Large diameter drilling

Large diameter drilling (LDD) sinks cased shafts and bored sockets at the scale needed to install foundation piles and anchors. Our team has world-leading experience in this field, including the design of some of the largest large-diameter drills ever built. That depth of design experience is rare outside an OEM, and it shapes everything on this page: the machines, the methods and the judgement about what will actually work in the ground.

Two installation methods, matched to the ground

• Cased open hole – for hard ground. A sacrificial casing is advanced to the seabed directly behind the cutters to hold the overburden open, then a rock socket is drilled through it. The pile lands into the completed socket, is clamped by the seabed frame and grouted in place. Because the drill string can be recovered and the casing left on the seabed with the hole open, the vessel can leave for weather and return to the same hole – a powerful weather-window advantage.
• Follow-on (drill-and-install) – for soft ground such as sands, gravels and clays. The pile is pinned to the BHA directly behind the cutters and installed in a single pass as the hole is drilled; under-reamers open the bore so the bit passes through the pile, then retract before the pile is unpinned, clamped and grouted.

Why it matters

The approach handles both vertical and raked piles and suits both hard rock and unstable soft sediments, directly relevant to floating and fixed offshore wind, where developers are pushing into ground and depths once considered unviable. Spoil removal is frequently the real constraint on rate of progress, not cutterhead power, which is why we model it explicitly, see airlifting and spoil removal.

Large diameter drilling can also be delivered from a converted geotechnical drilling vessel – see drilled anchor piles from a marine drill and geotechnical marine drills. That is a distinct offering with its own page.

Large diameter drilling – applications

The large-diameter drilling machine is the common platform behind several very different applications. The same core drilling technology, scaled from around 500 mm up to XXL monopile diameters of 10 m and beyond, is configured for each:

• Pile Top Drill – a drill that mounts on top of a pile to drill ahead of it, or a free-standing large-diameter drill, for foundation installation. Full page →
• Surgical Mining Solutions – precision large-diameter drilling for selective, low-footprint mineral extraction, with sensing built into the bit. Full page →
• Shaft Sinking – sinking cased shafts for mining and civil works. Full page →
• Decommissioning Drilling – drilling out and cutting redundant piles and foundations for removal. Full page →