Soilmec SR-40 rig forming soil-cement columns to 19 m — used for temporary and permanent retention, ground improvement, slip remediation, in-ground shear walls and hydraulic cut-off barriers.
Deep Soil Mixing (DSM) transforms weak or problematic ground into engineered soil-cement columns with reduced spoil generation compared to conventional bored piling techniques. Our SR-40 rig installs columns from 800 mm to 1.0 m in diameter to depths of up to 19 m, forming discrete improvement elements or overlapping them to produce continuous retention and cut-off walls. The DSM process mixes a cementitious binder directly into the soil, which means minimal soil displaced.
The technique is particularly efficient for large-volume ground improvement programmes and for projects where spoil disposal is constrained. DSM is also well suited to landslide repair — passive column inclusions installed through the failure plane can reinforce the sliding mass and restore road or site stability or used for end bearing support for MSE slopes or GCS walls used for structures like bridge abutments. DSM combines both mechanical and high pressure grout injection to cut and mix soils to create a homogenous column in most soil types. All DSM works are designed and supervised by GSI NZ's in-house geotechnical engineers, with QA confirmed through post-installation coring and UCS testing.
APPLICATIONS
GSI NZ CAPABILITY
THE GSI DIFFERENCE
Step 1
Soil sampling and laboratory testing define soil properties. Binder type and dosage are confirmed through mix design testing. Column layout (isolated, grid, or continuous wall) is designed to meet the specific load or cut-off requirement.
Step 2
The SR-40 rig penetrates to design depth while injecting grout binder under controlled pressure. Mixing is performed during both the penetration and withdrawal strokes. Steel reinforcement can be installed into fresh columns where structural capacity is required.
Step 3
Installation data (penetration rate, binder volumes, rotation) is recorded for every column. Coring at agreed intervals provides post-installation UCS testing, and permeability testing is carried out where cut-off performance is the primary criterion.
CASE STUDY
Central Hawke's Bay District Council engaged GSI NZ to repair an active landslide on Wimbledon Road that had closed a rural road. The solution used 126 DSM columns installed through the failure plane to reinforce the sliding mass and restore road stability.
The DSM approach avoided the need for full slope reconstruction, delivering a permanent repair at significantly lower cost and with minimal disruption to the surrounding farmland. The design/build model allowed the column layout to be refined in real time as performance data returned from the field.
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126 soil-cement columns to stabilise an active landslide mass, Central Hawke's Bay.
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Ground improvement and foundation works for major Christchurch aquatic facility.
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Soft ground improvement beneath a wastewater treatment plant without excavation.
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GSI NZ is among the most experienced deep soil mixing contractors in New Zealand, with a track record spanning infrastructure, retention, and landslide repair projects. Talk to us about your project.
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