1、Designation: D 7007 09Standard Practices forElectrical Methods for Locating Leaks in GeomembranesCovered with Water or Earth Materials1This standard is issued under the fixed designation D 7007; the number immediately following the designation indicates the year oforiginal adoption or, in the case o
2、f revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 These practices describe standard procedures for usingelectrical methods to locate leaks in ge
3、omembranes coveredwith water or earth materials containing moisture.1.2 These practices are intended to ensure that leak locationsurveys are performed with demonstrated leak detection capa-bility. To allow further innovations, and because various leaklocation practitioners use a wide variety of proc
4、edures andequipment to perform these surveys, performance-based opera-tions are used that specify the minimum leak detection perfor-mance for the equipment and procedures.1.3 These practices require that the leak location equipment,procedures, and survey parameters used are demonstrated toresult in
5、an established minimum leak detection sensitivity. Thesurvey shall then be conducted using the demonstrated equip-ment, procedures, and survey parameters.1.4 Separate procedures are given for leak location surveysfor geomembranes covered with water and for geomembranescovered with earth materials. S
6、eparate procedures are given forleak detection sensitivity tests using actual and artificial leaks.1.5 Leak location surveys can be used on geomembranesinstalled in basins, ponds, tanks, ore and waste pads, landfillcells, landfill caps, and other containment facilities. Theprocedures are applicable
7、for geomembranes made of materialssuch as polyethylene, polypropylene, polyvinyl chloride, chlo-rosulfonated polyethylene, bituminous material, and otherelectrically-insulating materials.1.6 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in th
8、isstandard.1.7 WarningThe electrical methods used for geomem-brane leak location could use high voltages, resulting in thepotential for electrical shock or electrocution. This hazardmight be increased because operations might be conducted inor near water. In particular, a high voltage could exist be
9、tweenthe water or earth material and earth ground, or any groundedconductor. These procedures are potentially VERY DANGER-OUS, and can result in personal injury or death. The electricalmethods used for geomembrane leak location should beattempted only by qualified and experienced personnel. Appro-pr
10、iate safety measures must be taken to protect the leaklocation operators as well as other people at the site.1.8 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety
11、 and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 4439 Terminology for GeosyntheticsD 6747 Guide for Selection of Techniques for ElectricalDetection of Potential Leak Paths in Geomembranes3. Terminology3.1 For g
12、eneral definitions related to geosynthetics, seeTerminology D 4439.3.2 Definitions of Terms Specific to This Standard:3.2.1 artificial leak, nan electrical simulation of a leak ina geomembrane.3.2.2 current source electrode, nthe electrode that isplaced in the water or earth material above the geome
13、mbrane.3.2.3 dipole measurement, nan electrical measurementmade on or in a partially conductive material using twoclosely-spaced electrodes.3.2.4 earth material, nsand, gravel, clay, silt, combina-tions of these materials, and similar materials with at leastminimal moisture for electrical current co
14、nduction.3.2.5 leak, nany unintended opening, perforation, slit,tear, puncture, crack, hole, cut, or similar breaches through aninstalled geomembrane. Significant amounts of liquids orsolids might or might not flow through a leak. Scratches,gouges, dents, or other aberrations that do not completelyp
15、enetrate the geomembrane are not considered to be leaks.3.2.6 leak detection sensitivity, nthe smallest size leakthat the leak location equipment and survey methodology are1These practices are under the jurisdiction of ASTM Committee D35 onGeosynthetics and is the direct responsibility of Subcommitt
16、ee D35.10 on Geomem-branes.Current edition approved June 1, 2009. Published August 2009. Originallyapproved in 2003. Last previous edition approved in 2003 as D 700703.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual
17、 Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.capable of detecting under a given set of conditions. The leakdetection sensit
18、ivity specification is usually stated as a diam-eter of the smallest leak that can be reliably detected.3.2.7 noise, nthe unwanted part of a measured signalcontributed by phenomena other than the desired signal.3.2.8 pole measurement, nan electrical measurementmade on or in a partially conductive ma
