Inner water pressure distribution law of the tunnel grouting circle in water-rich area

Abstract：To determine the appropriate parameters of grouting in the limited discharge tunnel in water-rich area,the inner water pressure distribution law of the tunnel grouting circle and the hydraulic linkage characteristics of the inside and outside of the grouting circle and the back of the secondary lining were studied by the indoor model test and numerical simulation.The influence of key factors such as the thickness of grouting circle,the permeability coefficient of grouting circle and tunnel depth on the inner water pressure of grouting circle was analyzed.The results show that when the grouting thickness varies,the water pressure is very close at the same part of the tunnel.And the effect of expanding the scope of grouting to reduce the water pressure is not obvious.The model test and numerical analysis have similar results.The water pressure of most measurement points gradually decreases from the outside of the grouting circle to the back of the secondary lining in both deep and shallow buried tunnel.But in shallow buried strata,the variation range of water pressure is bigger,and the influence of seepage is wider.Instead of the depth of tunnel,the water pressure of measurement points in the seepage field is interrelated significantly with the height of groundwater level in the seepage field,water pressure of arch crown and arch waist position of both deep buried and shallow buried tunnel presents the nonlinear characteristics of the gradually increased of attenuation.This trend is more obvious with the decrease of the permeability coefficient of grouting circles.The variation of water pressure is approximately linear at the bottom of arch.The external water pressure of secondary lining decreases synchronously with the decrease of grouting circle permeability coefficient.And water pressure of the outside of the grouting circle is increasing.But the amplitude of the change is small.It is not economical to control the water pressure of the surrounding rock-supporting system by reducing the permeability coefficient of the grouting circle continuously.