1、Designation: D 7007 03Standard 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This standard practice describes standard procedures forusing electrical methods to locate le
3、aks in geomembranescovered with water or earth materials containing moisture.1.2 This standard practice is intended to ensure that leaklocation surveys are performed with demonstrated leak detec-tion capability. To allow further innovations, and becausevarious leak location practitioners use a wide
4、variety ofprocedures and equipment to perform these surveys,performance-based operations are used that specify the mini-mum leak detection performance for the equipment and pro-cedures.1.3 This standard practice requires that the leak locationequipment, procedures, and survey parameters used are dem
5、-onstrated to result in an established minimum leak detectionsensitivity. The survey shall then be conducted using thedemonstrated equipment, procedures, and survey parameters.1.4 Separate procedures are given for leak location surveysfor geomembranes covered with water and for geomembranescovered w
6、ith earth materials. Separate 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. Theproc
7、edures are applicable for geomembranes made of materialssuch as polyethylene, polypropylene, polyvinyl chloride, chlo-rosulfonated polyethylene, bituminous material, and otherelectrically-insulating materials.1.6 WarningThe electrical methods used for geomem-brane leak location could use high voltag
8、es, 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 betweenthe water or earth material and earth ground, or any groundedconductor. These procedures are pote
9、ntially 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-priate safety measures must be taken to protect the leaklocation operators as well as other people at th
10、e site.1.7 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 and health practices and determine the applica-bility of regulatory limitations prior to use.2. Refer
11、enced 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 Definitions of Terms Specific to This Standard:3.1.1 artificial leak, nan electrical simulation of a leak i
12、na geomembrane.3.1.2 current source electrode, nthe electrode that isplaced in the water or earth material above the geomembrane.3.1.3 dipole measurement, nan electrical measurementmade on or in a partially conductive material using twoclosely-spaced electrodes.3.1.4 earth material, nsand, gravel, c
13、lay, silt, combina-tions of these materials, and similar materials with at leastminimal moisture for electrical current conduction.3.1.5 leak, nany unintended opening, perforation, slit,tear, puncture, crack, hole, cut, or similar breaches through aninstalled geomembrane. Significant amounts of liqu
14、ids orsolids might or might not flow through a leak. Scratches,gouges, dents, or other aberrations that do not completelypenetrate the geomembrane are not considered to be leaks.3.1.6 leak detection sensitivity, nthe smallest size leakthat the leak location equipment and survey methodology arecapabl
15、e of detecting under a given set of conditions. The leakdetection sensitivity specification is usually stated as a diam-eter of the smallest leak that can be reliably detected.1These practices are under the jurisdiction of ASTM Committee D35 onGeosynthetics and is the direct responsibility of Subcom
16、mittee D35.10 on Geomem-branes.Current edition approved Dec. 1, 2003. Published January 2004.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document
17、Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.7 pole measurement, nan electrical measurementmade on or in a partially conductive material using onemeasurement electrode and a remote reference ele
18、ctrode.3.2 Definitions:3.2.1 noise, nthe unwanted part of a measured signalcontributed by phenomena other than the desired signal.3.2.2 potential, nelectrical voltage measured relative to areference point.4. Summary of the Leak Location Methods4.1 The principle of the electrical leak location method
19、 is toplace a voltage across a geomembrane and then locate thepoints were electrical current flows through discontinuities inthe geomembrane.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 a geomembrane covere
20、d 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 electricallyconductive material under t
21、he geomembrane.4.2.2 When there are leaks, electrical current flows throughthe leaks, which produces high current density and a localizedabnormality in the potential distribution in the material abovethe geomembrane. Electrical measurements are made to locatethose areas of abnormal signal at the lea
22、ks.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 and alternating c
23、urrent 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 water covering a
24、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 over the geomembrane to locate the points ofabnormal potential distribution. The dipole spacing is typically0.2 to 1 metre.4.3.
