Study On Mechanical Response Of Granite Residual Soil Under Acid Rain

Granite residual soil is widely distributed in the humid and rainy southeast of China,which is often affected by acid rain because of its large industrial scale.Long time acid rain will change the mechanical properties of rock and soil,and become an important inducement of soil landslide and foundation failure and deformation.However,there are few experimental studies on the effect of acid rain on the mechanical properties of granite residual soil.In this paper,the granite residual soil in Bozhi town of Guangdong Province is selected as the test sample.The soil is treated with different ways of acid.The dissolution of metal ions is detected by atomic spectrum analysis.The disintegration test,permeability test and triaxial shear test are carried out on the acid polluted soil samples to explore the influence of acid pollution environment on the mechanical properties of granite residual soil.The applicability of Duncan—Chang model to remolded samples of residual soil under acid rain condition is studied,which can provide reference for related projects.The main work and research results are as follows:(1)The results of acid disintegration test show that the disintegration speed and disintegration amount of the sample are influenced by the compaction degree,water content and p H value of the solution.The water content has the greatest influence on the disintegration characteristics of the sample,and the anti disintegration of the sample decreases sharply with the decrease of water content.The anti disintegration property of the sample can be enhanced by increasing the compaction degree.When the sample disintegration rate is slow,with the decrease of p H value of soaking solution,the disintegration rate will accelerate and the disintegration amount will increase.(2)Under the condition of acid immersion,the metal oxides in the sample are dissolved,the cementation structure on the surface of the aggregate is destroyed,and the fine particles are released and filled in the internal pores of the soil,resulting in the decrease of the permeability coefficient of the soil sample,so the excess pore water pressure dissipates slowly in the process of Cu shearing.With the increase of soaking time and the decrease of p H value of soaking solution,the decrease of cohesive aggregates will increase,which will lead to the decrease of cohesion and peak deviatoric stress of soil samples.(3)The samples were treated by chemical mechanical coupling triaxial acid infiltration.The results show that the permeability coefficient of the samples decreases gradually with the extension of time.The higher the acid concentration,the greater the reduction.The increase and dissipation of pore water pressure become slow due to the decrease of permeability coefficient.The peak value of cohesion and deviatoric stress of acid permeation samples are affected by the permeation time,the p H value of the permeation solution and the permeation amount.However,acid infiltration treatment has little effect on the internal friction angle of soil samples.(4)The calculated deviatoric stress of Duncan Chang model for different acid treated samples is smaller than the experimental value at low strain level,but the overall fitting degree is high,which can reflect the variation trend of stress and strain of each sample and the difference of different samples.The model parameter E_i is positively correlated with the test confining pressure,but not affected by acid pollution;The parameter(?₁-?₃)_ult was positively correlated with confining pressure and negatively correlated with chemical damage.