摘要由于流变特性的影响，饱和粘土的不排水抗剪强度与加载速率有关。应变速率对粘土不排水抗剪强度的影响程度通常采用应变率参数(应变速率增长10倍下不排水抗剪强度的增长率)来反映。国外大量的试验结果表明这个参数为8%～20%，而大部分在12%左右，并且超固结比、固结状态、试验类型对应变率参数 r 的影响并不明显。介绍了一个用来研究应变率参数r 的各向异性弹粘塑性本构模型，在这个本构模型的基础上推导得出了应变率参数 r 的理论表达式。实际上，只要是采用滞后变形理论构建的流变本构模型，都可以推导得出这个公式。这个公式从理论上证明了应变率参数与固结状态、试验类型的无关性。众多试验结果表明，对于大多数粘土，压缩指数与次压缩指数的比值大都为0.03～0.05，代入公式中r 的计算结果为7.2%～12.2%。试验中所得到的高达20%的数值与灵敏性土在结构破损明显阶段所具有较高的压缩指数与次压缩指数的比值有关。计算结果与一些试验结果的对比表明了这个表达式的可靠性。
Abstract：For it¢s creep behavior，undrained shear strength of saturated clay is related to load rate. Strain-rate parameter (increase of undrained shear strength per log strain rate)is used to describe the change in undrained shear strength with strain rate by some researchers. Laboratory test data on a wide variety of clays show the value of this parameter is between 8% and 20%，most about 12%，and stress history，consolidation state (isotropic consolidation or anisotropic consolidation)，test type(compression test or extension test) have a little effect on this parameter. An anisotropic elastic viscoplastic model used to study the parameter is introduced. The theoretical equation of is deduced and shows it is only dependent on the ratio of secondary compression index to compression index，independent of the consolidation state and test type，which is shown by test results. Actually，this equation can be deduced from any model based on the delayed compression framework . For most clay，value of ratio of secondary compression index to compression index is about 0.03–0.05，and the value of calculated by the equation is 7.2%–12.2%. High value such as 20% shown by some tests for sensitive clay is related to the high value of ratio of secondary compression index to compression index caused by soil structure collapse. The validity of the equation is testified by some laboratory tests.
