Where does micropile technology come from?
- First use of micropiles dates back to the early 1950’s in Italy, where new methods of underpinning were needed to restore structures and monuments damaged during World War II. Dr. Fernando Lizzi is commonly recognized as the inventor of micropiles in the form of the tree root pile or "palo-radice". Micropiles currently are now widely specified and used in all terrestrial construction sectors worldwide.
Why hasn’t this been done offshore before?
- The more recent development of robotic seabed drilling equipment for geotechnical survey is a key enabling technology which provides an ideal means of installing drilled micropiles for a wide range of applications.
- While the offshore industry has historically been slow to adopt new technology, the sector is under increasing pressure to change and explore more innovative approaches to foundations which will help reduce both costs and environmental impacts.
How do use of micropiles save cost?
- In addition to representing a more materially efficient solution (i.e. less steel = less cost), one of the most significant factors in the cost of offshore construction is the hire of the installation vessel and ancillary equipment. Using smaller, local, and more available support vessels for we can avoid the high daily rates and mobilisation costs that are typical for many projects.
- Another potential savings arises from the fact that a micropile installations can be adapted to soil conditions as found; pile refusals and project delays are avoided as micropiles can be driven through rock obstructions which in turn, may contribute to the ultimate anchor holding capacity.
How are subsea micropiles better for the environment?
- Part of the appeal and increasing use of micropiles over the past 70 years derives from the fact they are a low noise and low noise alternative to other soil interventions and can be adapted to difficult sites with limited access. In the marine environment, we can expect minimal acoustic impact or seabed disturbances compared with conventional pilling or drag embedment anchors, to include low or zero discharge of spoils/drill cuttings.
- Other benefits would include reduced vessel traffic and associated GHG emissions using smaller and more local vessels. Another significant advantage that subsea micropiles bring to developers is the option of sitting projects in less congested areas, away from sensitive marine habitats. Given their suitability in a wide range of soil conditions, developers are afforded a greater number of site options with less regulatory risk.
How do micropiles create a more efficient anchor solution?
- The group effect of micropiles remain a central aspect of geotechnical engineering research - the ultimate holding capacity of a pile group is much greater compared with the load of a single pile multiplied by the number installed. The interaction between the anchor template or “pile cap”, and piles also provides synergistic effects, increasing lateral resistance.
In what soil types are micropiled anchors suitable?
- Micropiles have an extensive track record (onshore) of good performance in the full range of soil and rock conditions, including soft to stiff clays, sands and gravels. For subsea anchors, design parameters (e.g. size, number and length of piles) can be adjusted for conditions as found.
How would a micropiled structure respond to a seismic event?
- There is mounting evidence that micropile anchors will have an important role to play securing against this marine anchoring threat, particularly when persistent axial tension loads are in play.
- Micropiles have been successfully employed to resist seismic-induced soil liquefaction of upper sediment layers in many instances and recent research has shown that micropiles retain strong axial and lateral performance under a range of strong reverse cycle dynamic loadings as experienced during the Canterbury (NZ) earthquake in 2016.
When will micropiled foundations and anchors be available for commercial projects?
- Subsea Micropiles is continuing a program of research that began in 2008 with Lockheed Martin and the U.S. Dept. of Energy funding. Pilot projects will be carried out through 2022. Working with class bodies and leading research institutions to advance the technology for commercial applications, we expect to deliver our first commercial projects in 2023.
Will micropiled anchors come with a performance guarantee?
- Similar to other commercial anchor products and installations, micropiled anchors will come with a workmanship warranty on anchor template and piles. Both the engineering and installation of the anchor will conform to approved design guidelines and procedures, subject to review by marine surveyors and class societies.
What services do Subsea Micropiles provide?
- We provide turnkey solutions to include the design, planning and installation of micropiled anchor and foundation solutions.