Experimental Study And Numerical Simulation Of Geogrid-reinforced Foundation Under Dynamic Loading

Geogrid-reinforcement was widely used in reinforced foundation,reinforced embankment and other engineering areas.The study on the bearing capacity of reinforced foundation was mainly based on the static load,and the failure mechanism of the reinforced foundation under dynamic loading was still lack of enough understanding.Based on this,this paper was based on the “Experimental study and numerical simulation of geogrid-reinforced foundation under dynamic loading”.Through the previous research work on the relevant literature and experimental conditions of the project,a series of large-scale model tests were designed and completed to investigate the load-bearing characteristics and failure modes of square footing resting on unreinforced and reinforced foundation.The reinforcement parameters varying in the tests include the number of reinforcement layers(N),the depth of the first layer(u)and the wraparound way of reinforcement ends.In addition,the calculation formula of the ultimate bearing capacity of reinforced foundation under static and dynamic loading was derived and the optimum depth of the first reinforcement layer was modified.The corresponding recommendations are given for the design and application of reinforced-foundation engineering.The main conclusions are summarized below:1.Through a series of large-scale square footing tests,the influence of various reinforcement parameters like foundation whether to reinforcement or not,static and dynamic loading,the number of reinforcement layers(N),the depth of the first layer(u)and the wraparound way of reinforcement ends on the bearing capacity improvement of footings were studied.Bearing capacity and failure mode of footings on unreinforced sand and geogrid-reinforced sand were evaluted by analyzing the variation law of load-settlement(P-s),foundation earth pressure,strain-value of geogrid,acceleration response and other parameters.2.Based on the results of large-scale square footing tests under dynamic loading,through the bearing capacity ratio(BCR)and the dynamic acceleration response degree,the influence of the N,the u and the wraparound way of reinforcement ends on the bearing capacity of square footing and the ability of resisting dynamic load was emphatically studied.3.Based on the “FLAC3D Finite Difference” software,a static loading numerical method for reinforced foundation was established.The evolution law of the internal stress and strain field of geogrid-reinforced sand and the deformation characteristics of geogrid-reinforcement during loading were simulated.By comparing with the experimental results of the existing indoor model,the bearing performance and the reinforcement-mechanism of geogrid-reinforced foundation were revealed from the perspective of internal evolution of the reinforced-soil.4.Through the basic assumptions and simplified calculations,and based on the dynamic loading model test results and the existing literature research results,the calculation formula of the ultimate bearing capacity was developed for reinforced foundation under static and dynamic loading.Meanwhile,the calculation formula of the optimum depth of the first reinforcement layer(u’)was elaborately improved.5.Through the analysis of the design theory and failure modes of reinforced foundations,based on research results of the existing scholars on the reinforcement parameters,and then combined with the current national norms and standards,from the results of dynamic response in this paper,some beneficial suggestions for the optimum design of reinforced-foundation engineering were proposed.