Engineered Re-levelling for an Earthquake-Affected Apartment Block

The site conditions added significant complexity to the project. Heaving soils were anticipated across parts of the site, creating the potential for variable ground response during injection and lift activities. This meant the correction strategy needed to be adaptable and closely monitored, with the ability to respond to changing subsurface behaviour as the works progressed.

The project was time-critical, with the owners needing to complete the repair works within a defined timeframe. This created additional pressure to deliver a compliant, technically sound and efficient remediation outcome, while also minimising disruption to neighbouring properties.

Mainmark developed a staged remediation methodology combining JOG level correction and Teretek® resin injection to restore support, correct differential movement and achieve final levels within engineer-approved tolerances. The works comprised ground improvement, footing stabilisation, slab lifting, void filling and final level correction across the site.

JOG was selected as the primary solution due to its ability to deliver controlled, incremental lift while simultaneously improving support conditions beneath the affected structures. The methodology incorporated two injection phases. Phase one was used to initiate lift and target low points and footing zones, while phase two was used to consolidate treated areas and fill voids. This allowed Mainmark to progressively improve ground conditions while managing lift in a controlled manner.

Teretek® resin injection was used as a complementary solution for localised slab support, targeted lifting, re-support of specific areas and the filling of residual voids.

The integration of both technologies enabled Mainmark to address both large-scale level correction and more refined localised adjustments within a single coordinated program.

To support delivery, the site was configured into two operational compounds, allowing parallel work fronts to be established. Mainmark deployed 2.5 crews and two JOG setups lifting simultaneously, which increased efficiency while maintaining close control over sequencing and structural response. Injection points were drilled across the treatment areas, with valves, hoses, electrical systems, lasers and scale tapes installed prior to commencement. Existing services were exposed and verified, and a batch plant was established onsite to support the JOG operations.

As the project progressed, injection strategies were refined in response to actual site behaviour. In areas affected by heave, injector replacement and system reconfiguration were required to maintain a controlled and stable lift path. Multiple injection cycles were undertaken where necessary, with works sequenced to prioritise footing support, manage structural response and achieve the required level correction.

Continuous monitoring formed a critical part of the methodology. Daily level checks were completed using lasers and scale tapes to track movement and assess lift progression in real time. Overnight settlement was generally limited to approximately 1 to 2 millimetres, demonstrating a stable and controlled outcome throughout the process. Engineering oversight was provided by Miyamoto, including site inspections, level reviews and final approval of completed floor levels.

Mainmark successfully delivered a controlled remediation outcome that restored structural support, corrected differential settlement and achieved approved final floor levels across the affected buildings and garages of the complex.

By combining JOG and Teretek® resin injection, Mainmark was able to address both primary level correction and localised support requirements through a non-invasive, technically robust methodology. Despite the complexity of the site conditions, including earthquake-related settlement, heaving soils and the need to minimise disruption to surrounding properties, the works were completed within 23 days on site, ahead of schedule.

At completion, all treatment areas had been re-levelled, void filled and structurally re-supported. Final levels were reviewed and approved by Miyamoto, confirming that the required engineering outcome had been achieved. All injectors were removed, injection holes were grouted, the site was cleaned and full demobilisation was completed, leaving the structures restored to an acceptable condition and the owners in a position to meet the required repair timeframe.