Hobsons Bay Main Upgrade Project

Comprehensive ground, water and building movement monitoring, enabling safe tunnelling and shaft construction for Melbourne’s primary sewer system upgrade

The Hobsons Bay Main Upgrade Project

The Hobsons Bay main sewer project aims to prepare Melbourne’s primary sewer system for the future, ensuring it can manage up to 30% of the city’s wastewater. To accommodate the expected doubling of Melbourne’s population by 2050, the project involves building a new sewer and upgrading the existing one to significantly increase the sewer system’s capacity. To make this happen, four shafts will be constructed, with two on each side of the Yarra River. A tunnel boring machine will be used to create the new sewer.

The situation

John Holland has contracted Sixense to handle the supply, installation and monitoring of various instrumentation for the purpose of monitoring ground, water and building movement during the excavation and tunnelling of the Hobsons Bay Main Project.

What we’ve delivered

Sixense has provided and installed a comprehensive monitoring system that allows construction to be carried out at every stage in a safe manner.
Thirteen manual inclinometer casings were installed in the external piles or diaphragm walls. Site visits are conducted to manually read the inclinometers, the frequency of which varies between daily and weekly during periods of excavation.
Crackmeters were installed across the historical structures adjacent to the work site, strategically positioned within the zone of influence to monitor cracks in accessible areas.
Sixense installed vibrating wire piezometers in boreholes to assess groundwater pressures around the site. Connected to automatic dataloggers, the sensor results are recorded and then transmitted via a radio network. Additionally, four telemetered flow meters were supplied to measure dewatering from individual shafts.
The gathered data from all monitoring instruments is centralized in Beyond Monitoring, allowing for interactive views and graphs, as well as managing automated alarms and generating reports.