Kennacraig Ferry Terminal

Client: Graham Construction

Location: Scotland

Our project team provided extensive knowledge and world class equipment to successfully overcome the challenges of drilled foundations in unforseen hard-rock geology.

At the site in Scotland it was soon evident that our equipment was presented with much harder rock strengths than were anticipated from the client’s ground investigation. Despite this, the LDD project team provided an experienced crew and best-in-class equipment to successfully deal with these challenges and achieve the installation of 16 no. 1200mm diameter drilled and grouted piles.

Under-reaming drill bits, specifically designed and built for the project, were used to vary the diameter of the drilled sockets between 914 and 1200mm diameter as the design required.

Equipment was mobilised to the remote West coast of Scotland to carry out the piling work in the midst of an icy winter in North West Scotland; a further challenge that our site team coped with expertly.

Conditions of Silt and clay, overlying competent psammite and pelite schist formations were expected. However, on-site, the rock encountered was proven to be significantly harder than anticipated with a much greater quantity of quartz bands varying from a few millimetres to tens of centimetres in depth.

The hard and highly abrasive material offered a huge challenge to drilling progress whenever significant quantities were encountered. Despite this, and as a result of the focus and performance of our LDD crew, the overall time for completing the 16 rock sockets was consistent with the estimates given to the main contractor before work commenced.

Following drilling, LDD displayed its competence as a piling service provider; assisting with grouting the piles into position, ready for other works to be completed before the summer season.

Challenges:

  • Remote location and cold weather working
  • Maintaining drilling production rates in unforeseen and very hard geological conditions
  • Assisted main contractor with grouting circuits and methodology
  • Assisted main contractor with recovery of additional costs resulting from unforeseen ground conditions

Equipment:

  • 1 No. LD408 pile top drill rig including compressors and pumps
  • 914mm RC drill bits complete with 1220mm under reaming capability
  • No. of piles: 16
  • Pile diameter: up to 1200mm
  • Pile length: 26m
  • Water depths: 10m
  • Geology: Silt and clay overlying psammite and pelite with hard Quartz horizons.