Abstract

The sheet pile wall with relieving platform is a new type of retaining structure, which is composed of sheet pile wall and relieving platform. Because of the unloading effect of the relieving platform, the stress of the structure below reduced the relieving platform, and the relieving platform provides a reverse moment to the pile (relative to the moment caused by earth pressure), which brings about the internal force distribution of the integral structure more reasonable compared with the cantilever sheet pile wall. The sheet pile wall with the relieving platform is more convenient in construction, lower cost and higher durability than the anchored soldier pile and lagging wall, its mechanical behavior and failure mechanism are very complicated, great gap existed in current theoretical research, and its design theory isn't perfect. Therefore, carrying out the mechanical behavior and failure mechanism of in-depth, systematic study will help to improve the design method and construction method, which has important theoretical and practical significance.

Based on a project of the sheet pile wall with relieving platform in Shenzhen, a 1:7 scale model was designed and build, and the model test was taken on. In two cases of with and without external load on top of the wall, the stress and deformation characteristics of the sheet pile wall with the relieving platform were researched by the laboratory scale model test of this structure. Experimental focused on the following aspects: 1) the distribution pattern of earth pressure along the upper and lower wall; 2) the effect of the change of the releiving platform depth and width on the earth pressure distribution pattern; 3) the stress and deformation behavior of the structure during loading and destroying. On this basis, the earth pressure distribution patterns, the relieving diffusion angle, and the counter-force distribution pattern of embedded body were proposed.

Multiple sets of numerical simulation analysis were carried out in accordance with the model tests of the sheet pile wall with releiving platform with FLAC. The change rule of earth pressure, the displacement of the retaining wall and the internal force of structure along with the width and depth of the relieving platform were analysed in detail.And results were compared with those of model tests, which showed that numerical methods in the paper can be used to simulate model test. Then, choosing 0.4 times the high wall as the width of relieving platform and 0.45 times the high wall as the depth of relieving platform. A intensive research on effect of the pile length on the whole stability of the sheet pile wall with relieving platform was performanced.The numerical simulation results demonstrated that the failure mode of this structure was mainly overthrow damage.

Four groups of 1:50 geotechnical centrifuge model test was carried out for the sheet pile wall with releiving platform. Each group test with the different centrifugal acceleration simulated the normal load and destruction load. The overthrow damage and the overall sliding failure process of the sheet pile wall with releiving platform was studied. The results of centrifuge model test showed that: 1) the failure patterns of the sheet pile wall with releiving platform were overthrown damage and whole sliding failur; 2) the overthrown damage was prevailing, It occurred as circular sliding damage through the pile bottom when foundation soil strength was very low.

According to results from comprehensive analysis of the scale model tests, numerical simulation and geotechnical centrifuge test for the sheet pile wall with releiving platform, the overall slip mode was proposed and the corresponding formula was derived based on ‘Slice method', and anti-overthrow mode was forwarded and safety stability formula was deduced. And taken the model test as an example, based on MATLAB programming, the whole sliding stability and anti-overturning stability were calculated. At last, the optimization of the width and depth of the relieving platform and the length of pile were discussed, and the programming was developed for the optimization calculation.

Key Words:Sheet Pile Wall with Relieving Platform; Scale Model Test; Numerical Simulation; Geotechnical Centrifuge Model Test;Mechanical Behavior; Failure Mechanism