The town of Christchurch is bustling with commuters traveling from the Canterbury Region of New Zealand. Located in the South Island, Christchurch is the largest city of the region and the country’s third-largest urban area.
To better accommodate daily commuters coming from North Canterbury, the Christchurch Northern Corridor (CNC) hired International Earth Sciences (IESE) to monitor surface movement of a highway expansion construction project. The CNC is an alliance between the New Zealand Transport Agency, Christchurch City Council, Fulton Hogan, and Aurecon and Jacobs. The four-year highway project was designed and located east of Belfast and runs from the Waimakariri River bridge to Cranford Street. As part of the expansion, the effort also includes improvements to the stormwater systems, native tree planting, and the addition of a shared path for pedestrians and cyclists.
IESE is a geotechnical consulting company based in Auckland, New Zealand that manages a wide range of engineering, mining and geophysical projects across Australia, Africa, North and South America, Asia and Europe. The company specializes in high-touch project consultation and project delivery. Team leaders work with clients to design, implement, maintain and service complex seismic and geotechnical monitoring systems for a variety of projects, ranging from tunnel construction, dams, roadways, structures and more.
Video caption: This captivating overview of the Christchurch Northern Corridor project was created by Cirtex, a New Zealand provider of geosynthetic, civil and infrastructure materials and expertise. Cirtex installed high strength woven geotextiles used on the project.
Michael Cheng, senior project scientist at IESE, said he believes that as global populations grow, trade and transport will increase across the globe, resulting in a strong demand for large-scale infrastructure projects that will require monitoring capabilities. He continues, “We’re seeing how moving to fiber optic monitoring technology delivers our customers a more robust solution at a lower cost, which was not possible five years ago. Trimble 4D Control software is the backbone for these complex monitoring efforts, giving geographically-dispersed teams the data they need from any sensor to understand the speed, direction and magnitude of any movement in real-time. As all monitoring technology continues to evolve, our monitoring projects all over the world do as well.”
Challenging Factors Require Extensive Monitoring
On Feb. 22, 2011, Christchurch experienced a magnitude 6.2 earthquake that affected the entire Canterbury Region. Widespread damage was caused in Christchurch and the eastern suburbs five months earlier by a magnitude 7.1 earthquake and its aftershocks. The city continues to experience after-effects, most recently by a magnitude 4.0 aftershock centered nearby the construction site, which creates a risk for liquefaction and lateral spreading of the engineered road.
Aftershocks, combined with extremely soft ground, complicate the expansion of the four-lane CNC. A portion of the approximate 10-kilometer (6.21 miles) project is comprised of unconsolidated sediments on top of peat. That, with the consequent liquefaction from the aftershocks in the same area, requires embankments to be built first to stabilize and improve the ground conditions before the actual road can be constructed. This is where IESE and Trimble come in – to measure embankment displacement and monitor movement across the project during construction and for a period of two years after the build is complete.
Cheng noted it is essential to detect any ground movement at an early stage. With all the challenges – from the particularly soft ground, pore water pressure, perpendicular expansion of the soil and ground movement from earthquake aftershocks creating risk for liquefaction and lateral spreading of the engineered road – CNC project leaders and the project’s general contract wanted to better understand the behavior of the settlement of the motorway.
After reviewing the project, IESE designed and implemented a complete monitoring solution that uses innovative fiber optic embedded geotextile material. They also installed and attached vibrating wire piezometers to the fiber optic embedded geotextile sensors, which are connected to the IESE telemetry station. Inclinometers were installed at the toe of the embankment to monitor its horizontal movement.
In total, the team installed more than 2,000 monitoring sensors across the embankment fill area, spanning approximately 10 kilometers. Furthermore, IESE has set up the Trimble T4D Control software for data integration, management and reporting of these combined hardware/instruments. Due to the amount of data from all the instruments, an SQL server is also being used to integrate data into the Trimble 4D Control software package.
Cheng said the CNC project is one of the most massive undertakings of this caliber, and without Trimble 4D Control software, it would have been extremely challenging to manage all the moving pieces.
“Trimble 4D Control gives us one platform to gather and view all the data we are measuring,” Cheng said. “It streamlines management and allows us to share the information in a meaningful way that’s accessible and understood by engineers and non-technical audiences across the project.”
As the CNC consists of stakeholders from different organizations, it was essential the display software platform allowed for multiple users to access near-real-time data simultaneously – this is possible through the Trimble 4D Control Web interface.
Real-time alarms and alerts – Trimble 4D Control displays precise sensor location data and other movement data, which is critical to mitigating potential risks, such as unexpected landslides or embankment failures that can result in structural damage, natural loss or worse.
Controlling measurements, compiling data and analyzing results – The Trimble 4D Control monitoring software automatically manages measurement cycles, communications and the flow of incoming real-time data from more than 2,000 sensors and other geotechnical equipment.
Visualization and mapping – Results are visualized clearly using maps, charts and graphs. Real-time data from sensors is integrated into Trimble 4D Control and displayed via Trimble 4D Control Web for continuous displacement monitoring. Photographs and aerial images are also imported for greater context.
Ability to analyze and visualize results via a Web interface – From any Web browser, authorized remote stakeholders can access monitoring data to make informed decisions about their project in a timely manner.
Computation and analysis – Raw data gathered in this project, either via manual survey or automated via a telemetry system, is collated and processed on the IESE server. Here it is processed and formatted for Trimble 4D Control to store the data onto a dedicated SQL database, to ultimately be displayed in Trimble 4D Control Web.
Read more about this project in the complete Christchurch customer story here.
To learn more about the game-changing potential of systems sensing their environments and automatically aiding critical decision making, and how the Christchurch project provides an example of this, read the story in International Construction, here.