Evaluation of controlled landslides
Introduction
These are phenomena of fracturing and rock detachment of varying magnitude, due to the accumulation and release of energy within an underground mining work. They occur in a competent rock mass with fragile behavior, with a high resistance of the rock matrix and subjected to high stresses. This environment generally tends to occur at great depths. In simple terms, these instability mechanisms occur because competent rocks are capable of accumulating large amounts of energy and given their brittle behavior, they do not deform, but rather an abrupt release of energy occurs through the propagation of pre-existing fractures in the massif or the creation of new ones. Depending on the magnitude of energy released, phenomena can occur in the gallery ranging from hearing noises, slapping or cracking of the rock mass, rock projection at low speeds or Popping to high speed projection of large rock masses or Rockburst.
The Deformation Gradient is defined as the imaginary line perpendicular to the principal Stress σ1 and parallel to σ3. The different types of stress-controlled instability mechanisms occur in the area close to the intersection of the gallery with the gradient.
Parameters that favor the occurrence
Among the uncontrollable parameters that favor the occurrence of stress-controlled instability mechanisms, the in situ stress field, the lithology of the massif, the geomechanical properties of rocks, and geological structures (veinlets, cracks, faults, alterations) are considered.
Types of Mechanisms
Noise
This is the phenomenon that releases the least amount of energy from stress-controlled instability mechanisms. They are the sounds or crunches generated inside the mine as a result of the fracturing or propagation of fractures already existing in the rock matrix. This event is the first indicator that the gallery or mining work is in a high-stress environment.