| Coal measure soil is a kind of special soil with poor engineering performance because of its weak quality,large carbon content,easy weathering and disintegration when exposed to water,and easy structure destruction and loss of strength.Under the condition of rainfall,this kind of soft rock mass of coal measure is easy to cause slope instability.The study of coal measures soil carried out mainly from a macro level,the existing literature from the perspective of soil micro view not the mesoscopic mechanism of coal soil macro mechanical characteristics analysis and interpretation,this paper,taking jiangxi province pingxiang to lotus coal soil slopes of highway project as the engineering background,the discrete element method coupled with computational fluid dynamics methods,from the point of view of micro analysis coal soil slope under rainfall infiltration of the failure mechanism of instability.The main work content is as follows:1.Analysis of the influence of soil microscopic parameters on the macroscopic mechanical response(characteristics)of coal-measure soil.The strength parameters of coal-measure soil slope were obtained by triaxial test.From mesoscopic point of view,using the discrete element method,established the three-dimensional numerical model of compression triaxial test,the mesoscopic parameters of different particles(such as particle diameter,particle tangential shear stiffness and normal shear stiffness,particle friction coefficient,particle bonding strength,etc.),different degree of particle geometry and particle breakage on the influence law of macro mechanical response of soil are calculated.The results show that the geometry of particles has a great influence on the shear strength of soil,the bond strength,friction coefficient and stiffness of particles have a great influence on the shear strength of soil,and the breakage of particles will lead to the decrease of soil strength.2.The formation and evolution mechanism of coal measure soil shear zone were studied from the perspective of micro-observation.A three-dimensional numerical model of triaxial test for coal-measure soil was established by using the discrete element method to simulate the macroscopic mechanical response of the sample during the loading process of coal-measure soil,and the development and change rules of particle rotation,volume fraction,coordination number and force chain were analyzed,and the formation and evolution process of the shear zone of coal-measure soil was discussed from a microscopic perspective.The results show that the particle rotation is the main cause of the formation of shear band,and the particle rotation in the shear band area is more likely to occur during the loading process.The porosity of soil in shear zone increases gradually,the coordination number between particles decreases gradually,and the contact between particles is worse than that outside shear zone.At the same time,the softening of samples is closely related tothe formation of shear bands.3.Using DEM-CFD coupling method,the failure mechanism of coal measure soil slope under rainfall infiltration was studied from a microscopic perspective.Taking the outdoor slope model test of coal-measure soil as the simulation object,the DEM(Discrete element Method)and computational fluid Dynamics(CFD)are coupled to establish the THREE-DIMENSIONAL numerical calculation model of the coupled DEM(DEM)of coal-measure soil slope,and the failure process of the model of coal-measure soil slope under the action of rainfall infiltration is simulated and analyzed.Results found that the coal measures in instability and failure of soil slope is the main mode of the rain,the approximate linear prediction of sliding surface of slope,the slope model test results very close to the outdoor,use DEM-CFD fluid solid coupling method to analyze coal soil slope instability mechanism is feasible,for slope stability from the perspective of mesoscopic analysis provides a new train of thought. |
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