By Syl Kacapyr
The future looks “smart” for underground infrastructure after a first-of-its-kind experiment was recently conducted at the Cornell University’s Geotechnical Lifelines Large-Scale Testing Facility.
Like many of today’s household devices, modern infrastructure is gaining the ability to collect and exchange valuable data, using wireless devices that monitor the health of buildings and bridges, for example, in real time. But, wireless systems for underground infrastructure, such as utility pipelines, are much more difficult to test in the field, especially during rare and extreme events such as earthquakes.
The Cornell facility tested several advanced sensors developed by researchers at the University of California, Berkeley, and the University of Cambridge Centre for Smart Infrastructure and Construction. The sensors, which can collectively measure strain, temperature, movement and leakage, were installed along a 13-metre section of a hazard-resilient pipeline being tested for earthquake fault-rupture performance.
The pipeline is produced by IPEX, using a molecularly-oriented polyvinylchloride material engineered to stretch, bend and compress as it withstands extreme ground deformation, similar to that occurring during earthquakes, floods and construction-related activity. Engineers from Oakland, California, and Vancouver, British Columbia, traveled to Cornell to watch as the pipe experienced a simulated fault rupture, while buried inside a hydraulically powered “split basin” filled with 72 tonnes of soil.
The test was the first use of the advanced sensors for the purpose of monitoring buried infrastructure, and gave an unprecedented look at the pipe’s ability to elongate and bend while being subject to ground failure.
“It was able to accommodate 50% more ground deformation than the last design, based on modifications Cornell suggested from our testing four years ago,” said Brad Wham, a geotechnical engineering postdoctoral associate at Cornell.
In addition to the scores of instruments installed for the large-scale test, new technologies employed included:
- Distributed strain sensing – A laser pulse is injected through an optical fibre cable glued to a pipe. By examining the interaction signal that is generated at every point of the fibre, it is possible to obtain strain values continuously along the pipeline.
- Fibre Bragg grating sensing – A special fibre optic line that splits and diffracts light into wavelengths, allowing it to monitor bending and axial deformations accurately at discrete points, especially at pipe joints.
- Frequency-domain reflectometry, wireless sensor network – Metal prongs that use an electric field to measure changes in soil moisture and detect leaks. The device is battery powered and can wirelessly transmit data through soil, using a coupled magnetic induction and electromagnetic wireless sensor network system.
- Smart joint-opening detection – Small magnets are attached at pipe joint locations. Once a pipe has stretched or compressed to a specific limit, the magnets conjoin to trigger the wireless sensor network to initiate the monitoring.
The sensors drew interest from the attending municipal engineers, who need new ways to monitor the performance of underground infrastructure. As cities begin to adopt sensor technologies, more data will exist, not just for infrastructure, but for the surrounding environment as well.
“You can learn something about sources of subsidence or corrosion that affect other structures, or something about the geographic distribution of earthquake or hurricane damage, which then allows you to make improved decisions about emergency response,” said Tom O’Rourke, professor of civil and environmental engineering and principal investigator of the research project.
The test also proved that sensors provide valuable feedback to companies like IPEX that want to advance the engineering behind new products and improve system-wide performance.
“This is about having feedback and intelligence for underground lifeline systems, such as water supplies, electric power and telecommunications, which provide the services and resources that define a modern city,” O’Rourke said. “It’s pretty clear to me that within 20 years there will be intelligence integrated into every aspect of infrastructure.”
“The vision we have is that future infrastructure looks after itself by sensing and adapting to the changing environment,” said Kenichi Soga, professor at Berkeley and principal investigator for the Berkeley and Cambridge teams. “Rapidly developing sensor technologies and data analytics give us the opportunity to make this happen.”
The research team will excavate the pipeline and analyze the massive amount of data collected by the sensors. “It’s going to be game-changing,” said Wham, who added that some of the devices are capable of recording up to a thousand measurements per second or more. “We have many, many gigs of data right now for measurements that were previously unattainable.”
To see a video of the test basin being prepared, visit: www.cornell.edu/video/smart-infrastructure-test.
Syl Kacapyr is PR and content manager for Cornell University Engineering. For more information, visit: www.engineering.cornell.edu. This article appears in ES&E Magazine’s August 2017 issue.