Characteristics analysis and control measures for the deformation development in a water-rich loess tunnel

Abstract

Deformation is one of the most intuitive indicators for engineering safety in tunnel engineering, especially in weak surrounding rock tunnels. Field monitoring is an intuitive and efficient research method relying on typical engineering. The loess is affected easily by water to produce plastic deformation due to its collapsibility. In this study, the water-rich area is encountered during the excavation of the Guchengling loess tunnel in the northwest of China. According to the long-term deformation monitoring data of the waterless and water-rich area, firstly, the deformation characteristics of the loess tunnel in the water-rich area and the application effect of the actual deformation control measures are obtained after comparative analysis. The deformation developing rate became faster in early excavating stage, and the lower bench produced significantly larger deformation than before due to the water not being discharged in time. The cumulative deformation value is increasing continuously, even after 20 days. Deformation presents different development characteristics due to different spatial positions and different work conditions. Next, the regression analysis is made to indicate that deformation of the weak loess tunnel in this study accords with the exponential function that could predict the final cumulative deformation. In the end, after a series of control deformation measures taken, the performance of soil and support is improved and the deformation is significantly reduced and eventually converges to a stable value.