A Cost Effective and Innovative Solution
Queensland
The Wallumbilla LPG Facility owned by AGL is located approximately 13 km south of the township of Wallumbilla, in the Darling Downs region of Queensland.
The gas hub is a major transit centre for natural gas in Eastern Australia, with existing infrastructure and trade connecting multiple markets.
The land in the vicinity has weathered, lowland sediment soils characterised by duplex soils and cracking clays.
AGL’s lead Mechanical and Reliability Engineer noticed stress cracking and subsidence on some of the slabs that supported key infrastructure. The sunken infrastructure included a butane storage bullet, a propane storage bullet, six electric motors and pumps, and interconnecting pipework, which were all supported on concrete plinths.
A laser survey was used to measure and document the differences in plinth and piping elevation. Misalignment caused interconnecting pipe flange joint gaps to be uneven and this was measured against ASME PCC-1 guidelines. If left untreated the area would be unsafe and potentially unusable.
Conventional solutions considered were to:
All the above three options were possible but coupled with more downtime, were significantly more costly. AGL sought a more cost-effective and non-invasive solution.
The Resinject Structural Consultant concurred that there was subsidence across this area of the site.
Resinject provided a scope of works that had two main objectives, deliver a long-term solution to help strengthen the ground to prevent further subsidence and re-level the foundations by void filling under the slabs to remove any differential settlement.
Resinject proposed a tailored deep penetration solution to raise and stabilise the overlaying infrastructure using RSJ170 which is a unique two-in-one ground improvement and re-leveling solution that is a cost-effective and long-term solution. The level correction work would be continuously laser measured to within a tolerance of +/-1mm during the job.
The solution also needed to safeguard the structures from damage and over-lift and reduce any risk of harming personnel. AGL conducted a Job Risk Assessment which was attended by the AGL Lead Mechanical Engineer, AGL Asset Integrity Engineer, AGL Structural Engineer, a third-party Principal Structural Engineer engaged by AGL, and by Resinject.
RSJ170 was injected into the ground beneath the concrete plinths at multiple different depths ranging from 1.5m and 2.5m depths, targeting the problem areas in a grid-like fashion with 1.2m spacing across the surface area to ensure even distribution. The injection points for this treatment were targeted at these deep depths to provide strength and support for the overlaying infrastructure.
The expanding polyurethane resin mix is injected through very small tubes. On entering the ground, the components mix and expand by chemical reaction, strengthening the ground and re-leveling the treatment area quickly with minimal disruption.
Resinject worked closely with AGL engineers to ensure the works were undertaken in a controlled, monitored, and transparent manner
At the completion of the works, Resinject had successfully raised the concrete plinths, by up to 30 mm, filled the underlying voids, and compacted the foundations, to ensure a robust and enduring support structure remained for future heavy loading.
The works were completed over the course of three-days and during the planned shutdown which minimised the disruption to facility and operations. The collaboration between Resinject and AGL ensured the mitigation of risk and safety for personnel and the site.
Several months following the conclusion of the project, AGL organised an independent laser survey to validate the post-treatment concrete plinth elevations. Appendix 1 outlines the results from the independent survey.
AGL were delighted with the results, the efficiency of the service delivery and especially the response to safety given the nature of this project.
