Results
Immediate groundwater relief achieved, with water flowing freely during and after installation, significantly reducing instability risk.
Reduced likelihood of further slope failure by addressing the primary driver of movement.
Enabled safe ongoing management and long-term stabilisation of the site.
Demonstrated the effectiveness of horizontal drainage drilling as a front-line response to rainfall-induced landslips.
Project
Solution
Installed over 4000 metres of horizontal drainage bores, up to 110 metres in length and 150mm in diameter, targeting zones of water accumulation.
Drilled through variable ground conditions including clay, weak materials, and competent rock to achieve effective drainage coverage.
Installed slotted PVC pipes and filter systems to enable controlled groundwater discharge and long-term functionality.
Applied horizontal depressurisation drilling as the primary stabilisation mechanism, directly reducing pore water pressure within the slip mass.
Project
Challenges
Elevated groundwater pressures within the slope were actively driving instability following prolonged rainfall.
Required installation of long drainage bores into a large, active slip mass with uncertain ground behaviour.
Mixed ground conditions including clay, friable material, and hard rock impacted drilling consistency and bore performance.
Immediate risk of further slope movement required a solution that could deliver rapid, measurable results.
Project
Overview
Following sustained and intense rainfall, a significant landslip occurred above the coastal road at Kawakawa Bay, cutting off access to the local community. After initial clearance works reinstated access, Geovert was engaged to undertake large-scale horizontal drainage drilling to reduce groundwater pressures within the failed slope. The works focused on installing long-length drainage bores into the slip mass to relieve trapped water and reduce the likelihood of further movement. This depressurisation approach formed the critical first stage of stabilisation, targeting the underlying driver of instability rather than relying solely on structural support systems.