Citywide Subsidence Monitoring with Millimeter Precision
Seattle, WA
Civil Engineering
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Tunnels—especially underground excavations—are used to transport public utilities like water, sewage, electricity, or gas, along with transport infrastructure. In civil engineering, tunnels are often constructed to avoid pre-existing infrastructure, to avoid disturbance above ground, or to build more direct routes through varying terrain. The two most common methods of tunnel construction are the cut-and-cover technique and the use of a tunnel boring machine (TBM).
No matter the method of tunnelling, construction within a cityscape includes regulatory limitations for surface expression and monitoring of surrounding infrastructure. InSAR can monitor large civil infrastructure projects throughout their lifecycle with millimetre precision and cover thousands of square kilometres in a single footprint. 3vG’s InSAR monitoring plan is capable of supplementing or, in some cases, replacing existing on-ground solutions.
Monitoring for the impacts of TBM movement involves reporting on displacement along the tunnelling route including surrounding buildings and infrastructure. Traditional monitoring solutions can include manual or robotic total station surveying of prisms and building markers along the TBM path. These methods involve scheduled deployment of personnel, which can involve complexities that include property access, permits, and traffic interruptions. While InSAR can be complementary to ground-based surveys, it can also replace in-situ measurements. While optical surveys typically track dozens of points, InSAR actively reports on hundreds of thousands or millions of points with equivalent or higher precision.
When it comes to cut-and-cover techniques, monitoring may look a little different. However, reporting on surrounding buildings and transportation infrastructure, while minimizing public interruption, is still a priority. InSAR removes the requirement for local permits and access rights, and can provide frequent high-precision updates of the construction zone and surrounding areas.
3vG has developed tools to easily identify and alert on-site staff as early as possible when risks develop. 3vG boasts an unmatched data delivery turnaround of 24 hours after image delivery, leading to the fastest InSAR detection time in the industry. Paired with wide area coverage, displacement monitoring can be applied to the entire construction operation, as well as the dewatering impact, and existing tunnel networks.
Since 2010, 3vG’s InSAR technology has been applied to identify displacement as early as possible to allow civil infrastructure projects to respond and mitigate any risks. Our wide area coverage, frequent imaging repeat, and algorithms designed specifically for cities, provide high-precision monitoring. These factors allow for advancements in risk detection, such as highlighting areas of real displacement over measurement noise. In just one image footprint, 3vG’s InSAR technology can inform engineers on risks along the full length of the preexisting tunnel network, active construction zone, and all surrounding infrastructure.
InSAR data quality varies over time and spatially within individual images. For some areas, very precise displacement estimates are possible (2 mm or better). 3vG has developed the means to identify any statistically significant displacement, regardless of its magnitude. In contrast, more standard approaches use simple thresholding to distinguish between displacement and noise.
Interferometric synthetic aperture radar (InSAR) is a satellite remote sensing technology used for mapping ground displacement across a number of sectors.
Discover the benefits of using InSAR and learn more about this fascinating technology and how it can be applied to your next project by clicking the button below.
Learn MoreWe are very impressed with this data. We realized that we have problems right now in several areas caused by rain. We saw them shown in red on the map.”