Study On Size Effect Of Shear Properties Of Soil-Rock Mixture

As a commonly used filler for high fill embankments,soil-rock mixtures often use shear strength parameters obtained from indoor scale tests in engineering design.Due to the significant difference in particle size between the original grading and indoor scale grading,as well as differences in indoor sample size,there is a significant difference(i.e.size effect)between the shear strength parameters and the actual values.Currently,research on the size effect of soil and rock mixtures is still in the qualitative stage.Based on this,this thesis carried out a study on the size effect of shear characteristics of soil-rock mixture.The influence law of scaling method,maximum particle size and sample size on the shear strength of soil-rock mixture was studied through the combination of laboratory test and numerical simulation test,and the size effect mechanism of strength was revealed from the macroscopic and microscopic perspectives.It provides reference for slope stability research of high fill subgrade engineering in mountainous and heavy hilly areas.The main research contents and achievements are as follows:(1)By self-made direct shear instrument with variable size,laboratory tests were carried out on soil-rock mixture samples with different scaling methods,sample sizes and maximum particle sizes,and the influence law of size effect on shear stress-shear strain relationship curve,shear strength and strength parameters of soil-rock mixture was obtained.(2)Based on image processing technology,the shape of stone particles in the laboratory test was obtained from the computer,and the FISH language programming in PFC2 D software was used to generate a particle Cluster that could simulate the more real movement and fragmentation of stone.(3)The size effect of shear characteristics of soil-rock mixture was studied based on discrete element numerical simulation test.Based on the laboratory test results,the mesoscale parameters of the discrete element numerical simulation test were calibrated by the trial-and-error method,and the evolution laws of the force chain and particle velocity of the soil-rock mixture in the shear process,as well as the evolution laws of particle movement and crack under different scaling methods,sample size and maximum particle size were obtained,which were complementary to the results of the laboratory test.(4)Based on the constructed numerical simulation direct shear test,the influence of size effect factors on the shear characteristics of soil-rock mixture was studied.By changing the parallel bond strength and particle formation content,the direct shear tests of the soil-rock mixture with different strength and initial porosity were simulated,and the influences of the direct shear tests on the shear stress-shear strain relationship curve,shear strength and strength parameters,particle movement evolution process and crack evolution process were obtained.