Efficient drilling for piling

November 02, 2016

A new jetty

Leixoes harbour in Portugal was in need of a new jetty to handle 100 yachts, service and reception area and a passenger terminal. The piling work of the new jetty brought up some tough challenges to the project. Atlas Copco presented Symmetrix, a Casing Advancement System, as the solution to the work. Symmetrix offered several features including; high productivity, straight drilling in difficult formations and drilling through bedrock - features well suited for this project.

The execution of a jetty using Symmetrix system to install piles into the bedrock level was a big challange for the contracting consortium. To overcome these challenges, Symmetrix large diameter DTH system, worked as a perfect innovative solution.

Piling in Leixoes harbour

The new jetty, with a total length of 345 meters and various wide starting from 18 meters down to 13 meters, required 209 drilled piles with pattern of 3-4 piles per row. Piles with outer diameter of 1016 mm steel casings was installed, drilled into bedrock and completed by adding reinforcement and Concrete inside the casing. To construct the floating platform, additional 45 piles was drilled with 610 mm and 813 mm diameter casing that was filled with aggregate. The total depth of the piles varied between 33-41 meters through water and bedrock such as gneiss, granite, schist and a mix of loose overburden on top of uneven seabed.

“Symmetrix requires only one barge, whereas we need two for conventional piling. We achieve four piles in a 12 h-day, compared to two using conventional piling techniques.”

Mário Ferreira

Perna Longa, a conspicuous barge

When drilling the piles, the Contractor used a jack-up barge called “Perna Longa”, which was also the center of offshore activity. It was equipped with a huge crane and a drilling lead from Berminghammer, a BHD 40 rotation head, a QL200S DTH Hammer used to run Symmetrix system with reverse circulation drilling string and three Atlas Copco XRHS compressors. This set up made it possible to have a single pass string of 45 meters when drilling the piles, which the crane jib easily accommodated. Pile casings were equipped with sacrificial ring bit and casing shoe on the quayside, and had their ends sealed using inflatable balloons. They were then floated out to Perna Longa, where they were hoisted into position using the onboard winches. The Symmetrix 1,016 mm-diameter drill-through pilot bit and QL200S hammer were then lowered through the pile casing, which was aligned and positioned by GPS.

The Symmetrix requires only one barge, whereas two are needed using conventionalpiling techniques. This reduces non-productive time, a very important factor when drilling from a barge, and contributing greatly to the productivity achieved.

Using Symmetrix for productivity

Drilling-through Symmetrix system is especially used for foundation work that is needed for drilling rock socket with casings left in ground permanently. This drill-through system has the important advantage of not requiring a change of bit to drill the socket below the casing. For each pile, one ring bit and a casing shoe was left in the hole to gain high productivity. On the average, four piles per 12 hours shift was installed.

To complete the job after installation of the piles, the bridge platform was constructed by installing pre-casted concrete elements on top of the piles. The marine Project Leixoes was finished in August 2011.

Customer
Companhia Portuguesa de Trabalhos Portuarios, CPTP

Challenge

To drill beneath the waves to install the bridge piles.

Products
The piling system comprised a Birminghammer, BHD 40 rotation head, a QL200S DTH Hammer, a Symmetrix system with reverse circulation drilling string and three Atlas Copco XRHS compressors.

Benefits
Using Symmetrix Large Diameter system in Leixoes harbour enabled:
• Fast drilling through unconsolidated, fissured ground down into the hardest bedrock
• No changes of bit to drill the socket below the casing
• Saving time enabling four piles to be installed per a 12 hours shift compared to two piles using conventional methods
• Drilling a metre in twelve minutes instead of sixty minutes when using conventional methods
• One barge whereas in conventional piling two barges are needed

Conclusion
Drilling with Symmetrix saves you time, lowers your cost and leaves a job that you can be proud of!