Rock Strength Test Simulation

Understanding the Stress-Strain Curve

This graph shows how a rock responds to being squeezed (stress) and how much it deforms (strain) as a result. For brittle materials like rock, the process is typically characterized by a sudden, catastrophic failure after a period of elastic and plastic deformation.

1. Elastic Deformation

The initial straight-line portion. The rock deforms but would spring back to its original shape if the load were removed. The slope of this line is the Young's Modulus (E).

2. Plastic Deformation

The curve begins to flatten as it approaches the peak. This is not true plastic flow like in metal, but represents the internal structure of the rock breaking down. Micro-cracks form and link up, causing permanent, non-recoverable deformation.

3. Failure Peak (Peak Strength)

The highest point on the curve, representing the maximum stress the rock mass can handle (σ'cm). This is the point of ultimate failure. The height of this peak is determined by several factors, including:

• Intact Rock Strength (UCSi): The strength of a small, flawless piece of the rock. This is the starting point for the calculation.
• Rock Mass Condition (GSI/RMR): The number of joints, fractures, and their condition. More fractures mean a much lower peak strength compared to the intact rock.
• Confinement (σ₃): Pressure from surrounding rock. Higher confinement dramatically increases the peak strength, which is why this simulation's peak value increases as you raise the confinement stress.

4. Post-Peak Behavior (Brittle Failure)

The sharp drop after the peak. The rock can no longer sustain the load, and the stored elastic energy is released suddenly. This is the source of seismic events in a real-world scenario. 💥

5. Residual Strength

The final, low-stress portion of the curve. The rock is now a broken mass, but it still has some strength due to friction between the fractured pieces.