饱和冻结粉土扭转状态下应力应变分析

Constitutive relation of saturated frozen silt in torsion

在弹塑理论的基础上考虑冻土的流变特性，即应变速度对冻土本构关系的影响，提出冻土单轴压缩本构关系与冻土纯剪（扭转）状态下的本构关系之间服从单一曲线假定．由单轴压缩本构关系推导出冻土纯剪状态下的本构关系为τ＝Ａ３１＋ｍ２γｍγγｙｎ式中τ剪应力γ剪应变γ剪应变率γｙ初始屈服剪应变Ａ，ｍ，ｎ参数，可从单轴压缩试验得出当τ小于初始屈服应力时，ｎ＝１；当τ大于初始屈服应力时，ｎ＜１．通过饱和冻结粉土实心园柱体的扭矩实测资料验证，此法是可行的，剪应力与剪应变关系符合实际情况．

Because of the diffculty in making of the thin wall hollow cylinderic specimen of frozen soil, the relation of pure shear stress and strain cannot be directly obtained from torsion test. Based on the developed elasticplastic theory considering the effect of strain rate, the relation between pure shear stress and strain has been deduced from the constitutive relations under uniaxial compression. By verifying the rorsion moment acting on the solid cylinder of saturated frozen silt, it is shown that the theoretical torsion moments are identical with tested torsion moments. Thus, the developed elastic plastic theory is feasible to analyze the shear stress and strain of solid cylinder of frozen soil. The relation of pure shear stress and strain of saturated frozen silt is presented as follows:τ=A3 1+m2 mγγ y nwhere, γ,τ, and γ y are shear shtress, shear strain, shear strain rate and yield shear strain, especially. A, m , and n are parameters obtained from uniaxial compression test. When shear stress is less than yield shear stress, then n =1, and when shear stress is more than yield stress, then n <1.