Validation of a Semi-empirical Procedure for Estimating Steady-State, Groundwater Inflows in Shallow Rock Tunnels Through Case Study Analyses

Abstract

The construction of tunnels in rock terrain has increased in importance around the world as the need for new transportation routes and water and wastewater conveyances has grown. Large cities and nearby suburbs have limited space for extensive, above-ground thoroughfares; therefore, underground systems may be the only viable means for developing new infrastructure. Excessive groundwater inflow into rock tunnels under construction can injury personnel and terminate the construction of the tunnel project. Therefore, it is important to accurately estimate groundwater inflow into rock tunnels. A semi-empirical procedure for estimating steady-state, groundwater inflow in shallow rock tunnels is presented and discussed in this paper. In addition, this paper presents two case study analyses which include the Elizabethtown tunnel in New Jersey and the Toledo tunnel in Ohio. Packer test (i.e., pressure test) data was analyzed for both case studies utilizing this semi-empirical procedure. This paper reviews the basic theory behind the procedure and validates the procedure through case study analyses. It also describes previous proposed modifications and clarifies the need for any such modifications. In general, good groundwater inflow estimates were derived for shallow rock tunnels utilizing this semi-empirical procedure. This research will benefit large and small municipalities (e.g., owners of major infrastructure tunnels projects) who need to install underground conveyances for water supply lines, sewer lines, railway, and roadways. By knowing the amount of water that might flow into the rock tunnel during its construction, the owners will save money, but more importantly lives if groundwater inflow are estimated accurately.