| In the area of sandstone and mudstone,considering thisparticle mixture hasplenty of advantages,such as broad scope ofdistribution,high strength and small deformation,it is widely used in embankment engineering.Compared to the research status of common gravel-soil,the study of sandstone-mudstone mixture particles is in the stage of rapid development.The research based on numerical simulation technique,such as PFC software,is becoming a new research hotspot.As we all know that PFC simulation techniquewith a quick,economic and other advantages.But there is lots of factors effect on the reliability of result.This paper relies on the National Natural Science Foundation of China,which named “Mechanism and evolutionary process of deterioration on a sandstone-mudstone paticle mixture induced by periodic saturation(No.51479012)”.The modeling method andmesoscopic mechanical properties of sandstone,mudstone and their particle mixture are studied by basing on the traditional test data,combining the discrete element method's advantage of studing gravel-soil,and appling the digital image process method to analyze the mesostructure.The mainly results are listed as follows:(1)The microstructure of core sample and the mesostructure of granular material sample are analyzed by appling digital image process method.Moreover,in order to an efficient calculation,gradation characteristics of gravel-soil sample are studied and “fine particles” are replaced with big ones 4 times by the modification method based on PFC2 D software.Furthermore,particle size range of the basic particle element of sandstone's and mudstone's core samplewas identified,which is as well as the smallest particle size range of the granular material sample.And its value range is 0.5mm-1mm.(2)According to the microstructure of core sample and the mesostructure of granular material sample,core sample's PFC2 D model of sandstone and mudstone,as well as granular material sample's PFC2 D model of sandstone and mudstone werebuilt.In PFC2 D,the minimal element of core sample is the basic particle element,and the core sample is made up of deferent basic particles which are bonded together by viscous contact property.The minimal elememt of granular material is rock block,which is located by random region division.The properties of rock block is same to the core sample,and the rock block can regard as a part of core sample.However,the interaction of deferent rock block is simulated by non viscous contact property.The results show that the simulation effects of core sample's PFC2 D model and granular material sample's PFC2 D model accord with the actual circumstan and behave well.(3)According to the principle of the uniaxial compressive test indoor,the uniaxial compressive test system based on PFC2 D is built.Sensitivity of property parameters are analyzed by using the system and the model above-mentioned.Moreover,the impact of each micro parameter on the stress-strain curves and failure modes are comprehensively analyzed,the classification of micro parameter is divided,and the thought of determining the micro parameter is put forward.Whatmore,the micro parameters' value of sandstone and mudstone are fitted by basing on the stress-strain curves and failure modes.The results show that the relationship between macro property of the test sample and micro parameters is fitted well.(4)According to the principle of trixial shear test indoor,the triaxial shear test system based on PFC2 D is built.The triaxial shear test of granular material of sandstone and mudstone are simulated by according to the test system,the sample model of granular material,and the established micro parameters above-mentioned.Moreover,the simulation results are analyzed from mechanical and deformation characteristicsaspect and contacts falure aspect.Whatmore,the deformation evolution process of the gradual slope is explained by a micro-perspective way based on the result of the granular material'striaxial shear test simulation. |
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