含气软黏土的不排水抗剪强度计算模型

Calculation model of undrained shear strength of gassy soft soil

含气软黏土广泛分布在世界五大洲,大量离散气泡的存在对软黏土的不排水抗剪强度具有强化或损伤作用,然而目前仍缺乏能综合考虑气相强化与气相损伤竞争机制的含气土不排水剪切强度解析表达式。结合临界状态土力学理论,基于笔者提出的含气土屈服函数,建立了v-ln p’空间下临界状态线截距Γ与土体含气特性(u_(w0),ψ_(0))的数学关系,进而推导了含气软黏土在三轴应力状态下不排水抗剪强度su的理论显式表达式。同时,采用所提出的含气软黏土不排水抗剪强度理论计算公式,分别对比了3种典型的含气软黏土在不同含气特性下的不排水抗剪强度理论预测与试验结果,包括马来西亚高岭土、Combwich黏土和高岭黏土。另外,对比分析了4种不同的含气软黏土不排水抗剪强度理论计算模型的预测误差百分比,证明了提出的基于改进的含气软黏土本构模型的不排水抗剪强度理论计算式的合理性,能够更加准确地同时考虑含气软黏土的气相强化与气相损伤双重效应。

Gassy soft soil is widely distributed in five continents in the world.The existence of a large number of discrete bubbles can strengthen or damage the undrained shear strength of soft soil.However,there is still a lack of analytical expression for undrained shear strength of gassy soil,which can comprehensively consider the competition mechanism between gas-phase strengthening and gas-phase damage.Combined with the theory of critical state soil mechanics and based on the yield function of gassy soil proposed by the author,this paper established the mathematical relationship between the intercept of critical state lineΓand the gassy characteristics(u_(w0),ψ_(0)) of soil in the v-ln p’space,and then deduced the theoretical expression of undrained shear strength su of gassy soft soil in triaxial stress state.At the same time,using the deduced theoretical calculation formula of undrained shear strength of gassy soft soil,this paper compared the theoretical predictions and test results of undrained shear strength for three kinds of typical gassy soft soil under different gassy characteristics,including Malaysian kaolin silt,Combwich mud and kaolin clay.In addition,this study analyzed the predicted error percentage of four different theoretical calculation models for undrained shear strength of gassy soft soil,proving the rationality of the theoretical calculation formula of undrained shear strength based on the improved constitutive model of gassy soft soil.The proposed model can more accurately consider the dual effects of gas phase strengthening and gas phase damage of gassy soft soil simultaneously.