| During the construction of tunnel projects,the problem of water inrush is often accompanied,especially when the tunnel passes through the area with strong karst development,the characteristics of high pressure and rich water in the karst area can easily lead to water inrush disaster,resulting in huge casualties and property losses.This article relies on the project of China Railway Engineering Design Consulting Group Co.,Ltd.to build a new railway section from Chengdu to Wanzhou.Through geophysical prospecting,drilling and field testing,the relevant geological data of the Jiaojiaoshan tunnel area is obtained,and the topography and lithology in the tunnel site area are clarified.Features,structural types and hydrogeological conditions,systematically analyzed the karst development characteristics of the tunnel site,and used atmospheric precipitation infiltration method,groundwater dynamics method and numerical simulation method to predict the amount of water inflow that may occur during tunnel construction.The main results achieved are as follows:(1)The regional geological background information of the tunnel in Jiajiao Mountain was sorted out,and the engineering geological conditions of the tunnel site were clarified in detail,and the regional karst development characteristics,as well as groundwater types and flow characteristics were systematically analyzed.Through field hydrogeological tests and other means,relevant hydrogeological parameters were obtained.On this basis,a conceptual hydrogeological model of the tunnel site area was established.(2)According to the permeability of the water-bearing rock group through which the Jiaojiaoshan Tunnel passes,the tunnel is divided into 6 sections,and the water inflow of each section is predicted by the atmospheric precipitation infiltration method and the groundwater dynamics method.The atmospheric precipitation infiltration method predicts that the normal water inflow for the entire section is 22663m~3/d,and the maximum water inflow predicted by the groundwater dynamics method is 55045m~3/d.The largest water inflow section is the karst development section of the Jialingjiang Formation in the core of the Jiaojiaoshan anticline.The water volume reaches 35745m~3/d.(3)Use Visual Modflow software to transform the hydrogeological conceptual model of the tunnel site area into a three-dimensional groundwater numerical model,and use the Drain module and the regional water balance calculation module(Zbud)to simulate the tunnel water inrush to predict the inrush of the entire section of the Jiaojiaoshan tunnel.The water volume is 48692m~3/d,and the maximum water gushing section is 38550m~3/d.(4)The construction and excavation of the Jialingjiang Formation caused the groundwater level of the Jialingjiang Formation to drop,forming a relatively obvious lowering funnel.The maximum depth of the tunnel is more than 30 meters,and the radius of influence is about 450m.The water level changes in the remaining sections due to small water inflows.Not big.After the construction of the tunnel was completed,the tunnel was completely plugged.The prediction results showed that after two years of plugging,the groundwater level in the tunnel site area was basically restored to the state before the excavation.(5)The calculation results of the empirical method and the numerical simulation method are compared,and the reasons for the deviation of the calculation results caused by the different calculation methods in each section are analyzed.According to the“Regulations for Hydrogeological Survey of Railway Engineering”(TB10049-2018),the risk of water inrush in each section of the Jiaojiaoshan Tunnel is evaluated.The results show that the karst development section of the Jialingjiang Formation is Class A,which is prone to water inrush disasters and needs to be strengthened Advance support.There is no risk of water inrush in the remaining sections,just pay attention to timely plugging and drainage after excavation. |
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