Study On The Mechanical Properties And Microstructure Of Lead Contaminated Guilin Remolded Red Clay

The red clay widely distributed in the carbonate rock area of Southwest China,it is a kind of regional special soil,which formed by the weathering and the laterization of carbonate rocks in the hydrothermal environment.Because red clay's special engineering geological properties is different from the general clay,and it is mainly distributed in the karst area where the foundation had differential settlement and instability subgrade.In the mining process of nonferrous metal in the karst area,the problem of karst collapse in the vibrational perturbation of mining activity is increasingly prominent.The change of mechanical properties of red clay polluted by heavy metal which covered on the mining area and its surrounding area has become the focus of attention of engineers and scholars.In this paper,in order to offer some useful advices for the study of the dynamic behavior of the lead contaminated Guilin remolded red clay that covered on the karst area,which is considered the vibrational perturbation of mining activity.According the triaxial shear test,mercury intrusion porosimetry test and SEM test for the lead contaminated Guilin remolded red clay,combined with the theory of significance analysis,explored the mechanical properties and microstructure change of the lead contaminated Guilin remolded red clay.This paper consists the following contents:(1)The mechanical properties of the lead contaminated Guilin remolded red clay under different lead ion concentration,different working time and different confining pressures were analyzed by unconsolidated-undrained triaxial shear test.The test result shows that: with the increase of concentration of lead ions,the shear strength,cohesion and the friction angle of the lead contaminated Guilin remolded red clay were decreased;with the time increasing,the shear strength and shear strength index of the lead contaminated Guilin remolded red clay did not showed a significant change;with the increase of confining pressure,the shear strength of the lead contaminated Guilin remolded red clay were increased;the stress-strain curves show strain hardening.With the increasing of concentration of lead ions,the hardening tendency was increased;with the increase of confining pressure,the hardening tendency was decreased.(2)With the significant analysis principle,without considering the interaction of lead ion concentration,the reaction time and the confining pressure,the effect of lead contaminated to the shear strength of Guilin remolded red clay was weak.But it's significance when we considered the interaction of those factors.(3)In order to expound the micromechanical property and the microstructure formation mechanism of the lead contaminated Guilin remolded red clay,the mercury intrusion porosimetry test and SEM test were used to analysis the law of microstructure of the lead contaminated Guilin remolded red clay.The results show that: under the effect about the heavy metal ions,the pore was dissoluted.The small pores of the red clay were turned to big pores,which made the micro-fracture and the pore volume of the lead contaminated Guilin remolded red clay.Thus,the mechanical properties of red clay became weaken.