结构性花岗岩残积土三轴试验研究

A triaxial test study on structural granite residual soil

花岗岩残积工作为一种特殊土,在我国东南地区分布广泛,但其特殊的结构特性使得该类土体的工程事故频发。针对广东省肇庆市播植县某边坡残积土进行了一系列三轴试验,研究结构性花岗岩残积土在三轴应力状态时的应变和孔压变化特征,以及结构性花岗岩残积土的剪切结构性屈服特性,为相关工程提供借鉴。三轴压缩试验分别针对原状土、重塑正常固结土和重塑超固结土,试验结果表明,原状土和重塑超固结土均表现出一定的结构性,排水剪切时均表现出明显的剪胀性,应力-应变曲线均表现出应变软化,不排水剪切的超静孔压均为先增大后减小,但原状土超静孔压减小的幅度更大;超固结土的不排水抗剪强度符合SHANSEP理论,试验常数Λ_(0)为0.67;重塑正常固结土的归一化刚度随着加载的进行缓慢减小,ε_(1)=15%左右时完全屈服;原状土和重塑超固结土的归一化刚度曲线不能重合,分别于ε_(1)=1.5%和ε1=1%左右发生结构性屈服,并且均在ε_(1)=15%左右发生整体破坏,围压越大,结构性土的刚度曲线变化规律越接近于扰动土。

As a kind of special soil,granite residual soil is widely distributed in the southeastern part of China and usually leads to engineering accidents due to its special structure.In this paper,a series of triaxle tests was conducted on the slope residual soil from Bozhi County,Zhaoqing City,Guangdong Province,to study the strain and pore pressure characteristics of structural granite residual soil under triaxial stress state as well as the structural yield characteristics of granite residual soil,which could provide useful reference for corresponding projects.Triaxial compression tests were conducted on undisturbed soil,remolded normal consolidated soil and remolded over-consolidated soil.The results showed that both undisturbed soil and remolded over-consolidated soil had certain structural characteristics,and had an obvious dilatancy during the drained shear test.The stress-strain curves of both undisturbed soil and remolded over-consolidated soil showed strain softening.The excess pore pressure of both undisturbed soil and remolded over-consolidated soil increased first and then decreased during the undrained shear test,while the excess pore pressure of undisturbed soil decreased more.The undrained shear strength of over-consolidated soil was consistent with the SHANSEP theory and the test constant∧_(0)was 0.67.The normalized stiffness of remolded normal consolidated soil decreased slowly with loading process going on,and it yielded completely whenε_(1)=15%.The normalized stiffness curves of undisturbed soil and remolded over-consolidated soil were not consistent with each other,and the structural yielding occurs atε_(1)=1.5%andε1=1%respectively,and the overall failure occurs atε_(1)=15%.In addition,the larger the confining pressure was,the more similar the structural curve of the structural soil was to the disturbed soil.