Model Test And Parameter Study Of Geogrid-reinforced Soil Reinforced High-fill Roadbed

New reinforced geosynthetics and retaining wall structures are widely used in subgrade slope and embankment engineering due to their unique advantages in improving subgrade instability,saving cost and protecting ecological environment.Based on this,this paper takes"model test and Parameter Research of geogrid reinforced soil reinforced high fill subgrade"as the topic,constantly consulting relevant literature to complete the preparation of subgrade model test,so as to complete the large model test of Geogrid Reinforced Subgrade and retaining wall subgrade under graded load on square foundation.Firstly,the influence of different first layer reinforcement depth,reinforcement layer number and reinforcement spacing on the settlement and bearing characteristics of high fill subgrade and retaining wall subgrade and the change of lateral displacement of retaining wall panel under graded load is analyzed.Secondly,on the basis of laboratory test,the parameters of reinforcement are refined,and the mechanical characteristics of different working conditions under graded load are simulated and utilized by FLAC^3D program of finite difference method.Thirdly,the best first layer buried depth formula of single-layer reinforcement,the prediction model of subgrade additional stress and subgrade settlement are used to verify and study the relevant parameters of high fill reinforced subgrade.Finally,combined with the relevant national norms and standards,the research conclusions are applied to the actual subgrade engineering,and relevant verification and analysis are carried out.The main research results are as follows:(1)With or without reinforcement,load series,buried depth of the first layer,reinforcement spacing and number of reinforcement layers and other parameters as variables,the reinforced subgrade model tests under different working conditions are carried out,and the vertical load deformation,post construction settlement time relationship and reinforcement strain law of composite subgrade are analyzed.The test results show that the bearing capacity of reinforced subgrade is improved under the load,and the uneven settlement is also effectively improved.Among them,the best first layer buried depth u,the best reinforcement spacing B and the maximum reinforcement depth h are 0.22B(70mm),0.45B(140mm)and 2.19B(700mm)respectively.(2)FLAC^3D program of finite difference method is used to simulate high fill reinforced subgrade,and the simulation results are in good agreement with the test results.By studying the displacement and stress nephogram under different working conditions,it is concluded that the reinforcement mechanism and stress diffusion of reinforced subgrade are basically consistent with the law of indoor test.When the reinforcement parameter variable is increased,the best buried depth U of the first layer changes from 0.22B(70mm)to 0.33B(105mm).Due to too many reinforcement parameter variables,the simulation results are further analyzed with the help of orthogonal test.It is concluded that the most influential factor on the subgrade settlement is the number of reinforcement layers,followed by the buried depth of the first layer,but the most influential factor on the subgrade ultimate load is the buried depth of the first layer,The number and depth of stiffeners are the second,and the spacing of stiffeners is the least.(3)Based on the indoor model test and related theoretical research,it is concluded that the optimal reinforcement depth of the first floor is about 0.33B(105mm)by numerical simulation,and the error is only 0.71%compared with the theoretical formula u'of the first floor reinforcement depth is 105.75mm;By comparing the theoretical calculation with the experimental data,it is concluded that the data is highly feasible and the reduction coefficient is defined.The reduction coefficient relationship is obtained by linear quasi cooperative regression analysis;The exponential model and logarithmic model can well reflect the central settlement law of high fill unreinforced and reinforced subgrade respectively.(4)For the reinforced high fill retaining wall subgrade,the reinforcement can also effectively reduce the subgrade settlement and the lateral displacement of the retaining wall panel.When the buried depth U of the first layer of single layer reinforcement is 0.22b(70mm),the subgrade settlement is the smallest,and when the number of reinforcement layers n is 5,the reinforcement effect is the best.When the stiffness of retaining wall or grid is increased,it has little effect on the ultimate bearing capacity of subgrade,but it can effectively reduce its settlement,and the effect of grid stiffness on settlement is more obvious;Regardless of the number of reinforced layers,increasing the stiffness of retaining wall or grid can effectively reduce the lateral displacement of retaining wall panel.(5)The research results are applied to the actual subgrade engineering,and the reinforced subgrade engineering is designed.The soil mechanics limit equilibrium method is used to check,analyze and check the tensile strength and uplift stability of its internal stability.Finally,when the grid reinforced earth retaining wall is applied to road engineering,the construction period is effectively shortened,the waste of land resources is greatly reduced,and the project cost is reduced.At the same time,the reinforced earth retaining wall has withstood the test of Chishui River flood and achieved the expected effect of the project.