Document ID: chunk:federal_register_of_legislation:F2016L00416:reg:4:p10
Version: federal_register_of_legislation:F2016L00416
Segment Type: reg
Provision Reference: reg 4 (pt 10/21)
Character Range: 56300–59379

finished tunnel.
The design should also include information on the excavation methods and ground conditions considered in the design. This will allow the design to be reviewed if another excavation method is chosen or the ground conditions differ from that expected as the excavation proceeds.

The design also needs to take into account the construction methods that may be used to construct the tunnel so that a safe design for construction purposes is achieved.

Tunnelling hazards and risks
Common hazards and risks in tunnel construction generally relate to the confines of working underground including:
    * tunnel stability – rock or earth falls and rock bursts
    * changing ground conditions – strata and stress fluctuations
    * limited space and access, with possible confined spaces involved
    * air contamination or oxygen depletion
    * fire or explosion
    * the use of fixed and powered mobile plant
    * the interaction of people and powered mobile plant
    * temporary electrical supplies and circuits including loss of power for lighting and ventilation
    * compressed air use and high pressure hydraulics
    * large scale materials and equipment handling
    * overhead seepage, ground and process water
    * uneven and wet or other slippery surfaces
    * falls of people or objects
    * contaminated groundwater
    * ground gas and water in-rush
    * noise
    * vibration
    * heat and humidity
    * ground loss or settlement at surface level, and
    * hazardous substances.
Control measures include:
    * ground support, for example tunnelling shields, mesh, rockbolts and shotcrete
    * appropriate fall protection, for example temporary work platforms
    * plant and vehicular traffic management systems
    * regular plant maintenance
    * pumps or dewatering systems to remove ground water
    * mechanical ventilation to control airborne contaminants and air temperature/humidity
    * dust extraction
    * plant fitted with water scrubbers
    * plant fitted with catalytic converters, and
    * provision of breathing equipment when a hazardous atmosphere is present and cannot be effectively ventilated by external means.
Using ground support designed for the unique circumstances of the work is essential to control the risk of a collapse or tunnel support failure. All excavation for tunnelling should be supported.

    5.3              Shafts

Shafts are often constructed to provide access or ventilation to a tunnel. Comparatively shallow shafts can be sunk for investigating or constructing foundations, dewatering or providing openings to underground facilities.
Shafts vary greatly in design and construction technique, depending on their purpose and the local conditions. They may be vertical or inclined, lined or unlined, various shapes, and excavated using various techniques.

Shaft sinking involves excavating a shaft from the top, with access and spoil removal from the top. Other construction methods include raise-boring, which is a method of constructing a shaft (or raise) where underground access has