On the design of the fiber reinforced shotcrete applied as primary rock support in the Cuiabá underground mining excavations: A case study

The Cuiabá mine is an underground gold operation located in Sabará (Minas Gerais, Brazil), which began to use fiber reinforced shotcrete as rock support since 2012. In order to carry on a mechanical analysis and to design the steel and polypropylene fiber reinforced shotcrete linings, the work in hand presents an experimental investigation on the mechanical behavior of the applied composite material inside the Cuiabá mine. Through standardized panel tests, the paper evaluates the toughness performance levels for each studied fiber reinforced shotcrete and applies the current design guidelines for mining works. Based on the rock mass classification of the analyzed mine slopes, while the use of 4.2 kg/m3 of polypropylene fiber volume fractions seems to be suitable where fair rock quality is observed, the addition of 25 kg/m3 of steel fibers is more indicated where severe ground movement is expected. On the other hand, a mismatch between the standardized panel tests (ASTM C1550 and EN 14488-5) on the shotcrete design guidelines was also assessed in the present research. The analyzed fiber reinforced shotcrete received different classifications depending on the used standardized panel test, resulting on an overestimation of the PP fiber reinforced shotcrete for the square panel tests. Safety factors can be applied in order to mitigate the possible mismatch between square and round panel tests.