Complementary Site Groundwater Rating (SGR) method in the prediction of water inflow to tunnels in rock using real data

Abstract

Groundwater inflow into rock tunnels depends on the geologic and hydrological conditions. There is no complete standard method for estimating the exact volumes and locations of groundwater inflow that may be encountered in the rock tunnels. The discharge rate of the water inflow into the tunnel depends on several factors like permeability and groundwater head. Site Groundwater Rating (SGR) system based on initial site investigations to classify tunnel length qualitatively and quantitatively from the point of groundwater seepage hazard view. In this rating system, we score parameters like frequency and aperture of joints, schistosity, crushed zones, karstification, soil permeability, water head above the tunnel, and annual rainfall. According to the SGR method, the conditions of the tunnel with respect to the main parameters of the risk of leakage of underground water and the way it is done are evaluated. But this method needs to be completed. Some parameters must be corrected and even deleted, and some new parameters must be proposed. In this paper, the SGR method has been optimized with respect to new parameters. According to the experiences of the Kerman and Karaj tunnel excavations, the authenticity of the SGR method validations was studied. As a result, the optimized SGR method (SGRm) is introduced. The results of SGRm compared to the results of SGR are closer to the actual results. This method is a new method to estimate the water entrance to the tunnel. © 2025 The Author(s).