富水混合花岗岩地层地铁隧道施工中地面注浆止水帷幕的设计参数优化

Optimization of Design Parameters of Ground Grouting Waterproof Curtain in Water-Rich Mixed Granite Stratum

[目的]富水混合花岗岩地层新建隧道施工受地下水的影响显著,通常采用地面预注浆形成止水帷幕的措施来降低地下水对隧道施工过程的影响。但止水帷幕设计参数的选择大多以经验为主,可能存在隔水效果不佳、水位降低显著导致地层沉降超限,以及隧道周围突涌水等现象,故需要对富水混合花岗岩地层注浆帷幕设计参数进行优化。[方法]依托广州地铁18号线番禺广场站—南村万博站区间工程,基于正交试验设计,通过数值模拟分析了止水帷幕设计参数(帷幕深度、帷幕厚度、帷幕渗透系数及帷幕与隧道间距离)对注浆隔水效果的影响;采用SPSS软件进行多元线性回归分析,拟合了选取止水帷幕设计参数的经验公式,获取了止水帷幕最优设计参数并进行工程应用。[结果及结论]止水帷幕的影响因素按影响程度排序依次为:帷幕渗透系数、帷幕深度、帷幕厚度、帷幕与隧道间距离;现场选取的止水帷幕设计最优参数中,帷幕深度为58 m、帷幕厚度为2.0 m、帷幕渗透系数为1×10-10m/s、帷幕与隧道间距离为0.5 m。现场工程实践表明,采用最优参数后,止水帷幕降低地下水位效果较好,隧道开挖时的围岩稳定且开挖面干燥,地下水对隧道开挖的影响得以有效降低。

[Objective]Construction of new tunnel in waterrich mixed granite stratum is significantly affected by groundwater,so ground pre-grouting is usually adopted to form a waterproof curtain in order to reduce the effect of groundwater on the tunnel construction process.However,the design parameters of the waterproof curtain are selected mostly on the basis of experience,probably leading to phenomena like poor waterproof result,excessive ground settlement caused by significant water level decrease,and sudden water inrush around the tunnel.Therefore,it is necessary to optimize the design parameters of ground grouting waterproof curtain in water-rich mixed granite stratum.[Method]Based on the section project between Panyu Square-Nancun Wanbo Stations on Guangzhou Metro Line18 and with orthogonal experimental design,the influence of waterproof curtain design parameters(curtain depth,curtain thickness,curtain permeability coefficient and distance between curtain and tunnel)on the grouting waterproof result is analyzed by numerical simulation.The SPSS software is used for multiple linear regression analysis,an empirical formula is fitted for selecting the design parameters of waterproof curtain,the optimal design parameters of waterproof curtain are obtained and applied in engineering.[Result&Conclusion]The influencing factors of the waterproof curtain are listed in order of influence degree as permeability coefficient,curtain depth,curtain thickness,and distance between curtain and tunnel.The optimal design parameters selected on site are as follows:the curtain depth of 58m,the curtain thickness of 2m,the permeability coefficient of 1×10~(-10)m/s,and the distance between curtain and tunnel of 0.5 m.The on-site engineering practice shows that after using the optimal parameters,the waterproof curtain performs well on reducing the groundwater level,the surrounding rock is stable and the excavation surface is dry during tunnel excavation,and the influence of groundwater on the tunnel excavation is effectively reduced.