In our joint webinar with GKM Consultants, we discussed the background, challenges, and solution developed for the Finch West Light Rail Transit Line 6 construction project. Here is Part 2 of our Q&A series. You can read Part 1 here.

We appreciate everyone’s interest and participation, and remain available to answer additional questions. Feel free to submit your questions using the form at the bottom of this page. Webinar replay is available on-demand for those who were unable to attend the live presentation.

Q. Do you have examples of when warning thresholds have been modified in response to the observed response that varies from that expected? These definitions are often hard to establish at the start of a project?

Wesley Saunders, P. Eng. | Business Development Manager, GKM Consultants

A. One example of thresholds that are being evaluated would be the warning levels on some tilt meters. The initial warning level for some sensors was set at +/- 0.008 degrees but this level has been passed when not applying empirical temperature corrections or data smoothing techniques to the recorded readings. What is important is that the instrument selection and warning levels are representative of meaningful behaviour, closely related or reflective of the parameter that needs to be controlled. For example, if rail movement of 2mm is the controlling behaviour which cannot be allowed to occur it is better to monitor the rail or the crossties for deformation directly and alarm at representative values such at 1mm and 2mm than to monitor the tunnel wall section for rotation and try calculate the associated rail movement from that measurement.

Q. How are the sensors connected with SCADA and how they are monitored?

Todd Roberts, P.G. | Director of Infrastructure, sensemetrics

A. For this project, sensors were cloud-connected and SCADA was not required/utilized. However, it is possible to connect to a supervisory control system by directly connecting a Thread device and enabling a switching analog interface to indicate status or alarm states. SCADA integrations are diverse, and effort would be required to understand the specific SCADA system architecture to recommend an optimal interface method.

Q. Can you use accelerometers to provide displacement data?  An example may be measuring displacement of a train rail or track bed in an area that is not accessible during the passage of a train?

Wesley Saunders, P. Eng.

A. Regarding the use of accelerometers to provide displacement data, although possible the measurement frequency would need to be suitably high to capture the period of movement in detail. It may be easier to measure directly utilizing an instrument such as a potentiometer.

Q. How far is it from a digital twin?

Todd Roberts, P.G.

The monitoring platform alone is not a digital twin but rather a component of what makes up a larger digital twin environment. For example, by using sensemetrics API, it is possible to connect and associate empirical sensor data with spatial objects present in a Digital Twin, to provide key data regarding condition and performance metrics.

Q. What is the maximum allowable settlement on this project? Have you had any issues with access for installation of targets?

Wesley Saunders, P. Eng.

A. The specific allowable settlement varies dependent on the structural and geotechnical site conditions and susceptible infrastructure along the project corridor. For example, some infrastructure may have allowable total settlement of 25mm and differential settlement of 15mm, and others may only have 2mm allowable settlement.

Q. Is it real time monitoring? How automated is it? What is the monitoring frequency and accuracy?

Todd Roberts, P.G. and Wesley Saunders, P. Eng.

A. The capability for the system would fall under what we consider as near real time. This reflects data collection that can be as frequent as 1 per min, 1 per 5 min, or even 2 per day. For this specific project,  it is dependent on the sensor but most of the automated sensors are being recorded at a frequency of once per hour. For accuracy, the specific biaxial tilt meter that is being used has an accuracy of 0.005 degrees but this is in a lab setting and doesn’t consider site specific influences.

Q. In vibration monitoring, which standard are you comparing against? City of Toronto and MECP?

Wesley Saunders, P. Eng. and Todd Roberts, P.G.

A. For this project GKM is not performing any vibration monitoring but sensemetrics is able to support vibration monitoring within the platform.

Q. How can a real time monitoring system be integrated to action plans in construction projects such as excavation or tunneling?

Todd Roberts, P.G.

A. sensemetrics users are able to set threshold alerts based on project specifications that may or may not be directly linked to ‘action plans’.  In addition, the platform allows users to associate documents, such as Action Plans, within the platform for quick reference using a single interface thereby co-locating pertinent and critical information with real time information and alerts.

Q. Is sensemetrics a subscription based service?

Todd Roberts, P.G.

A. sensemetrics primarily offers our platform as a subscription based service – providing a simple and flexible purchasing mechanism for clients, and a bundled solution inclusive of all data processing, hosting, and support. sensemetrics also offers perpetual software licenses and on-premise solutions for clients who require alternative methods of platform delivery.