4.5 Dumping method

Mass dumping leads to rotation failures where the fine grained material behaves as a weak homogeneous mass. In the end-dumped dump state, it is very sensitive to pore pressure increases caused by rapid loading, precipitation, and foundation seepage pressures.

Face dumping causes formation of a plane of weakness along the face. Under such condition, continued use of the dump, even for dumping of good quality material is susceptible to failure along this plane.

Crest Dumping or rapid dumping of fine grained material on the crest may result in local oversteepening. This is due to the apparent cohesion imparted by an increase in moisture content. Oversteepening has been documented to have caused crest slopes in excess of 43o.

The problem of poor quality material is exacerbated by addition of water in the form of runoff or direct precipitation. It is important therefore to minimize the impact of precipitation on dump using various measures such as diversion of surface runoff, and adequate foundation preparation to minimize seepage inflows.

Handling and Placement: Mechanical handling of dump material causes some breaking of poor quality rocks. The more handling-intensive is the placement method, the more is the breakage expected. Of the commonly used placement methods, end dumping usually causes the minimum degradation. Dumping short and dozing adds an extra degree of breakage. Designs requiring placement in lifts and those requiring compaction suffer the effects of further degree of breakage. Heavy equipment (e.g. dozers and haul trucks), which by necessity travels on dump surfaces, also have a deleterious mechanical effect on the materials.