Fiber Optic Pavement Monitoring
MoMacMo has developed a novel system for monitoring strain using standard optical fiber cables used in the telecommunications industry. Many roads already have fibers installed along the right of way for telecommunications and high speed internet. During resurfacing, it would also be possible to install fibers specifically for the purpose of monitoring strain in areas that are prone to damage or landslides. Unlike other systems for pavement monitoring, the MoMacMo Macadam Monitoring (5M) system is relatively inexpensive, and allows for continuous or more episodic monitoring of strain along the fiber.
Fiber cost is around $500 per mile, and installation can be integrated as part of resurfacing operations. The fiber can be simply laid prior to gravel installation, and covered with gravel. If trenching is required, the cost would increase significantly to $5000 per mile. For example, a 10 mile stretch of highway could be initially instrumented for less than $10,000 if the fiber is laid under gravel. If trenching is required, the costs could rise by $1-$5 per linear foot, depending on trenching costs.
The 5M system uses low cost off-the-shelf fiber optic test equipment to monitor the change in strain of the fiber. MoMacMo’s software systems for acquiring and analyzing the data are currently hosted by Amazon Web Services (AWS), providing world-wide cloud-based availability of the analysis service. The 5M system provides the ability to monitor real time changes in strain, sampling the fiber as often as once per minute. In most cases, monitoring changes daily, weekly, or even monthly will be more common. Depending on the frequency of monitoring, costs are in the range of $100 - $1000 per month.
An initial test deployment of the 5M system for a 10 mile stretch of highway could then be conducted for a cost of $10,000 for installation, and $10,000 for one year of monitoring. The data from the 5M system provides a measurement of the change in strain at 1-10 ft intervals along the cable, depending on the magnitude of the required strain measurement. The 5M system can detect changes in strain as low as 0.1 kg acting on 1m of fiber, and temperature changes of 1 deg per hour. This level of sensitivity would allow the system to detect many of the types of stresses that lead to pavement failures that occur along highways. This information could be used to optimize the timing and need for repairs and resurfacing, and to detect potential hazardous slumps or landslides before they damage the roadway.