19、terial using onemeasurement electrode and a remote reference electrode.3.2.9 potential, nelectrical voltage measured relative to areference point.4. Summary of the Leak Location Methods4.1 The principle of the electrical leak location method is toplace a voltage across a geomembrane and then locate
20、thepoints of anomalous potential distribution where electricalcurrent flows through leaks in the geomembrane. Additionalinformation can be found in Guide D 6747.4.2 General Principles:4.2.1 Figs. 1 and 2 show diagrams of the electrical leaklocation method for a geomembrane covered with water andfor
21、a geomembrane covered with earth materials respectively.One output of an electrical excitation power supply is con-nected to a current source electrode placed in the materialcovering the geomembrane. The other output of the powersupply is connected to an electrode in contact with electricallyconduct
22、ive material under the geomembrane.4.2.2 When there are leaks, electrical current flows throughthe leaks, which produces high current density and a localizedanomaly in the potential distribution in the material above thegeomembrane. Electrical measurements are made to locatethose areas of anomalous
23、signal at the leaks.4.2.3 Measurements are made using a dipole or pole mea-surement configuration. Various types of data acquisition areused, including audio indications of the signal level, manualmeasurements with manual recording of data, and automateddigital data acquisition.4.2.4 Direct current
24、and alternating current excitation powersupplies and potential measurement systems have been usedfor leak location surveys.4.3 Leak Location Surveys of Geomembranes Covered withWater:4.3.1 Leak location surveys for geomembranes coveredwith water can be conducted with water on the geomembraneor with
25、water covering a layer of earth materials on thegeomembrane.4.3.2 For leak location surveys with water on the geomem-brane, usually a dipole probe is systematically scanned throughthe water covering the geomembrane to locate the points ofanomalous potential distribution. The dipole spacing is typi-c
26、ally 0.2 to 1 metres.4.3.3 Various types of probes can be used to perform thesurveys. Some are for when the operator wades in the water;some are for towing the probe back and forth across thegeomembrane; and some are for raising and lowering alongvertical or sloping walls.4.3.4 The probe is typicall
27、y connected to an electronicdetector assembly that converts the electrical signal from theprobe to an audible signal that increases in pitch and amplitudeas the leak signal increases.4.3.5 When a leak signal is detected, the point with themaximum signal is then determined. This point of maximumsigna
28、l corresponds to the location of the leak. The location ofthe leak is then marked or measured relative to fixed points.4.3.6 The leak detection sensitivity depends on the conduc-tivity of the materials within, above, and below the leak, theelectrical homogeneity of the material above the leak, theou
29、tput level of the excitation power supply, the design of themeasurement probe, the sensitivity of the detector electronics,the distance away from the leak, and the survey procedures.Leaks as small as 1 mm in diameter have been routinely found,including tortuous leaks through welds in the geomembrane
30、.Leaks larger than 25 mm in diameter can usually be detectedfrom several metres away.4.3.7 The survey rate depends primarily on the spacingbetween scans and the depth of the water. A close spacingbetween scans is needed to detect the smallest leaks.FIG. 1 Diagram of the Electrical Leak Location Meth
31、od for Surveys with Water Covering the GeomembraneD70070924.4 Leak Location Surveys of Geomembranes Covered withEarth Materials:4.4.1 For leak location surveys with earth materials cover-ing the geomembrane, point-by-point measurements are madeon the earth material using either dipole measurements o
32、r polemeasurements. Dipole measurements are typically made with aspacing of 0.5 to 5 metres. Measurements are typically madealong parallel survey lines or on a grid pattern.4.4.2 The survey procedures are conducted in a systematicdata collection mode. The measurements and positions arerecorded manua
33、lly or using a digital data acquisition system.4.4.3 The data is typically downloaded or manually enteredinto a computer and plotted. Sometimes data is taken alongsurvey lines and plotted in raster. Sometimes data is taken in agrid pattern and plotted in two-dimensional contour, shade ofgray, or col
34、or contour plots, or in three-dimensional represen-tations of the contours. The data plots are examined forcharacteristic leak signals.4.4.4 The approximate location of the leak signal is deter-mined from the data plots and additional measurements aremade on the earth material in the vicinity of the
