冻结粉土的动强度特性及其破坏准则

Dynamic Strength Characteristics and Failure Criterion of Frozen Silt

在恒应变速率增长的等应变幅动力模式下，冻结粉土的动强度最初随静有效正应力增大而增加；在后者为７～８ＭＰａ时，动强度达到峰值；以后随着静有效正应力的继续增大，动强度趋于减小。不同应变速率下的动强度包络线呈现相似形式，服从抛物线破坏准则。研究中引进当量动内摩擦角φｅ和当量动内摩擦系数ｔｇφｅ概念，从而使抛物线破坏准则方程与线性破坏准则方程在形式趋于一致。当量动内摩擦角φｅ是一个动态变量，除取决于静有效正应力外，还与土温、应变速率、振频和土类有关，它小于σｓ＝０时的初始动内摩擦角φ０，并随静有效正应力增长而逐渐减小。

Under a cyclic loading with constant amplitude strain controlled by constant strain rate, dynamic strength of frozen silt increases at first with increase of static effective normal stress, reaches the peak strength at the static effective normal stress of 7～8 MPa and then decreases with further increase of static effective normal stress. The failure envelopes of dynamic strength of frozen silt under different strain rates resemble each other in shape, namely, obey the parabola failure criterion. Equivalent angle φ e and coefficient tgφ e of dynamic internal friction are derived in this paper, so the parabola failure criterion equation formally coincides with the linear one. φ e is a dynamic variable one depending on temperature, strain rate, frequency and soil behaviour beside static effective normal stress. It is less than initial angle of dynamic internal friction when there is no static effective normal stress and decreases with increasing static effective normal stress. The nomogram of φ e is also provided in this paper.