Research On The Interface Of Geogrid-Reinforced Sands Under Different Loading Conditions

Geogrid reinforced soil structure has been widely used in retaining wall,subgrade foundation and slope engineering field,which is based on economy,stability,convenience,applicability and beauty.Load of reinforced earth structure under normal circumstances changes arbitrarily,and in the long-term fixed loads of reinforced soil structure will creep in the deformation.Therefore,researches on the characteristics of the interface of geogrid-reinforced sands were carried out through laboratory tests and numerical simulation,considering the loading rate and loading mode,which provides a technical reference for the reinforced soil engineering practice.The main research work of this paper is as follows:(1)Based on the large direct shear test of geogrid reinforced sands,the strength characteristics of reinforced sands were analyzed under different vertical loads.The deformation and strength characteristics of reinforced soil interface were studied under different conditions which contain constant rate of loading,variable rate of loading,creep and stress relaxation.The stress variation law of geogrid-reinforced sands was analyzed quantitatively in the case of variable shear rate.The displacement characteristics of geogrid-reinforced sands during shear creep and the stress variation in the process of stress relaxation were analyzed.(2)Based on the results of laboratory direct shear test,numerical simulation of direct shear test was carried out for geogrid-reinforced sands under various loading conditions.The characteristic analysis of the changing rate case by indoor experiment was expanded.An empirical formula and the rate sensitive coefficient were proposed for the variation of shear stress under variable rate condition.In this paper,the coordination number,porosity and average stress of sands near the interface between reinforcement and soils were analyzed,which reflect the variation characteristics of meso parameters in the vicinity of the interface between reinforcement and soil in the process of direct shear.(3)The displacement of reinforced sands under the condition of complex loading was analyzed by the plane strain compression test of geogrid-reinforced sands.The migration law of sands and the formation of shear bands were revealed.(4)Based on laboratory plane strain compression test,numerical simulation of strain compression test was carried out for geogrid-reinforced under various loading conditions.The superiority of the Burger's contact model in the simulation of creep and stress relaxation was shown by comparing the linear elastic contact model with the Burger's contact model.Through the simulation of particle flow,the rate dependent characteristics,creep and stress relaxation characteristics are verified and reproduced.Based on the analysis of the sands near the reinforcement,the internal characteristics of the reinforced sand in the compression process are obtained,which provides the basis for the analysis of the whole strength and deformation characteristics.