Determination of in Situ Stresses for the Underground Pumping Chamber of Southern Nevada Pumping Plant No. 1

摘要

The borehole stress relief method was used to determine the in situ stress in the rock mass surrounding the underground pumping chamber for Southern Nevada Pumping Plant No. 1. A 3-directional borehole gage was used to measure the deformation of 1-1/2-in.-dia boreholes overcored with 6-in. drill bits to relieve stress. Three 25-ft boreholes having different orientation were drilled so that a 3-dimensional stress field could be computed. The stress field was determined at one location within the pumping chamber after excavation was completed, to check the estimated values used in designing the chamber, with available geological data. (Author)