Study On The Law Of Deformation And Failure Factors Of Reinforced Soil Subgrade Of Yan'an Highway In Operation Period

It is of great practical significance to study the deformation and failure factors of reinforced soil roadbed in operation period and to understand the law of action of each factor for disaster prevention and mitigation of reinforced soil roadbed and its popularization and application.Based on the reinforced soil roadbed of Yan'an trunk highway,through on-site investigation,indoor test and theoretical formula deduction,this paper mainly explores the action factors of deformation and failure of reinforced soil roadbed in operation stage and the law of action of each factor.The main research contents and results are as follows:(1)Based on the field investigation of eight reinforced soil subgrades in the study area,the deformation and failure modes of reinforced soil subgrade are summarized: the overall failure mode,the local failure mode and the accumulation mode of deformation.The load factor,the environmental factor and the time factor are the three main factors affecting the deformation and failure.(2)Static load model tests with a similarity ratio of 1:0.25 were carried out.The maximum horizontal displacement is about 0.02% of the roadbed height after the stage loading,which occurs at the height of 0.61 times of the roadbed,and the maximum vertical settlement is about 0.24% of the roadbed height,which occurs near the side of the loading plate.The earth pressure on the upper part of the roadbed is greatly affected by the external load.The increase of static load has little effect on the deformation of subgrade and strain of geogrid,and the deformation of subgrade is mainly controlled by the compactness of filler.(3)Dynamic triaxial tests were carried out to simulate the cyclic effect of vehicles.The cumulative plastic strain of reinforced soil specimens increased steadily with the increase of loading cycles at low amplitude.The regularity can be well fitted by the improved Monismith model.The stability value of cumulative plastic strain,the growth rate of dynamic strain and the number of load cycles needed to achieve deformation stability all changed with the increase of loading cycles.In the analysis of numerical simulation examples,the maximum vertical settlement of subgrade occurs at the outer wheel,the maximum horizontal deformation occurs at the height of 0.36-0.41 times of the subgrade,the deformation increases significantly with the increase of vehicle load,and the deformation value tends to be stable with the increase of the number of dynamic load cycles.(4)The direct shear friction test of reinforced soil interface was carried out.When the moisture content of filler was constant,the shear stress of reinforced soil interface increased with the increase of shear displacement,and then gradually stabilized.The higher the moisture content of filler,the smaller the peak value of interface shear stress and the friction coefficient between reinforcement and soil,the lower the uplift stability coefficient of reinforced soil roadbed.(5)Based on the self-consistent theory,the calculating method of the micro-strain ratio of reinforced soil in reinforced composites is deduced.Then the formula is applied to the derivation of the stress-strain relationship of reinforced composites considering time factors.The expression of the horizontal strain of reinforced composites is obtained,and the key parameters affecting the development speed of deformation and the final deformation amount are determined.Then an example is selected to analyze the regularity of the formula.The horizontal strain of reinforced composites mainly occurs in the plastic deformation stage,which increases with the development of time,but decreases gradually,and finally tends to be stable.