METHOD AND APPARATUS FOR MONITORING ELEVATION

Abstract

Elevation monitoring apparatus includes an enclosed base reference station (10) a 2000 m long, elongate housing (11) extends along the length of a traverse. A pair of conduits (12, 13) are filled with air (14) and water (15) respectively and extend through the elongate housing (11). 200 differential piezo pressure sensors (16) are spaced at 10 m intervals along the pair of conduits (12, 13) and are selected to sense the pressure difference between the respective fluids (14, 15). A dedicated microprocessor (17) associated with each pressure sensor (16) collects and distributes pressure difference data over a CANbus compatible network comprising twisted pairs (20) extending to the base reference station (10). A main data processor (21) relates the data to form a database of elevations. A modem (24) and antenna (23) outputs the data to remote management. A precision GPS unit (25) monitors the base reference elevation to assure the reference standard.

Claims

1. A method of monitoring elevation along a traverse over an earthen ground substrate, said method comprising: establishing a base reference point of known elevation on said traverse from which an elongate housing extends along a length of said traverse, said housing adapted to be buried in the substrate and having an interior protected from the environment along the traverse; selecting a plurality of measurement points along said traverse; interconnecting said base reference point and said plurality of measurement points by a pair of conduits extending from said base reference station through the interior of and substantially along a length of said elongate housing, each said conduit being filled with a respective one of a pair of fluids having different densities, wherein one of the pair of fluids is a gas; continuously monitoring data corresponding to a pressure difference between the pair of fluids at said base reference point and each of said plurality of measurement points over a network; relating said data for each of said measurement points to said known elevation to form a database of elevations; and monitoring said database of elevations for changes in elevation at one or more of said measurement points.

2. The method of claim 1, wherein the base reference point is monitored by external means selected from high precision radar altimetry, GPS and laser measurement, any variation in externally-derived elevation data for the base reference point being used to calibrate the database of elevations.

3. The method of claim 1, wherein the plurality of measurement points are evenly distributed at a selected pitch along the traverse.

4. The method of claim 1, wherein the conduits each comprise a tube of a material selected from polyamide 11 or 12, HDPE or low/medium density polyethylene resin pipe.

5. The method of claim 1, wherein the fluids are water and air respectively.

6. The method of claim 1, wherein the continuously monitoring data is by electronic pressure sensors.

7. The method of claim 6, wherein the electronic pressure sensors are piezo transducer devices interconnected on a data bus comprising said network.

8. The method of claim 7, wherein the piezo transducer devices are each a single, differential-pressure, smart transducer assembly.

9. The method of claim 8, wherein each differential-pressure, smart transducer assembly has a digital output selected from RS232, RS485, and CANbus compatible outputs.

10. (canceled)

11. The method of claim 1, wherein the continuously monitoring data is performed collectively by monitoring means associated with the base reference point.

12. The method of claim 11, wherein the monitoring means includes a microprocessor and reports a recorded pressure at each transducer to a central data processor when polled.

13. The method of claim 12, wherein the relating of the data for each of said measurement points to said known elevation to form the database of elevations is done by said central data processor.

14. (canceled)

15. The method of claim 13, wherein the database of elevations is monitored for changes in elevation at one or more of the measurement points via interface with the central data processor by user interrogation, automatic signalling or both.

16. The method of claim 1, wherein the conduits and the network are located in an elongate housing having an interior protected from the environment along the traverse.

17. (canceled)

18. An elevation monitoring apparatus for a traverse over an earthen ground substrate, said apparatus comprising: a base reference station located at a base reference point of known elevation on said traverse; an elongate housing extending from said base reference station along a length of said traverse, said housing adapted to be buried in the substrate, said housing having an interior protected from the environment along the traverse; a pair of conduits, each said conduit being filled with a respective one of a pair of fluids having different densities, wherein one of the pair of fluids is a gas, said conduits extending from said base reference station through the interior of and substantially along a length of said elongate housing; a plurality of pressure sensors spaced along the pair of conduits and selected to sense a pressure difference between the fluids at said base reference station and at a plurality of measurement points along said traverse defined by said sensors; monitoring means for continuously monitoring and collecting data corresponding to said pressure difference between the fluids at said pressure sensors over a network; data processing means relating said data for each of said measurement points to said known elevation to form a database of elevations; and output means for monitoring said database of elevations and producing an output of changes in elevation at one or more of said measurement points.

19. The apparatus of claim 18, wherein the base reference station comprises a housing adapted to protect internal components from the environment and be securely located at the base reference point.

20. The apparatus of claim 18, wherein the point of known elevation is monitored by GPS with an antenna co-located with the housing, any variation in externally-derived elevation data for the base reference point being used to calibrate the database of elevations.

21. (canceled)

22. The apparatus of claim 18, wherein the conduits are formed of a polymer selected from polyamide 11 or 12, HDPE and low/medium density polyethylene resin.

23. The apparatus of claim 18, wherein the fluids comprise water and air.

24. The apparatus of claim 18, wherein the plurality of pressure sensors are piezo transducer devices.

25-36. (canceled)

Description

BRIEF DESCRIPTION OF DRAWINGS

[0050] FIG. 1 is a transverse cross section of apparatus in accordance with the present invention, taken through the traversing part at a measurement point;

[0051] FIG. 2 is a longitudinal section detail of the apparatus of FIG. 1, detailing two measurement points;

[0052] FIG. 3 is a detail scheme of a base reference station of the apparatus of FIG. 1;

[0053] FIG. 4 is a cross section diagram of an earth fill dam, showing the typical location for installation of the apparatus of FIG. 1; and

[0054] FIG. 5 is a section diagram along a highway fill, again illustrating typical installation of the apparatus of FIG. 1.

