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

Abstract

Objective Construction of new tunnel in water-rich 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 Line 18 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.

Keywords

• metro
• tunnel construction
• waterproof curtain
• orthogonal experiment
• design parameters