Subsurface Investigation
Geotechnical Investigation
Geotechnical investigations are carried out in order to assess the likely ground conditions and geotechnical hazards that may be present at a site in relation to a proposed development / project.
A geotechnical investigation for a ‘routine’ commercial or residential site generally comprises the following stages:
- Desktop study and site reconnaissance
- Ground investigation(s)
- Analysis and reporting
Investigations can range from high level feasibility studies to detailed ground investigations.
The scope of the investigation will be dependent on the type and scale of the development and the anticipated ground conditions.
KGA is vastly experienced in carrying out geotechnical investigations ranging from simple to complex, having investigated thousands of sites around New Zealand and further afield. We will cater the investigation to your needs, using our extensive database to determine the optimal level of investigation for the best outcome for your project.
Subsurface Investigation
Understanding Ground Conditions
‘Unfortunately, soils are made by nature and not by man, and the products of nature are always complex.’ Karl von Terzaghi, 1936
Subsurface investigations are essential to understand and assess underlying soil, rock, and groundwater conditions before detailed design and construction begins. By exploring what lies beneath a site, these investigations can help identify potential geotechnical hazards. These hazards include problematic soils (soils that have the potential to expand, collapse, disperse, liquefy and settle), materials prone to slope instability, defects within rock (such as faulting, slip surfaces and voids) and groundwater related hazards.
Unforeseen ground conditions can have a significant impact on the success of a project, a robust subsurface investigation will reduce the uncertainty related to the ground conditions, which in turn allows for a safe and economical design, and a reduction in construction cost variations.
Groundwater Monitoring
Groundwater levels can influence the stability and suitability of a site for development. A detailed understanding of the groundwater regime at a site is key to determining optimal design. Standpipes and piezometers can be installed in boreholes to allow accurate measurements of water levels. The data can then be used to assess potential effects of changing groundwater conditions on the site and neighbouring properties. Assessments of potential groundwater take and diversion can be carried out to determine compliance with the Resource Management Act.
These insights help engineers design earthworks, retaining and foundations that account for changing groundwater conditions, reducing risks during and after construction.
Methods of Subsurface Investigation
A cost-effective method for shallow exploration in soils, reaching depths of up to 5m with regular soil strength testing.
Trenches or pits dug using a hydraulic excavator exposing soil profiles, allowing geologists to observe materials and transitions directly.
Ideal for deeper investigations, collecting core samples and enabling in-situ and laboratory testing of soil and rock materials.
A quick and efficient method for obtaining data for analysing soil properties, liquefaction potential, and subsurface conditions.
Advanced techniques providing detailed soils data for settlement, liquefaction, and foundation analysis.
KGA utilises our extensive in-house experience and our relationship with 3rd party ground investigation contractors to determine the optimal subsurface investigation for your site. We take safety seriously and will carry out the necessary checks to ensure the safety of all involved. We understand the importance of being discrete and causing minimal disturbance to the site.