Groundwater Seepage Rate (GSR); a new method for prediction of groundwater inflow into jointed rock tunnels

The main purpose of this research is to introduce a new method for estimating the groundwater inflow rate into tunnels excavated in rock environments. The Groundwater Seepage Rate (GSR) is a novel analytical method that has the capability to assess the rock mass potential in conducting the groundwater into tunnels. Geological and hydraulic parameters and radius of the tunnel are the main parameters used in the GSR method. In this method, geological parameters are defined based on the characteristics of the joint sets including the strike, number, spacing and aperture of joints of each joint set. In addition, hydraulic head and hydraulic conductivity are other principle inputs of the proposed model. In GPR method, the rate of groundwater inflow has been evaluated in 3D dimensions and efforts were made to obtain acceptable values by creating rational correlations among input data. The taking account of joints condition in tunnel and the direct effect of tunnel radius, the separate study of the joint sets and the role of fracture systems in the groundwater conductivity into excavated openings are the main advantages of this model. According to the results of this study, GSR method can provide better estimations of the inflow volume for rock masses with elastic behavior in which fracture systems have been developed. Finally, in the end this paper for validation of GSR values, the results of this method were compared with the obtained results of empirical methods and observed groundwater inflow in various geological units of the Zagros tunnel in Iran. Additionally, the calculated value of groundwater inflow based on GSR method shows good compatibility with empirical methods.