Study On Macroscopic And Meso Mechanical Characteristics Of Coarse-Grained Soil Fillers Based On Triaxial And CT Test

Coarse-grained soil is an indispensable roadbed filler during the construction of the highway.There will be large differences in mechanical properties,due to the influence of internal and external factors,resulting in a decrease in the serviceability of coarse-grained soil embankments.In order to fully understand the variation of macro-mechanical properties of coarse-grained soil filler under various influencing factors,this paper analysis of the coarse-grained soil stress-strain characteristics of packing under static load and structure of CT damage evolution law through the indoor test analysis,combined with the National Natural Science Fund Project "The temporal and spatial evolution law of the temporary saturated zone of high embankment slope with coarse soil under extreme rainfall conditions and the mechanism of disaster(51508042)",taking Coarse-grain soil roadbed filling for the first contract section of Longlang highway in Hunan Province as the research object And this paper systematically and deeply studies the mechanical properties and influencing factors of coarse-grained soil from both macroscopic and microscopic perspectives,by using numerical simulation analyse the microscopic mechanical properties of the stress chain and velocity field in the sample.The main research achievements are as follows:(1)When the strain rate of coarse-grained soil specimens does not reach 3%,this stage is mainly the compaction between coarse-grained soil particles,compaction to compress mainly between particles,supplemented by lateral expansion,the density increase caused by the compression and compaction between particles is much larger than the density reduction caused by the lateral expansion deformation of the transverse test piece;When the strain rate of the test piece exceeds 3%,the density reduction caused by the lateral deformation of the test piece increases rapidly,and the increase in density caused by compression and compaction between particles slows down,therefore,showing a gradual phase in later stages.(2)Through the stress-strain curve of coarse soil filler under static load,it can be inferred that confining pressure,degree of compaction and moisture content are all factors that control the mechanical strength of the filler.as the main control factors including moisture content,can cause the softening and rheological effect between particles,makes the sharp decline in the shear strength and more likely to occur large sliding deformation;As a secondary control factor,degree of compaction and confining pressure can cause compression deformation.(3)There is a big difference in density and CT value during Coarse grain test piece initial state,with the triaxial test,the extrusion density of local particles in the cross-section increased,and the proportion of high-density areas increased significantly,the proportion of low-density areas decreased gradually,and the difference of CT values in the scanning layer decreased in the final state;The sample particles have the phenomenon of compaction,dislocation and fusion under the action of partial stress.(4)Analysis of the development trend of the velocity field and contact force chain of coarse-grained soil particles in numerical simulation,the shear deformation distribution inside the sample is obtained,the higher the confining pressure and the higher the water content,the earlier the formation of the bond chain break and the shear plane formed in the sample,the internal evolution law is consistent with the change law of stress-strain curve.The research results of this paper have certain guiding significance for the design of roadbed,stability evaluation in highway construction,and have certain theoretical and engineering practical significance.