两种固结方式下软黏土三轴不排水剪切的模量

Undrained Modulus of Soft Clay Under Triaxial Shear with Two Consolidation Modes

摘要:

原位软土处于K₀固结状态因此变形具有显著的非线性和各向异性，然而室内三轴剪切试验通常采用等向固结方式，目前对K₀固结和等向固结两种方式下不排水剪切的模量E_u的差别还未系统的对比总结过。采用上海软黏土的原状土样和重塑土样，进行了三轴等向固结压缩（ICUC）、K₀固结压缩（ACUC）和K₀固结拉伸（ACUE）三种不排水剪切试验，对比分析了应力?应变曲线、不排水模量E_u的非线性特性以及双曲线模型的参数值。研究结果表明，同等应变下ICUC试验的E_u与ACUE试验相近，但要大于ACUC试验值；ACUC试验与ACUE试验具有相近的初始模量和破坏比。结合试验结果和双曲线模型，推导给出了适用于这三种试验的归一化模量的统一表达式，并给出了上海软黏土的参数值。

Abstract:

In-situ soft clays are in K₀ consolidation state and present mechanical nonlinearity and anisotropy， However， in laboratory triaxial shear tests isotropic consolidation is usually adopted. At present， there has been no systematic comparison and summary of the differences in the modulus E_u of undrained shear between K₀ consolidation and isotropic consolidation. Three kinds of triaxial shear tests， isotropic consolidation undrained compression （ICUC）， K₀ consolidation undrained compression （ACUC）， and K₀ consolidation undrained extension （ACUE）， were conducted on undisturbed and remolded specimens of Shanghai soft clay. The stress-strain curves， nonlinearity of the undrained modulus E_u and the parameter values of the hyperbolic model are presented and compared. The results show that at the same strain level， the E_u of the ICUC test is close to that of the ACUE test， but larger than that of the ACUC test； The ACUC test and ACUE test have similar initial modulus and failure ratio. Based on the test results and the hyperbolic model， a unified equation of the normalized modulus for the three kinds of undrained shear tests was developed and the parameter values for Shanghai soft clay were summarized.