July/August 2023 - 20

The design solution remained the same throughout all
construction phases, which speaks for its validity. Even though
the project duration was longer than anticipated, much of the
assignment was completed at an accelerated pace. Early
phases of construction provided the design team with an
understanding of the geotechnical conditions, soil anchor
installation challenges, construction costs/productivity and
validated the design approach, which allowed the team to
incorporate lessons learned in subsequent construction
contracts. Because of the importance of shear capacity, pile
integrity testing was completed using the thermal integrity
profiling method, which proved very successful. This method
identified the need for smaller diameter reinforcing cages on
the few occasions where it was necessary to complete the
lower portion of the bored pile within the undifferentiated
glacial sediments using open hole methods, resulting in a
smaller diameter pile shaft with a more irregular exterior
surface than the usual cased shafts.
Conclusion
Ten Mile Slide has been successfully stabilized, significantly
reducing the operating costs of this stretch of BC Highway 99.
This solution addressed stabilization for the unique landslide
and offered many firsts for the ministry in terms of innovative
design and monitoring during the construction phase. As a
result, the ministry has contemplated this solution at other
slide sites, including those impacted by recent flood events.
The project has not only resulted in a safe and reliable highway
alignment and minimized maintenance costs for this important
corridor to national transportation routes, but it has been
essential for Xaxli'p: by maintaining community connectivity
and cohesiveness, by providing the most direct connection
between Lillooet and Kamloops, and by providing community
benefits and economic reliability.
Acknowledgements
The success of this project is due to many parties. The Xaxli'p
Nation worked for many years with the ministry to develop a
viable long-term stabilization solution and contributed
labour to its construction. Contractors were Peter Kiewit and
Sons (initial upslope work); Flatiron Construction, with
subcontractors KanArm (upslope anchors) and Henry
Drilling (pile wall). The authors were supported by Scott
McKenzie and Brent McAfee (Ministry of Transportation and
Infrastructure); Hamid Karimian, Andrew Mitchell, Michael
Porter and Mark Pritchard (BGC); Ernie Naesgaard and
Masoud Yazdi (Naesgaard-Amini Geotechnical); and Adam
Williams (GEA).
Adrian Gygax, P.Eng., Struct.Eng., is the founding principal of Gygax Engineering Associates based in Vancouver, British Columbia. He has been
undertaking structural and geostructural designs for large civil infrastructure projects throughout the world for more than 40 years.
Rod Kostaschuk, P.Eng., is a principal geotechnical engineer with BGC Engineering in Kelowna, British Columbia. He has more than 35
years of experience in infrastructure development, including slope stabilization, retention and foundation engineering.
Sarah Gaib, P.Eng., M.Eng., is an engineering director with the British Columbia Ministry of Transportation and Infrastructure. As a
geotechnical engineer she has focused her 25-year career on foundation design and testing, risk assessments, and slide stabilization.
Completed stabilization
20 * DEEP FOUNDATIONS * JULY/AUG 2023

July/August 2023

Table of Contents for the Digital Edition of July/August 2023