Study On Settlement Behavior Of Geosynthetic-reinforced And Pile-supported Embankment In Coastal Soft Soil Area

In recent years,with the fast development of high-speed railways construction in China,it is inevitable for a large number of railways lines to pass through coastal areas.However,the geology conditions of coastal areas are quite special and have an adverse impact on the construction of high-speed railways.The soft soil in the coastal area has special properties and has the timeliness of soft soil creep deformation.The long-term operation of high-speed railways in a coastal soft soil areas often causes serious post-construction settlement,which endangers the normal and safe passage of the road.The Geosynthetic-Reinforced and Pile-Supported Embankment can solve the problem effectively.However,due to the complicated geology conditions of coastal soft soil area,there are analysis on the stress and deformation of Geosynthetic-Reinforced and Pile-Supported Embankment in coastal soft soil area in the current research.What’s more,the soft soil foundation in the numerical simulation of Geosynthetic-Reinforced and Pile-Supported Embankment is rarely constructed based on a coastal soft soil area.Besides,the design of it is still lack of systematic theoretical basis.Therefore,I did some research on the Geosynthetic-Reinforced and Pile-Supported Embankment in coastal soft soil area and studied its settlement influence characteristics by means of theoretical analysis and numerical simulation.The main points and conclusions of the research are as follows:(1)The reinforcement mechanism and formation mechanism of soil arching effect and tensile membrane effect will be discussed,and then the load transferring mechanism of Geosynthetic-Reinforced and Pile-Supported Embankment will be analyzed;Next,a two-dimensional equal eccentricity semi elliptical the soil arch model will be constructed,and the soil arch balance equation under limit state will be established;Finally,the calculation formulas of pile-soil load sharing ratio and the tension of geogrid will be deduced.(2)According to the stratum distribution characteristics of coastal soft soil layer,the finite element analysis model of Geosynthetic-Reinforced and Pile-Supported Embankment in coastal soft soil area is constructed and the correctness of the finite element analysis model is verified with the help of ABAQUS finite element software.Based on the finite element model,by analyzing the elements,such as the stress and displacement of reinforced body,pile stress and displacement,and the embankment stress and displacement under different working conditions,the influences of different pile spacing,the filling height and reinforcement modulus on the settlement deformation of Geosynthetic-Reinforced and Pile-Supported Embankment will be studied.The distribution law of settlement deformation of Geosynthetic-Reinforced and Pile-Supported Embankment will be revealed.And this study can provide a reference for future construction design.(3)With the increase of pile spacing,the stress and displacement of reinforced body increase significantly,the stress and displacement of the pile increase significantly,and the load sharing ratio of the pile increases approximately linearly.Reducing the pile spacing can not only enhance the overall bearing performance of the embankment but also reduce the load borne by the soft soil between the piles.(4)When the filling height of the embankment is lower than the maximum height of the soil arch,increasing the filling height of the embankment can make the soil arch more effectively.Thus,it will reduce the overall settlement of the embankment.However,when the filling height of the embankment is higher than the maximum height of the soil arch,increasing the filling height of the embankment will increase the risk of damaging the reinforcement and pile and the risk of the overall settlement of the embankment.(5)Although the reinforcement modulus has little effect on the embankment settlement or the overall bearing performance of the embankment,it can still help increase the reinforcement modulus of the reinforcement in the area under train load and improve the bearing performance of the embankment in the area under train load.With this method,improving the bearing performance of the embankment has an better effect than that of the overall reinforcement modulus.(6)When the minimum arching height of the embankment is about 1.2～1.4 times of the clear distance between piles,and the filling height of the embankment is about 2.65 times of the clear distance between piles,the soil arching effect will be brought into full play.