3.0 Methods of Stability Calculation

The method of stability calculation for a dump design is dependent on the anticipated mode of failure. The potential modes of failure for a specific site conditions are often difficult to assess. In most cases, the method of stability calculation is based on a generalized slip surface, which may be a plane, an arc, or a combination of both. These generalized analyses include identification of the slip surface with the lowest determined factor of safety while treating the dump mass as a homogenous body. The shear strength of dump depends on the following parameters (Hawley, 2001; Holtz and Kovacs, 2003):

Particle shape and roughness of grain surface

Grain quality: weak rock materials such as shale has lower friction angle compared to strong rock materials such as granite

Grain size: friction angle increases or decreases with increase in grain size

Grain size distribution: friction angle typically decreases with decreasing coefficient of uniformity of grain size

Specific gravity

State of compaction or packing : friction angle typically increases with increasing density or decreasing void ratio

Applied stress level: friction angle decreases with increasing confining stress, resulting in a curved strength envelope passing through the origin instead of the classical straight line

Definition of failure conditions: drained or undrained, and

Degree of saturation


 

 

Types of slope failure in mine dump:

Figure 5 shows the common types of failure occurring in mine dumps.

 

Surface slide                                                                Edge slide

 

Shallow flow slides                                              Base failure (spreading)

     

Block Translation                                     foundation circular failure

         

Circular Arc  failure                                              Toe spreading

 

Figure 5: different types of possible dump failure types