Attenuation Law Of The Mechanical Properties Of Granite Residual Soil And Design Of Compensation Layer For Roadbed

Granite residual soil is a special soil that spread widely in China.It has some special features such as low deformation resistance,inferior water stability,poor dynamic stability and mean intensity index.When Granite soil is used as highway's roadbed,its stiffness and strength decay when exposed to external moisture and load from long-term operation,which impacts highway's performance and service time.Therefore,studying granite soil's decay law of strength and stiffness is of practical significance.Our paper is based on findings from the GUANGFOZHAO highway project.Our main work and research achievements are:(1)Firstly,we obtained geotechnical parameters of granite residual soil from indoor geotechnical experiment.Then we gain the soil-water characteristic curves under different dry densities using Arya-Paris models and grain analysis curves.After that we measured the saturation permeability coefficient from geotechnical tests.Finally,based on soil-water characteristic curves,saturation permeability coefficient,and V-G models,by fitting to GeoStudio software we get the unsaturated permeability coefficients of granite residual soil in different dry densities.(2)Secondly,this paper simulated the impact of climate and groundwater on granite residual roadbed internal moisture field with GeoStudio software.Researches show that when a new roadbed was first built,internal humidity increases for a while;after a period of time,humidity stop increasing and an equilibrium is achieved.Impacts of rainfall on roadbed humidity could be negligible after the equilibrium.(3)We tested the strength and stiffness of compacted granite residual soil in different moisture content.Results suggest that there is a close relationship between granite residual soil strength&stiffness and moisture content&stress state.Based on our experimental parameters,by fitting to NCHPR1-28A model,we get the correlation curves of granite residual soil roadbed.resilient modulus and moisture.(4)Using ABAQUS software,this paper simulated the long-term loading displacement field of granite residual soil roadbed with and without compensation layer.Our research shows that:laying compensation layer on the top of granite residual soil roadbed is an effective compensatory.Effectiveness of compensation layer on different location,thickness and material can be compared so we can choose appropriate compensation layer after balancing the economy and security cost.