Antarctica is an extraordinary continent. Most of the land mass is permanently covered in ice, and the continent can “double in size” in winter due to thick ice sheets that grow out from the shoreline.
Visiting Antarctica is a geologist’s dream. It’s also a geotechnical challenge for foundation design, which begins with the process of borehole drilling.
Borehole sampling is the basis for most geotechnical site investigations. Usually, core drilling is water flushed. However, in Antarctica, water freezes quickly, and water flushing can melt the ice within the ground being sampled to give inaccurate core records. So alternative methods must be used.
A team of Golder’s New Zealand-based engineering geologists and geotechnical engineers have been conducting geotechnical investigations in Antarctica for the last three years, aided by Golder’s experienced permafrost engineer team based in Alaska.
Drilling, sampling and testing the ground in a climate where one’s body can at times withstand only 30 to 60 minutes exposure at a time, and where work outside usually only takes place for just three to four months of the year is challenging. Our Golder team surmounted these climate challenges to analyze the subsurface conditions and advise three research stations on foundation designs for planned construction.
Golder’s work began in 2015 at Scott Base on Ross Island, Antarctica New Zealand’s scientific base for 50 years. We were then asked to do similar work for the neighboring U.S. National Science Foundation’s research facility, McMurdo Station. In 2016, work began at the Antarctic Peninsular at the U.S. NSF base at Palmer Station. And we revisited McMurdo Station in 2017 to complete additional investigations.
Each base contracted Golder to investigate ground conditions and advise on suitable foundation designs for new facilities. The analysis and advice provided included:
- Managing permafrost effects
- Future-proofing against effects of climate change on foundation performance
- Anchor design
- Blasting of rock
- Assessing seismic hazard
- Minimizing environmental impact of any activity on site
Approved “Extreme Cold Weather” Gear Only
During the brief Antarctic summer, temperatures with the wind-chill reach minus 40 degrees Fahrenheit and ambient temperatures hover around minus 10 degrees Fahrenheit. The Antarctica New Zealand and the U.S. Antarctic Program issue approved “extreme cold weather” gear to each visitor. In addition, visitors undergo a thorough medical preflight, and a detailed safety training session upon arrival. Extreme low temperatures and geographical isolation require visitors be fit and well prepared.
Borehole Drilling With Cooled Compressed Air
Golder teamed up with Webster Drilling, a specialized New Zealand-based drilling company. Webster has a purpose-built drilling rig that flushes borehole cuttings with pre-cooled compressed air.
Under Golder’s supervision, specially trained operators from Webster drilled approximately 80 boreholes at McMurdo Station to obtain the necessary frozen soil and rock samples. The deepest boreholes reached 90 feet, the average depth was about 20 feet. Similar drilling programs were also implemented at Scott Base and Palmer Station.
Managing Permafrost, Climate Change and Environmental Effects
The foremost consideration for any construction in Antarctica is the freeze-thaw effects on foundation design. Golder installed thermistors in specified boreholes to read temperature changes in the ground seasonally and over time. This will ensure new buildings will be founded beneath the freeze-thaw zone, and will future proof their foundations against climate change.
Anchor design is also important. Steel bars were installed in some boreholes using different grout combinations, then hydraulically tested to measure their strength for future ground anchors beneath foundations.
The New Zealand team, with the assistance of Golder’s specialist seismic engineering team, also provided an assessment of seismic hazard and implications for building design.
A Life-Changing View
For a geologist who has worked in many varied environments around the world in the past 25 years, visiting Antarctica was a high point in my career.
Harsh, yet uniquely beautiful, I will always remember watching seals and Adele penguins jumping up onto the ice shelf and the patterns in extensive sea ice in the bay as it rises and falls. It is the first time in my career a plane landing was repeatedly aborted due to penguins on the runway!
Also memorable was visiting the huts dating back to when early explorers such as Robert Falcon Scott and Sir Edmund Hillary visited Antarctica. It has been my privilege to share these opportunities with my Golder Antarctica team Sophie Bainbridge, Joel Bensing, Matt Howard and Sean Templeton.
When it’s time to return for further testing and monitoring, there won’t be a shortage of hands going up for the assignment.
ABOUT THE AUTHOR
Tim McMorran is a Principal Engineering Geologist, working with Golder clients throughout New Zealand, and the Asia Pacific area. Tim has a bachelor’s geology and master’s in engineering geology from University of Canterbury in New Zealand. He has worked as a consulting engineering geologist, mainly based in Christchurch, NewZealand, for 25 years.