Numerical Simulation Study Of Disaster Evolution And Water Inrush In Filling Type Structure Of Tunnel

With the construction of major infrastructure such as transportation, water conservancy and hydropower, China has become the largest country in the world. But in the tunnel construction process, it’s very frequent filling disaster structure leads to water inrush and burst mud and other disasters. It causing serious economic losses. So there is an urgent need to carry out research on disaster caused by tectonic catastrophe evolution process of tunnel filling, for disaster avoidance and control effectively.Disaster evolution process of filling type structure and water inrush are the main research objects in this thesis.The application of smoothed particle hydrodynamics (SPH) method in fluid and filling medium and the program development of fluid-solid coupling are discussed in this paper by means of theoretical analysis, mathematical deduction, program development and example verification. The feasibility of the constitutive relation model and fluid solid coupling method is verified by a variety of numerical examples. The numerical calculation program was applied to the numerical simulation of exposed water inrush and filling type medium disaster evolution process in tunnel. Comparing with the practical engineering examples, the feasibility of the theoretical system of the paper is verified and some useful conclusions are obtained.(1) The basic principle of SPH method and the kernel functions used in SPH method are discussed; Based on the basic principles of the SPH method and the relevant numerical calculation problems, the SPH program process is determined. And the numerical examples of shock tube in one dimensional and square cavity shear flow in two dimensional are calculated, which shows that the improvement of the numerical program is effective and accurate.(2) The constitutive relation model of fluid (water) and filling medium based on SPH is established, and the constitutive relation is verified by numerical examples.In the preparation process of numerical program, the program is modified and improved, so that the SPH program can be used in the numerical simulation of water and filling medium, and the feasibility of the program is verified by numerical examples.(3) The mathematical model of fluid-solid coupling based on SPH is derived and verified by numerical examples. And the numerical simulation of fluid-solid coupling between water and filling medium is realized. At the same time, the numerical program based on SPH method is applied in numerical simulation of water inrushing on workface and side wall in tunnel. The simulation results are good correspondence with the field practices.(4) The establishment of complex model with the filling type structure in tunnel is described. Optimization methods for the calculation program of complicated model are proposed in the paper. Using the SPH compiled program, the evolution process of exposed water inrush in front of working face in tunnel, filling pipeline type structure with solid filling medium only and water above solid medium, filling type structure on the workingface and tunnel sidewall containing water and filling mdium are studied by numerical simulation. Through the simulation results, we can conclude that:SPH calculation program can be applied to simulation of disaster evolution process of the filling type structure. (I)To the simulation results of exposed water inrush in front of the tunnel wokingface, the groundwater’s gravity plays a leading role for water inrushing.The wate inrushed in a very short time and the water jet distance was related closely to the w water pressure. Under the condition of no compensation of groundwater, the velocity of the water decreased with the decrease of the water quantity until to stop. In the construction, the pressure relief method should be adopted to ensure the safety and drainage to avoid water injection to the construction equipment and personnel to ensure the safety. (Ⅱ) To the simulation of filling pipeline type structure with solid filling medium only, the damage of the filled medium is mainly affected by the self weight. Under the influence of the selfweight, the filling medium is damaged, resulting in the slip deformation, and eventually the large area collapse of and accumulation in the tunnel. But this type of damage is related to the physical and mechanical properties of the filling medium itself. If filling medium cementation ability is good, the occurrence of damage process is slow; if filling medium cementation ability is poor, the damage occurred suddenly,which is easily injured persons or buried instruments. There is large displacement and deformation before damage will occur. Therefore, the monitoring work should be strengthened in the construction to avoid the occurrence of disaster. To the simulation of filling pipeline type structure with solid filling medium and water, the groundwater will accelerate the destruction process of the solid medium after the excavation, which will lead to the destruction of the acceleration. If the cementation ability of solid particles is increased, the groundwater can be able to produce effect on the filling medium through seepage, so that the filling medium can be still destroyed. (Ⅲ) To the simulation of filling type structure on the workingface, the filling medium become the mixture of water and solid filling medium due to the seepage of groundwater after the expose of the karst pipe, which make the solid filling medium turn into a flow plastic mixture. Due to the role of water enormous pressure and fluid solid gravity, the water and filling medium mixing slurry inrush into the tunnel along the karst pipe after the excavation of tunnel face. At first a small amount of water and solid medium is outflow during the failure process. Then the volume of the filling medium increased, and eventually formed a large volume of water and filling medium mixture inrush flow in the tunnel until all the water poured out. Due to the different groundwater pressure, the lower the pressure of the groundwater, a clear slip zone produced in the karst pipeline in the end. Under the higher water pressure, the combination of the filling medium and the karst wall surface will be weakened. And the filling medium is all brought into the tunnel by the underground water. The results are similar to the actual engineering practice. (Ⅳ) To the simulation of filling structure in sidewall of tunnel, the failure types are basically the same with the one filling type structure on the workingface. When the groundwater pressure is relatively small, there is an obvious slip surface in the karst pipe. When the water pressure is relatively large, there is no obvious slip surface. Through the analysis of the results, the main control factors of the disaster evolution of different types filling structure can be obersved, which is great significance to the safety of the tunnel construction.