Experience of in situ stress measurement with hydrofracturing and overcoring techniques in Ekou mine, China

The Ekou mine is located in Daixian County in the Shanxi Province of China. It is an open-pit mine with an ore production of five million tons per year. The vertical height of its slope is 720 m of which ca. 300 m are below ground level. The current height of the slope is approximately 400 m. Increased bench sliding and other failure events have occurred as the slope becomes higher and steeper. To ensure normal and safe production at the mine, it is necessary to carry out a systematic analysis of the stability status of the mine. The in situ stress state is the most important because most failures at the open pit are caused by the action of in situ stress. Both hydraulic fracturing and borehole overcoring techniques were used for in situ stress measurement at the mine.