Water Well Design for Earthquake-Induced Motions

Earthquake records indicate negligible damage to adequately constructed water wells that are located away from faults or areas of unstable ground. For nuclear power plants, three factors are considered for design of wells: siting, critical outage time, and effects of ground motion. The computational steps required for the casing analysis under earthquake loads are based mainly on the effects of the free-field soil deformations. Axial and tangential stresses are computed for soil pressures and seismic shear and compressional waves. Shear stresses are obtained from shearing distortion of the ground above bedrock. These are then combined conservatively to obtain principal stresses in the casing. The ductility of steel provides a wide safety margin to accommodate any local stress concentrations. The discharge system supported by lateral leaf springs is analyzed with a lumped-mass model, and the apparent mass of the water surrounding the discharge pipe is included in the model formulation. A parametric study was performed to investigate the effect of various parameters used for the dynamic analysis of the discharge system.