Controlled blasting at Albert Street
As part of excavation of the tunnel access shaft at Lot 2 and the main station entrance at Lot 1, the Cross River Rail Tunnel & Stations contractor will soon commence controlled blasting at the Albert Street station site.
Controlled blasting has major benefits for both the project team and the surrounding communities.
Excavation using rock hammers alone has a higher impact and longer duration. Using controlled blasting in conjunction with reduced hammering will significantly reduce the duration of these high impact works.
What is controlled blasting?
Controlled blasting involves the pre-planned and safe use of small explosive charges to break up hard rock.
Blasting will be carried out on the Cross River Rail project – for the vertical shafts and cavern at Albert Street, the Roma Street cavern and the horizontal caverns at both Albert Street and Woolloongabba.
There are four stages of blasting which include:
- Pre-drilling the rock with a series of holes
- Loading the holes with small charges and other materials
- Electronically detonating the charges in a timed sequence, which results in the rock being broken up into small, removable pieces
- Removing the dislodged rock.
Following the blast, machines will grind away any uneven rock, including the use of rock hammers before installing rock anchors to stabilise the rock face. Surveying is then undertaken to prepare for the next blast.
How is dust and vibration managed?
Once the charges are loaded, the ‘blast lift’ is covered by multiple layers to prevent flyrock and dust, as well as to decrease the impact of noise, overpressure and vibration from the site. These layers include:
- Up to two metres of gravel which acts like a cork to contain pressure
- ‘Blast mats’ made of thick, shock-absorbing rubber
- Sand bags to secure blast mats.
Dust, noise and vibration monitoring will occur during blasting.
Is blasting safe?
Controlled blasting is strictly regulated by the Department of Natural Resources, Mines and Energy (DNRME), the Coordinator-General and SafeWork QLD. Blasting operations are conducted to the highest safety standards including Australian Standard AS2187.
Controlled blasting is a widely adopted excavation methodology used successfully around the world and in Australia, including CLEM7, AirportLink and Legacy Way in Brisbane.
The project team has developed a comprehensive blast management plan to manage and monitor the safety of our team, nearby properties and the environment during these works.
Other safety measures include:
- Strict controls and safety processes for each blast including safe transportation and storage of materials
- Engagement of specialist contractors to conduct controlled blasting operations
- Compliance monitoring by an independent third party before and after each controlled blast.
Prior to controlled blasting commencing, a number of trials are undertaken. Trial blasting involves a smaller scale blast which is carried out prior to production blasting to confirm predicted impacts, understand ground conditions and confirm noise and vibration levels of local receivers.
Trial results will inform any required exclusion zones for future production blasting.
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