Rocscience - Slide3 Crack Link

The workflow for utilizing the Crack Link functionality involves three primary stages: Geometric Definition, Hydraulic Coupling, and Meshing.

When performing a Shear Strength Reduction analysis (in the FEM module), Slide3 automatically weakens the material properties. The Crack Link ensures that as the strength reduction factor ($SRF$) increases, the interaction between the water pressure and the joint strength is recalculated. The failure surface is forced to respect the geometry of the crack; the solver cannot calculate a failure surface that ignores the discontinuity, forcing a more realistic (often more conservative) failure mechanism.

Users define a crack by specifying a plane orientation (Dip and Dip Direction) and extent, or by importing a triangulated surface. The crack is treated as a "Joint" entity. In Slide3, this is often managed under the Geology > Joints menu, where a joint network or a single persistent joint can be defined. rocscience slide3 crack link

[Slide transition – “Crack Link”]
“Now that we have introduced the basic fracture network in the previous slide, let’s focus on how individual cracks interact to form a crack link—the fundamental conduit for progressive failure in rock masses.

1️⃣ Definition – A crack link is a continuous path of intersecting or closely spaced cracks that permits stress redistribution and, ultimately, the propagation of a macro‑fracture.
2️⃣ Why it matters – In engineering practice, the existence of a crack link dictates the stability of slopes, tunnels, and foundations. A seemingly isolated set of micro‑cracks can coalesce into a critical failure plane when the link becomes hydraulically or mechanically active.
3️⃣ Rocscience’s approach – Both RS2 (finite‑element) and Phase2 (boundary‑element) embed crack‑link detection in their pre‑processor. You can: The workflow for utilizing the Crack Link functionality

In short, the crack‑link concept provides a bridge—literally and figuratively—between the micro‑scale fracture geometry we generate in Rocscience and the macro‑scale stability assessments we need to deliver to clients.”

| Concept | Equation / Principle | Relevance to Rocscience | |---------|----------------------|------------------------| | Stress intensity factor (K) | ( K = \sigma \sqrt\pi a ) | Rocscience evaluates K for each crack; linking increases the effective a (crack length) and reduces the shielding effect. | | Energy Release Rate (G) | ( G = \fracK^2E' ) | When two cracks are within Lₗᵢₙₖ, the software adds a bridge element whose stiffness is derived from G. | | Linear Elastic Fracture Mechanics (LEFM) | Assumes linear elasticity until crack propagation. | Both RS2 (FEM) and Phase2 (BEM) are LEFM‑based; crack‑link detection respects LEFM criteria (K₁c, K₂c). | | Statistical Fracture Network Theory | Weibull‑type spacing distribution. | The Fracture Generator uses a Weibull or log‑normal distribution to seed cracks; link detection is applied post‑generation. | [Slide transition – “Crack Link”] “Now that we

In Slide3, a Crack is defined as a planar surface or a polygonal volume that bisects the mesh. Unlike a simple material boundary, a Crack introduces a discontinuity in the displacement field. The software treats the interface as a potential failure plane where slip can occur independently of the surrounding rock mass.

*FRACGEN
  TYPE     = RANDOM
  ORIENT   = 30 60 90          ! mean dip, dip direction, std dev
  SIZE     = 0.5 5.0           ! min, max length (m)
  DENSITY  = 0.12              ! fractures per m³
  APERTURE = 0.001 0.01        ! min, max aperture (m)
*LINKAGE
  APER_TOL = 0.00025          ! Δa = 0.25 mm
  ANGLE_TOL = 15              ! θₘₐₓ = 15°
  DIST_TOL = 0.005            ! Lₗᵢₙₖ = 5 mm

Running the model with the above block produces a crack‑link map that can be visualised by toggling the LINKAGE layer.