Study On Long Term Performance Of Back-to-Back Reinforced Earth Retaining Wall For High Speed Railway

The rapid development of high-speed railways has put forward higher requirements for the long-term stability of high-speed railway subgrade structures.The back-to-back mechanically stabilized earth wall,as a derivative structure of the reinforced earth retaining wall,inherits the many advantages of the reinforced earth retaining wall as a roadbed,and is widely used in road construction projects.At present,there are few studies on back-to-back mechanically stabilized earth walls at home and abroad,and there are not many descriptions of the design of back-to-back mechanically stabilized earth walls in related codes and guidelines,and further research is still needed.Conducted field data collection on the back-to-back mechanically stabilized earth wall of the Rongcheng section of the Qing-Rong Intercity Railway,and analyzed the stress and deformation laws of the back-to-back mechanically stabilized earth wall within 6 years of completion;Establish a model with PLAXIS finite element software to simulate the long-term mechanical behavior of the back-to-back mechanically stabilized earth wall;Finally,the influencing factors of the long-term performance of the double-sided reinforced earth retaining wall are further explored.The main research contents are as follows:(1)The types and potential failure modes of back-to-back mechanically stabilized earth walls are summarized.(2)In the field test,after 6 years of testing,the vertical stress,horizontal earth pressure,lateral earth pressure coefficient,strain of reinforcement,potential failure surface,vertical settlement and the horizontal displacement of the back-to-back mechanically stabilized earth wall was analyzed.The research results show that:6 years after the completion of the construction,the vertical stress and horizontal earth pressure of the back-to-back mechanically stabilized earth wall have not changed much over time;The strain of the geogrid and the vertical settlement of the retaining wall will gradually increase over time,but the growth rate will gradually decrease and gradually stabilize.There was no obvious change in the horizontal displacement of the wall within 6 years after construction.It can be seen from the above that the back-to-back mechanically stabilized earth wall is in a stable state 6 years after the completion of the construction.(3)In terms of numerical simulation,a model was established with PLAXIS finite element software to analyze the changing laws of vertical stress,horizontal earth pressure,lateral earth pressure coefficient,vertical settlement and horizontal displacement of the wall within 6 years after the completion of the wall.Comparing the measured value and the simulated value,it is found that although there are some differences in the data,the measured value and the simulated value are relatively similar,which shows that the model established by PLAXIS software can effectively simulate the long-term mechanical behavior of the double-sided reinforced earth retaining wall.(4)The influence of wall type,length of reinforcement and top load on the vertical settlement of the top of the wall,horizontal displacement of the wall,horizontal earth pressure and overall safety factor of the back-to-back mechanically stabilized earth wall18 years after its completion is analyzed.The results show:the horizontal displacement of the integrally cast-in-place concrete panel modular wall is greater than that of the integrally cast-in-place concrete wall,while the horizontal earth pressure and the overall safety factor of the retaining wall near the wall are smaller than the integrally cast-in-place concrete panel retaining wall;As the length of the reinforcement increases,the settlement of the wall top and the horizontal displacement of the wall after construction will decrease,and the overall safety factor will gradually increase;The reinforcement length Li is obtained by adding and subtracting the reinforcement length L of the original model,When L_i<L,the reinforcement length has a great influence on the settlement,horizontal displacement and overall safety coefficient of the back-to-back mechanically stabilized earth wall after the top work.When L_i>L,the reinforcement length has little influence on the three factors;As the load on the top of the wall increases,the settlement of the top of the wall after construction will increase,and the overall safety factor of the retaining wall will decrease,but both can still meet the requirements of the code when the q=54.1 k N/m~2(The additional load on the top of the wall is the sum of the track load and the train load).This shows that the back-to-back mechanically stabilized earth wall is still in a stable state after the train load is applied to the top of the retaining wall.