Study On Size Effect Of Granite Residual Soil Triaxial Test And Its Effect On Slope Stability Analysis

Granite residual soil is widely distributed in southeast China,especially in Fujian region.Because of the incomplete weathering,the granite residual soil often contains over-size particles.However,most previous triaxial tests carried out for granite residual soil are based on small scale tests,which often ignore the influence of coarse particles on shear strength.The granite residual soil is often treated as embankment fill material.In general,embankment is constructed above ground water level and in an unsaturated state,and the moisture content has marked effect on shear strength.Therefore,based on the basic physical experiment and the conventional triaxial test,this paper focuses on granite residual soil containing over-size particles in Fujian region and studies the influence of the sample size and particle size on shear strength of the granite residual soil.This paper also discusses the effect of water content on shear strength of unsaturated granite residual soil.Furthermore,the paper reveals the influence of size effect and water content on the stability of granite residual soil slope.The main contents and results are as follows:(1)A series of conventional consolidated undrained triaxial compression tests on three different diameter specimens of granite residual soil were performed,the specimens including undisturbed soil,remolded samples and remolded samples without over-size particles.The stress-strain behavior and shear strength of the specimens were investigated.Then the effect of specimen size on the behavior was studied.The test results showed that the stress-strain relation for specimens with different size exhibit similar trendency,while the value is different.The presence of over-size particles result in the higher effective cohesion and the lower effective angle of internal friction.After got rid of the over-size particles,with the increase of sample size,both the effective cohesion and the total angle of internal friction soil sample increase,while the effective angle of internal friction and the total cohesion decrease.(2)Conventional triaxial consolidation drained shear tests have been carried out for granite residual soil remolded samples with different water content,which gaining shear strength parameters:cohesive strength c and internal friction angle(p.Based on the testing results,the influence of moisture content on the granite residual soil shear strength is analyzed and the relation between the granite residual soil shear strength index(cohesive strength c and internal friction angle ?)and moisture content is established.(3)By combining the granite residual soil strength parameters under different sample sizes and different water content tested in the laboratory with engineering practice data,and making use of Geo-Slope software to research into the practical slope and assuming slope,the influence of the granite residual soil strength parameters under different sample sizes and different water content on the stability of granite residual soil slope is analyzed respectively,and the error influence of previous strength parameters of engineering on the slope analysis is investigated.