Scour detection and monitoring apparatus adapted for use in lossy soils and method of employment thereof

• US 6,909,669 B1
• Filed: 04/19/1999
• Issued: 06/21/2005
• Est. Priority Date: 04/19/1999
• Status: Expired due to Fees

• Current Assignee: US Army Corps of Engineers (U.S. Department Of Defense)
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Zabilansky, Leonard, Yankielun, Norbert E.
• Primary Examiner(s): Lobo, Ian J.
• Application Number:
  US09/293,781
• Time in Patent Office: 2,255 Days
• Field of Search: 367/131, 367/178, 367/13, 735/94, 736/28, 405/73
• US Class Current: 367/131
• CPC Class Codes: H04B 13/02 Transmission systems in which the medium consists of the earth or a large mass of water thereon, e.g. earth telegraphy

Abstract

A sensor for detecting and monitoring scour in sediment positioned beneath a body of water, which includes a probe at least partially embedded in the sediment. Sensor electronics are superimposed on the probe. Such electronics include a reflectometer, a battery supply and a telemetry transmitter to display an interface boundary between the water and the transmitter. The sensor is particularly well adapted for use in lossy soils.

Claims

1. A system, at least part of which is buried as a probe, for instantaneously detecting a level of scour, in particular, scour about a structure that may be at least partially submerged in water, comprising:

at least one first conductor of electromagnetic energy having a characteristic impedance, a source end, a distal end configured to have an impedance different from said characteristic impedance, and a length much greater than any of said first conductor'"'"'s other dimensions,

wherein at least part of said at least one first conductor is buried as part of said probe;

at least one electromagnetically conducting ground plane electromagnetically isolated from and adjacent said at least one first conductor,

wherein at least part of said at least one electromagnetically conducting ground plane may be buried as part of said probe; and

at least one sub-system, in operable communication with said source end of said first electromagnetic conductor, for providing analog signals to and processing analog signals from said at least one first conductor, said processing to include capturing reflections of said analog signals from said at least one first conductor,

wherein at least part of said at least one sub-system may be buried integral with and atop said probe,

wherein said processing yields information for decision making, and

wherein said system is particularly suited for use in lossy soils.

2. The system of claim 1 in which said first conductor is a transmission line.

3. The system of claim 2 in which said transmission line is selected from the group consisting of:

electrically conductive rods, pipes, tubes, and combinations thereof.

4. The system of claim 1 in which said sub-system comprises at least one time domain reflectometer (TDR).

5. The system of claim 4 in which said TDR comprises:

at least one signal generator for providing pulsed analog electromagnetic signals as said signals;

a circulator in operable communication with said at least one signal generator for coupling said pulsed analog electromagnetic signals to said at least one first conductor and coupling said reflections from said conductor to said TDR; and

a processor for processing said reflections and at least portions of said signals and providing results of said processing.

6. The system of claim 5 in which said processor comprises a personal computer.

7. The system of claim 1 in which said sub-system comprises at least one FM-CW reflectometer.

8. The system of claim 7 in which said at least one FM-CW reflectometer comprises:

a linear sweep generator for generating said analog signals;

a circulator in operable communication with at least said linear sweep generator for coupling said analog signals to said at least one first conductor and coupling said reflection from said conductor to said FM-CW reflectometer;

a mixer in operable communication with said circulator for combining said at least one reflection with a portion of said analog signal to yield a first output signal;

a low pass filter in operable communication with said mixer for passing only the low frequency spectra in said first output signal, yielding a second output signal having a frequency spectra in the audio range;

a high pass audio filter in operable communication with said low pass filter for passing only the high frequency spectra of said second output signal, yielding a third output signal having a frequency spectra in the high end of the audio range;

an audio amplifier in operable communication with said high pass audio filter for amplifying said third output signal, yielding a fourth output signal; and

a processor in operable communication with said audio amplifier for comparing said data on features of said reflected analog signal with at least one reference and displaying results of said comparison,

wherein employment of said FM-CW reflectometer at least partially buried in sediment enables alerting to scour occurring at least at a pre-specified level.

