**4. Mining status**

In the scheme of mining with respect to Kolihan Copper Mine the following methods have been adopted:


In the sub level open stoping method, sub levels are developed at vertical intervals of 18-20 m with a crown level at 9 m below uppermost levels. The size of the stope block is 30 m along strike which consists of 20 m of stope and 10 m of Rib Pillar.

In the blast hole stoping method a drill level is prepared below the crown pillar of 9 m. The size of the stope block is 30 m along the strike, which includes 16.6 m stope and 13.4 m Rib Pillar. The proposed stopes will be developed at the lower levels.

The mine extends from 486 ML to 0 ML with the surface RL of 486 m. Mining up to 306 ML is complete and presently it is active at 246 ML and 184 ML. Mine development has to commence at lower level soon.

**ii.** A new induced fracture is not essentially required to be created for stress evaluation.

**Figure 2.** Status of Mining activities in Kolihan mine (ML= Meter level which indicates altitude from mean sea level)

Estimation of the Impact of Mining on Stresses by Actual Measurements in Pre and Post Mining Stages…

http://dx.doi.org/10.5772/56017

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A schematic diagram showing set up of the hydrofracture system assembly is shown in Fig.3.

The straddle packer assembly (Hydrofrac assembly Fig 4) was used for fracture initiation/ opening and further extension. The straddle packer assembly consisted of a test interval of length 200 mm and two 250 mm steel reinforced packer (42 mm dia, burst pressure = 70 MPa) units attached at either end of the test interval. In the case of hydrofrac experiments in the 48 mm diameter boreholes at the present Project, the straddle packer unit was operated by 1500 mm long and 32 mm diameter tubes (dual line packer inflation + injection unit combined in one). The maximum injection rate of the electrically driven pump was 10 lit /min using water for pressurisation. All the events of injection were recorded in continuous real time digital

Stress can be evaluated both from preexisting/induced fractures

mode.
