Drainage For Mining Changes

By Steleanor Bella


Protection works shall consist of rock pitching adjacent to outlets and headwalls of drainage conduits and at intersections of open drains. Protection works shall be carried out to the details indicated on the drawings. Before placing rock pitching, the bank on which it is to be placed shall be trimmed to a uniform slope as detailed on the drawings. Mortar bedding shall first be placed commencing at the lowest point of the slope and placing shall then progress upward. Depth of the bedding shall be as indicated on the drawings.

Additional backfill material will be placed on top of the concrete stabilised backfill as required to obtain correct finished levels. All open drains will be constructed to the levels and grades shown on the drawings. All backfill will be compacted to 90% of maximum dry density as measured by AS 1289 Part 3, except under roadways and access areas where the backfill will be compacted to 95% of maximum dry density.

Open drains shall include table rains, catch drains and dispersal drains. All open drains shall be constructed to the levels and grades shown on the drawings. All open drains shall be cut to natural surface and shall not contain fill material unless otherwise directed by the Superintendent. Embedded steelwork included in the concrete structures such as open grating, support channels, manhole cover and the like shall be constructed to the details shown on the drawings and in compliance with the specification.

Embedded metalwork included in the concrete structures such as open grating, support channels, manhole cover and the like will be constructed to the details shown on the drawings and in compliance with the specification. Before placing rock pitching, the bank on which it is to be placed will be trimmed to a uniform angle as detailed on the drawings. Mortar bedding will first be placed commencing at the lowest point of the angle and placing will then progress upward.

On the day after the concreting of the rocks, a stiff concrete mortar mix will be carefully worked in to the joints between adjacent rocks to provide an even, solid, tight surface. Compaction will not be used within 150 mm of the pipe. Suitable backfill material will be placed around the pipe to a height of 300 mm above the top of the pipe or as detailed on the drawings. The remainder of the trench will be backfilled to finished ground level with material previously excavated from the trench.




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