Rome Underground Testbed

 

 

 The goal of Rome B1 Underground test-bed was to monitor the construction of the 700m tunnel connecting the Conca d’Oro  and Jonio  new metro stations. The construction involved the use of a 9m diameter Tunnel Boring Machine (TBM) long 70 meters. The excavation started at the end of November 2011 and finished in mid February 2012. GENESI system was deployed  to monitor 4 concrete sections instrumented with vibrating-wire strain gauges to monitor the concrete and steel deformations that are a critical parameter to evaluate the forces which act over the structure. The sampling period has been set to 5 minutes for system stress tests, and then  to 1 hour as requested by the construction works companies. Specifically, according to the requirements of the construction project the Conca D’Oro-Piazzale Jonio tunnel is monitored through no.4 instrumented sections, each having three concrete segments equipped with one commercial data loggers and six Sisgeo vibrating strain gauges. Commercial data loggers are connected to the remote centre through a cabled network, while the same type of monitoring system has been replicated  interleaving the commercial instrumented sections envisioned for monitoring the tunnel with four GENESI instrumented sections. This allowed to benchmark the two types of systems, proving the value of the new features of GENESI system (cableless, long lasting oepration, ability to provide data also in critical situations when traditional systems fail, low maintenance).

B1 line Genesi section Monitored section and segments in the tunnel lining

The deployment is displayed in the following pictures. Three types of nodes have been deployed:

  • The Gateway is responsible to collect data generated by the deployed network and transmit it to an external server where data are stored and processed. The gateway is in fact a wireless node, acting as a Sink for the WSN. It is connected to an embedded system which is able to set the required sampling period of the network, collect and store the incoming data. The embedded system is also connected to the internet through an UMTS modem which enables the embedded system to synchronize the data with an external server. Finally, a UPS is used to prevent possible power failures that are common in a construction site.

  • The Sensing Node is a wireless node which substitutes the data-logger of the wired solution. Thus, it is installed in each steel box of each sensor-equipped concrete block and connected to the strain sensors through a newly-built GENESI sensor interface which can read data from 6 strain sensors and communicate the readings to the wireless node through an UART interface. Based on the sampling period, the wireless node asks the sensor interface to read data from strain gauges: then, the wireless node forwards the gathered data to the Gateway through the multi-hop Wireless Sensor Network.

  • The Relay Node is a wireless node which supports the multi-hop forwarding of data toward the Sink. The goal of the relay node is to provide wireless connectivity to the sensing nodes. In fact, the Sensing Nodes may be far from each other and, hence, may not have direct wireless connectivity to the gateway. In addition, the steel box and the concrete all around the node sensibly reduce the radio range performance. Thus, a set of relay nodes deployed over the tunnel and over the TBM provides the wireless connectivity required by the WSN to forward data from the Sensing Nodes to the Gateway during the excavation phase.

Testbed topology  by the end of November 2011Position of gatewayRelay nodesSensing node in concrete elementSealing of housingSoftware architecture

While the tunnel was excavated sensor nodes where also depoyed on the Tunnel Boring Machine, to enable reliable communication of data even when the TBM was covering the instrumented sections. Communication is enabled by the  low power DISSense protocol which is  used to wirelessy instruct the nodes and reconfigure the system and to convergecast the measured vaues from the source sensing nodes to the gateway, and from there to a remote server, in real time. Use of DISSense allows to seamlessy add, remove nodes, and results in high reliability (96,1% average packet delivery ratio, with all nodes above 90%), and very low energy consumption (averahe duty cycle: 0,22%). The protocol has been extended to gather information on the node status, reconfigure (e.g., changing the sampling rate) and restart nodes upon need. 


The final sensing platform used in Rome deployment is now being engineered to become a commercial products: MagoNode.

The MagoNode has been interfaced with  different sensor families used in structural health monitoring applications, i.e., current loop sensors, resistive sensors, voltage-based sensors and vibrating wire strain gauges. Structural Health Monitoring commercial products are enabled by a combination of the MagoNode sensing platforms integrated with different SHM sensors, and of the SW architecture used for monitoring the Rome B1 line.


A spinoff company of University of Rome La Sapienza, WSENSE Srl, has been founded to commercialize sensing systems developed within GENESI.

We thank Roma Metropolitanefor allowing access to the site and supporting the deployment.

 


 


Structural health monitoring
at Rome Underground White Paper