Archives

News 18.06.2020

Webinar Q&A – Finch West Light Rail Transit June 2020 | Project Highlights

In a joint webinar with sensemetrics and GKM Consultants, we discussed the background, challenges, and solution developed for the Finch West Light Rail Transit Line 6 construction project. GKM’s demonstrated experience is evident with their execution and scheduled rollout of monitoring activities encompassing 1,200+ monitoring points across the length of the 11-km light rail transit alignment, and 18 associated stations. 

We were both delighted with the large webinar turnout and received many fantastic questions. Since time was limited during the live session, we have compiled many of the questions & answers that were not initially responded to – as a further resource to attendees.

We appreciate everyone’s interest and participation and remain available to answer additional questions. Feel free to contact us at sales@gkmconsultants.com or call us direct at 450 441-5444.

The webinar replay is available for those who were unable to attend the live presentation, simply click here, Webinar recording.

Q. What constraints had to be imposed on the monitoring program to achieve good quality communication with instrument locations?

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

A. Typically to maintain good quality communication between the gateway and wireless node locations we need to minimize the disturbance of the fresnel zone.  We can achieve this by strategic positioning of the antennas at suitable height and clearance from impacting structures, selection of appropriate hardware such as roadway rated antennas as well as the selection of materials such as fiberglass enclosures or PVC caps that don’t impede transmission.

Q. What is the reason for using both the Loadsensing nodes and the sensemetrics nodes? Could the system work directly with instruments plugged directly into the sensemetrics nodes? 

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

A. The sensemetrics Thread is an advanced connectivity and edge computing device, providing secure communication and direct interface controls for complex, high-power, and high-frequency devices like robotic total stations, variable frequency drives, multiparameter weather stations, shape arrays, accelerometers, cameras, and many more. It also can connect directly to one or many MUX devices to support dense sensor requirements of 100+ per location. Each Thread simultaneously serves a secondary role as a secure gateway for the connection of wireless sensors, including Geokon Geonet nodes and smart sensors that communicate using the MQTT protocol. 

For low power, low-frequency geotechnical sensors there are connectivity solutions such as Geokon Geonet, RST rStar, Loadsensing, and Ackcio Beam, which are a more economic means of connecting low-cost sensors. sensemetrics cloud provides administration and data management for all of these wireless products – giving customers a choice in selecting the best mix of connectivity solutions for their project. 

Q. Once the project is completed, what is the frequency of readings after construction?Wesley Saunders, P. Eng. | Business Development Manager, GKM Consultants

A. For this project, various monitoring frequencies are being used for post-construction. These range from none in less critical areas to up to 3 months for more critical locations. Typically the monitoring frequency would ramp down over this period – an example would be weekly for the first month, biweekly for the second month and monthly for the third month. Of course, decisions to continue or forego monitoring need to be based on the conditions encountered during the project work and not necessarily limited to what was written into the initial monitoring program. 

Q. How do you know the direction of movement on “directional/movement” type instruments? In the sensemetrics app, you only see delta x and delta y. Can you customize the axis names?

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

Xtilt and Ytilt are the base metrics generated by the biaxial tilt sensors installed. After connecting the sensor to the platform, the user is prompted to provide additional properties that can be used to transform these metrics into a surrounding geospatial context. For example, after defining the location, sensor azimuth, and structure azimuth – the platform will present users additional metrics for calculation of Northing/Easting tilt and Transverse/Longitudinal tilt. These properties are applied at run-time and are not pre-processed against the raw metrics – allowing users the flexibility of changing these values at any time and rendering the entire historical record for the sensor to reflect the updated properties. This data model and calculation architecture provides ultimate flexibility to users and retains the integrity of the original observations as a true system of record.

Q. How do you define critical points to secure with the monitoring?

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

A. There are many considerations when determining critical points for monitoring. For each project and site, you should evaluate risk events based on the consequences of the potential event as well as the probability of occurrence. From this evaluation, you can determine which risk events are acceptable, which need to be monitored, which require insurance as well as which are not acceptable and therefore require improvements in the project design.

Q. How is the data collected being used and who is using it? Often the data is just collected and performance is not evaluated until something happens or a trigger is set off.  Should we rely on computers to monitor the facilities or should we include a human?

