GEOTECHNICAL ENGINEERING
Resins to the rescue Left unattended, foundation failures eventually undermine their suppor ting structures, whether it’s a bridge, a building or a concrete slab. Traditionally, demolition and reconstruction were among the remediation options available. However, the latest geopolymer resin technologies offer a far more viable, non-disruptive alternative, says Tony Pappalardo, director, URETEK Geo-systems SA.
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ater ingress is one of the main causes of undermining in any structure, whether it be a gradual penetration of the underlying soils or a sudden event. The latter was the case for the new Chuma Mall in Dieplsoot, Gauteng. Just as it was nearing completion in November 2019, the first storm of the season caught the contractors unprepared. Some 30 mm of rain fell in just 20 minutes, with the bulk of the run-off accumulating between the north-east corner of the building and a retaining wall. Subsequently, water infiltration caused the main corner concrete column at the Chuma Mall to settle by 60 mm, affecting seven additional columns, 25 m of strip footings, 1
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as well as some 200 m2 of internal floor slabs. DCP (dynamic cone penetrometer) tests revealed that the layer works between the strip footing and the retaining wall were compromised to a depth of 4 m. After considering their options, which included the possibility of extensive rebuilding, the client’s technical team decided to appoint URETEK Geo-systems SA to employ its revolutionary non-disruptive approach to complete the necessary ground support interventions. Remarkably, the columns, foundations and slabs were successfully resupported and relevelled in five days, ensuring that the contractor could meet the handover date. “This result seems amazing, and it is. URETEK’s pioneering solution increases the load-bearing capacity of the subsoil and
is a revolutionary technology that involves injecting the ground with structural resins to achieve permanent consolidation of the foundation soil below any concrete built structure,” Pappalardo explains, adding that different types of URETEK-patented resin are specified, depending on each project requirement. URETEK Geo-systems SA is a licensed partner of the URETEK network – spanning some 70 countries worldwide.
Deep injection and slab lifting For the Chuma Mall project, the two URETEK methodologies employed were deep injection and slab lifting. The resins are injected via tubes inserted to predetermined depths through 14 mm diameter holes spaced in a grid pattern. As it expands, the resin immediately starts to improve the
MAYDON WHARF WAREHOUSE FLOOR REINSTATEMENT 1 Resin injection operations in progress, with the rising concrete slab level being verified by continuous laser measurement 2 Resin being extruded to the surface through one of the drilled holes as the floor nears its original level KHWEZELA COLLIERY 3 A side view of the dragline service pads 4 Drilling into the pad
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IMIESA July 2020
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