CLASSIFICATION AND DISCUSSION ON CAUSES OF ABNORMAL STRESS RELIEF CURVES IN OVER-CORING STRESS MEASUREMENTS USING A HOLLOW INCLUSION GAUGE

Abstract

In order to discuss causes of abnormal stress relief curves obtained in over-coring stress measurements, the authors classified 267 stress relief curves into four patterns. Consequently, the authors found that two of the four patterns reflect stress condition and should be used for stress determination, while the other two do not. One of the two abnormal stress relief patterns was most likely caused by existence of cracks in rock or improper gauge setting condition. The other one was found to be caused by temperature change due to cooling water in coring, when difference in temperature between the water and rock exists.