limate change is putting additional pressure on the already complex, yet vital, role geotechnical engineers play in the Last Frontier’s mining industry. It is an issue the engineering community is working to address according to HDL Geotechnical Services Manager Doug P. Simon.

"We are often designing projects that we hope will last for decades, and climate predictions are estimates at best with no one knowing for certain what the climate will look like in ten years, let alone decades from now," says Simon. "Geotechnical engineers need to stay informed about the latest information on the climate predictions and how to incorporate the uncertainties into designs.”

Projects with proper funding and organization usually bring on a geotechnical engineer as one of the first planning steps, explains Cody Kreitel, a geotechnical engineer for PDC Engineers. The goal of the suite of geotechnical services offered by engineering firms is to characterize the subsurface conditions at a project site so that developers are aware of any challenges involved with creating the stability necessary for a structure, road, airfield, dam, or even to keep a mine from failing.

Alaska’s diverse geology creates a variety of challenges for such engineers, who must rule out various solutions depending on the soil matrix of a site, which can include deep organics that have no load bearing capacity, permafrost, and the liquefaction potential of saturated sands.

"Liquefaction is when, due to cyclic-loading, a saturated loose soil will build up excess pore pressure in between the soil grains and, during the shaking [from an earthquake], the soil behaves like a fluid," Kreitel says. "We saw the effects of that during the earthquake last year."

Kreitel says that despite the necessity of having a geotechnical report for a project, developers sometimes get "sticker shock" from the price of the services, particularly for projects being developed in remote locations since transporting the tools and sending a team to such sites to collect samples is an expensive endeavor.

Once a geotechnical engineer has collected samples and conducted laboratory tests on them, he or she will put together a report for the client, Kreitel explains.

"A geotechnical report presents all of the data I’ve collected and then recommendations to the designers for the design and construction of whatever project they’re working on," Kreitel says. "Sometimes it’s a pretty lengthy geotechnical report that lays out what they need to know about the subsurface so they can proceed with their design."

“A geotechnical report presents all of the data I’ve collected and then recommendations to the designers for the design and construction of whatever project they’re working on,” Kreitel says. “Sometimes it’s a pretty lengthy geotechnical report that lays out what they need to know about the subsurface so they can proceed with their design.”

One industry that doesn’t tend to balk at joining forces with geotechnical engineers is the mining industry, which has a long history of relying on their services to safely extract resources.

"While the science and engineering of geotechnics [became] more fully developed as a separate field in the early 1900s, the art of geotechnical engineering has been an integral part of mining as long as mining has existed. For centuries, the people operating mines have figured out how steep they could cut slopes or stack stockpiles. This process was often by trial and error and, at times, resulted in deaths at the mine," Simon says.

"As our understanding of the principles of soil mechanics grew, so did our ability to predict how materials would behave. Thus, the role of geotechnical engineering has evolved from one of purely trial and error to one where we can better predict how soils will behave and provide safer designs."

Geotechnical engineering plays a critical role in the mining industry in Alaska, agrees Kyle Brennan, vice president and manager of the geotechnical department of Shannon & Wilson’s Anchorage office.

“Geotechnical engineers work with civil and structural engineers to support mining operations by designing mine features as simple as a gravel road that supports mining activities and access and as complex as a tailings dam,” Brennan says.

Simon notes that geotechnical engineers are responsible for ensuring that the materials stored as part of the mining process will be stable and the stockpiles and storage piles won’t fail through unacceptable settlement or movement.

Geotechnical data and analysis are used to help maintain the safety of the mine and those working there. It provides operators the information necessary to make educated decisions about the potential impacts of changes in the way materials are handled and stored.

“Geotechnical engineers will develop designs for facility foundations [buildings, conveyors, communications towers, dams, roads]; develop recommendations for retaining walls and other earth-retention structures; evaluate slope stability [earthen fills, excavations in rock and soil]; and evaluate groundwater hydrology for dewatering and mine drainage,” Brennan says.

How water interacts with the surface and subsurface at a mining site significantly impacts the design recommendations put forward by a geotechnical engineer.

“By their very nature, mines are large earth disturbing operations, and thus are required to follow strict regulations to control surface and subsurface drainage of water off of the mine site,” Brennan says. “Controlling, collecting, and treating mine run-off requires an understanding of surface and subsurface interflow to efficiently and reliably handle water run-off from a mining site. Geotechnical engineering is used to help design the facilities that handle the run-off, and hydrological environmental services are employed to determine how specifically the run-off is to be treated before discharge.”

Because mines typically have a variety of facilities that are constructed during development and maintained over the life of the mine, nearly all geotechnical subdisciplines are required for mine work, including soil and rock mechanics, seismic engineering, and subsurface thermal modeling.

In providing these services, geotechnical engineers face an array of obstacles presented by the state’s geological and climate conditions. These mining developments are further complicated by limited ground transportation and access to resources.

