A Preliminary Study on the Detections of Potential Support Degradation in Deep Hydraulic Tunnels
摘要
Understanding the time-dependent performance changes in tunnel supports through the monitoring data is crucial to predict the long-term stability of deep hydraulic tunnels. This paper provides an analytical solution for assessing the long-term stability of the diversion tunnels from the perspective of support permeability degradation. An evaluation factor Rgl, which denotes the ratio of the hydraulic conductivities of the grouted rock and the concrete lining, is proposed to analyse the degradation characteristics of tunnel support performance over time. The time-dependent changes in Rgl and its controlling factors are discussed using the monitoring data of the Jinping II diversion tunnel. The results show that there are ascending or descending trends of Rgl over time, linking to the evolutions of hydraulic conductivity in the grouted rock and the lining. The reliabilities of the analytical model for explaining the changes in tunnel support permeability are examined using numerical methods. The comparisons between the numerical solutions and monitoring results show good agreements in the hypothetical cases characterising the potential degradation of support of the diversion tunnel.