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Ground Penetrating Imaging Radar Print E-mail

1. To develop a high resolution Ground Penetration Imaging Radar (GPIR) for detecting water pipes with their dimensions and material, for detecting leaks and damage in such pipes and for imaging the damaged region.

  • The above GPIR will be able to detect water pipes made of all types of materials.
  • It will also be able to detect leaks and damages in water pipelines of all types of materials.
  • It will have a penetration capability of up to 2 meters into the ground.
  • The image resolution capabilities of the damaged pipe will be less than 5 cm.
  • The survey time (detection and imaging) will be 10 sec/meter along the pipe axis. It will thus take 2.8 hours to survey a kilometer of the pipeline.

Regarding the operating procedure:
The GPIR will be mountable on a 4x4 wheel car. A lap top computer will also be inside the car while the antenna system and transceiver-analog/digital signal processing units will be placed in the front of the car. The antenna will be of a square shape of 1x1 m2 in horizontal dimensions while the thickness will be about 10 cm. In each position, the system will be able to survey a length of 5 meters along the pipeline. Thus, to survey a pipe length of 100 meters, the car must stop at 100/5=20 points along the line of the pipe.

The system and subsystem interface specifications are derived by carrying first a system analysis and then description of the operation principles of the various subunits of the GPIR. The essential part of the system is the imaging algorithm which will generate the images concerning the underground medium. Ultra wide band signal processing techniques are utilized to measure and record the reflected-scattered waves on a plane of 1×1 m2 with a pixel size of 10×10 cm2 along the time axis following the illumination of the ground medium with a short pulse signal radiated by a wide band transverse electromagnetic horn antenna. The recorded sampled time domain data at the 100 points (10×10) is equivalent to 400 sampling points and are utilized to obtain the underground medium images in three dimensions using coherent electromagnetic “holographic” techniques in real time. Two alternative three dimensional imaging methods are formulated and will be tried. Both mechanical and electronic scanning is used to obtain the measurements of the reflected-scattered wavefronts from the underground medium.


Figure 1. Photos of the GPIR System.
In the first photo, the User Interface can be discriminated,
while at the photo below, the procedure of measurements is presented

Decision-Support-System for the Rehabilitation Management of Water pipelines
A Decision-Support-System (DSS) has been developed for the rehabilitation management of the underground water pipelines that will use input from inspections to assess probabilistically and as a function of time, the structural reliability, leakage, and conformity to water quality standards of the pipes. In the same DSS a risk-based methodology for rehabilitation decisions considers the overall risk, including financial and social criteria.
Fig. 2 presents an overview of the above DSS.


Figure 2. Integrated System for the Rehabilitation Management
of the Trunk and Distribution Water Mains

Structural Reliability Module; Leakage Module; Water Contamination Module
To assess the structural reliability of a water pipeline, input on damages from inspection will be taken into account and structural analyses will be performed of the damaged pipeline to assess its structural condition at the time of the inspection. Similar analyses will be performed at future times but with different parameters based on the evolution of (1) loads, (2) materials’ deterioration, and (3) soil-structure interaction. Some of the parameters will be treated as random variables and thus, the probability of structural failure as a function of time will be estimated. Figs. 3 and 4 show some of the results.
There will be leaking from local fractures seen in the inspection and/or determined in the structural analyses.

A hinge, permitting free rotation, will be assumed at the points of local fractures and the analyses will continue for future points in time (when the pipe material will be more deteriorated and there will be less soil support) until the combination of local fractures produces a kinematic mechanism (and thus, structural failure of the pipe).

At the point of structural failure all water in the pipe will be lost. Before this point is being reached, though, local failures produce leakage which increases with time because of increases in both the number and the extent of local failures with time.

A formula has been used to assess the rate of leakage at each point in time. This rate is positively related to the area of the opening in local fractures. A methodology has been developed to estimate the size of the above opening in the case of circumferential cracks while inspection results will be used to assess the length of horizontal cracks.

Some of the parameters in the formula on leakage rate will be treated as random variables and thus the leakage rate with its average value and standard deviation will be estimated as a function of time. For a threshold value for leakage the probability of leakage failure as a function of time will also provided.
When the pipe has lost its structural integrity, in the presence of negative pressures and a neighbouring source of contamination, contaminants might enter into the pipe affecting water quality particularly in terms of bacteriological quality.

A methodology has been developed to assess probabilistically and as a function of time compliance with water quality standards in regards to pathogens. Moreover, a methodology has been developed to assess probabilistically and as a function of time the aesthetic quality of water because of the release of corrosion products as particulate and dissolved iron from unlined, corroded iron mains.


Figure 3. Structural Failure Probability Over Time for Different Operation Pressures


Figure 4. Structural Failure Probability Over Time for Different Depths of Installation

 

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