HighWorkers must enter deep jacking shafts (typically 3-8 metres depth) to install jacking frames, position pipes, and monitor jacking operations. These excavations meet the definition of confined spaces under WHS regulations due to limited entry/exit points, potential for atmospheric contamination, and restricted working space. Hazards include oxygen deficiency from underground respiration or displacement by heavier gases, accumulation of toxic gases such as hydrogen sulphide from decaying organic matter or methane from underground deposits, carbon monoxide from nearby equipment exhaust entering the shaft, and carbon dioxide accumulation from soil respiration. Workers may lose consciousness without warning in oxygen-deficient atmospheres, and rescue attempts without proper atmospheric testing and breathing apparatus have resulted in multiple fatalities when rescuers enter contaminated spaces.
Consequence: Loss of consciousness, asphyxiation, toxic gas poisoning, or death from atmospheric hazards. Multiple fatalities can occur when untrained rescuers enter contaminated spaces attempting to assist affected workers.
HighDeep excavations for jacking and reception shafts create environments where atmospheric conditions can rapidly become hazardous. Oxygen depletion occurs as soil respiration consumes oxygen in enclosed spaces, with levels dropping below the safe minimum of 19.5% required for human respiration. Heavier-than-air gases including carbon dioxide and argon can accumulate in shaft bottoms, displacing breathable air and creating invisible deadly zones. In areas with organic soil or near sewerage infrastructure, hydrogen sulphide gas may be present, causing immediate loss of consciousness at concentrations above 500ppm and death within minutes at higher concentrations. Methane gas from decomposing vegetation or underground coal seams can accumulate to explosive concentrations, creating risk of fire or explosion from ignition sources. Excavations near industrial areas may encounter contaminated ground releasing volatile organic compounds or other toxic vapours.
Consequence: Sudden loss of consciousness, asphyxiation from oxygen deficiency, hydrogen sulphide poisoning causing immediate collapse and death, or explosion from accumulated flammable gases contacting ignition sources.
HighPipe jacking operations disturb ground conditions, creating potential for soil collapse into jacking shafts, ground subsidence above the bore alignment, and instability of adjacent structures or services. Shaft walls can collapse if shoring is inadequate for soil conditions or if groundwater creates hydraulic pressure on supports. During boring operations, if insufficient face pressure is maintained or excessive material is removed, the ground ahead of the pipe can collapse into the void creating surface settlement or sinkholes. Conversely, excessive bentonite pressure can cause ground heave, lifting pavements or damaging underground services. Vibration from jacking operations can destabilise loose or saturated soils, and changes in groundwater conditions can undermine shaft stability. Clay soils may shrink upon drying when dewatering is undertaken, while sandy soils can suddenly collapse if groundwater support is removed.
Consequence: Workers buried in collapsed excavations causing death by crushing or asphyxiation, surface subsidence causing damage to roads, buildings, or underground services, or collapse of adjacent infrastructure creating public safety hazards.
HighHydraulic jacking frames generate extremely high thrust forces, typically ranging from 500 tonnes to over 2000 tonnes depending on pipe diameter and drive length. These systems operate at pressures of 200-350 bar (3000-5000 psi), storing enormous energy in hydraulic accumulators and pressurised lines. Workers positioning pipes, adjusting alignment, or conducting maintenance must work in close proximity to pressurised components. Sudden pressure release can occur from hose failure, seal rupture, or inadvertent valve operation, resulting in high-pressure hydraulic fluid injection injuries that can penetrate skin and cause severe internal tissue damage. Pipe movement from uncontrolled pressure release can crush workers positioned between pipes or between pipes and shaft walls. Hydraulic fluid under pressure can ignite if contacting hot surfaces or electrical equipment, and failed hoses can whip violently, striking workers or severing other lines.
Consequence: Hydraulic injection injuries causing severe tissue damage requiring amputation, crush injuries from pipe movement, lacerations from whipping hydraulic hoses, or hydraulic fluid fires in confined excavations.
MediumBentonite slurry circulation systems maintain face stability during boring by applying fluid pressure to the excavation face while removing excavated material. These systems operate under pressure (typically 0.5-2.0 bar above groundwater pressure) and involve large volumes of slurry being pumped continuously through enclosed pipes. Workers can be exposed to slurry spray from failed connections or hose rupture, with the material causing eye injuries and creating extremely slippery surfaces. Bentonite powder handling during mixing operations creates inhalation hazards and dust explosion risks in enclosed spaces. Slurry pumps operate at high pressure with rotating components creating entanglement and crushing hazards. Blockages in slurry lines can cause pressure surges leading to pipe rupture and slurry release. Environmental hazards include accidental discharge of contaminated slurry into waterways or stormwater systems.
Consequence: Eye injuries from slurry spray, slip injuries on contaminated surfaces, inhalation injuries from bentonite dust, entanglement in pumping equipment, or environmental contamination from slurry discharge.
