Rock-mechanical investigations for safe leaching and storage operations
In the course of exploration and cavern drilling operations, rock samples are taken in the surroundings of a projected cavern to determine stability and tightness.
Following the geological interpretation, an independent rock mechanics lab will examine the strength and deformation behaviour and the tightness properties of selected rock samples.
These tests are required by the responsible mining authorities for the determination of the parameters of the planned cavern operations. They ensure continued stability and tightness of the caverns during leaching and storage operations.
The results of the rock-mechanical tests will be used for a computer simulation of the planned cavern operations. Thermodynamic simulations of storage operations are included to take also more challenging storage scenarios into account.
An expert opinion based on the results of the simulation will then provide recommendations for cavern operations:
- Determination of the admissible cavern depth;
- Minimum distances from other caverns in the field or from above/neighbouring rock formations;
- Definition of a maximum thickness of the bearing structures in the salt as well as above and neighbouring rock formations (cross-structures and pillars) to ensure continued load-bearing capacity and tightness;
- Minimum and maximum internal cavern pressures during storage operations;
- Requirement to document operating times under minimum pressure;
- Requirement to document operating conditions to protect the cavern shape in the long term;
- Forecast of the convergence for different storage sceanarios and their effects on the terrain surface (settling forecast).
These recommendations are the basis for planning caverns that are safe and economical to operate.