## 1 Introduction  
The permeability coefficient of rock mass is a very important hydrogeological parameter in groundwater movement, especially for large-scale water diversion projects with deep buried tunnels. The permeability of the rock mass through which tunnels pass directly affects the construction safety and project cost. Meanwhile, the tunnel construction will disturb the surrounding groundwater environment and affect the drinking groundwater resources for residents in the surrounding mountain areas. Therefore, it is necessary to determine the permeability coefficient of rock mass in the study area during the preliminary investigation. Traditional test methods for determining the permeability coefficients include the pumping test, water pressure test, water injection test, etc. The traditional test methods have obvious disadvantages in practical application. For large-scale water diversion projects, test holes are often arranged in mountain areas with varying topographical conditions. The span between test holes is large, and the hydrogeological conditions are significantly different among them. The pumping test is time-consuming and laborious; meanwhile, it often requires multiple observation wells for auxiliary observation. Furthermore, the pumping test cannot be carried out in test holes of deeply buried rock mass with low permeability. Therefore, it is difficult to apply the pumping test in mountainous areas with complex hydrogeological conditions. Although the water pressure test can be carried out in a single hole, the equipment of the water pressure test is complicated. Meanwhile, it is difficult for the water pressure test to achieve the effects of water sealing and water pressure in broken rock mass, and it easily causes the test hole wall to collapse during the test. The water pressure test obtains a Lugeon value of the water permeability, which needs to be converted into the permeability coefficient according to empirical formulas. Meanwhile, the water pressure test requires a large number of water resources, and in many mountain areas, it is difficult to meet the water requirements, so the water pressure test also has obvious limitations. The water injection test is easy to operate and requires relatively little manpower and few material resources; however, the theory of the water injection test is relatively imperfect and is greatly influenced by the structure of the test well. Meanwhile, the rock mass with high permeability is suitable for the constant water head water injection test; it requires a large number of water resources. The rock mass with low permeability is suitable for the variable water head water injection test, which has a longer test period. Therefore, it is necessary to choose the slug test method proposed in recent years to carry out an investigation of the hydrogeological parameters of the rock mass of long-distance deep buried tunnels. Compared to traditional tests such as the pumping test, water pressure test, water injection test, etc., the slug test is a relatively novel technical method. The slug test method can obtain the permeability coefficient of the aquifer in a small range around the test holes, which is based on the principle of increasing or decreasing the small amount of water in the test hole instantaneously in order to cause the water level to rise or drop. Then, the law of the water level change over time is studied, and the hydrogeological parameters of the aquifer are calculated [1]. [PERSON] [2] first proposed the slug test method to determine the permeability coefficient of an aquifer and then obtained the permeability coefficient of the site soil by observing the time lag of the water level response in a test hole. As a novel test method for the rapid determination of hydrogeological parameters in the field, the slug test has a research history of 70 years since its successful application.