Document ID: chunk:federal_register_of_legislation:F2016L00416:reg:4:p19
Version: federal_register_of_legislation:F2016L00416
Segment Type: reg
Provision Reference: reg 4 (pt 19/21)
Character Range: 79705–82605

where access is available for an excavator or backhoe to lower and raise the boxes or shields into and out of a trench. They are generally not suitable where as access is difficult and ground conditions prevent the use of lifting equipment.

Steel boxes for trench work can be light or heavy duty construction depending on the depth
of the trench and ground conditions. Trench shields and boxes should be designed by a competent person, for example an engineer, and be pre-manufactured to job specific dimensions.

Used correctly, shields and boxes can provide a safe work space for workers needing to enter
an excavation. Trench shields and boxes should be adequately maintained or they may fail unexpectedly, particularly if they have been abused or misused. The manufacturer's instructions for the installation, use, removal and maintenance of shields and boxes should always be followed.

Trench boxes should not be subjected to loads exceeding those which the system was designed to withstand. Earth pressures are reduced when correct benching and battering practices are used.

Shields and boxes should be stored and transported in accordance with the manufacturer's instructions. Heavy duty equipment may require disassembly for transport.

Boxes should be regularly inspected for damage. They should only be altered or modified with the approval of a competent person.

    6.5              Other ground support methods

Support to the face of an excavation can sometimes be effectively provided by the use of chemical stabilisation techniques. These techniques involve injection under pressure of chemical solutions which bind and solidify soil. This method of stabilisation is only possible in porous soils.

    6.6              Regular inspection

The condition of soil surrounding excavations can change quickly due to the soil drying out, changes in the water table or water saturation of the soil. The soil condition and the state of shoring, battering and trench walls should be frequently checked by a competent person for signs of earth fretting, slipping, slumping or ground swelling. Where necessary, repair the excavation or strengthen the shoring system from above before allowing work below ground to continue.
APPENDIX A – DEFINITIONS
Barrier means a physical structure which blocks or impedes something.
Barricade means any object or structure that creates a barrier obstacle to control, block passage or force the flow of traffic in the desired direction.

Backfill means material used for refilling excavations.

Battering means to form the face or side or wall of an excavation to an angle, usually less than the natural angle of repose, to prevent earth slippage.

Bench means a horizontal step cut into the face or side or wall of an excavation to provide horizontal bearing and sliding resistance.

Benching means the horizontal stepping of the face, side, or wall of