Equivalent well analysis of construction dewatering systems

The application of the cumulative drawdown method in designing of groundwater lowering system - Golden Hill project

“…This approach is theoretically correct in confined aquifers, but is invalid in unconfined aquifers where the changes in saturated thickness that occur during drawdown complicate the interaction of drawdowns. It has also been successfully applied in unconfined aquifers where the final drawdown is less than around 30 percent of the initial saturated aquifer thickness [16][17].…”

“…Therefore, this problem will be analyzed assuming confined behavior throughout. The cumulative drawdown is calculated using equation [17][18][19][20].…”

“…The method requires that the plan layout of the well array be sketched, and the x-y coordinates of each well be determined [17][18]. The co-ordinates then allow the radial distances ri (from each well to the point where drawdown is being checked) to be calculated.…”

“…In this case the initial guess was twenty-two wells evenly spaced at 15 m centres (Figure 5). A spreadsheet program is then used to evaluate equation (1) for the cumulative drawdown at selected locations within the excavation [16][17][18][19][20][21]. For circular or rectangular excavations with evenly-spaced wells it is normally sufficient to determine the drawdown in the center of the excavation, because drawdown everywhere else will be greater.…”

Contributions to Géotechnique 1948–2008: Groundwater

“…By modelling groundwater control systems around excavations as a single equivalent well, Powrie & Preene (1992) identified appropriate simple models (i.e. essentially plane or radial flow) for excavations of different aspect ratio and the distance to the recharge boundary.…”