Ground water pressure relief wells in shaft sinking

Abstract

The pattern of pressure relief produced in a confined aquifer by a ring of vertical relief wells is conventionally evaluated by summation of simple contributions from individual wells. Where the wells surround an open excavation such as a shaft, the pattern is modified. This paper outlines the appropriate modifications. The resulting pattern of pressure relief and of shaft inflow is calculated for typical practical situations for an open circular shaft and also for a shaft protected by an annular zone of grouted ground. The examples show the influence of number and location of relief wells and the degree of permeability reduction in the annulus.