Sensor deployment for modular pavement slabs
A roadway segment includes a body having a length along a direction of travel, a width along a width axis, and top and bottom halves along a depth axis. The segment also includes a strain sensor array with one or more optical fiber cables embedded in the bottom half of the body. The strain sensor array includes vehicle-strain sensors configured to detect strain on the body resulting from vehicles traveling across the top surface. The segment also includes a processor that operates the plurality of vehicle-strain sensors at a resolution of not greater than one picometer (1 pm). Any segments of the optical fiber cable(s) that intersect are separated from one another depth wise by at least two-tenths of an inch (0.2 in.). Each of the sensors is separated from each other along the width axis by at least two inches (2 in.).
1. A segment of roadway comprising:
a body having a top surface, a length along a direction of travel, a width along a width axis perpendicular to the direction of travel, and top and bottom halves delineated along a depth axis perpendicular to the direction of travel and to the width axis;
a strain sensor array comprising one or more optical fiber cables embedded in the bottom half of the body, the strain sensor array including a plurality of vehicle-strain sensors configured to detect strain on the body resulting from vehicles traveling across the top surface; and
a processor that operates the plurality of vehicle-strain sensors at a resolution of not greater than one picometer (1 pm),
the plurality of vehicle-strain sensors each having a length extending substantially parallel to the direction of travel,
wherein—
any segments of the one or more optical fiber cables that intersect in a plane parallel to the top surface are separated from one another along the depth axis by a distance of at least two-tenths of an inch (0.2 in.),
each of the plurality of vehicle-strain sensors is separated from each other of the plurality of vehicle-strain sensors along the width axis by at least two inches (2 in.).
2. The segment of roadway according to claim 1 , the processor being configured to collect multiple electrical signals across time from each of the plurality of vehicle-strain sensors and to analyze the electrical signals to determine one or more of: (A) risk of a structural defect in the body, (B) risk of a problem with underlying sub-grade beneath the body, and (C) movement of passing objects across the top surface.
3. The segment of roadway according to claim 2 , wherein the plurality of vehicle-strain sensors operate at a scanning rate of at least five hundred Hertz (500 Hz).
4. The segment of roadway according to claim 1 , wherein the one or more optical fiber cables are embedded in a configuration that includes a bend with a bend radius of at least twenty millimeters (20 mm).
5. The segment of roadway according to claim 4 , wherein each of the plurality of vehicle-strain sensors is separated from the bend along the optical fiber cable by at least one centimeter (1 cm).
6. The segment of roadway according to claim 1 , wherein each of the plurality of vehicle-strain sensors is separated from each other of the plurality of vehicle-strain sensors along the at least one optical fiber cable by at least one centimeter (1 cm).
7. The segment of roadway according to claim 1 , wherein the body comprises a precast slab, further comprising a plurality of load-transferring connectors embedded along at least one of a plurality of sides of the slab and attached to an adjacent structure, the plurality of load-transferring connectors being configured to transfer load on the precast slab corresponding to the passing vehicles between the precast slab and the adjacent structure.
8. The segment of roadway according to claim 7 , further comprising a reinforcement layer embedded in the body.
9. The segment of roadway according to claim 8 , wherein the one or more optical fiber cables are fixed to the reinforcement layer.
10. The segment of roadway according to claim 8 , wherein the plurality of sides of the slab respectively define the length and the width of the body, and the reinforcement layer is configured in a grid pattern and extends across at least seventy percent (70%) of the length of the slab and across at least seventy percent (70%) of the width of the slab.
11. The segment of roadway according to claim 1 , further comprising a temperature sensor embedded in the body.
12. The segment of roadway according to claim 11 , wherein the temperature sensor and the plurality of vehicle-strain sensors comprise one of the one or more optical fiber cables.
13. The segment of roadway according to claim 11 , the processor being configured to determine movement of passing objects across the top surface at least in part by using temperature data from the temperature sensor to analyze or interpret electrical signals from the plurality of vehicle-strain sensors.
14. The segment of roadway according to claim 11 , wherein the temperature sensor comprises an optical fiber cable surrounded by an air gap encased in a housing.
15. The segment of roadway according to claim 14 , wherein the optical fiber cable enters and exits the housing respectively at entry and exit points, and the length of the optical fiber cable within the housing is at least one percent (1%) greater than a shortest distance between the entry and exit points of the housing.
16. The segment of roadway according to claim 11 , wherein the temperature sensor operates at a scanning rate within ten percent (10%) of scanning rate(s) of the plurality of vehicle-strain sensors.
17. The segment of roadway according to claim 1 , further comprising an integrity sensor having at least one of a length and a spatial resolution of greater than fifty centimeters (50 cm), the integrity sensor being configured to monitor for structural damage.
18. The segment of roadway according to claim 17 , wherein the integrity sensor operates at a scanning rate of less than two hundred Hertz (200 Hz).
19. The segment of roadway according to claim 1 , wherein—
the length of the body is bisected by a length midpoint,
the width of the body is bisected by a width midpoint,
the plurality of vehicle-strain sensors are distributed across the body such that at least thirty percent (30%) of the vehicle-strain sensors are positioned on a first side of the length midpoint, at least thirty percent (30%) are positioned on a second, opposite side of the length midpoint, at least thirty percent (30%) are positioned on a first side of the width midpoint, and at least thirty percent (30%) are positioned on a second, opposite side of the width midpoint.
20. The segment of roadway according to claim 1 , wherein the plurality of vehicle-strain sensors are distributed across at least fifty percent (50%) of the length of the body and the plurality of vehicle-strain sensors are oriented lengthwise substantially parallel to the direction of travel.