云贵高原山区高速公路软土路基滑移处治技术

A Treatment Technology for Soft Soil Subgrade Slip of Expressway in Yunnan-Guizhou Plateau Mountainous Area

高速公路软土路基外侧分布有稻田或沟渠时,易引起路基坡脚软化,从而导致路基整体失稳。为研究该类软土路基的失稳机理和处治措施,选取云贵高原某山区高速公路软基整体滑移路段,对其工程病害特征、失稳机理和处治措施进行了分析,并对处治后路基的水平位移与沉降进行了跟踪观测。提出了设置抗滑桩、拆除滑移挡墙、重新处理挡墙基底后再浇注挡墙和反压护道+CFG桩3种初步处理方案,从工程费用、减少报废工程、节省工期及施工过程中对路基影响等方面进行了比选分析,并对反压护道+CFG桩处治后路基的水平位移与沉降进行了跟踪观测。结果表明:连续强降雨入渗,致使路基的抗剪强度产生一定衰减,路基填方体重力增大,对挡墙施加的侧土压力也随之增大,加之挡墙外侧即是稻田,坡脚处地基软化造成挡墙发生了向外滑移,滑移同时牵引路基体,引起路基坡面和顶面均产生纵向拉裂缝,进而发展为路基体纵向拉裂和错台式垂直下沉;反压护道+CFG桩的软基处治为最优方案;路基的沉降和水平位移量均可控且逐步收敛,地基和路基的整体稳定性良好。采用CFG桩+反压护道综合处治山区高速公路软土失稳路基有效可行,技术优势和经济优势显著。

When rice fields or ditches are distributed outside the soft soil roadbed of expressways,it is easy to cause the slope toe of the roadbed to soften,leading to overall instability of the subgrade.In order to study the instability mechanism and treatment measures of this kind of soft soil subgrade,selecting the overall sliding section of the soft foundation of a mountainous expressway in Yunnan-Guizhou Plateau,the engineering disease characteristics,instability mechanism and treatment measures of the section are analyzed,and the horizontal displacement and settlement of the treated subgrade are tracked and observed.Three preliminary treatment schemes(setting up anti-slip piles,removing sliding retaining wall,and pouring retaining wall and using back berm+CFG piles after reprocessing the base of the retaining wall)are proposed.Comparison and analysis are conducted from the aspects of engineering costs,reducing scrap projects,saving construction time,and the impact on the subgrade during the construction process.The result shows that(1)The continuous heavy rainfall infiltration leads to a certain attenuation of the shear strength of the subgrade.The gravity of the subgrade filling body increases,resulting in an increase in the lateral soil pressure applied to the retaining wall.In addition,the outside of the retaining wall is rice field,and the foundation at the slope foot softens,causing the retaining wall to slide outward.The sliding also pulls the subgrade body,causing longitudinal tensile cracks on both the slope surface and the top surface of the subgrade,and it develops into longitudinal cracking and staggered vertical sinking of the road subgrade,and the horizontal displacement and settlement of the subgrade after the treatment by back berm+CFG piles are tracked and observed.(2)The soft foundation treatment using back berm+CFG piles is the optimal scheme.(3)The settlement and horizontal displacement of the subgrade are controllable and gradually converge,and the overall stability of the foundation and subgrade is good.It is effective and feasible to comprehensively treat the unstable soft soil subgrade of mountainous expressways by using CFG piles+back berms,with significant technical and economic advantages.