A Study on Estimation of Rock Stress based on Variation of Tangent Modulus

Abstract

Tangent modulus method was investigated as one of core-based methods for rock stress measurement and was compared to DRA method. It was clarified that the preloaded stress level was accurately estimated as the stress level at the bending point on the stress-tangent modulus curve by the tangent modulus method. Relationship between duration of load application and maximum delay time for stress memory was investigated by carrying out the both methods. The bending point gradually became vague as the delay time increased in the both methods. The accuracy of estimated stress level of the preloading was almost the same for the both methods. It was shown that the preloaded stress level was accurately estimated from the rock specimen which had been preloaded for approximately one week and had been left for approximately six weeks.