Seepage Law And Prediction Of Water Inflow In Surrounding Rock Of Weathering Trough In Xiamen Subsea Tunnel

Xiamen Subsea Tunnel,as an important transportation project to promote the industrial development of Xiamen and Jiangxi,has some construction conditions under the weathering trough strong weathered granite stratum in some sections along the line.The tunnel underpasses the weathering trough section and accounts for about half of the mileage and strong wind.The layer has recently reached approximately 8m and is approximately 300 m through the weathering section.Weathering trough is a bad geological structure often encountered in the construction of submarine tunnels.Its rock mass has the characteristics of high degree of weathering,poor integrity and strong permeability.Therefore,the existence of weathering trough affects the distribution of seepage field in the stratum,especially for the construction of submarine tunnels.The process has great bad meaning.In this paper,the groundwater seepage law and tunnel water infiltration during the construction stage of the surrounding rock of Xiamen Haidi Tunnel are discussed.The main research contents include the following three aspects:1.Establish a simulation experiment for the engineering background,simulate the distribution of the water head of the surrounding rock(strong weathering layer)and the bedrock surrounding rock(middle,micro-unweathered layer)under the same buried depth of the tunnel,according to the total head and The theory of pressure head shows that the closer the groundwater flow rate in the excavation area is,the faster the groundwater migration is above the excavation area and the precipitation funnel is formed within the surrounding rock.The permeability of the surrounding rock after tunnel excavation is more Stronger,the lower the pressure head,the faster the groundwater migration and the simulation verification using Midas GTS.2.According to the relevant geological exploration data and research data,carry out the geological model generalization of the tunnel site and use Midas GTS to conduct a preliminary investigation of the overall seepage field in the tunnel site,aiming at the tunnel under the weathering tunnel encountered during the construction of the subsea tunnel.Through the two conditions of weathering tank,the seepage field of unlined surrounding rock is compared and analyzed from the aspects of total head,pore water pressure and flow velocity.When the tunnel passes through the weathering trough,the parameters of the seepage field of the surrounding rock and the amount of water inflow from the tunnel are positively correlated with the depth of the weathering trough.The deeper the depth of the weathering trough is,the larger the value of each parameter is.When the tunnel runs through the weathering trough,the stratum of the stratum interface is different.The field distribution is different.When the formation interface is relatively low in permeability of the upper formation,the total head of the area is lower and the pore water pressure is smaller.The groundwater flow rate at the weathering tank is larger and the tunnel water inflow increases after the construction enters the formation interface.3.Based on the project background,nine representative areas are selected as the study area from the buried depth of the tunnel and the distribution of the stratum.The three kinds of calculation formulas and numerical simulations are used to compare the water inflow during tunnel excavation and to explore the prediction of each water inflow.The reason for the difference in the method results is that the average value of each method is used as the prediction result.The calculation result is more safe by using the Sato Bangming calculation formula as the prediction method.