With tunnel construction in Australia is at an all-time high there is an influx of new industry participants, which brings a substantial deficit in awareness of health risks related to tunnelling and the necessary skills and experience in managing these risks. Additionally accelerated construction programs and the requirement to build very large tunnels mean that more work activities are being undertaken concurrently. Subsequently there is potential for exposing more workers to RCS than previously before (Cole, 2017).
Over time research and development into ventilation systems and dry dust collectors has led to a substantial improvement in underground dust management (Kanaoka, et al., 2000; Li, et al., 2017; Nie, et al., 2017; Torano, et al., 2011). However works behind the primary tunnel excavation to excavate service trenches generate high levels of dust, but typically rely on water sprays for dust suppression. These water sprays have low efficiency against respirable dust, consume large volumes of water, and are easily damaged, which due to production constraints may result in failure to repair and maintain (Li, et al., 2017).
To improve dust management during rock sawing, a shroud was designed and constructed to fit to a 3m diameter rock saw attachment, which connects to a dry type dust filtering system to capture dust as it is generated at the source.
A comparative trial between conventional water suppression and the LEV system was undertaken during rock sawing activities associated with tunnel construction. Worker exposure to RCS and respirable dust was evaluated in accordance with Australian Standard AS 2985 with gravimetric analysis for respirable dust and quartz determination by infrared spectroscopy. Samples were collected from workers breathing zones to evaluate RCS exposure.
Static area samples were collected to control for variability associated with personal exposure monitoring. Direct reading aerosol monitoring was conducted concurrently using a calibrated TSI 8532 Dusttrak II aerosol monitor. This supplementary method was employed to control for variation by standardising sample location and duration. To control for other confounding variables, measurements were taken of production rates and environmental conditions including tunnel ventilation air velocity and direction relative to the cut, LEV flow rate and water flow rate. Other variables such as operator experience, excavator cabin hygiene and down times were also accounted for.
The RCS and respirable dust concentrations from the two methods were compared using a paired T- test. It was found that using LEV significantly reduced exposure to RCS and respirable dust when compared to using water suppression.
This project has wide application across tunnelling, civil infrastructure and building operations and demonstrates a well-designed higher order control such as LEV can significantly reduce operator exposures to RCS and improve health outcomes.