High-capacity hydraulic shoring backed by in-house innovation

Keller turned to Coates when it needed a high-capacity internal bracing solution – find out why

 

The project

Work is underway at Bowline Wickham, a luxury residential development being constructed by Eastern Pacific alongside the Newcastle Interchange, a major transport hub serving the city, in NSW. Due for completion in 2024, the 16-storey development will feature commercial and residential lots.

In early 2022 Coates was engaged by civil works and retention specialist Keller to provide an internally braced retention solution for Bowline’s 3-level basement structure.

The challenge

The shoring solution for this large basement excavation was determined by the site’s size, location and ground conditions.

Supporting high structural loads

Bowline is situated close to the Hunter River, resulting in poor soil stability and a naturally high water table. Excavating the southern half of the basement to a depth of 10m in these conditions - an area of approximately 42 x 25m - created high loads for the internal bracing and additional water management challenges for Keller.

“We needed a high-capacity lateral support system, and as Coates’ proprietary system is one of the largest capacity solutions available on the market, they were a good fit for delivering this solution,” says Eric Lin, Design Engineer for Keller.

A hybrid approach to shoring

Ground anchoring under neighbouring properties was Keller’s preferred option, to provide clear spacing within the basement with minimal obstruction to work around. However, this was not possible on the southern boundary due to the adjacent rail asset. “To safely excavate close to the rail corridor and interchange, Keller needed a solution that could utilise both ground anchors and internal bracing,” explains Coates Temporary Works Design Engineer, Jorge Valencia.

Maintaining low deflection

Design criteria issued by Transport for NSW required the basement retention system to achieve deflection of 20mm or less throughout installation, excavation and construction. “This required high-capacity support and the ability to apply pre-load,” says Jorge. “Keller also needed to be alerted quickly if the deflection deviated outside of this range.”

Capping beam step

Accommodating a 1.1m step in the capping beam level from one side of the excavation to the other was another significant design challenge for the project team.

A telemetry-enabled system allowed Keller to monitor displacement at all times

The solution

Keller designed an anchored retention system for the northern half of the excavation and collaborated with Coates to design a 2-level wirelessly monitored internal bracing system for the southern half. The design incorporated a range of bespoke technologies and innovations:

The MP375 strut connected to the HW500 waler system

The impact

Working with Coates Engineering Solutions was a positive experience for Keller. “Coates were professional, proactive and able to respond quickly to questions and provide the support that we needed,” says Eric.

Understanding shoring system performance

The use of telemetry sensors allowed Keller to accurately measure the displacement and rotation between the two ends of the props. “In conjunction with other instruments and survey monitoring, Coates’ solution provided a good indication of where the movement was in the wall and created a much clearer picture of how the whole system was performing,” says Eric.

Consistently reliable support

Using Coates’ hydraulic struts instead of prefabricated steel struts improved the performance of Keller’s basement retention system. “You can normally fabricate sections to the right size with made-to-order steel propping systems. The downside is that you can’t pre-load these sections,” says Eric. “But with Coates’ hydraulic shoring system, pressure can be pre-loaded during installation to support the wall and minimise deflection.”

Ease of installation

The modular design also saved Keller time during transportation and installation. “Compared to the anchoring that we installed at the northern end of the site, installing Coates hydraulic shoring solution seemed quite quick and straightforward,” says Eric. “Despite the need to brace from within the excavation, it was also reasonably easy to work around.”

Connect with Coates’ Engineering Solutions team to find out how Coates can improve the cost efficiency, reliability and safety of your next excavation.