Underground pipeline construction

IS in high demand in Canada due to our expanding resource economy. Currently, about one third of pipelines throughout Canada are characterised as moderately cracked or near imminent collapse, raising serious concerns from a service perspective. Additionally, traditional open-cut methods for underground pipeline construction or rehabilitation are not the most efficient, economically viable, or environmentally friendly option for these projects.

Underground trenchless construction is an attractive option in many cases. Trenchless construction methods have advantages in navigating through complex existing underground pipes and utility lines, as methods can be adapted to mitigate varying geotechnical conditions and construction in cold climates, extending the construction season. Increasingly, trenchless construction methods meet the social, economic, environmental, and risk management requirements of modern urban and rural communities.

However, the trenchless construction industry is still relatively new, and thus industry and government lack the fundamental and applied understanding, tools, and standards necessary to make an informed decision about the application of trenchless methods.

Consortium for engineered trenchless technologies

The need for further research into trenchless technologies, along with their increasing importance, led to the establishment of the Consortium for Engineered Trenchless Technologies (CETT) at the University of Alberta in 2012. With Alireza Bayat as director, CETT is the only research initiative in Western Canada dedicated to advancing the design and application of trenchless technology.

In less than a decade, CETT has established an influence in the trenchless construction industry extending across North America. Collaborations with industry partners have informed the research carried out at the University of Alberta: as a result, CETT research has impacted a variety of industrial sectors across the province, including oil and gas, construction, and telecommunications.

NSERC IRC program

Building on the solid industry partnerships formed under CETT, The Natural Sciences and Engineering Research Council of Canada Associate Industrial Research Chair (NSERC IRC) in Trenchless Technologies was established in 2017 with The Crossing Company, Telus Communications, BGC Engineering, UniqEnergy Solutions, and Inrock. Bayat is the current chairholder of the NSERC IRC program, bringing both a strong geotechnical background and interest in trenchless technologies to advancing research in underground trenchless construction technologies, with an emphasis on cold-climate applications.

Ongoing research being carried out at the University of Alberta under the NSERC IRC program centres around risk assessment and mitigation strategies for horizontal directional drilling (HDD) and microtunnelling, improving trenchless geotechnics, and enhancing construction and design for trenchless projects.

By developing and testing new discoveries, standards, and applications, these innovations will help the underground trenchless construction industry revolutionise the way underground infrastructure is constructed, maintained, and rehabilitated in Canada, across North America, and in other cold-climate regions around the world.

Risk assessment

While the application of underground trenchless construction methods such as HDD and microtunnelling reduce environmental impacts relative to traditional open-cut methods – for instance, construction near environmentally sensitive areas such as wetlands – there are also risks associated with trenchless construction methods. These include, for instance, the risk of blowout in HDD due to exceeding the maximum pressure supported by the surrounding geotechnical conditions, or encountering unforeseen ground conditions leading to project delays.

NSERC IRC researchers focused on underground trenchless construction are working to identify the risks related to various trenchless construction methods, and developing mitigation strategies to ensure successful completion of trenchless construction projects. A robust understanding of the risks and mitigation strategies associated with various underground trenchless construction methods will help to increase uptake of these methods by industry.

Improving trenchless geotechnics

Specific energy is defined as the energy required to remove a given amount of material from the borehole. Ideally for an HDD project, drilling would take place using only the minimum amount of energy required. However, getting at this value is complex; the amount of specific energy required depends on a multitude of parameters, including geotechnical conditions, the specific drilling machine being used, tooling of the drill head, borehole diameter, torque, thrust, and a multitude of other variables, both controlled and uncontrolled.

Teasing out the known and measurable quantities to get at the actual amount of energy required for a given HDD job is a complex task. Such information,consequently, will be a valuable addition to industry, giving them a benchmark to measure against and an indication of when more energy is being expended then necessary.

NSERC IRC researchers, working closely with industry partners, are currently engaged in this challenging and rewarding area of research.

Drilling fluid optimisation

In HDD, one of the easily controlled factors that can improve drilling is the drilling fluid – that is, the fluid that carries the cuttings out of the borehole to the surface. It is known that drilling fluid composition can be adjusted to improve the carrying capacity by addition of various additives, some more costly than others. It is highly desirable to have a laboratory method of evaluating the effectiveness of various additives and how they change the flow profile, as this information is not easy to get at from actual HDD project data.

To facilitate research in this area, researchers are designing and building a fluid loop. The fluid loop will simulate fluid flow during HDD drilling in a carefully controlled laboratory setting, allowing researchers to investigate parameters such as flow rate and fluid composition.

The fluid loop has been designed with both horizontal and tilted sections, with the ability to set up the apparatus to take measurements at different angles. The basic structure includes a pump and control devices, unistrut frame, clear glass tubes for ease of observation, multiple instrumentation gauges and monitors, and both physical and programmable safety features. When complete, the fluid loop will be a valuable contribution to applied research within the University of Alberta, with results directly applicable to the HDD industry.

Clogging potential

Additional research conducted by Bayat’s group has included looking at the clogging potential of Edmonton clays. Problems with clogging of tunnelling machinery such as TBMs in clay conditions, when they occur, can lead to schedule delays, budget overruns, and other significant costs to society.

Researchers at the University of Alberta have developed an experimental apparatus to test the clogging potential of soil samples. Using this apparatus, the effects of penetration rate, rotational velocity, and drill bit size on clogging potential can be examined.

In previous research, it had been observed that clogging potential of tunnelling equipment encountering clay depends on the amount of bentonite in the soil, another factor that has been studied using the newly-developed apparatus. Research results will hopefully enable effective strategies to be developed for decreasing problems with clogging in tunnelling projects in Edmonton and beyond.

Education and outreach

The intent of CETT and the recently established NSERC IRC program is not only to carry out research relevant to the trenchless construction industry, but also to provide training and outreach to both students and industry practitioners. This allows the gap between industry and academic research to be effectively bridged and directly benefits the trenchless technology industry as a whole by allowing industry practices to be soundly based on current research results.

Currently, CETT offers five workshops in the Trenchless Technologies series, offered through the University of Alberta Faculty of Extension. These workshops are designed to educate industry professionals on various aspects of trenchless construction. All courses are taught by well-known industry leaders and researchers, and aim to facilitate the successful design and delivery of trenchless projects.

The topics covered in the trenchless technology series include Horizontal Directional Drilling (HDD), Trenchless Technologies 101, Microtunneling and Pilot Tube Microtunneling, Geotechnical Consideration for Underground Trenchless Construction, and Pipe Materials for Trenchless Construction.

Partnerships and research

Throughout the NSERC IRC program, the emphasis will remain on the relationships developed over time with industry partners. These strong industry partnerships enhance both the training opportunities for students and the research outcomes for all involved in the process.

Research has been pushed forward in addressing risks associated with trenchless construction projects, improving trenchless geotechnics, drilling fluid optimisation, and addressing clogging potential.

The extent to which research under CETT and now the NSERC IRC program remains relevant depends on continued success in addressing current problems in industry.

The solid relationships and connections already formed will contribute to this ongoing endeavor, resulting in positive impacts in the trenchless community in Alberta and beyond.