Study On The Deformation Behavior Of Sheet Pile Wall With Relieving Platform

Sheet pile wall with relieving platform is a new type of retaining structure, which is composed of piles, lintel beam, post-board wall, relieving platform (unloading plate) and other components. The unloading plate connected rigidly with the retaining wall reduces soil pressure applied on the substructure below the unloading plate, and provide a counter moment on the pile (relative to the bending moment caused by soil pressure). In this case, the internal force distribution on the structure is more balanced. Meanwhile, the movement of the retaining wall against soil trends to be smaller. Due to the existence of the unloading plate, the stress-deformation behavior is more complicated than other types of pile-supported retaining walls. In previous studies, the mechanical behavior has been carried out, but the deformation behavior of sheet pile wall with relieving platform is not fully revealed. The deformation calculation and controlling method need to be improved. Therefore, it is absolutely necessary to study the deformation behavior of sheet pile wall with relieving platform, propose a practical and reliable calculation method for the internal forces and deformation of the retaining structure, and refine the calculation method. This study has important theoretical and practical significance for engineering.In this paper, based on the elastic foundation beam theory, the author derived the analytical calculation method for the internal force and deformation of sheet pile wall with relieving platform using two-segment-method. The newly developed calculation method fits well with the simulation results using beam-spring FEM. Furthermore, it can be found that the calculated results in good agreement with the model test results and field test results. Thereliability and rationality of the newly developed method have been verified.Based on the analytical methods, the effects of position and width of the unloading plate on the deformation of the retaining structure were investigated. The reasonable position and appropriate width of the unloading plate were analyzed. The calculation results were confirmed using model test and numerical simulation. In addition, the effects of dimension of piles and soil properties on the deformation of the retaining structure were also studied in this thesis.Taking structure-soil as a whole, the deformation behavior of the retaining walls under different construction sequences including the fill and excavation sequences was studied using a two-dimensional elastic-plastic finite difference program named FLAC. Comparing the simulation results using beam-spring FEM with the results calculated by the newly developed method, it can be found that the deformation become smaller considering the interaction between soil and retaining structure, there is no big difference between the internal force and deformation of the excavation retaining wall using incremental and totalizing method. The deformation of the fill retaining wall calculated by the incremental method is bigger than that calculated by the totalizing method which fits well with the field test result.Considering the interaction between soil and structure, finite difference method was used to analyze the settlement behind the sheet pile wall with relieving platform. The settlement is related to the position of the unloading plate. The settlement curve is a parabolic curve if the position of the unloading plate is reasonable. The settlement is about1.6H, the maximum value appear at the position about0.5H from the wall surface, the maximum value is equivalent to the displacement of the wall head.A fill and an excavation retaining structures were selected to study the soil pressure, internal force and deformation of retaining structure on site. The field tests were employed to verify the effectiveness of the unloading plate. It can be found that the soil pressure, internal force and deformation fit well with the numerical results using the newly developed method.Finally, the author summarized the deformation characteristics of the sheet pile wall with relieving platform. The reasonable range of the position and width of the unloading plate was given for the designers. Moreover, the measures used to control the deformation of retaining structures were listed simultaneously.