Impact of the Groundwater Drawdown on The Instability and Deterioration of Water Well Screens

Vertical effective stress (σ'V) as well as horizontal effective stress (σ'h) are increased when groundwater levels declines. This in turn increases the stresses on the water well casings and screens resulted in deteriorated and ruptured casing/screens. In this research, the impact of water level drawdown on the increasing stresses on the water well casings is investigated. By studying yield strength of casings and screens, and the stresses imposed by the aquifer materials on them, it has been found that the stresses gradually increases during water table drawdown. Critical drawdowns can even destroy and break the casings/screens. The effect of diameter, thickness, and the slot specifications of the screens on their strength has also been assessed in this study. Based on the results, it is a worthwhile practice to use small diameter, thick casings/screens, with large number of slots, and thick filter packs for the problematic plains; plains with a high rate of well destructions.