Estimation of the impact of mining on stresses by actual measurements in pre and post mining stages by hydrofracture method – A case study in a copper mine

Abstract

To sustain and increase the productivity in a large underground copper mine in India the management of the mine decided to design and develop stopes below the mined out area. For the design of the stopes a detailed stress measurement programme was carried out by hydrofracture method at different depths from the developments available near the proposed stope. The result indicated a post mining induced high stress tensor with the direction of the maximum compression (maximum principal horizontal stress) rotated 70- 750 from the pre-mining stress tensor and oriented almost transverse to the ore body as against sub parallel to the orebody during pre- mining stage. A 3-D numerical modeling of the mine with pre mining stress tensor as input parameter substantiated the field result at the post mining stage. The generation of post - mining stress helped in understanding the impact of mining on the stress and was used for design and sequencing of the stoping operation for the safe and optimum extraction of the ore.