Solutions
In-situ ground treatment across New Zealand — strengthening, stabilising and improving weak ground without excavation.
New Zealand's soil conditions present a wide range of ground engineering challenges that cannot be solved by simply removing and replacing weak material. Soft alluvial peats and clays in lowland settings, loose liquefiable soils in coastal and riverside zones, variable volcanic deposits in the central North Island, and weak weathered rock in hilly terrain — these are conditions where in-situ treatment is more practical, more sustainable and more cost-effective than excavation.
GSI NZ's Specialist Grouting division treats the ground in place, using a suite of complementary techniques that modify the engineering properties of the soil without removing it. We select the right technique — or the right combination of techniques — based on the specific ground conditions, treatment depth, performance requirement and site constraints. In many cases, the most effective solution combines two or more methods: for example, jet grouting beneath a structure combined with in-situ mass stabilisation of the surrounding ground, or foamed concrete filling a void alongside polyurethane slab lifting to re-level the overlying pavement.
WHY GSI NZ
Step 1
We assess ground conditions, treatment depth, target performance, and site constraints. Our in-house engineers select the most cost-effective method — or combination of methods — from IMS, DSM, jet grouting, foamed concrete, and polyurethane grouting.
Step 2
The treatment programme is designed and confirmed through laboratory testing before production begins — binder type and dosage, column layout, density, and QA criteria specified by our engineering team.
Step 3
Ground treatment is delivered by our own crews under engineering supervision. Installation data is recorded in real time, field samples are tested for QA, and a completion report with full documentation is provided on handover.
Mechanical binder mixing to 5.5 m depth for soft soil improvement, foundation support, and contaminated soil treatment.
SR-40 rig forming soil-cement columns to 19 m, for retention walls, ground improvement, and hydraulic cut-off barriers.
High-pressure soilcrete columns from 600 mm to 2,000 mm diameter, for underpinning, liquefaction mitigation, and groundwater control.
Pumpable, self-compacting, lightweight cementitious fill, for pipeline abandonment, void stabilisation, and abutment backfill.
Expanding resin injection for slab lifting, void filling, waterproofing, and ground strengthening, with same-day return to traffic.
OUR PHILOSOPHY
Our grouting technologies treat the ground in place rather than removing it — which means less disruption, reduced spoil, faster programme, and in most cases a lower overall project cost than excavation and replacement. From high-pressure jet grouting with our Soilmec SM-3 rig, to deep soil mixing columns to 19 m with the SR-40, to lightweight polyurethane resin injection that returns a surface to traffic on the same day; the breadth of this division means we can match the right technology to the specific ground conditions and project constraints rather than applying a single-solution approach.
GSI NZ has deployed specialist grouting across some of New Zealand's most technically demanding projects — including 107 jet grout columns to 15 m depth beneath the Metrosports Christchurch aquatic facility rebuild, and 126 deep soil mixing columns for landslide repair on Wimbledon Road in Central Hawke's Bay. Our Specialist Grouting capability was strengthened through the 2019 acquisition of Hiway Geotechnical, which brought IMS, DSM, jet grouting, foamed concrete, and polyurethane grouting under the GSI roof. All grouting works are designed and supervised by our in-house geotechnical engineers, with full quality assurance documentation provided on completion.
SPECIALIST GROUTING
107 jet grout columns to 15 m for liquefaction mitigation, Christchurch post-earthquake rebuild.
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126 soil-cement columns to stabilise an active landslide mass, Central Hawke's Bay.
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Soft ground improvement beneath a wastewater treatment plant without excavation.
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Our ground stabilisation team holds more specialist techniques in-house than any other firm in New Zealand. Tell us your problem and we'll find the right solution.
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