Study On Meso‐mechanical Properties Of Rubber‐sand Composite Soil

On the one hand,the "black pollution" caused by waste tires is more and more serious,on the other hand,the Inner Mongolia region to repair the road there is a big part in the desert,sand to build roadbed generally USES local materials,in order to solve the problem of the above-mentioned two aspects: in the aeolian sand mixed with rubber particles,sand formed by rubber composite soil can improve the shear strength of the aeolian sand.The shear strength and bearing ratio tests of rubber-sand composite soil were carried out in the laboratory.On the basis of the laboratory tests,the structural characteristics of rubber-sand composite soil were studied by means of meso-analysis method,and the influences of various factors on its deformation and shear strength were analyzed,and the main influencing factors and rules were determined.The numerical model of direct shear test was established by comparing the microstructure parameters with the macroscopic state.The microscopic mechanical properties of basic mechanics were studied and analyzed by using PFC2 D software.The variation of force chain and velocity field in the shear process of granular materials in numerical model is studied.The influences of the friction coefficient,porosity,contact stiffness and shear rate on the macroscopic mechanical properties of cement-sand composite soil were analyzed.The conclusions are as follows:(1)through the heavy compaction method,respectively,of aeolian sand and rubber sand mixed soil compaction test,determine the optimum moisture content and maximum dry density,and analyzes the relationship between dry density and moisture content changes,the change trend of both types of as the "double peak" curve,with the increase of water content,dry density decreases first increases and then decreases.In the case of rubber particles with the same particle size,with the increase of the mixing amount of rubber particles,the dry density showed a decreasing trend.(2)Through the load-bearing ratio test,the penetration of rubber-sand composite soil increases with the increase of unit pressure.When the content of rubber particles is0%-40%,it can meet the technical requirements of subgrade use,thus further verifying the feasibility of mixing rubber particles into sand.(3)Through the direct shear test,it was found that under the same particle size of rubber particles,with the increase of the content of rubber particles,the internal friction and cohesion of rubber sand composite soil first increased,then decreased,and then increased.Under different rubber particle size,with the increase of rubber particle size,the internal friction Angle and cohesion of rubber-sand composite soil decreased as a whole.Under the same vertical pressure,with the increase of rubber particle content,the shear strength of composite soil showed a trend of first increasing,then decreasing and then increasing.Under the action of rubber particles with different particle sizes,the shear strength of composite soil decreases.The shear strength of composite soil with rubber particles is the highest when the content of rubber particles is 30% and the particle size is1.18 mm.Therefore,the content of rubber particles is 30% and the particle size is 1.18 mm.(4)The numerical model of PFC2 D direct shear test was established,and the simulation parameters of the model were calibrated.The numerical simulation of direct shear test was carried out for the composite soil with 30% rubber particle size of 1.18 mm.The simulated stress-strain values were basically consistent with the laboratory test results,which indicated the accuracy of the simulation test results of discrete element particle flow software.(5)Sensitivity analysis was conducted on the corresponding mesoscopic parameters(contact stiffness,friction coefficient,porosity ratio,shear rate,effective modulus)to study the effect of mesoscopic parameters on macroscopic mechanical properties.