Parameters of hydraulic fracturing and disintegration of impervious rocks while preparing blocks for leaching

Conclusions

1. The maximum water injection pressure for hydrofracturing of Blyava ores was 12.1–12.9 MPa and for hydrodisintegration, 4.5–5.5 MPa. The calculated values of these pressures differ from the experimental ones by 20–25% and 25–36% respectively, which is satisfactory for natural-scale studies.

2. The probability of hydrofracturing or hydrodisintegration of the mass depends a great deal on the distance between the packer and the borehole face. It has been demonstrated experimentally that hydrofracturing occurred at a distance of 0.1–0.6 m and only hydrodisintegration was noticed at a distance of 4–10.2 m. These data show that, all other conditions being equal, the packer (interpacker) spacing of the boreholes is of great importance for producing, in practice, some type of hydrodynamic impact on the rock mass.

3. Water injection through boreholes into the ore body under conditions of hydrofracturing and hydrodisintegration showed the real possibility of establishing a hydrodynamic link between boreholes at distances of 5 m, 10 m, and greater.

4. The technology and equipment developed by the Institute of Mining make it possible to prepare blocks of impervious ores for leaching by employing hydrofracturing and hydrodisintegration of rocks and creating in the block a borehole — slit — borehole system.

5. As a result of suffosion of the ore, slime is released intensely from the drainage boreholes, which is typical for hydrofracturing and hydrodisintegration processes and for subsequent fluid injection under pressure. This may be used to augment the performance of the borehole — slit — borehole system.

6. If conditions in the mining industry become favorable, it would be advisable to continue the operations, the essential features of which are elucidated in this paper.