“The key in overcoming the challenges associated with conducting geotechnical work for mining projects in Alaska is the same for all geotechnical work in the state regardless of the type of development. Geotechnical solutions need to be tailored to the specific conditions at each site because prototypical solutions seldom work from site to site,” Brennan says.

“As geotechnical engineers, we are often tasked with figuring out creative ways to use the local conditions or locally-available resources to solve design problems. Coming up with these solutions requires a strong knowledge of geotechnical fundamentals and broad experience with Alaska’s unique geotechnical challenges and unconventional design approaches and how to apply them to meet today’s design and safety standards.”

For mining projects in northern parts of Alaska, permafrost is a primary concern. Permafrost, in general, is relatively stable when it stays frozen. However, ground-disturbing activities or development of buildings in permafrost regions can significantly change the thermal regime of the subsurface and thereby have significant impacts on how a site performs over the life of the facility, Brennan explains.

Designing structures that don’t warm the ground allows the Arctic and near-Arctic cold climate to keep the frozen ground stable. Conversely, heating methods can be used to melt the permafrost and allow it to settle. Either way, Brennan says careful consideration is needed when working on a permafrost site.

“Some basic strategies for addressing permafrost issues include using insulation and thermal siphons to help maintain cold ground temperatures,” Simon says. “If you are looking to thaw portions of the permafrost, you can let our warming summers help you, or there are ways to actively thaw the permafrost with heat pumps.”

One of the more difficult challenges geotechnical engineers face in Alaska is not permafrost; it’s intermediate geo-materials. Such material will usually appear to be solid bedrock but end up behaving more like soil from an engineering standpoint.

“One of the challenges is that the behavior of the materials may not be known or anticipated until you are in construction or have exposed the materials,” Simon says. “Dealing with these materials often involves a process of observing the materials, developing and implementing one or more strategy, monitoring the performance, and making further adjustments as needed.”

For example, to account for intense rainfall in the Southeast, geoengineers rely on surface drainage with armoring, capping stockpiles, and adding drainage/collection systems under the stockpiles.

Given the scope of geoengineering services and the massive quantities of materials used, creating sustainable solutions to the complex problems faced is tough, says Simon.

“However, some of the ways we can try to incorporate sustainability into our designs is to keep it simple and apply the principles of OHIO [only handle it once] so that the large quantities of materials only have to be hauled once, thereby reducing emissions and costs. Other ways include trying to use the materials already available at a site rather than importing materials,” Simon says.

Another way to improve sustainability is to incorporate waste material from mining operations in the construction and expansion of mine sites, says Steve Adamczak, vice president and manager of the geotechnical department of Shannon & Wilson’s Fairbanks office.

“Mine tailings and crushed reject material is used on projects at mine sites to stabilize cut slopes, provide subbase and surfacing materials for haul roads and access roads, compacted subgrade bearing material for structure and conveyor foundations, and material to construct earthen structures; this reduces the need for disturbing natural areas and developing borrow sites,” Adamczak says.

Despite the upfront expenses faced by the mining industry and developers when contracting a geotechnical engineer, the results save companies money in the long term, Kreitel says.

“It’s all about managing that risk, trying to reduce the risk of either construction-related cost overruns or performance issues down the road,” Kreitel says.

Brennan agrees that the services not only create safer mines but create more profitable mines.

Mining operations require extraction of resources as efficiently as possible to maximize the return on the investment, Brennan and Adamczak both say. The role of geotechnical engineering is to provide creative and efficient solutions to soil and rock stability and support capacity for mine infrastructure design challenges that are encountered during mine development and operations, they explain.

When engineers investigate subsurface conditions and geologic terrain and use local materials to provide lower-cost sustainable design alternatives, they have a direct impact on the bottom line of a mining operation, Brennan says.

“Sustainable mine development requires the input of geotechnical engineering to assess seismic, slope stability, permafrost thaw, and erosion hazards, as well as water supply on infrastructure and mine operations,” Brennan says.

However, the impacts of the rapidly changing climate conditions are forcing geotechnical engineers to make assumptions about an uncertain future when assessing sites.

“Geotechnical designs for long term projects must consider the impacts of possible warming permafrost on the stability of slopes, infrastructure, and foundations; changes in precipitation/snowfall and effects on earth structures and surface water; and accessibility of sites if ice road construction or exploration sites must be accessed in the winter,” Adamczak says.

“Climate change has a significant impact on geotechnical engineering in Alaska, especially in zones where permafrost is present and can also impact non-permafrost areas. In order to determine how a project will impact the thermal regime of the subsurface, assumptions need to be made regarding natural climate conditions into the future over the life of a project,” Brennan says.

“Small changes in the climate can have significant impacts to the stability of permafrost soils and accommodating these impacts can often have substantial cost implications.”