25、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 typically connected to an electro
26、nicdetector 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 maximumsignal corresponds to the loca
27、tion 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, theoutput level of the excitat
28、ion power supply, the design of themeasurement probe, the sensitivity of the detector electronics,and the survey procedures. Leaks as small as 1 mm in diameterhave been routinely found, including tortuous leaks throughwelds in the geomembrane. Leaks larger than 25 mm indiameter can usually be detect
29、ed from 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.4.4 Leak Location Surveys of Geomembranes Covered withEarth Materials:4.4.1 For leak location surveys with e
30、arth materials cover-ing the geomembrane, point-by-point measurements are madeFIG. 1 Diagram of the Electrical Leak Location Method for Surveys with Water Covering the GeomembraneD7007032on the earth material using either dipole measurements or polemeasurements. Dipole measurements are typically mad
31、e 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 manually or using a digital data acquisition system.4.4.3 The
32、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 color contour plots, or in three-dimensional represen-tation
33、s 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 plots and additional measurements are made onthe earth material in the vicinity of the detected leak signal toaccurately determine the position of t
34、he 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 output level of theexcitation power supply, the sensitivity of the dete
35、ctor elec-tronics, the survey procedures, and data interpretation methodsand skill. Leaks as small as 5 mm in diameter can be locatedunder 600 mm of earth material. Leaks larger than 25 mm indiameter can usually be detected from several metres away.4.4.6 The survey rate depends primarily on the spac
36、ingbetween 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-equately replicate the leak signals and to detect smaller leaks.5. Significance and Use5.1 Geomembranes are used as
37、impermeable barriers toprevent liquids from leaking from landfills, ponds, and othercontainments. The liquids may contain contaminants that ifreleased can cause damage to the environment. Leaking liquidscan erode the subgrade, causing further damage. Leakage canresult in product loss or otherwise pr
38、event 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 be caused by poor quality ofthe subgrade, poor quality of the material placed on thegeomembrane, accidents, po
39、or 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 placed on thegeomembrane, accidental punctures, and punctures caused bytraffic over rocks or debris on the geo
40、membrane 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 material on thegeomembrane. Such damage also can breach additional layersof the lining system such as geosynthe
41、tic 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 Procedures6.1 The following measures shall be taken to optimize theleak location survey:6.1.1 Conductive paths such as m
42、etal pipe penetrations,pump grounds, and batten strips on concrete should 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 i
43、s cov-ered with earth materials that overlap the edges of thegeomembrane, if practical, measures should be taken to isolateFIG. 2 Diagram of the Electrical Leak Location Method for Surveys with Earth Material Covering the GeomembraneD7007033the edges. If earth materials overlap the edges of the surv
44、eyarea 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. Isolationcan be accomplished by either: performing the leak locationsurvey before the edges of the geomembrane are c
45、overed;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 shall be a conductive material below thegeomembrane being tested to conduct electrical currentthrough the leaks. The
46、 detection of a leak depends on theamount of electrical current flowing through it. The currentmust flow through the subgrade to complete an electricalcircuit. Therefore, the conductive material below the geomem-brane must have adequate conductivity. Most earth materialsand geosynthetic clay liners
47、will have sufficient conductivityfor surveys with water on the geomembrane. This is becausewater leaking through the leaks will increase the conductivityof the material under the geomembrane. For surveys with earthmaterial on the geomembrane, most earth materials will havesufficient conductivity. Un
48、der proper conditions and prepara-tions, geosynthetic clay liners (GCLs) are also adequate forsurveys with earth materials on the geomembrane. However,for surveys with earth material on the geomembrane, if theearth materials or GCL below the geomembrane is desiccated,the conductivity may be insuffic
49、ient to detect leaks.6.1.4 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 pressure less than the pressure exerted by the water and anyearth materials on the primary geomembrane. When the headpressure of the water under the geomembrane exceeds thedownward pressure exerted by the weight of the water and anyearth materials on the geomembran
