高速铁路柔性路基下CFG桩弯曲破坏研究

水泥粉煤灰碎石桩(CFG桩)复合地基因其成本低、桩体刚度大、沉降小,广泛应用在对工后沉降要求较高的高速铁路路基加固工程中,但是关于柔性路基下复合地基稳定性和破坏模式的研究尚不成熟。结合工程实例,采用理论分析和数值模拟的方法,研究了铁路柔性路基下CFG桩地基稳定性和破坏模式。研究表明:与复合地基剪切破坏准则和BS 8006-1:2000规范获得的稳定系数相比,基于弯曲破坏强度理论计算得出的CFG桩复合地基稳定系数最小;基于CFG桩弯曲破坏模式得出的最危险圆弧滑动面与不加CFG桩时不重叠;对于柔性路基下CFG桩加固的复合地基,当下伏地层土质较差时,可在路基外设置1~2排桩;CFG桩顶加筋垫层可以提高桩体承受侧向荷载的能力,从而提高桩网结构复合地基的稳定系数,降低弯曲破坏发生的概率。

Study on Bending Failure of CFG Pile Under Flexible Subgrade of High Speed Railway

Cement fly-ash gravel pile(CFG pile)composite foundation has low cost,large pile stiffness and small settlement,which is widely used in high speed railway subgrade reinforcement projects with high post construction settlement requirements.However,the research on the stability and failure modes of composite foundation under flexible subgrade is not mature.The stability and failure modes of CFG pile foundation under flexible subgrade of railway were studied by theoretical analysis and numerical simulation.The results show that compared with the shear failure criterion of composite foundation and the stability coefficient of BS 8006-1:2000 code,the stability coefficient of CFG pile composite foundation calculated based on bending failure strength theory is the smallest.The most dangerous circular sliding surface based on the bending failure mode of CFG pile does not overlap with that without CFG pile.For the composite foundation reinforced by CFG pile under flexible subgrade,1~2 rows of piles can be set outside the subgrade when the soil quality of the current layer is poor.The reinforced cushion layer on the top of CFG pile can improve the lateral load bearing capacity of the pile,so as to improve the stability coefficient of the pile net structure composite foundation and reduce the probability of bending failure.