Study On Structure Behavior And Influencing Factors Of Three-Stage Composite Panel Wrapped Reinforced Soil Retaining Wall

With the rapid development of economy,the scale of infrastructure construction has been expanding,and the background of engineering construction has gradually shifted from plain low fill to high fill projects in mountainous areas.Single-stage reinforced earth retaining wall can no longer meet the needs of engineering,and multi-stage reinforced earth retaining wall and new panel form of reinforced earth retaining wall continue to emerge.In this thesis,the three-stage composite panel-wrapped reinforced soil retaining wall of Yichang East Railway Station from Jingmen to Yichang of Shanghai-Chongqing-Chengdu high-speed railway is taken as the research object.Based on PLAXIS^2D finite element numerical simulation,the design and optimization technology of three-stage reinforced soil retaining wall is studied,and its deformation trend and stress characteristics during construction are analyzed.The main research contents and conclusions are as follows:（1）The reinforcement principle and failure form of composite panel wrapped reinforced earth retaining wall are introduced.The design of two-stage reinforced earth retaining wall is based on FHWA code,and the design calculation method of three-stage reinforced earth retaining wall is discussed from two aspects of internal stability and external stability.（2）The material properties of reinforced soil retaining wall,such as field filling and geogrid,are measured by screening test,triaxial test,geogrid tensile test and pull-out test of reinforced soil interface,which provides a reference for the subsequent numerical simulation of three-stage reinforced soil retaining wall.（3）The numerical model of reinforced soil retaining wall during construction is established by using PLAXIS^2D finite element software.The safety check of the retaining wall design scheme is carried out,and the structural behavior change is studied.The results show that the overall deformation trend of the retaining wall at all levels is different,and there is a sudden change in displacement at the steps.Due to the step load reduction effect,the horizontal earth pressure on the back of the wall presents a"sawtooth"distribution along the height of the retaining wall.With the increase of the depth behind the wall,the abrupt trend of"sawtooth"is weakened,and the horizontal earth pressure gradually tends to the active earth pressure value.The vertical stress at different heights of the retaining wall is nonlinearly distributed along the length direction of the reinforcement,and concave deformation occurs at the end of the reinforcement.The tensile force of each layer of grille shows a curve distribution along the horizontal direction of the wall back,and there are two peak phenomena of“single peak”and“double peak”.The potential fracture surface formed by the connection of the maximum tensile point of each layer is close to the theoretical fracture surface.（4）Using the method of controlling variables,the influence of filling properties（elastic modulus,cohesion,internal friction angle）,reinforcement properties（vertical spacing,length,stiffness）,step width,anti-slide pile and post-construction time on the settlement deformation of retaining wall,the maximum tension of reinforcement,safety factor and potential fracture surface is simulated and analyzed.The results show that the horizontal displacement of the retaining wall is significantly affected by the nature of the fill,the width of the steps and the presence or absence of anti-slide piles.The length and stiffness of the reinforcement are not the main factors affecting the horizontal deformation of the retaining wall within the scope of the study.The settlement of the wall top is significantly affected by the nature of the fill,the length and spacing of the reinforcement and the anti-slide pile.The cohesion of the filling soil,the internal friction angle and the step width have the most obvious influence on the maximum tension of the first and second retaining wall grilles.When the cohesion,internal friction angle,reinforcement length,spacing,step width and anti-slide pile are changed,the safety factor of the retaining wall is obviously improved,and the potential rupture surface of the retaining wall moves towards the non-reinforced area and the depth of the foundation.In the study range of filling modulus and reinforcement stiffness,the safety factor changes little,and the potential rupture surface of the retaining wall does not change significantly.In different periods after construction,the settlement deformation and safety factor of the retaining wall change little,which meets the requirements of the specification.（5）The construction technology,monitoring scheme and various monitoring instruments of the three-stage composite panel wrapped reinforced soil retaining wall are introduced.