Block Search
Search for non-circular block-style slip surfaces.
The block search generates non-circular polyline surfaces. You draw a block polyline that defines where surfaces enter and exit the slope, and the search generates many candidate surfaces that pass through those windows.
How it works
- You draw a two-point block polyline. Its endpoints define a left window and a right window through which candidate surfaces are routed.
- For each candidate, an entry point is chosen in the left window and an exit point in the right window, according to the point-generation mode.
- From each window, the surface is projected toward the boundary along a randomized direction within the configured projection-angle range, and internal vertices are inserted to form the non-circular polyline.
- The configured number of surfaces is generated and evaluated, and the lowest factor of safety is reported.
The block polyline only defines the search windows; the generated surfaces are non-circular and need not lie on the drawn polyline.
Parameters
| Parameter | Unit | Default | Description |
|---|---|---|---|
| Surfaces | — | 1,000 | Number of candidate surfaces generated and evaluated. |
| Left point generation | — | Any line segment | How the left entry point is chosen along the window (see below). |
| Right point generation | — | Any line segment | How the right exit point is chosen along the window. |
| Left projection angle (start / end) | degrees | 135 / 135 | Range of projection angles used to route the surface from the left window toward the boundary. |
| Right projection angle (start / end) | degrees | 45 / 45 | Range of projection angles for the right window. |
Point generation modes
| Mode | Description |
|---|---|
| Any line segment | Points may fall anywhere along the window segments. Broadest coverage. |
| End line segment | Points are restricted toward the end segments of the window. |
| End point | Points are fixed at the window endpoints. Narrowest coverage. |
Applying a metaheuristic
The same block-search windows drive the metaheuristic methods. Selecting Particle Swarm Optimization, Cuckoo Search, or Differential Evolution instead of the plain polyline search optimizes the non-circular surface within the same windows using a population-based algorithm. See Metaheuristic Search.
When to use block search
Block searches suit non-circular mechanisms — sliding on a weak seam, a bilinear or wedge-type failure, or a surface constrained by a stiff layer. Follow the search with surface-altering optimization to refine the critical surface further.