Study On The Effects Of Acid Rain-high Temperature Alternation On Physical And Mechanical Properties Of Marl

The high temperature in Chongqing is abnormal in summer and the acid rain occurs frequently.The mudstone strata exposed to the surface and developed along the Jialing River are seriously damaged under the alternating action of acid rain and high temperature for a long time.Therefore,it is very important to study the physical and mechanical characteristics and deterioration effect of marl under the alternating action of acid rain and high temperature.In this paper,the alternating action of acid solution and high temperature is used to simulate the alternating action of acid rain and high temperature.Firstly,the laboratory test is used to simulate triaxial compression,and then the variation law of physical and mechanical properties of marl is analyzed.The deterioration effect of marl under the alternating action of acid rain and high temperature is obtained.The main research contents and results are as follows:(1)By means of X ray diffraction,electron microscope scanning and heavy measurement,it is found that the calcite content decreases gradually with the increase of acid rain-high temperature alternating action times,the proportion of calcite content decreases by 3% after acid rain-high temperature alternating action 20 times,and the clay mineral content has no obvious change rule;the shape of marl mineral particles will gradually change,and the connection between each mineral particle will gradually change from tight to loose;The quality is continuously reduced,the stage quality loss rate shows the trend of rising first and then decreasing,and the dry weight changes more than the mass loss.(2)Uniaxial compression test,conventional triaxial compression test and Brazilian splitting test for rock specimens subjected to acid rain-high temperature alternation.Under uniaxial compression test,with the increase of acid rain-high temperature alternating times,the uniaxial compressive strength of marl is more uniform in each stage before 15 times of acid rain-high temperature alternating action.The elastic modulus decreases rapidly and then stabilizes with the increase of action times.Under the same confining pressure,with the increase of acid rain-high temperature alternating times,the triaxial compressive strength,triaxial elastic modulus and triaxial deformation modulus of marl show a decreasing trend,and the decreasing trend is generally the same,while the cohesion and internal friction angle decrease rapidly and then tend to stabilize with the increase of acid rain-high temperature alternating times.The effect of acid rain-high temperature alternation on the triaxial mechanical properties of marl is inhibited by confining pressure.Under the splitting test in Brazil,the effect of acid rain and high temperature alternation on tensile strength was only 0.65,but the proportion of marl tensile strength decreased in 5 to 10 stages.After 15 times of acid rain and high temperature alternation,the rate of marl tensile strength decreased.(3)Through the analysis of the PFC numerical triaxial marl failure model,it is found that with the increase of acid rain-high temperature alternating times,the more cracks and the more severe deterioration of marl specimens,the development trend of the cracks is similar to that of indoor tests.At the same time,with the increase of alternating times,the shear crack of marl specimen increases gradually,the brittleness weakens gradually,the ductility increases gradually,and the failure crack increases.The pressure contact force chain and the tensile contact force chain are distributed inside the specimen under different alternating times,but the distribution of the internal pressure contact force chain is obviously more than that of the tensile contact force chain under the compressive stress.And the load is larger than the tensile contact force chain.Under the same confining pressure,the contact force chain of particles increases with the increase of acid rain and high temperature,and the load of marl specimen is proportional to the number of times of alternating action.The more acid rain-high temperature alternating times,the more serious the marl particle strength deterioration.(4)The deterioration degree of mud limestone property parameters under the alternating action of acid rain and high temperature is defined,and the total deterioration degree,stage deterioration degree and average deterioration degree in stage are calculated.The mechanical and physical deterioration effects of marl under alternating acid rain and high temperature are analyzed.The process of marl deterioration under alternating acid rain and high temperature is divided into primary water absorption deterioration stage,deterioration aggravation stage,damage expansion stage and damage stability development stage.