Study On Scaling Effects Of Large-scale Direct Shear Tests Of Soil-rock Mixtures With Particle Breakage

The economic prosperity of Southwest China cannot be separated from the contribution of the Western Development Strategy.The construction of transportation lines is in full swing,especially the airports.The southwest region is mostly mountainous and has complex topography,forming many high filling slopes.As the main filling material,the soil-rock mixture has also been more widely used in airport engineering construction.Due to the large scale of the soil-rock mixture in actual engineering,the prototype scale ingredients need to be scaled down when carrying out laboratory tests to determine its physical and mechanical parameters,which results in the difference in mechanical properties between the indoor sample and the real soil-rock mixture,that is,the scale effect.And during the loading process,the particles of the soil-rock mixture will be obviously broken,which has a significant effect on the shear characteristics.Therefore,the analysis of the scaling effect of soil-rock mixture considering particle fragmentation can provide reference for the stability research of high fill slope engineering in mountainous area.Based on laboratory and numerical experiments,the scale effect of soil-rock mixture with particle fragmentation is studied.In this paper,four scaling methods and three groups of different maximum particle sizes are adopted to scale the original grading of soil-rock mixture of Xiannushan airport construction project in Wulong,Chongqing.The influence of the scaling method and the maximum particle size on the shear stress-shear displacement curve of the soil-rock mixture is revealed by the large-scale direct shear test.The indoor sieving test is used to determine the grain composition after shearing,and the effect of the scaling method and the maximum particle size on the changes of the grain group content of the soil-rock mixture before and after shearing is studied.The programming of FISH language based on Monte Carlo method is carried out by using PFC particle flow program.The particle size,position,azimuth,and unevenness of the stone are comprehensively considered to realize the simulation of random polygonal stone.Based on the theory of cohesive particle method,Cluster is used to realize the simulation of particle fragmentation.Through parameter calibration,the microparameters of the numerical model are determined,so that the established numerical model can invert the real test process.Numerical experiments are performed using the constructed soil-rock mixture numerical model,and the effects of the scaling method and the maximum particle size on the shear strength and strength index of the soil-rock mixture are analyzed.In order to quantitatively study the characteristics of particle crushing,the definition of relative crushing rate is introduced,and the influence of the scaling method and maximum particle size on the particle crushing degree is discussed.The numerical simulation of the prototype full-scale batch sample is carried out,and the combination of the best scale method and the largest particle size is selected.Ensure that other conditions are the same,set different sample sizes and parent rock strengths,and establish multiple numerical models for experimental research.And the influence of the two factors of scaling effect on the shear characteristics and particle crushing degree is discussed.