刚性桩加固软弱地基上路堤稳定性问题(Ⅱ)——群桩条件下的分析

Stability of embankment on soft subgrade reinforced by rigid inclusions(Ⅱ)——group piles analysis

针对刚性桩支承路堤,笔者已进行的对单桩位于路堤下不同位置时路堤稳定性的研究表明,复合抗剪强度极限平衡法不能反映不同位置单桩的强度及刚度对路堤稳定性的影响以及桩的弯曲破坏机理,将显著高估路堤稳定性。通过对群桩条件下刚性桩加固路堤分别采用三维和二维数值分析方法,研究了路堤填筑及趋于失稳破坏过程中,桩、土的内力与变形规律、桩的破坏形式等。结果表明:群桩条件下,不同位置的刚性桩的破坏模式不同,对路堤稳定性的贡献机理也相应不同,弯曲破坏比剪切破坏更易于发生,剪切破坏并非是桩最危险的破坏方式;提出了考虑路堤趋于失稳破坏过程中桩弯曲破坏的cut-off退出方法,在进行数值分析时可反映路堤趋于失稳过程中桩的破坏形式,从而合理地评估路堤稳定性。对素混凝土桩加固路堤的稳定分析,提出了桩可使用抗剪强度概念,并提出了按桩体可使用抗剪强度采用极限平衡法进行路堤稳定分析的方法。

The stability analysis of embankments reinforced by a single pile carried out by the authors shows that the limit equilibrium method can not consider the failure mechanism of the single pile at different locations and thus will overestimate the embankment stability when the composite shear strength is used.3D and 2D numerical analyses are performed to study the stability of embankment supported by group rigid piles.The relative soil-pile displacement,internal forces and failure modes of piles are analyzed.The analysis results show that for the piles at different locations related to the embankment,the failure patterns and contribution to the embankment stability are different.The bending failure is more possible to occur than the shear failure.The cut-off mechanism is suggested and introduced into numerical analysis to consider the possible bending failure of piles when the embankment is approaching failure.The allowable shear strength of the piles is suggested when the limit equilibrium method is employed to analyze the stability of rigid piles supported embankment.