No abstract

Mine owners demand that structures perform optimally at the primary point of commercial mining operations, which force the designers’ attention to the critical contributions of the material characteristics. The extreme rainfall conditions and high loads exerted on the structures, required careful consideration of the design methodology and parameters used to cause the least amount of disruption during the full operating life span of the Mechanically Stabilized Earth Wall (MSEW) structures, through the varying conditions present on site. To design the low risk MSEW structures in Liberia, where the most common backfill construction material used is often of a lower grade laterite, combined with a rainfall condition classed as monsoon (above 4,000mm rain fall per annum), generated a scenario that forced the design approach and choice of geosynthetic materials to exclude any compromised solutions. Simplicity in the construction installation using geosynthetics and gabion materials have satisfied design requirements and minimized risk to mine operators and management.

The stability of over-steep road embankments often worsens with time. In many cases the slope deterioration can be ascribed to continual downslope creep of a surficial layer of soil that has been affected by infiltration of rainfall. Such infiltration reduces the suction in the surficial layer interacting with the environment. With every season the surficial layer moves further downslope, often resulting in cracks in theslow lane and placing structures constructed at the crest of fill slopes in potential jeopardy. A slope on the National Route 3 (N3), in the South African Province of KwaZulu-Natal, constructed at roughly 40° from the horizontal showed signs of distress in the slow lane many years after construction. The rehabilitation of this slope required stabilisation design using unsaturated soil testing, modelling, and in-situ suction measurement. The slope was stabilised using soil nails, a high-tensile steel mesh, and a suction measurement system was installed. An overview of the emergency works design, subsequent investigation, and monitoring is provided in this paper. It was found that the suction profile determined by transient finiteelement analysis matched well with the measured suction profile and provided a good basis for the emergency design works prior to full investigation.