Study On Shear Strength Of Rock Under Acid Corrosion

Mineral resources as the pillar industry of the national economy,the safe exploitation of mineral resources is conducive to the steady and rapid development of the national economy.Safety issues are paramount in the process of mining mineral resources,and as such,it is important to study the deformation and failure characteristics of rock materials.Minerals make up rocks,the most common rock-forming minerals are anisotropic and often contain impurities consisting of minerals.The mineral particles are joined together by mutually intersecting particle boundaries,mineral cement,and cohesive particle aggregates.Rocks,as a collection of minerals,have an inseparable relationship between the physical and mechanical properties of the rock and the mineral composition of the rock and its association.The water environment in the mining area is very complicated,and the chemical substances in the water environment will react with the rocks.This chemical corrosion causes changes in the mineral composition of the rock and even the internal structure of the rock,which in turn changes the mechanical properties of the rock,causing deterioration of the mechanical properties of the rock.In the long run,it poses a great threat to the safety of rock engineering.Therefore,it is of great engineering significance to study the corrosion effect of chemical solutions on rock strength and deformation,and this is one of the hotspots of rock mechanics research at home and abroad in recent years.This article relies on the Natural Science Foundation project:Hydration erosion and rheological damage mechanism of fractured pillar under high stress and high humidity environment,In this paper,the rock shear strength characteristics of rock specimens taken from the Taiping pre-Copper iron ore in Anhui Province under oxalic acid corrosion were studied.The main research contents of this paper are as follows:1.The rock specimens were subjected to direct shear test under different normal stress conditions,and the full stress strain curve was found to be divided into four stages:Compaction phase(OA segment)?Elastic deformation stage(section AB)?Shear failure stage(BC segment)and Post-destruction phase(CD segment).2.The characteristics of each stage of the full stress strain curve are as follows:(1)Compaction phase(OA segment):The slope of the shear stress-strain curve is very small,the displacement is greatly increased,and the shear stress increment is very small;(2)Elastic deformation stage(section AB):The shear stress-strain curve is approximately straight and the slope is larger than the OA segment,and the B point stress is the elastic limit;(3)Shear failure stage(BC segment):After a short period of time after point B,the slope of the shear stress-strain curve is greatly reduced,the strain continues to increase,and the shear stress remains substantially unchanged.Then the slope of the shear stress-strain curve is greatly increased,and the slope is greater than the AB segment of the elastic deformation stage until the shear failure occurs in the test piece;(4)Post-destruction phase(CD segment):The shear force peaked at point C,the rock specimen was destroyed,and the shear force was greatly reduced.3.The rock specimen is immersed in a weak acid solution of different pH and then subjected to a direct shear test,The variation of each characteristic quantity of the direct shear test is as follows:(1)Under the same pH conditions,the shear strength of rock specimens increases with the increase of normal stress.Under the same normal stress conditions,as the pH of the soaking solution decreases,the shear strength of the rock specimen decreases.(2)The rock specimens of each pH group were subjected to direct shear test under the same normal stress conditions,The shear strength of the rock specimens immersed in the 6-day group was smaller than that of the rock specimens immersed in the 3-day group.(3)Cohesion:As the pH of the soaking solution decreases,the cohesive force decreases.(4)Internal friction angle:As the pH of the soaking solution decreases,the internal friction angle decreases.4.The pH of the soaking solution was measured by a pH meter during the soaking process,and it was found that the pH of each group of the soaking solution finally showed a weak alkalinity.5.In different soaking solutions,the degree of corrosion of the rock specimens in the soaking solution is different,and the way of corrosion is different.In the soaking solution with pH 7,it can be found that the main solution of the soaking solution is the adhesion between the attached material on the surface of the rock specimen and the rock mineral crystal,and the pore crack develops.In the soaking solution with pH 4,the soaking solution not only corrodes the cemented material between the attached material on the surface of the rock specimen and the mineral crystal,but also corrodes the mineral crystal.The particle size of the mineral crystals is made smaller,the contact mode between the particles and the particles is changed,the pore cracks are developed in a large amount,and the pores are dissolved.These changes between the mineral particles of the rock specimens eventually led to changes in the mechanical properties of the rock specimens.