[0055] In the figures there is provided elevation monitoring apparatus for a traverse over a substrate and including an enclosed base reference station 10 (FIG. 3) located at a base reference point of known elevation on the traverse. A 2000 m long, elongate housing 11 is formed from 25 mm diameter hydraulic hose and extends from the base reference station 10 along the length of the traverse, and having an interior protected from the environment along the traverse. The elongate housing 11 is typically buried to a depth of 30 centimetres in the substrate.

[0056] A pair of conduits 12, 13 of 6 mm-bore, low/medium density polyethylene resin drip irrigation pipe are filled with air 14 and water 15 respectively and extend from the base reference station 10 through the interior of and substantially along the length of said elongate housing 11. 200 differential piezo pressure sensors 16 are spaced at 10 m intervals along the pair of conduits 12, 13 and are selected to sense the pressure difference between the respective fluids 14, 15 via barbed tail connectors 31. The 200 pressure sensors 16 provide discrete measurement points along the traverse.

[0057] Monitoring means comprises a dedicated microprocessor 17 associated with each pressure sensor 16 and collecting data corresponding to said pressure difference between the respective fluids 14, 15 at the pressure sensor 16 and distributing the data over a CANbus compatible network comprising twisted pairs 20 extending the length of the elongate housing 11 to the base reference station 10. The twisted pairs 20 include a power-over-network function to provide the low power necessary to drive the pressure sensors 16.

[0058] Data processing means includes a main data processor 21 relating the data for each of said measurement points to the known elevation to form a database of elevations. The main data processor also includes power management and is connected to a battery 22. Output means for monitoring the database of elevations and producing an output of changes in elevation at one or more of the measurement points is provided by a modem 24 and antenna 23, outputting the data to remote management.

[0059] The elevation of the base reference station 10 is assured by periodic reference to a precision GPS unit 25 and its associated GPS antenna 26. The pressure sensor 16 associated with the base reference station 10 measures the differential pressure between the air 14 and water 15 in terminal reservoirs 27, 30 respectively, which terminate the respective conduits 13, 12.

[0060] The 200 measurement points defined by the sensors 16 may be evenly distributed at a selected pitch along the traverse, as described above, to service a made structure such as an earth-fill embankment, revetment, impoundment wall or other like structure. In a more heterogeneous environment, the sensors 16 may be located at the sites along the traverse which are expected to be more prone to settling or subsidence.

[0061] FIG. 4 is a cross section diagram of an earth fill dam having an upstream wall 32, a downstream wall 33, an earth core 34 and a viaduct upper drainage surface 35. The elongate housing 11 is installed in a 30 cm deep trench near the top of the fill material 34.

[0062] FIG. 5 is a section diagram along a highway fill batter. Fill material 36 has been placed over the original ground surface 37 to create a new highway surface stabilised by a rock formed batter. The elongate housing 11 is placed in a shallow trench on the highway shoulder. The base reference station 10 is installed on undisturbed ground.

[0063] Apparatus and methods of the foregoing embodiment has the advantage that the elevation of a multiplicity of points is continuously measured. Real time monitoring allows alarms to be triggered if subsidence values exceed preset limits. Instrumentation is permanently buried in the ground and can continue to operate for many years without interfering with use of the surface. The method of the invention is more accurate and much less costly than alternative methods.

CITATION LIST

Non Patent Literature

[0064] Land Subsidence in the United States (1999) United States Geological Service Circular 1182. Edited by Devin Galloway. David R. Jones and S. E. Ingebritsen http://pubs.usgs.gov/circ/1999/1182/report.pdf Retrieved August 2016 Pages 141-158 review methods for monitoring and measuring subsidence.

[0065] Real Time Monitoring of Subsidence along 170 in Washington Pennsylvania (2000) Authors: Kevin M. O'Connor, Ronald J. Clark, David J. Whitlatch and Charles H. Dowding http://www.iti.northwestern.edu/tdr/publications/Dowding_et_al-2001-Real _Time_Monitoring_of_Infrastructure_of_Subsidence_Along_I-70_in_Washington_PA.pdf retrieved August 2016.

[0066] Background paper on subsidence monitoring and measurement with a focus on coal seam gas (CSG) activities. (2013) Paper prepared for the NSW Chief Scientist and Engineer. Authors: Simon McClusky and Paul Tregoning Research School of Earth Sciences The Australian National University Canberra. http://www.chiefscientist.nsw.gov.au/_data/assets/pdf_file/0016/33028/Subsidence-Monitoring _McClusky-Tregoning_ANU.pdf Retrieved August 2016. Chapter 2 (pages 9-31) reviews methods for monitoring and measuring subsidence.

[0067] Monitoring and management of subsidence induced by coal seam gas extraction. (2014) Review prepared by Coffey Geotechnics Pty Ltd and revised by the Commonwealth Government Department of the Environment following peer review. https://www.environment.gov.au/system/files/resources/632cefef-0e25-4020-b337-80a9932d1c67/files/knowledge-report-csg-extraction_0.pdf Retrieved August 2016 Chapter 11 (pages 90-117) reviews methods for monitoring and measuring subsidence