Groundwater Forecasting And Mechanical Assessment Of Water-Rich Tunnel

With the rapid construction of railway, highway tunnels and subways, as well as the increasing public attention on structural safety problem of rich water tunnel, forecast of water inflow in tunnel and mechanical properties analysis have gradually been a hot yet difficult area of research in tunnel engineering. More and more scholars and tunnel designers are keeping an eye on the investigation of rich water tunnel. Rich water tunnel will inevitably encounter all sorts of different geological conditions during the tunneling process. When tunnels pass through different stratums, various geological disasters such as water and mud bursting will happen. This not only increases the difficulty of construction, endangers personnel safety, but also delays the construction period which increasing the costs of project management. Taking the current situation into account, forecast of water inflow in tunnel and mechanical properties analysis becomes more urgent and important for rich water tunnels.Combining with the field monitoring measurement and numerical simulation, the current paper adopts fuzzy mathematics theory to give a case study of KANGJIALOU tunnel to investigate the structural stability of the rich water tunnels. It is concluded as follows:1. The existing engineering experience is summarized, and5factors and10evaluation index, which affect the size of tunnel water inflow, are collected through the experience for future assessment of the groundwater forecast and disease treatment of similar rich water tunnels, providing valuable experience;2. A case study of KANGJIALOU tunnel is carried out. The factors affecting the size of the tunnel water inflow are selected and divided into the primary and secondary weight index bins. Using these factors and evaluation index, evaluation system of assessing the size of tunnel water inflow is established. At the same time, Philip method is used to determine the weights of index at all levels. According to the weight results, the largest weight factors in the primary weight index bin are the surrounding rock properties factors. Among these factors, the rock rank factor is the largest weight factors in the secondary weight index bin. And each factor is determined according to the existing literature and codes. Then the fuzzy comprehensive evaluation model which evaluating the size of tunnel water inflow is established.3. The mechanical properties analyses are conducted through the comparison of the arch sedimentation, peripheral convergence, surrounding rock stress and the steel arch shelf of the drying sections and rich water sections of tunnels, and the comparison of the arch sedimentation, peripheral convergence, surrounding rock stress and the steel arch shelf of three rich water sections at different water inflow.4. Using the software FLAC-3D, numerical simulation is carried out to study the influence of different conditions of water inflow on the surrounding rock. The results are compared with on-site monitoring measurement values to account for mechanical properties of rich water tunnels.