###### Abstract  
When shield tunneling is carried out in poor geological areas with high water head and low strength, there is a great construction risk, and the external water pressure is one of the key factors affecting the stability and safety of the tunnel during shield tunneling. Taking the Yinguruxin tunnel of Xin'an County as the engineering background, the geological conditions and water-bearing characteristics of the water-rich area in the tunnel excavation path are analyzed by means of drilling and high-density electrical method, and the pumping test is used to evaluate the groundwater linkage in the water-rich area. The 2022 version of Midas GTS NC is used to study the distribution characteristics of external water pressure during tunnel excavation in fault zones, and the influence of different drainage rates on the external water pressure of the tunnel is analyzed. The results show that the rock mass in the unfavorable geological section of the tunnel excavation is broken and rich in water, but the complexity of the stratum leads to uneven water richness in the axis direction of the tunnel. The drainage rate is the key to affecting the external water pressure of the lining. The drainage rate is the key to affecting the external water pressure of the tunnel. The correct drainage rate is an effective measure to reduce the external water pressure of the tunnel. The internal and external water pressure of the tunnel decreases with the increase of the drainage rate. When the drainage rate reaches 66.67% of the water inflow, the external water pressure of the tunnel can be reduced to 0.3 MPa to ensure the safety of the earth pressure balance shield machine in the tunneling process. The conclusion provides a useful reference for the high water pressure control of the tunnel shield tunneling process. deep buried water-rich tunnel; external water pressure; water plugging and drainage limiting; high-density electrical geophysical prospecting technology; pumping test +
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inrush often occur, which destroys the machine and even causes major safety problems, which has a significant impact on the economic and social benefits of the project [5]. In the complex groundwater environment, determining the calculation and value of the external water pressure of the tunnel is the premise to ensure the safety of the project construction, and it is also the key to the safety and economy of the tunnel structure in the design of the water pressure resistance of the tunnel [6]. If the calculation of the external water pressure is too small during the design, it will cause water leakage, cracking and other diseases that seriously affect the safety of the tunnel. If excessive consideration of external water pressure makes the safety reserve of the lining structure too large, it will cause a waste of resources and reduce the economy of tunnel construction [7]. Therefore, how to reasonably calculate the external water pressure load is very important. At present, many scholars at home and abroad have carried out extensive and in-depth research on the calculation method and treatment method of tunnel external water pressure in high water head areas [8]. At present, the commonly used calculation methods of tunnel external water pressure at home and abroad mainly include the reduction coefficient method [9; 10], theoretical analysis method [11; 12; 13], and so on. The reduction coefficient method is based on the state of groundwater activity in the surrounding rock of the cavern, and the permeability coefficient is empirically valued, and then the value of the reduction coefficient is determined. [PERSON] et al. [14; 15] think that the reduction coefficient method is affected by many factors, the empirical value is the main, and the applicability of the method is limited in the deep buried tunnel with high groundwater head.