James Price Point, Fragile Pindan Tableland

Pindan is a collapsible silty-sand or clayey-sand soil that occurs extensively in the Kimberley region of Western Australia, and is typically red in colour. James Price Point, the proposed location for the LNG Gas Hub will be basically built on a Pindan tableland. Pindan is usually considered deleterious, but many pindan display a self-cementation property upon dryback during construction, with a substantial strength gain in dry moisture conditions which was thought to be due to the bridging effect of clay in the pindan. This strength is lost upon re-wetting. The use of pindan sand-clay presents particular problems where it could be subject to dynamic or vibrating loads such as foundations for large motors and generators, since these could destroy the clay bridges when the material is dry and cause a collapse. Collapse potential can be minimised by ensuring that the pindan is compacted to a high asdensity as possible (100% standard MDD), but cannot be avoided entirely. The material may well still densify (and strain) after construction and continued exposure to the vibrating load.