Prediction Method Of Reinforcement Load And Design Method Of Reinforcement Stiffness For Vertical Reinforced Soil Retaining Walls

Geosynthetic-reinforced soil retaining walls have been widely used in engineering fields with the development and promotion of reinforced soil technology.The core of reinforced soil retaining wall design is the calculation method of reinforcement load.The existing design codes are mostly based on the limit equilibrium methods without considering the interaction between soil and reinforcement under working stress conditions,and do not design the reinforcement stiffness,which may result in either conservative or non-conservative design.This thesis is targeted at the vertical geosynthetic-reinforced soil retaining wall under working stress condition.Behavior of reinforced soil retaining wall was investigated by centrifugal model tests and numerical simulations.The prediction approaches of reinforcement load were proposed from the mechanism of interaction between soil and reinforcement,and then a design method for reinforcement stiffness was developed based on these methods.The main research methods and results are as follows:(1)In order to investigate the behavior of reinforced soil retaining walls with different reinforcement stiffness values,geotechnical centrifuge tests were carried out,in which the geogrid strains,facing horizontal displacements and earth pressures were monitored.The results showed that,the reinforcement strain is linearly distributed along the height of the wall except that the strain of bottom layers suddenly decreases because of the restriction of ground.The deformation of the reinforcement is more significant and the potential failure surface is more easily formed when using less stiff reinforcement.(2)To simulate the centrifugal model tests,three-dimensional models were established by ABAQUS software,Duncan-Chang model was used to describe the nonlinear behavior of soil,and the influence of boundary friction of the model box side wall on the centrifugal model was considered.The numerical simulation results were compared with the experimental ones.The results indicated that,the reinforcement strains and panel displacements of the numerical models are considerably close to the measured ones of the centrifuge tests.The applicability of the numerical model was validated.(3)Two-dimensional models of reinforced soil retaining wall were established by ABAQUS software.Effects of reinforcement stiffness,backfill soil parameters and toe restriction on the reinforcement load,earth pressure and horizontal displacement of the facing were analyzed.The behavior of the reinforced soil retaining wall with different service years is also analyzed by considering the long-term stiffness of reinforcement.It can provide a basis for improving the prediction method of reinforcement loads and the design theory of reinforced soil retaining wall.(4)Based on the nonlinear elastic theory and Rowe's dilatancy theory,new prediction methods were proposed by combining the compatible deformations and force equilibrium between soil and reinforcement.The earth pressure coefficients and reinforcement loads can be determined from the derived implicit functions of earth pressure coefficient through self iteration.The new methods also take into account the effect of backfill compaction and facing restrictions,and were verified by experimental or numerical simulation results.It was demonstrated that the proposed methods have good prediction performance.(5)Based on the new prediction method considering stress dilatancy,the design method of required long-term reinforcement stiffness for given mobilized soil strength was deduced.The required long-term reinforcement stiffness and the corresponding reinforcement strain can be calculated by one step.The new design method was verified by numerical models established by PLAXIS software.