Drilling technologies for shaft structures and offshore foundations-Paper

Paper

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The paper presents two mechanized drilling technologies adapted from tunnelling to address the limitations of conventional deep-foundation methods: Vertical Shaft Sinking (VSM) for onshore shafts and Offshore Foundation Drilling (OFD) for seabed foundations.<br /><br />VSM constructs reinforced-concrete-lined shafts in varied ground, including groundwater-bearing soil and rock. Excavation and lining proceed together, while the machine is operated remotely from the surface, avoiding the need for workers to enter the shaft during construction. By maintaining water pressure and avoiding groundwater drawdown, VSM helps reduce settlement risk. Its compact, flexible site setup, lower noise, and ability to work in confined urban locations make it suitable for shafts and deep foundations where conventional methods are challenging. More than 100 shafts have been built, reaching depths of 115 m. Examples include three shafts in Barcelona and a 65 m-deep underground parking project in Nanjing.<br /><br />OFD uses a remotely controlled, full-face drilling machine to install offshore foundations in variable ground, including hard rock where impact piling may be unsuitable. Continuous drilling, adaptable cutting tools, and controlled spoil removal support reliable installation with substantially lower noise than conventional hammering, helping limit impacts on marine life. The process can install piles directly or use temporary casing.<br /><br />At France’s St. Nazaire wind farm, OFD was used to drill and grout 73 monopile foundations in rocky seabed and water depths of 15–25 m. The 7.7 m-diameter rig was the largest offshore drilling machine at the time, and the work was completed in less than a year.<br /><br />The paper concludes that mechanization can improve safety, construction performance, and planning reliability while reducing environmental impacts. These technologies may enable shaft and offshore-foundation projects in locations and ground conditions that have previously been difficult or uneconomic.

Keywords

Vertical Shaft Sinking

Offshore Foundation Drilling

mechanized drilling

deep foundations

tunnelling technology

reinforced-concrete-lined shafts

groundwater-bearing soil

offshore monopile foundations

St. Nazaire wind farm

environmental impact reduction