Teretek® and JOG Computer-Controlled Grouting | Underpinning
Summary
Two-storey brick home | VIC, Australia
The owner of a residential property in Woombah, NSW, contacted Mainmark after noticing multiple cracks around the home and was concerned that one corner of the house was subsiding.
The single storey, brick veneer house is built on clay subsoil. This type of soil typically causes the ground to expand and contract as moisture levels change. Upon inspection, Mainmark found the home had subsided 30mm in one corner where a blocked storm water downpipe was located. When it rained, the blockage would cause isolated flooding, weakening the surrounding ground, causing the corner of the home to subside.
The subsidence had caused multiple cracks to appear in the home’s external brick work and large walls cracks were evident through the internal plasterboard around the windows. There was also a noticeable fall in the floor, which had dropped due to the subsidence.
The property’s owner wanted to address the subsidence however was worried about damaging the immaculate gardens and the surrounding concrete path. Conventional underpinning would have required excavation with the use of heavy equipment, resulting in the need to remove and replace the footpath surrounds.
The client was seeking a less invasive remediation option. Mainmark used its proprietary Teretek resin injection solution to deliver a non-invasive and cost-effective alternative.
JOG Computer-Controlled Grouting and Teretek® Resin Injection Combined
Mainmark were contracted to deliver a unique solution by using two of its proprietary non-invasive re-supporting and re-levelling solutions together to remediate the property.
Objectives
On behalf of the original builder, Expertise Building Services sought a cost-effective and logistically viable solution that would raise, re-level and re-support the property, bringing the differential settlement back to a level of +/- 10mm of the home’s target relative level (RL).
The client’s consulting engineer specified Mainmark’s Teretek resin injection which was required to provide a cost-effective solution that would avoid the need to demolish the house.
Solution
Due to the significant depth of the footings and the site’s reactive clay soil, Mainmark recommended using a combination of JOG Computer-Controlled Grouting and Teretek resin injection to remediate the home. JOG was used as the primary technology to re-level the slab, with Teretek used as a supplementary solution to provide additional slab support and void fill.
JOG is a computer-controlled multi-point cementitious levelling process. It precisely monitors re-levelling to the millimetre, with the cementitious grout mix delivered sequentially via narrow injection ports to targeted depths beneath a building’s footings. Unlike traditional underpinning methods, the process is relatively non-invasive and requires no digging or excavation, causing no damage to the structure being treated. To improve the differential settlement, Mainmark needed to locate the edge beam of the central raft slab and drill through the footings to depths of up to 2.4m below ground. Achieving adequate lift at such depth was challenging due to side wall friction, therefore a controlled, multi-point approach using JOG was required to avoid placing undue stress on the central area of the slab.
Teretek resin injection was then applied as a secondary solution to provide added support to the foundation and fill any resulting internal voids. Teretek is a two-in-one ground engineering solution that can both improve ground-bearing capacity and re-level structures. It can quickly and effectively fill voids, and is applied via a process similar to keyhole surgery.
Mainmark successfully re-levelled the entire length of the three affected side walls, lifting the slab to within +/- 10mm of its target RL without the need for soil removal. Mainmark is uniquely placed to be able to deliver projects of this size and scope utilising two complimentary, proprietary non-invasive solutions. The project took Mainmark a total of only 14 days to complete and was delivered within budget to the client’s complete satisfaction.
Client's Review
Paul Richey, Expertise Building Services, said,
“My dealings with Mainmark were nothing but professional. They ensured all aspects of the work, including any queries I had, were thoroughly explained so all parties were aware of the process and that the outcome would be achievable prior to the project commencing. This gave the owner the reassurance and confidence that the home could be stabilised and that there would be no surprise costs or variations to the work.”
