Study Of Sub-sea Tunnel Seepage Field Distribution And Prediction Method Of Water Inflow

As the rapid development of economic and technological in our country, increasing Cross-Strait transportation highlights its importance. For the stable weather and climate impacts and advantages of the traffic volume, Sub-sea Tunnel becomes an important development direction in the future cross-strait transport.However, relative to the Mountain Tunnel, Sub-sea Tunnel has more agnostic. There are too many difficulties in constructing Sub-sea Tunnels, such as difficult and low accuracy geological survey, higher cost and so on. In the construction process, overburden has unlimited supply of water on the tunnel. This takes greater security risks for sub-sea tunnels. In the event of big water inflow incident, it will take devastating damage to the tunnels. At the same time, forecasting of Sub-sea Tunnel water inflow is an important basis for drainage design. It plays a crucial role in the tunnel's drainage design. Accurate forecasting can provide the correct design parameters to improve the anti-drain effect, extend the life of the tunnels. Therefore, this article discussed the Sub-sea Tunnel seepage distribution and water inflow forecasting from the analytical method, model test method and numerical method of three aspects. The main contents are as follows:(1)Analysised the distribution function of fractures in fractured rocks. Monte-Carlo method is used to simulate two-dimensional fractures. And then based on the permeability tensor and permeability elliptic concept, many groups of parallel fractures and crossover fractures permeability tensor equivalent method is analyzed. This laid a foundation for the fractured rock mass equivalents to the equivalent continuum calculation of rock seepage.(2) According to the characteristics of the Sub-sea Tunnels and on the research of others, this article simplified the Sub-sea Tunnel as elliptic. Complex-variable function was used to deduce the Sub-sea Tunnel water inflow with the height-span ratio relation formula. The relationship among the water inflow, height-span ratio, tunnel burreid depth, water height and wall rock permeability coefficient were analyzed. At last, the correction factor between round tunnel and oval tunnel in calculating water inflow was proposed.(3) Jiao Zhouwan Subsea Tunnel in Tsingtao was chosen as the prototype. In the process of the model test, we produced the test bench which made by high-strength steel and composition of PVC board. Automatic water divice and discharge measuring device were designed. We selected the appropriate similar materials and fiber optic monitoring system. On this basis, study of FSI model test was carried out. The data of osmotic pressure and tunnel water inflow in the key points of the test were systematically analyzed. And the test results were compared with the analytical solution.(4) With the finite difference calculation software of FLAC3D, the model test of selected prototype period was firstly simulated. The calculated results and experimental results were compared and analyzed. Then we analyze the seepage and water inflow changes when different grouting circle thickness, different water depths, different rock layer thickness and different grouting circle of permeability coefficient. The influence of various factors on the seepage distribution and water inflow were analyzed.