Systems and methods for monitoring structural integrity of slopes

Abstract

A system is described in which one or more loops of single mode optical fiber are buried in a face or crest of a slope such as a tailings dam. An optical interrogator such as a Brillouin frequency domain interrogator sweeps the optical fiber to measure strain and temperature at locations distributed along the length of the optical fiber.

1 . A system for monitoring structural integrity of a slope, the system comprising:
 one or more loops of single mode optical fiber in contact with the slope; and   a Brillouin frequency domain interrogator for measuring strain at one or more locations along a length of the one or more loops of single mode optical fiber.   
     
     
         2 . A system according to  claim 1  wherein at least one of the one or more loops of single mode optical fiber are embedded in one or more substantially vertical boreholes formed in the slope. 
     
     
         3 . The system of  claim 2  wherein at least one of the one or more substantially vertical boreholes extends substantially vertically from a crest of the slope and into the slope. 
     
     
         4 . The system of  claim 2  wherein at least one of the one or more substantially vertical boreholes extends substantially vertically from a bench (e.g. a generally horizontal bench) on a face of the slope. 
     
     
         5 . The system of  claim 4  wherein the one or more benches are on a downstream surface of the slope. 
     
     
         6 . The system of  claim 2  wherein the substantially vertical boreholes extend downwardly to a stable foundation underlying the slope. 
     
     
         7 . The system of  claim 6  wherein the stable foundation comprises one or more of: bedrock and stable ground predating the formation of the slope. 
     
     
         8 . The system of  claim 1  wherein the Brillouin frequency domain interrogator measures temperature at one or more locations along a length of the one or more loops of single mode optical fiber. 
     
     
         9 . The system of  claim 1  wherein at least one of the one or more loops of single mode optical fiber comprises one or more elongated sections, each elongated section is located in a corresponding substantially horizontally elongated channel embedded in the slope. 
     
     
         10 . The system of  claim 9  wherein the one or more substantially horizontally elongated channels are disposed substantially parallel to a crest of the slope. 
     
     
         11 . The system of  claim 10  wherein each elongated section is embedded in a corresponding channel disposed substantially parallel to a gradient of the slope. 
     
     
         12 . The system of  claim 10  wherein each elongated section is embedded in a corresponding channel disposed substantially transverse to a gradient of the slope. 
     
     
         13 . The system of  claim 1  wherein the one or more loops of single mode optical fiber comprise a jacket and an optical core and the jacket is closely coupled to move with the optical core for transferring external strain to the optical core. 
     
     
         14 . The system of  claim 13  comprising a second loop of optical fiber alongside the one or more loops of single mode optical fiber comprising a second jacket and a second optical core and wherein the second jacket is loosely coupled to the second optical core such that the second loop of optical fiber is less sensitive, than the one or more loops of single mode optical fiber, to external strain. 
     
     
         15 . The system of  claim 14  wherein measurements from the second loop of optical fiber are compared to measurements from the one or more loops of single mode optical fiber to arrive at temperature measurements representative primarily of strain without the effect of temperature. 
     
     
         16 . A method of monitoring structural integrity of a slope, the method comprising the steps of:
 sweeping one or more loops of single mode optical fiber with a source of light;   recording a signal in the single mode optical fiber; and   analyzing the signal using Brillouin optical frequency domain analysis (BOFDA) and, by the BOFDA analysis, identifying locations within the optical fiber experiencing strain;   wherein at least one of the one or more loops of single mode optical fiber are embedded in one or more substantially vertical boreholes formed in the slope.   
     
     
         17 . The method of  claim 16  wherein at least one of the one or more substantially vertical boreholes extends substantially vertically from a crest of the slope and into the slope. 
     
     
         18 . The method of  claim 16  wherein at least one of the one or more substantially vertical boreholes extends substantially vertically from a bench (e.g. a generally horizontal bench) on a face of the slope. 
     
     
         19 . The method of  claim 18  wherein the one or more benches are on a downstream surface of the slope. 
     
     
         20 . The method of  claim 16  wherein the substantially vertical boreholes extend downwardly to a stable foundation underlying the slope.