Simplified theoretical calculation and stress-seepage coupled numerical modeling on reduction of external water pressure of tunnel lining due to grouting and drainage in water-rich soft rock

Abstract

A simplified theoretical method is proposed and stress-seepage coupled numerical modeling conducted to calculate the reduction effects of grouting zone thickness and hydraulic conductivity variations, under prescribed drainage condictions, on the external water pressure and internal forces of lining. The calculations reveal the following observations:(1)When the drainage flux is not so large, e.g. less than 4 m³/(d.m), the simplified theoretical method can be employed to calculate the reduction effects with less than 10% errors.(2)When the drainage flux is quite large, e.g. larger than 4 m³/(d·m), the simplified theoretical method can still correctly refelect the variation trends, but possibly with no smaller than 10% errors.(3)Only when there is drainage, can the grouting zone contribute to the reduction effects, otherwise it can only serve as an impediment to seepage.(4) Within certain limits, the larger the drainage flux, the larger the grouting zone thickness, and the smaller the grouting zone hydraulic conductivity, the more significant the reduction effects.

Keywords

water-rich soft rock mass / grouting zone / drainage flux / external water pressure on lining / internal force of lining / simplified theoretical calculation / stress-seepage coupled numerical modeling