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

A. The data is being collected via sensemetrics Threads or GKM’s Loadsensing gateway and end node combination and loaded directly into sensemetrics software for access by assigned and authorized users. The sensemetrics platform is designed to be operated and maintained by a human user.  sensemetrics’ platform is a tool that simplifies data collection, data management, and processing; all under human oversight. In doing so, the operator of the system becomes more efficient overall and is able to manage larger data sets, manage more frequent readings which reduces risk and can ultimately reduce overall monitoring costs in a relatively short period of time.  

Q. Do you input the sensor data into engineering software and how easy is that process?

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

A. Our mature and secure sensemetrics API provides both REST and subscription data connections for standardized and secure data access by Third Party Applications. Integrations with industry-leading analytical applications provide best-in-class solutions for critical operations.

Q. Is it possible to accurately eliminate the temperature effects, and is it sensor dependent?Wesley Saunders, P. Eng. | Business Development Manager, GKM Consultants

A. With a large dataset, you can empirically correct for the variations of readings due to temperature however it must be used carefully. The variations in readings can be caused by three main parts, first is the temperature effect on the performance of the sensor chip itself which can be lab calibrated relatively easily, second is the thermal expansion and contraction of the mounting hardware for the instrument and third is the associated movement of the structure itself. These second and third factors can be difficult to assess proportions and are specific to each individual installation location. As such you need to exercise caution when applying manual data corrections as you have the potential to remove true movements that are being caused by the coefficient of thermal expansion of structures like tunnel sections. 

Q. How do you deal with fluctuated data on Tiltmeter readings? How do you interpret TIL readings if no rotation center can be determined?

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

A. We find there are a couple of ways to manage data fluctuations on tiltmeters. One method is to increase the measurement frequency compared to the reporting period and to present the median or average value, this would be similar to the data averaging feature that sensemetrics includes in their graphing functions.

Your second question highlights one of the significant limitations of the tiltmeter as a sensor. It is a point measurement and can only be truly representative of the condition at that specific location. We tend to use tiltmeters in combination with other instruments such as tilt beams, which provide a much larger measurement gauge, as well as survey prisms or convergence meters such that we have comparative measurements to help confirm assumptions used in interpretations.

Q. How complex is the back-end of sensemetrics compared to other competitors for the initial setup? Is it manageable by the user or does someone from sensemetrics need to perform the setup?

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

A. sensemetrics was developed so that any user can set up a monitoring system with minimal technical training. Most projects that utilize sensemetrics are installed by the end user with minimal up-front training in a sensemetrics certification course.

Q. Can the sensemetrics platform be used fully-locally – for example in applications where Internet access is not possible, such as in mining in remote areas?Nathan McGee | Technical Director, sensemetrics

A. sensemetrics does offer an on-premise solution that we call sensemetrics Enterprise. This product has some limitations compared to cloud computing, but in many cases is a good option for owners to bring their process of collecting and standardizing sensor data at the site which can be easily migrated to a cloud-based system as connectivity becomes more widely available.

Q. How can the data be shared with the operations control room of the city of Toronto and First Respondents for crisis management?

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

A. We offer a few options. Data can be directly shared with the City of Toronto by providing users a secure account on our platform, applications can query sensor data programmatically using our REST or subscription API, and/or through data export utilities that we have made available – including our Microsoft Excel plugin. This range of tools and interfaces were developed to provide owners like the City of Toronto options about how they integrate condition monitoring data into their larger decision making processes and systems.  

Q. How are you uploading manual data? Do you upload inclinometer manual readings? Where is the data stored? Wesley Saunders, P. Eng. | Business Development Manager, GKM Consultants

A. Manual import of survey data is being completed by creating individual position sensors similar to how you would with an AMTS. Readings are then recorded with date, time, and position and imported as a data record using .CSV files. For the manual inclinometer data, a typical software such as GTILT or SiteMaster are used to produce a PDF output file which is then saved in a document control registry. All data for the project is stored in a cloud server.

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 tiltmeters. 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 behavior, closely related or reflective of the parameter that needs to be controlled. For example, if rail movement of 2mm is the controlling behavior 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 to 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 the 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. | Business Development Manager, GKM Consultants

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. | Director of Infrastructure, sensemetrics

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 the installation of targets?

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

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 are 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 tiltmeter 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. | Director of Infrastructure, sensemetrics

A. sensemetrics users can 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. | Director of Infrastructure, sensemetrics

A. sensemetrics primarily offer 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.


Please contact us at sales@gkmconsultants.com if you have any questions about the webinar.