The Regent of Rotorua Hotel proposed an extension which included the development of a new two-storey building within the existing hotel complex. Some key geotechnical constraints affecting the site include:
- The presence of uncontrolled fill
- The presence of compressible soil (alluvium)
- The risk of unacceptable total and differential static load-induced settlement due to fill and/or building loads
- Liquefaction-induced settlement risk
- The site is located within the Rotorua Geothermal Field
Our team commenced work during the due diligence phase of the project, providing comment on the potential geotechnical risks and constraints as well as conceptual foundation and ground improvement options. As the project progressed, we provided guidance on an appropriate ground improvement option for the development. To minimise settlements to a structurally tolerable level, the project team opted for the foundation beams to be supported by rigid inclusion ground improvement columns.
Giving consideration to the geothermal environment as well as the other geotechnical constraints, our rigid inclusion ground improvement design comprised timber elements. Since undertaking the design, our local CMW Geosciences team has completed construction observations, including observing the installation of the timber elements and testing of the load transfer platform.
What we achieved
The use of rigid inclusion ground improvement columns is more efficient than conventional piles, as they are designed for working loads and ultimate capacities for settlement control. Our involvement added value throughout the lifecycle of the project, from initial geological based planning / geohazard studies to detailed geotechnical investigation / evaluation, and specific geotechnical design of ground improvement works through to construction observations.