BLUFF WHARF GEOTECHNICAL INVESTIGATIONS, SOUTHLAND

South Port New Zealand Ltd has owned and operated the commercial port at Bluff, Southland since 1877. GeoSolve has been involved in several projects for South Port as they embark on a series of wharf upgrades and renewals.

Our work involved the geotechnical investigation and assessment of ground conditions supporting various wharf structures. By utilising our dynamic probe heavy (DPH) rig, we were able to determine the thickness and strength of the soil from the sea floor to the point of test refusal – inferred as bedrock.

The practical constraints of working around aged structures surrounded by water means that careful planning and execution was required to undertake the work safely.

One engagement required controlling up to 12 m of suspended DPH rods before contact was made with competent soils on the sea floor. Another involved mounting our DPH rig on a small vessel similar in design to a landing craft. This vessel was modified with a watertight hole through the hull to accept the DPH rods. The vessel was securely tethered to nearby wharf structures in order to remain as stationary as possible for the duration of each test. The work was only possible in favourable wind conditions and was completed inside 2 days with excellent cooperation between all parties involved.

Our inputs will assist with detailed design of any modifications or extensions to the wharf structures, help to determine the geotechnical properties and whether pile embedment is achievable without rock socketing.