Study On Microstructure And Mechanical Properties Of Argillaceous Siltstone In Acidic Environment

The occurrence of geological disasters,such as collapse,rockfall and debris flow,is often related to the internal structure of rock and the long-term action of water solution.Rock structure is complex,in addition,with the development of modern industry in China,acidic gas emissions,aqueous solution is often in（weak）acidic.Under the acid environment,the rock will dissolve the minerals and precipitate the ions,which will lead to the deterioration of the microstructure of the Rock,thus causing the change of rock mechanical properties,and finally induce geological disasters.The red beds are widely distributed in China,there are obvious differences in the structural and climatic characteristics of the red beds in various regions.The upper part of the red beds in Gansu is often covered with loess,which is a significant feature that distinguishes the red beds in this area from those in other regions.This paper mainly studies the changes of the microstructure and mechanical properties of red beds in Gansu Province under acidic environment,which can provide some scientific significance for the protection of geological disasters and in this area.In this paper,the argillaceous siltstone of Chengxian County,Longnan,Gansu Province,is studied in the aspects of microstructure,disintegration and mechanical properties under specific acid environment.The main research work and understanding are as follows:（1）In acidic environment,the argillaceous siltstone gradually evolved from dense pinnate and lamellar structures to irregular clastic or agglomerate lamellar structures,and the contact mode was mainly surface-to-surface contact to point-to-surface contact,the surface particle area decreases continuously until the steady state,and the smaller the p H value is,the greater the change rate of morphology is.The four kinds of ion precipitation rate and concentration sequence of Ca²⁺、K⁺、Mg²⁺、Na⁺in solution under different acidic environment are:p H=3 group>p H=5 group>p H=7 group.（2）The variation trend of the disintegration particle content of Argillaceous siltstone in different acid environments is basically consistent with the increase of dry-wet cycles.The disintegration resistance index and disintegration ratio decreased with the increase of dry-wet cycles,and the disintegration rate increased with the increase of dry-wet cycles.The fractal dimension D_s of argillaceous Siltstone has a positive correlation with the number of dry-wet cycles,and the fractal dimension of argillaceous siltstone increases with the increase of cycles,and decreases with the decrease of p H value of solution,with the increasing of fractal dimension,the disintegration products of rock samples become more and more broken.（3）The failure mode of argillaceous siltstone in acid environment has the tendency of brittle failure to ductile failure.The change law of stress-strain of argillaceous siltstone in different acidic environments accords with the change law of typical stress–strain curve.The uniaxial compressive strength and elastic modulus decrease to different degrees,and the smaller the p H value of the solution,the more the mechanical index of argillaceous siltstone decreases.