9. The system of claim 1 in which a single said sub-system operates multiple said at least one conductors of electromagnetic energy by multiplexing said analog signals and at least said reflections from said distal end.

10. The system of claim 1 in which said at least one electromagnetically isolated ground plane comprises a second conductor similar to said first conductor, wherein said first and second conductors are disposed in the same plane and parallel at a pre-specified distance one to the other and at least partially buried in a location that may be adjacent said structure.

11. A method for instantaneously detecting a level of scour, in particular, scour about a structure that may be at least partially submerged in water, comprising:

disposing near said structure at least one transmission line having a characteristic impedance, a source end, and a distal end having an impedance different from said characteristic impedance,

wherein said at least one transmission line is electromagnetically isolated from said structure and is at least partially buried;

providing at least one electromagnetically conducting ground plane adjacent said at least one transmission line;

providing at least one analog electromagnetic signal at said source end,

wherein portions of said analog electromagnetic signal are distinguishable over at least pre-specified time intervals;

receiving at said source end at least one reflection of said at least one analog electromagnetic signal from at least one boundary along said at least one transmission line defined by a change in dielectric coefficient of material surrounding said at least one transmission line; and

extracting at least one quantifiable feature from said at least one reflection;

wherein at least one value associated with said at least one quantifiable feature may be compared to at least one reference value to at least detect a pre-specified level of scour that serves to at least partially uncover said at least partially buried transmission line, and wherein said method is particularly suited for use in lossy soils.

12. The method of claim 11 in which said analog electromagnetic signal is a pulsed signal,

wherein each pulse may be simulated using a step function with a fast rise time.

13. The method of claim 11 in which said analog electromagnetic signal is a frequency modulated continuous wave (FM-CW) signal provided on an RF carrier frequency.

14. The method of claim 11 in which said at least one electromagnetically isolated ground plane comprises a second transmission line similar to said first transmission line, wherein said first and second transmission lines are disposed in the same plane and parallel at a pre-specified distance one to the other adjacent at least part of said structure.

15. The method of claim 11 in which said processing provides at least a measure of the time interval for a known portion of said analog electromagnetic signal to travel from said source end to said distal end and return to said source end as at least a partial reflection from said distal end.

16. The method of claim 11 in which said processing further provides at least a measure of the time for a known portion of said analog electromagnetic signal to travel from said source end to at least a first location along the length of said transmission line and the at least partial reflection of at least part of said known portion back to said source end,

wherein said at least a first location is defined by the closest boundary to said source end of a first region around said transmission line, said first region incorporating at least one material other than the medium surrounding said transmission line in a reference at least partially buried state.

17. The method of claim 11 in which said processing further employs an algorithm to extract said at least one feature.

18. The method of claim 11 further comparing said at least one feature of said at least one reflection to at least one reference to yield additional information for decision making.

19. The method of claim 18 in which said additional information is selected from the group consisting of:

depth of burial of said probe, location of scour relative to said structure, amount of material scoured from adjacent said structure, rate of accumulation of scour occurring adjacent said structure, and combinations thereof.

20. The method of claim 11 further providing for conveying said information for decision making to a decision maker.

21. The method of claim 11 further providing for displaying said at least one quantifiable feature directly on an audio-frequency spectrum analyzer,

wherein spectral peaks may be correlated to said at least one quantifiable feature.

22. The method of claim 11 further providing for digitizing said reflected signal and processing it using a Fast Fourier Transform (FFT) algorithm,

wherein said processing yields a power spectrum from which said one quantifiable feature may be identified and displayed on a computer.

23. The method of claim 11 further providing for displaying said at least one quantifiable feature by extracting it via a bank of tuned, narrowband, audio band-pass filters (BPF) that are closely spaced in center frequency, interfacing each of said filters to a light emitting diode (LED), and correlating the number of said LEDs that are lit to said at least one quantifiable feature.