Study On Wetting Deformation Characteristics Of Metamorphic Soft Rock Fillers

Soft rock filler will disintegrate and expand under the action of water,which will cause wetting deformation of filler,which will affect the service life of highway and driving safety.Therefore,it is necessary to study the properties of metamorphic soft rock,especially the deformation after immersion.In this paper,the soft rock roadbed filling is taken as the research object,and the deformation properties and Micro-changes of metamorphic soft rock before and after immersion are studied through laboratory tests and discrete element method.The main work is as follows:(1)The mineral composition of the test material was analyzed by means of abrasive discs and scanning electron microscopy test of rocks.Meanwhile,the material was named according to the specifications,and the internal structure characteristics and mineral content of the rock were studied.The uniaxial compressive strength of rocks was tested by uniaxial compressive test.The results show that the saturated uniaxial compressive strength of the test material is less than 30 MPa and belongs to soft rock category.(2)The triaxial compression tests of metamorphic soft rock were carried out under airdried and saturated conditions respectively,and the stress-strain characteristics of the material under air-dried and saturated conditions were obtained.According to the test results,the variation characteristics of axial stress-strain and volume-strain-axial strain of materials are analyzed.The relationship between maximum deviating stress and confining pressure of samples under various confining pressures is studied,and the empirical formulas between maximum deviating stress and confining pressure of materials under saturated and air-dried conditions are obtained.(3)According to the triaxial compression test results of the material,the wetting deformation of metamorphic soft rock is calculated by subtracting the strain value of the material under the condition of saturation from the strain value under the condition of air drying,and the law of the wetting deformation of metamorphic soft rock is obtained.According to the experimental results under three confining pressures,the empirical formula of the material's wetting deformation is given,and the formula is verified by the laboratory test results under the fourth confining pressure.(4)The discrete element method is used to simulate the triaxial compression test of metamorphic soft rock.The empirical formula between macro and micro parameters is given through calibration.The contact force,force chain,contact fabric and average displacement between particles were studied,and the changing rules of these microstructures were obtained.The changing rules of air drying and saturation were compared,and the influence of humidification on the change of particle microstructure was obtained.