Research On Water Migration And Structural Change Laws Of Soil And Rock Mixture Subgrade Fillers Under Seepage

A large number of loose accumulations are distributed in the mountainous areas.This geological body is mainly composed of a mixture of soil and rock.This kind of material is widely used in road construction.The types of loose accumulations are complex and diverse,which makes its engineering characteristics fall between the engineering characteristics of soil and boulders.Subgrade diseases caused by the seepage characteristics of soil-rock mixed fillers have gradually been discovered in engineering practice.The thesis takes the soil-rock mixed filler formed by alluvialdiluvial deposits in Luonan,Shaanxi as the research object,and uses the method of combining experiment and numerical simulation to study the influence of seepage effect on the road performance of the soil-rock mixed filler from the Macro and Mesoscopic.Based on the analysis of the research data on the southern line of Sichuan-Tibet Highway,Lingyan Road in Lueyang County,Luonan 344 National Road,and Ankang East Section of Shitian Highway,the following five types of typical disease forms are summarized in the soil-rock mixed subgrade: uneven settlement of subgrade,subgrade slope instability,water damage along river subgrade,debris flow on slope and surface gullies.The factors affecting soil-rock mixed filling subgrade diseases are also analyzed.The research group independently developed a test device for the seepage characteristics of soil-rock mixed fillers,and used it to conduct seepage tests of soilrock mixed fillers under different rainfall conditions to monitor the changes in the water content of the fillers.The results show that the process of water infiltration can be divided into two stages.The water content of the filler gradually increases to the saturated water content,and the rate of change of the water content is positively correlated with the rainfall intensity;Compared with the shallow part,the deep part of the filler has a hysteresis in the moisture content change;The seepage effect leads to the difference in the density and water holding capacity of the filler,and the moisture content of the filler at different depths is inconsistent in the process of water loss.The research team conducted experiments on particle loss of soil-rock mixed filler under different rainfall conditions and gradation conditions to analyze the effect of seepage on the structural characteristics of the filler.The results show that there are obvious stages of permeation and settlement;Permeable water quality,loss of finegrained components,vertical migration of particles,uneven settlement of fillers and positive correlation with rainfall intensity;When the gradation n value is 0.55,the loss rate and vertical migration of fine particles in each sample are the least,the amount of sedimentation is the smallest,and the phenomenon of uneven sedimentation is the least obvious.Based on the discrete element fluid-solid coupling calculation method,the research team monitored the particle displacement and velocity,the porosity and gradation of the filler in the seepage test from the meso scale,and analyzed the changes in the structural characteristics of the filler in the seepage effect.The results show that the particle migration process can be divided into the initial failure stage,the erosion stage and the relatively stable stage;The migration distance of coarse particles is small,and the migration distance of particles in the connected pores is large;Particle migration leads to differences in porosity and gradation of different parts of the filler.