From the magazine

Rehabilitating Ti Tree Court’s pipeline roots

The performance of the stormwater pipeline at Ti Tree Court, located in Melbourne’s north-east, was first brought into question by a resident who alerted the local Yarra Ranges Council to the persistent collapse of sections of their driveway. In response, the council commissioned civil contractor M. Tucker & Sons’ Specialised Services department to conduct a full CCTV inspection of the 1,050 mm RCP stormwater line and report on the extent of the damage along a length of 136.5 m.

The survey revealed an extensive array of defects, including infiltration, lifting holes, angular and longitudinal displacement, circumferential and longitudinal cracks, exposed and corroded reinforcing mesh and visible voids. Council engineers were brought in to review the report and site.

They determined that, given the sensitivities of the residential setting, a combination of two complimentary trenchless systems – the QUICKLOCK mechanical point repair system and the common EPROS cured-in-place pipe (CIPP) lining system – would be the quickest and least disruptive methods of repair. As one of the few local certified installers of QUICKLOCK, M. Tucker & Sons were engaged to rehabilitate the drainage system in January 2014.

Trenchless discretion

The Ti Tree site consisted of water-charged reclaimed ground and an ageing pipeline (approximately 30 years old) that had moved significantly in the unstable earth, thereby allowing the ingress of groundwater and soil to the pipeline. This ground movement caused multiple issues to the pipeline including tunnel erosion, land subsidence, and the potential to compromise nearby structures if remediation techniques were not implemented.

Because the pipeline’s alignment was positioned very close to neighbouring buildings and structures, trenchless remediation works were necessary to protect the structural integrity of the pipeline and nearby buildings. Trenchless rehabilitation allowed for a discrete repair with minimal excavation and minimal disruption to access for the residents of the court.

In order to provide improved access to the length of the pipe, a new pit was designed and constructed at the edge of the driveway in the adjacent lot, enabling repair in either direction and to a maximum distance of 65 m upstream. The front yard was designated and fenced off as a storage and preparation area for the crew of four – the CCTV operator and three installers. With the QUICKLOCK system permitting installation during times of low flow, bypass measures were not required.

Quick and quicker

For the Ti Tree rehabilitation, Trelleborg’s well-known EPROS CIPP Point Repair was used to patch defects on the lobster back bends (radius) not suitable for repair by the QUICKLOCK system.

M. Tucker & Sons installed all twelve of the CIPP patches required throughout the length of the pipe first, at a rate of three-to-four patches per day, erecting a tent on site to ensure the system’s sensitive materials were kept out of direct sunlight during preparation.

Unlike EPROS and other conventional CIPP repair methods, the chemical- and resin-free QUICKLOCK mechanical point repair allows multiple defects to be sealed quickly and efficiently as there are no curing times involved in the installation process. The self-locking steel QUICKLOCK sleeve/ring is surrounded by a rubber gasket (as opposed to fibreglass or resin) which forms a structurally sound mechanical seal.

For this reason, the QUICKLOCK system was the solution chosen for the remaining 27 defects. These proved to be significantly faster to install, with a 30 minute process for each seal allowing for around ten installations per day.

QUICKLOCK on the uptake

Developed in Germany in 1999 and refined over the last 15 years, UHRIG’s intelligent QUICKLOCK system is at last available to the Australia market via QUICKLOCK Australia Pty Ltd. Installed at a rate of 15,000 units each year throughout Europe alone, the QUICKLOCK system has earned standards approval in accordance with the requirements of Germany’s DiBT and North America’s ASTM, WRc and NSF (Drinking Water).

In order to facilitate its introduction into the Australian market, the QUICKLOCK system is currently being subjected to a full formal appraisal by local peak industry body Water Services Association of Australia. For training purposes, an AQTF training course for QUICKLOCK installers has also been established.

The standard QUICKLOCK system services pipes ranging from 150-800 mm in nominal diameter. Manufactured from a self-locking V4A stainless steel sleeve encased in a seamless EDPM rubber gasket, the system is usually positioned and expanded in place by a specially designed pneumatic packer.

In the case of the Ti Tree Court project, however, the 1,050 mm diameter pipes required the QUICKLOCK BIG solution, whereby instead of a single stainless steel sleeve, a two-part stainless steel ring forms the seal (together with its EDPM gasket), with its ratchets tightened manually to obtain the optimum pressure. The unique built-in locking mechanism is what allows for such rapid installation and adjustment and locks the seal permanently in place.

According to rigorous testing conducted on behalf of QUICKLOCK engineers UHRIG, the QUICKLOCK seal also improves the structural integrity of the host pipe. Once in place, its high-grade materials and design are durable enough to cope with high pressure cleaning and natural ground movement.

A successful repair for Ti Tree Court

The Ti Tree Court repair was completed with minimal fuss over the course of six workdays in hot summer conditions. Post-repair inspections for the Ti Tree storm water line rehabilitation showed the two trenchless technologies complemented each other well to stabilise the pipe, with no issues for either patch system observed.

The minimal impact of the repair on the site itself ensured the streetscape quickly returned to normal and the driveway of the resident who made the initial call to the Yarra Ranges Council is no longer susceptible to collapse.

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