参数表征。强度应变率参数ρ仅取决于次固结系数与压缩指数的比值,与土体固结应力、固结历史及试验类型均无关;先期固结压力应变率参数ρn则与该比值及压缩参数Λ都有关,且一般有ρn>ρ。对于无机质软黏土,应变率增大10倍时,先期固结压力增长8%～21.2%,不排水强度增长7.2%～12.2%,与试验结果较吻合。考虑到室内试验与原位的应变率差异,建议先将试验所得先期固结压力及不排水抗剪强度按本文规律进行应变率修正,再应用于原位情况。OCR越大,不排水强度比随应变率增长越快。

Strain-rate dependent behaviors of K0 consolidated clays

Based on the newly developed anisotropic elastic visco-plastic constitutive model for K0 consolidated clays,the expressions of preconsolidation pressure and undrained triaxial shear strength were presented,and their strain-rate dependencies were investigated.The strain rate parameter of undrained shear strength was a constant which just depends on the ratio of the consoliation coefficient to the secondary compression index,but the corresponding parameter of preconsolidation pressure was dependent on this ratio as well as the compression parameter Λ.For most inorganic clays,the preconsolidation pressure and undrained strength would increase by 8%²1.2% and 7.2%¹2.2% respectively with a tenfold increase in the strain rate.Considering the differences of strain rate between the laboratory test and the field condition,it is suggested that the measured preconsolidation pressure and undrained strength should be modified before applied to the in-situ condition.As OCR increases,the increasing rate of the strength ratio with strain rate becomes faster.