Flow toward storage tunnels beneath a water table: 1. Two‐dimensional flow

A system of parallel tunnels is excavated in saturated rock of low permeability for storing oil or LPG. In order to contain the product, permanent water inflow has to be maintained. In absence of recharge this flow causes a continuous drop of the water table. A numerical scheme, based on the boundary integral elements method, is used in order to determine the water table motion, the inflow to galleries, and the velocity on the perimeter. Both oil‐filled and empty galleries are considered. The shape of the galleries is maintained fixed, while the spacing and the distance to an impervious bottom is varied. An analytical approximate solution, valid for sufficiently high water table above the galleries top, is also derived. This solution is extended to the cases of vertical recharge above the free surface and LPG filled galleries. The solution of the two‐dimensional flow problem can be used in order to determine: (1) the time required for the water table to drop from its initial position to the gallery top, or to the product level, in absence of recharge; (2) the water velocity on the gallery perimeter; and (3) the total inflow to the gallery.