水泥粉煤灰碎石桩处理桥头跳车效果动静力分析

Dynamic and Static Analysis of the Effect of Cement Fly-ash Gravel Pile on Bridgehead Bumping Treating

为研究水泥粉煤灰碎石桩(CFG桩)对桥头跳车现象的改善作用,依托实际工程,采用模型试验方法,分析动静荷载作用下CFG桩桩长、桩径和桩间距对桥头处路面沉降和桩土竖向剪切应力分布规律的影响,依据复合模量方法,验证CFG桩对桥头跳车现象的改善效果。研究结果表明,随着CFG桩桩长、桩径的增加及桩间距的减小,桥头处路面沉降逐渐减小,能够改善桥头跳车现象;随着车辆行驶时间的增加,不同桩长和桩径CFG桩加固后桥头处路面竖向位移和桩顶竖向剪切应力均呈先增大后减小最终趋于稳定的趋势,车辆驶过桥头后,路面出现较小幅度的向上隆起;公路服役4年后,不同桩长和桩径CFG桩加固后桥头处路面最大沉降趋于稳定;采用CFG桩处治桥头处不良土质时,CFG桩桩长宜为12~16m,桩径宜为450~500mm,桩间距宜为1.6~1.8m。

In order to study the improvement effect of cement fly-ash gravel pile(CFG pile)on bridgehead bumping treating,based on the actual project,the model test method was used to analyze the influence of CFG pile length,pile diameter and pile spacing on the pavement settlement at the bridge head and vertical shear stress of pile and soil under dynamic and static loads.According to the composite modulus method,the improvement effect of CFG pile on the phenomenon of bridgehead bumping is verified.The research results show that with the increase of CFG pile length,pile diameter and the decrease of pile spacing,the pavement settlement at the bridge head decreases gradually,which can improve the phenomenon of bridgehead bumping.With the increase of vehicle travel time,the pavement vertical displacement and the vertical shear stress of the pile top at the bridge head after the reinforcement of CFG piles with different pile lengths and pile diameters increase first and then decrease and finally tend to be stable.After the vehicle passes through the bridge head,the pavement has a small upward uplift.After four years of service,the pavement maximum settlement at the bridge head tends to be stable after CFG piles reinforcement with different pile lengths and pile diameters.When the CFG pile is used to treat the bad soil at the bridge head,the CFG pile length should be 12~16m,the pile diameter should be 450~500mm,and the pile spacing should be 1.6~1.8m.