| JinPing Ⅱ Hydropower Station is the world’s largest hydraulic tunnel engineering now. Because of construction delay and duration shortage, its3auxiliary construction tunnel had been added for more working faces, in order to rescue the TBM and other construction equipments buried by strong rock-burst and ensure project completed on schedule. Obviously, it is essential to the hydraulic tunnel engineering of JinPing Ⅱ Hydropower Station for3#auxiliary construction tunnel had been completed successfully. It is the largest heavy and difficult point of this project that3#auxiliary construction tunnel’s water gushing has the characteristics of sudden, big flow, high water pressure, however. Reasonable prediction of its water inrush is one of the largest difficulties in the process of engineering construction.Take the3#auxiliary construction tunnel of JinPing Ⅱ Hydropower Station as the background, this paper comprehensively use the theoretical analysis, numerical simulation and field test and other methods to study of tunnel water gushing prediction. On the basis of the traditional methods to predict the tunnel gushing in detail,"the prediction model of hydraulic tunnel water gushing with water-rich area large buried depth and ultra-high osmotic pressure" is established by BP neural network method. At the same time, the numerical fuzzy mathematics and MODFLOW analysis are used to calculate the water inflow. Take the calculation results to compare to verify reliability of "the prediction model of hydraulic tunnel water gushing with water-rich area large buried depth and ultra-high osmotic pressure". The main research contents and conclusions of this paper are as follows:1. Analyzed the engineering geology and Hydrogeology conditions of the3#auxiliary construction tunnel of JinPing II Hydropower Station, reveals that It is the largest heavy and difficult point of this project that3auxiliary construction tunnel’s water gushing has the characteristics of sudden, big flow, high water pressure. The water inrush factors of the3#auxiliary construction tunnel are mainly divided into three major categories of a total of11factors, respectively, the engineering geology conditions, hydrogeology conditions and tunnel conditions. Among them, the engineering geological conditions includ geological structure, the maximum buried depth, the rock level, permeability coefficient and the development of karst a total of5influence factors; Hydrogeology conditions mainly consider the influence of water level, the precipitation and surface water environment; Factors influencing tunnel conditions for tunnel radius, construction conditions and tunnel length.2. They are the most significant influence for water gushing that Include geological structure, water level, permeability coefficient, the precipitation and tunnel radius, by a synthesis of the influential factors of tunnel water gushing. The geological structure factors, according to the tectonic level using1-100transform from qualitative to quantitative indicators, can be used to calculate the tunnel water inflow. Based on the relationship between these five factors and tunnel water gushing,"the prediction model of hydraulic tunnel water gushing with water-rich area large buried depth and ultra-high osmotic pressure" is established by BP neural network method.3. By comparative analysis of three methods of forecasting water inrush, the basic premise of water inrush prediction is fully mastering inrush geological condition of tunnel engineering and water environment information. On the basis of this, BP neural network and Mod-flow method are more objective for water gushing prediction, and hierarchy analysis and fuzzy mathematics method is more subjective. So, The BP neural network and Mod-flow method are the preferred ways other than hierarchy analysis and fuzzy mathematics method.4.In the light of the water gushing prediction of the3auxiliary construction tunnel of JinPing II Hydropower Station,"the prediction model of hydraulic tunnel water gushing with water-rich area large buried depth and ultra-high osmotic pressure", hierarchy analysis and fuzzy mathematics method and Mod-flow method are taken to predict the water gushing of three key water gushing section of the3auxiliary construction tunnel of JinPing II Hydropower Station, which are the auxiliary (3)0+020～0+050, the auxiliary (3)0+170～0+200, and the auxiliary (3)0+280～0+310. Various methods of value prediction are compared with the measured discharge. The results show that using "the prediction model of hydraulic tunnel water gushing with water-rich area large buried depth and ultra-high osmotic pressure" value is larger than the actual value for predicting water inrush, which relative error is in the range of10%. It can reasonably predict the tunnel water inflow. |
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