Controlled blasting is specifically designed so as not to cause vibration at a level that would cause damage to any property
Controlled blasting is an excavation method commonly used in tunnelling
Controlled blasting is strictly regulated by the Environment Protection Authority, Department of Planning, Industry and Environment and SafeWork NSW
This methodology is used widely across Australia and around the world on tunnelling projects
Vibration will be carefully monitored at several locations during controlled blasting to ensure vibration levels remain within allowable limits
Some noise and vibration may be experienced for up to 15 seconds during each controlled blast
Controlled blasting is a tunnelling method commonly used to excavate hard rock by using small charges to break up the rock. It involves pre-drilling a series of small diameter holes in the rock face, loading the holes with small charges and detonating them to break the rock into removable pieces.
In late July 2020, the M4-M5 Link Tunnels Contractor carried out a small-scale controlled trial blast below Reserve Street, Annandale to confirm how the local ground conditions respond to controlled blasting. Extensive vibration monitoring was carried out in several locations to measure vibration levels at various distances from the blast.
Since the trial, the project team has worked with the NSW Environment Protection Authority (EPA) and the Department of Planning Industry and Environment (DPIE) to prepare a Controlled Blast Management Plan should controlled blasting be needed in the future.
Controlled blasting is currently being considered by the Contractor for a section of potentially hard rock within the tunnel between the 36th Battalion Park and the Pioneers Memorial Park in Leichhardt. Tunnel excavation is expected to reach this location in February 2021. The section of the tunnel where controlled blasting is being considered is between 40 and 50 metres deep.
The Contractor has engaged an industry expert with over 30 years’ experience to design and oversee the controlled production blasting, should it be required.
While a decision has not yet been made by the Contractor as to whether controlled blasting is required, the project is committed to engaging with residents and the community early to discuss the potential use of this excavation methodology.
The Contractor will host a number of in-person and virtual Community Information Sessions in December. The sessions will be attended by subject matter and project experts who can answer questions you may have. Information on when the sessions are and how to register will be provided in the coming weeks.
The Contractor will also be contacting all residents that are likely to hear or feel the controlled blasting between now and February 2021 to speak with them directly.
More information on controlled blasting
Controlled blasting is a tunnel excavation method commonly used to excavate rock using small charges that break up the rock. It involves pre-drilling a series of small diameter holes in the rock face, loading the holes with small charges and detonating them to break the rock into removable pieces.
Read our fact sheet on controlled blasting here.
Tunnel excavation on the M4-M5 Link Tunnels Project has to date mainly been done with machines called roadheaders. Sometimes additional tunnelling methods such as rock-breaking, jack-hammering or controlled blasting are required to break up sections of harder rock.
Controlled blasting is a common tunnel excavation method used in areas of hard rock that can result in reduced duration of ground borne noise and vibration impacts for local communities as well as a reduction in the overall construction time in comparison to using rock-breakers and roadheaders alone.
Yes, controlled blasting is strictly regulated by the Environment Protection Authority (EPA), Department of Planning, Industry and Environment (DPIE) and SafeWork NSW. It is a common tunnel excavation methodology that has been safely used on many other Australian tunnel projects and was also included in the project’s EIS as an option.
Every controlled blast is monitored to ensure vibration remains within allowable limits. The Project has engaged a specialist blasting expert to design, prepare and oversee each controlled blast in accordance with stringent Australian safety standards.
Following the trial blast in July 2020, it has been determined that controlled blasting is a viable excavation method for the project and may be used to excavate section of the tunnels in Leichhardt between then 36th Battalion Park and Pioneers Memorial Park (refer to map below).
A decision has not been made by the Contractor as to whether controlled blasting will be carried out in this location, however we want to engage the community as early as possible about the potential for this work occurring.
If the Contractor does decide to proceed with blasting in Leichhardt, they would look to carry out up to two controlled blasts per day, per tunnel between 7:00am and 6:00pm Monday to Friday and 8:00am to 6:00pm on Saturdays.
Typically, there will be a blast at the start and end of each day, with minimal impacts in between these times. Regular tunnelling activities such as rockbolting and shotcreting will continue.
Residents will be provided with further notification prior to a controlled blast taking place near their property.
Residents close to the potential work area may experience some ground borne noise and vibration for around 15 seconds during each blast. This would however replace the impacts of 24-hour roadheader excavation.
Vibration will be monitored at several locations while controlled blasting is taking place to ensure vibration levels remain within allowable limits.
The maximum vibration limits are determined by the EPA and are based on human comfort recommendations of both the Australian Standard AS2187.2 and the ANZEC Guideline. The internationally used German standard DIN 4150 has been adopted to ensure no adverse impacts to properties from vibration work including controlled blasting.
Controlled blasting is designed to generate a maximum vibration level of 10mm/s at the nearest residential property at a frequency that does not present a risk of damage to properties.
Examples of controlled blasting on Australian infrastructure projects include:
- WestConnex M8, NSW - between 15 and 45 metres under residential areas in Kingsgrove, Sydenham and Tempe
- Sydney Metro City and Southwest, NSW - shaft excavation of Victoria Cross station near residential and commercial areas in North Sydney
- NorthConnex, NSW - excavation of tunnel shafts near residential areas of Pennant Hills, Thornleigh and Wahroonga
- Clem 7 in Brisbane, QLD - under urban residential areas at a depth range of 9 – 54 metres
- Airport Link Brisbane, QLD - excavation of a cut and cover tunnel in Toombul as well as production blasting in a residential area and within 100m of a school
If you have an enquiry or complaint or you want to provide feedback about this work, please contact the M4-M5 Link Tunnels team on toll free 1800 660 248, email firstname.lastname@example.org or write to PO Box 63, Mascot, NSW 1460.
For more information drop into the Community Information Centre at 201-205 Parramatta Road, corner of Alt Street, Haberfield 9.00am to 5.00pm Monday, Wednesday and Friday or by appointment on Tuesday and Thursday (excluding public holidays and the period between Christmas Day and New Year's Day).