The ‘tools’ in the rock engineer’s toolbox are a combination of methods to predict the outcome of a certain set of circumstances and procedures to follow in order to mitigate unfavourable conditions. Commonly, the procedures involve reinforcing the rock mass and providing support to an area of exposed rock mass. Area support usually comprises shotcrete, mesh and newer surface membranes. Shotcrete is both a product and a process. As a product it is a fine aggregate concrete mix with or without additives and admixtures. The aggregate is usually smaller than 10 mm in diameter.

The placement of the material is the shotcrete process. This can range from dry-mix where materials remain in the dry state as they are conveyed to the placing nozzle where water and accelerator are added immediately prior to being shot onto the receiving surface. Wet-mix placement uses equipment similar to that used for concrete pumping. The plastic mix is conveyed to the delivery nozzle where air is added to accelerate the materials for compaction on the receiving surface.

Engineering design of shotcrete is commonly carried out using empirical methods, backed up by numerical models, if required. Shotcrete application suitability, mix design, placement specifications, pre-construction testing requirements, acceptance criteria are part of the range of services offered.

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