Research On The Stability Analysis Of Rigid Pile Supported Embankment

Due to the need of rapid construction of embankment on soft subgrade, stability of the embankment is one of the main concerns need to be considered, engineers have gradually tend to various types of rigid inclusions such as plain concrete pile and reinforced concrete pile as reinforcement elements instead of using sand column, stone column, or deep mixed column, which has been commonly used before. The stiffness and strength characteristics of rigid inclusions have significantly differences with that of traditionally used soft ground reinforcing column. However, for embankment on soft subgrade reinforced with rigid inclusions, traditional limit equilibrium method is employed when performing stability analysis.Research carried on embankment supported on deep mixed column treated soft subgrade has indicated that the deep mixed column does not necessarily subject to shearing failure. The assumption of shearing failure for DM column will lead to overestimation of the overall stability of the embankment. The centrifuge model test obout the deep mixed column reinforced subgrade indicated that the pile occurs bending failure other than shearing failure, the stability analysis basing on the bending failure of the column is more accurate and more consistent with the test results. The result of the stability analysis was overestimated by stability analysis basing on the shearing failure of pile.The stability analysis of the soft subgrade reinforced with different types of columns all use the limit equilibrium method, the British standard proposed another method to consider the reinforce mechanism of the rigid pile in a different way. The British standard can not fully discover the failure modes of the pile judging from the analysis results of this paper, the reinforce mechanism and the method of stability analysis should be carefully studied about the rigid pile supported embankment.The numerical method used to analyze the pile internal force was verified first, the results obtained using the method of this paper was compared with that of the reference's, the rules to reasonably determine the parameters were also obtained. The numerical stability analyses about the pile reinforced slope have been thoroughly studied. Using the numerical model of the pile reinforced slope adopted in a reference paper, the effects of the pile position and the pile bending stiffness on the slope stability were studied, and then the reinforcing mechanism and the failure mode of the single pile under the embankment was studied. Furtherly, the 3D numerical model of group piles supported embankment was used to analyze the reinforce mechanisms and the failure modes of the piles, the bending failure of the plain concrete piles are more likely to occur than shearing failure. The 3D numerical model was converted to 2D numerical model to perform the stability analysis using the shear strength reduction numerical method, and the stability analysis basing on the bending failure of the pile was performed, the stability analysis basing on the anti-slip resistant moment supplied by the pile friction force at the broken points contact face of the pile was performed.The allowable shear strength of the pile computed basing on the anti-slip mechanism of the British standard was used in the stability analyses. The allowable shear strength computed basing on different anti-slip mechanism and failure modes of the pile can be used in the shear strength reduction numerical method and the limit equilibrium method in the stability analysis.The geogrid were usually established on the top of the pile in the cushion layer at the base of the embankment, the effect of the elastic modulus and the layers of the geogrid on the internal force and the failure modes of the piles were studied. The numerical analysis about the anti-slip mechanism, the failure modes of the piles, the stability analysis basing on different failure mechanism of the piles were performed using a actual model in the above chapter, then in this chapter these analysis method were summarized in general situations in order to use this method more broadly.