AS 2758.6:2019 Aggregates and rock for engineering purposes
8.5  Existing quarries — Blast damage
When it is proposed to supply armourstone from existing aggregate quarries, it will be necessary to examine the proposed faces and floor of the operating quarry for backbreak (blast induced fractures behind the current quarry face or below the current quarry floor) from previous quarry blasts. Typically, quarry operations attempt to fracture the rock mass extensively using blasting and thereby minimize the energy requirement for crushing and reduce or eliminate the need for secondary breakage. This practice results in incipient fracture in the quarry faces and floor. It will also mean that rock pieces picked from the blast face of a normal aggregate production blast may contain blast fracturing that is not immediately obvious.
For large projects requiring heavy rock blocks, it may be necessary to commence by trimming back existing faces beyond any backbreak zone using blasts designed to minimize rock fracture. Similarly, at the end of the project, the quarry operator may expect that initial blasts in the area used for the armourstone project will return an excessive number of blocks requiring secondary breakage.
8.6  Access
Transport of large rock blocks by the public road system is not possible in normal quarry trucks. For projects where the armourstone is being supplied from quarries remote from the project site, consideration should to be given to transport methods. The rock blocks are likely to be moved by low loaders and it will be necessary to consider load limitations, width restrictions and transport permits as part of the assessment of the ability to obtain materials. For quarries adjacent to the project, where transport over public roads will not be required, consideration of the local haul roads for grade and turning circle radius may still be required.
9.1  Sampling
Sampling will be conducted to provide material for durability tests completed by laboratory testing. Sampling should be conducted following the procedures in AS 1141.3.2. Where the project requirements result in the development of alternate sampling methods and sampling plans, such methods and plans should be documented and included in the works specification. At a minimum, the requirements for consideration and the sampling report of AS 1141.3.2 should be met. The use of photographs to support the sampling procedure is highly recommended.