Study On The Mechanics And Wave Characteristics Of Granite Residual Soil In Hot And Rainy Environment

In the southeastern China,it's hot and rainy during summer.Besides,the temperature of the ground surface changes frequently and greatly.In some places,the harm of acid rain is more and more serious.Under the long-term effects of environmental factors exert significant influences on mechanical and acoustic properties of saturated granite residual soil.In this paper,the saturated granite residual soil is selected as the research object.Three kinds of indoor simulation tests are carried out on the environmental factors under these climatic conditions.Immersion test is used to simulate long time rainfall and acid rain environment.Wet and dry cycles are used to simulate fine-rainy alternation in summer.The water content cycles at different temperature is used to simulate the effect of rainfall on residual soil at different surface temperature.Based on these above,the variation law of residual soil of saturated granite under different environmental factors was studied.The test contents and results are as follows:(1)The residual soil samples were soaked respectively in water and H2SO4 solution whose concentration were 1%,3%,5%and 7%.The direct shear tests and acoustic tests were carried out on these soil samples at different time gradient in 40 day after the samples were saturated.Results show that as follows.The cohesion,internal friction angle and average p-wave velocity of the residual soil samples that were soaked in clear water all showed exponential decay.With the immersion time increasing,the shear strength and average p-wave velocity descended fast firstly,then slow,then fluctuated slightly,then descended slightly and lastly stable.The damage modulus increased with the concentration of the H2SO4 solution increasing at the same time gradient and at the same immersion time.But the increasing range of the damage modulus was slight in the concentration of 5%-7%.(2)Saturating-drying-saturating cycles test was carried out on the granite residual soil.And after each cycle,the direct shear tests and acoustic tests were carried out on these soil samples to study the law of wet and dry cycles of residual soil.Results show that as follows.The cohesion,internal friction angle and average p-wave velocity of the residual soil samples showed exponential decay as the number of cycles increased,but the change of internal friction angle was not obvious.The damage modulus defined by the wave velocity was the same with that defined by the cohesion on the whole in the same cycle times.The damage modulus increased fast firstly,then slow and lastly stable as cycle number increased in the same cycle times.(3)Taking the water content of soil samples range from 25%to 10%to 25%as a cycle,direct shear tests and acoustic test was used to research temperature effect on strength evolution of saturated granite residual soil under multiple water content cycles at 30?.40 ??50 ??60 ? and 70 ? respectively.Results show that as follows.In each temperature,the cohesion and P-wave velocity descended fast firstly,then slow and lastly stable as cycle number increased.The decreasing range of cohesion was obvious when cycle number was 2 and cycle temperature was 50 ??60 ? and 70 ?.The cohesion and P-wave velocity was larger with increasing cycle temperature under the,same cycle number.The damage variable increased fast firstly,then slow and lastly stable as cycle number increased.The damage variable was larger with increasing cycle temperature under the same cycle number.The relation between average P-wave velocity and cohesion obeys the logarithmic correlation well.The results of this paper are of great significance to the strengthening treatment of slope engineering and underground engineering and the prevention and control of geological disasters of granite residual soil in the southeastern China.