35、 detected leaksignal to more accurately determine the position of the leak.4.4.5 The leak detection sensitivity depends on the conduc-tivity of the materials within, above, and below the leak, theelectrical homogeneity of the material above the leak, thedesign of the measurement electrodes, the outp
36、ut level of theexcitation power supply, the sensitivity of the detector elec-tronics, the distance away from the leak, the survey procedures,and data interpretation methods and expertise. Usually leaks assmall as 5 mm in diameter can be located under 600 mm ofearth material. Leaks larger than 25 mm
37、in diameter canusually be detected from several metres away.4.4.6 The survey rate depends primarily on the spacingbetween the measurement points, the type of data acquisition,and whether data interpretation is accomplished in the field. Aclose spacing between measurement points is needed to ad-equat
38、ely replicate the leak signals and to detect smaller leaks.5. Significance and Use5.1 Geomembranes are used as impermeable barriers toprevent liquids from leaking from landfills, ponds, and othercontainments. The liquids may contain contaminants that ifreleased can cause damage to the environment. L
39、eaking liquidscan erode the subgrade, causing further damage. Leakage canresult in product loss or otherwise prevent the installation fromperforming its intended containment purpose. For these rea-sons, it is desirable that the geomembrane have as little leakageas practical.5.2 Geomembrane leaks can
40、 be caused by poor quality ofthe subgrade, poor quality of the material placed on thegeomembrane, accidents, poor workmanship, and carelessness.5.3 The most significant causes of leaks in geomembranesthat are covered with only water are related to constructionactivities including pumps and equipment
41、 placed on thegeomembrane, accidental punctures, and punctures caused bytraffic over rocks or debris on the geomembrane or in thesubgrade.5.4 The most significant cause of leaks in geomembranescovered with earth materials is construction damage caused bymachinery that occurs while placing the earth
42、material on thegeomembrane. Such damage also can breach additional layersof the lining system such as geosynthetic clay liners.5.5 Electrical leak location methods are an effective finalquality assurance measure to locate previously undetected ormissed leaks.6. General Leak Location Survey Procedure
43、s6.1 The following measures shall be taken to optimize theleak location survey:FIG. 2 Diagram of the Electrical Leak Location Method for Surveys with Earth Material Covering the GeomembraneD70070936.1.1 Conductive paths such as metal pipe penetrations,pump grounds, and batten strips on concrete shou
44、ld be isolatedor insulated from the water or earth material on the geomem-brane whenever practical. These conductive paths conductelectricity and mask nearby leaks from detection.6.1.2 In applications where a single geomembrane is cov-ered with earth materials that overlap the edges of thegeomembran
45、e, if practical, measures should be taken to isolatethe edges. If earth materials overlap the edges of the surveyarea to earth ground, electrical current will flow from the earthmaterial to earth ground, causing a large signal that will masksmall leak signals near the edges of the survey area. Isola
46、tioncan be accomplished by either: performing the leak locationsurvey before the edges of the geomembrane are covered;removing the earth materials from a narrow path around theperimeter of the geomembrane; or allowing the edge of thegeomembrane to protrude above the earth materials.6.1.3 There must
47、be a conductive material directly belowthe electrically-insulative geomembrane being tested. Typicallyleak location surveys on a properly-prepared subgrade willhave sufficient conductivity. Under proper conditions andpreparations, geosynthetic clay liners (GCLs) can be adequateas conductive material
48、. There are some conductive geotextilesor other conductive materials with successful field experiencewhich can be installed beneath the geomembrane to facilitateelectrical leak location survey (i.e. on dry subgrades, or as partof a planar drainage geocomposite).6.1.4 For lining systems where an elec
49、trically-insulativegeomembrane is overlain by a drainage geonet geocomposite,if the geocomposite is not saturated or is not manufactured tobe conductive, only leaks that penetrate both geosynthetics canbe detected; as a dry drainage geonet geocomposite iselectrically-insulative.6.1.5 For lining systems comprised of two geomembraneswith only a geonet or only a geocomposite between them, thevolume between the geomembranes shall be filled with waterto provide the conductive material. The water level in the areabetween the geomembranes should be limited so that it exertsa press
