$1\mathrm{.}3.$ You are the rock engineer for a platinum mine that is operating at a depth of $900$ meters below the surface. Recently, the mine has experienced a series of rock falls, prompting a review of the current support systems. The rock mass has a density of $2800k\frac{g}{m^3},$ and based on recent surveys, the $95\%$ cumulative fallout height has been determined to be $1\mathrm{.}4$ meters. The mine uses elongates with a load capacity of $180$ kN each. Your task is to design a new elongate support system to improve safety and reduce the risk of rock falls. Your design must also include support resistance, area supported by each elongate, and the support spacing on dip and strike.

$1\mathrm{.}4.$ Explain the role of backfill in underground mining support and list Five types of backfill systems used.

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