The correct knowledge of in-situ stress state is necessary for mining design, construction and excavation, especially in 6 aspects. Stress relief by overcoring technique with hollow inclusion strain cell is mainly used for in-situ stress measurement in Chinese mines, during which a series of new improving techniques have been developed for increasing reliability and accuracy of the measurement. The results and applications of in situ stress measurement in 6 metal mines are introduced. Hydraulic fracturing technique is used for stress measurement in the early exploration stage of the mines. To solve problems caused by great measuring depth and complicated geological condition of the mines, some improvements on hydraulic fracturing equipment have been made and successfully used at more than 1000m depth.
In-situ stress is the basic natural force to cause deformation and failure of mining engineering. Correct information of in-situ stress state is necessary for reliable and safe mine construction and mining excavation (Cai M 2001, Kang et al. 2007). In every stage and every aspect of mining design and operation, information of in-situ stress state plays important guiding role. During the last 20 years, the authors have completed in-situ stress measurement in about 30 engineering projects within China, including 20 mines in which 12 are metal mines, such as Xincheng gold mine and Linglong gold mine in Shandong Province, Shuichang iron mine in Hebei Province, Ekou iron mine in Shanxi Province, Meishan iron mine in Jiangsu Province and Jinchuan nickel mine in Gansu Province (Cai M, Qiao & Li 2000a). The Shuichang iron mine and Ekou iron mine are open pit mines and the other four above mentioned are underground. Stress relief by overcoring technique was used for in-situ stress measurement in most of the 30 projects.