Determination of Rock Mass Deformation Modulus in Closely Jointed Columbia River Basalt

摘要

The basalts delineated for the repository feasibility study are located on the Hanford Site in southeastern Washington. One of the rock properties of interest is the deformation modulus. In order to properly apply a deformation modulus value to construction design or numerical models, it is necessary to understand the range of value the modulus can exhibit. The modulus values can vary as functions of sample size, stress level, location, and orientation. No single test method allows an evaluation of all these variables, so several different types of modulus tests must be performed. The three types of tests discussed are: laboratory testing of recovered core; borehole jacking tests using the Goodman Jack; and borehole deformation measurements during a flat jack test. The following conclusions can be inferred from data collected in tests in the closely jointed Pomona basalt: deformation modulus decreases with increasing specimen size; laboratory tests indicate a deformation modulus of approximately 87 gigapascals; borehole deformation measurements in a flatjack test indicate a deformation modulus of approximately 40 gigapascals; borehole jacking test with a Goodman Jack indicate a deformation modulus of approximately 20 gigapascals; and there is no significant temperature effect on modulus values (up to 100 exp 0 C). (ERA citation 08:016425)