Slope Failure Case Study

James P. Reed
4/30/06

Introduction

This paper describes a hypothetical slope-failure analysis that was performed with RockWorks.  The source data is available within the \samples\movement.atd file.


Input Data

The XYZ coordinates for a series of 40 monitoring stakes (stations) were entered into the RockWorks Geological Utilities datasheet.  Notice that two sets of coordinates are recorded.  The first set were measured (via a total station) on 3/14/98.  The second set were recorded one month later, after a significant slope failure, on 4/12/98.


Input data (stored as \samples\movement.atd).


Generating Pre-Failure and Post Failure Maps

The Geological Utilities / Map / Grid-Based Map program was used to generate contour maps depicting the pre-failure and post-failure surface elevations.


Grid-Map program menu.

The grid models for the pre-failure and post-failure elevation computation were stored as "pre_failure.grd" and "post_failure.grd" respectively.


Pre-failure surface elevations (grid model saved as pre_failure.grd).


Post-failure surface elevations (grid model saved as pre_failure.grd).


Generating Displacement Vector Maps

The Geological Utilities / Linears / Arrow-Map program was used to create a map depicting the movement of the survey stations.


Arrow Map program menu.


Displacement vectors.


Estimating The Volume of Displaced Material

The Geological Utilities / Grid / Math / Grid-&-Grid Math program was used to subtract the nodes within the post-failure model from the pre-failure model.


Grid-Math program menu.

The output model was saved as "displacement.grd".  Regions with negative values represent areas with a net loss of material ("cut") whereas regions with positive values correspond to areas with more material ("fill").


Displacement model (saved as "displacement.grd").


Computing The Relative Station Movement

The Geological Utilities / Grid / Directional Analysis / Movement Analysis program was used to compute the direction, inclination, distance, and velocity of the relative station offset.


Movement Analysis program menu.

The Movement Analysis program automatically created four new columns within the datasheet listing the results.


Datasheet with new, computed columns (direction, inclination, distance, and velocity).


Putting It All Together

Finally, the displacement map was "draped" over the post-failure elevation model to create a visual summary of what relative soil movement.


Displacement (cut & fill) map and displacement vectors draped over post-failure surface model.