1、Designation: D7007 15Standard Practices forElectrical Methods for Locating Leaks in GeomembranesCovered with Water or Earthen Materials1This standard is issued under the fixed designation D7007; 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 cover standard procedures for usingelectrical methods to locate leaks in geome
3、mbranes coveredwith water or earthen materials. For clarity, this practice usesthe term “leak” to mean holes, punctures, tears, knife cuts,seam defects, cracks, and similar breaches in an installedgeomembrane (as defined in 3.2.5).1.2 These practices are intended to ensure that leak locationsurveys
4、are performed with demonstrated leak detection capa-bility. To allow further innovations, and because various leaklocation practitioners use a wide variety of procedures andequipment to perform these surveys, performance-based opera-tions are used that specify the minimum leak detection perfor-mance
5、 for the equipment and procedures.1.3 These practices require that the leak location equipment,procedures, and survey parameters used are demonstrated toresult in an established minimum leak detection distance. Thesurvey shall then be conducted using the demonstratedequipment, procedures, and survey
6、 parameters.1.4 Separate procedures are given for leak location surveysfor geomembranes covered with water and for geomembranescovered with earthen materials. Separate procedures are givenfor leak detection distance tests using actual and artificial leaks.1.5 Examples of methods of data analysis for
7、 soil-coveredsurveys are provided as guidance in Appendix X1.1.6 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 for geomembranes made of materialssuch
8、 as polyethylene, polypropylene, polyvinyl chloride, chlo-rosulfonated polyethylene, bituminous material, and otherelectrically-insulating materials.1.7 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.8 (WarningThe electrical
9、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 betweenthe water or earthen material an
10、d earth ground, or anygrounded conductor. These procedures are potentially VERYDANGEROUS, and can result in personal injury or death. Theelectrical methods used for geomembrane leak location shouldbe attempted only by qualified and experienced personnel.Appropriate safety measures must be taken to p
11、rotect the leaklocation operators as well as other people at the site.)1.9 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 th
12、e applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D4439 Terminology for GeosyntheticsD6747 Guide for Selection of Techniques for Electrical LeakLocation of Leaks in Geomembranes3. Terminology3.1 For general definitions related to geosynthetics, seeTer
13、minology D4439.3.2 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 earthen material above the geomem-brane.3.2.3 dipole measurement, nan electrical m
14、easurementmade on or in a partially conductive material using twoclosely-spaced electrodes.1These practices are under the jurisdiction of ASTM Committee D35 onGeosynthetics and is the direct responsibility of Subcommittee D35.10 on Geomem-branes.Current edition approved Jan. 1, 2015. Published Febru
15、ary 2015. Originallyapproved in 2003. Last previous edition approved in 2009 as D700709. DOI:10.1520/D7007-15.2For 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 st
16、andards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.4 earthen material, nsand, gravel, clay, silt, combina-tions of these materials, and similar materials with at leastminimal moisture
17、for electrical current conduction.3.2.5 leak, nfor the purposes of these practices, a leak isany unintended opening, perforation, breach, slit, tear,puncture, crack, or seam breach. Significant amounts of liquidsor solids may or may not flow through a leak. Scratches,gouges, dents, or other aberrati
18、ons that do not completelypenetrate the geomembrane are not considered to be leaks.Types of leaks detected during surveys include, but are notlimited to: burns, circular holes, linear cuts, seam defects, tears,punctures, and material defects.3.2.6 leak detection distance, nThe distance that a leaklo
19、cation equipment and survey methodology are capable ofdetecting a specified leak. The leak is usually specified as acircular leak with a specified diameter. For surveys withearthen materials on the geomembrane, the leak detectiondistance is usually measured from the surface projection of theleak.3.2
20、.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 material using onemeasurement electrode and a remote reference electrode.3.2.9 potential, nelectrical voltage
21、 measured relative to areference point.4. Significance and Use4.1 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. Leakingliquids can
22、erode the subgrade, causing further damage.Leakage can result in product loss or otherwise prevent theinstallation from performing its intended containment purpose.For these reasons, it is desirable that the geomembrane have aslittle leakage as practical.4.2 Geomembrane leaks can be caused by poor q
23、uality ofthe subgrade, poor quality of the material placed on thegeomembrane, accidents, poor workmanship, manufacturingdefects, and carelessness.4.3 The most significant causes of leaks in geomembranesthat are covered with only water are related to constructionactivities including pumps and equipme
24、nt placed on thegeomembrane, accidental punctures, and punctures caused bytraffic over rocks or debris on the geomembrane or in thesubgrade.4.4 The most significant cause of leaks in geomembranescovered with earthen materials is construction damage causedby machinery that occurs while placing the ea
25、rthen material onthe geomembrane. Such damage also can breach additionallayers of the lining system such as geosynthetic clay liners.4.5 Electrical leak location methods are an effective finalquality assurance measure to detect and locate leaks.5. Summary of the Electrical Leak Location Methods forC
26、overed Geomembranes5.1 The principle of the electrical leak location method is toplace a voltage across a geomembrane and then locate thepoints of anomalous potential distribution where electricalcurrent flows through leaks in the geomembrane. Additionalinformation can be found in Guide D6747.5.2 Ge
27、neral Principles:5.2.1 Figs. 1 and 2 show diagrams of the electrical leaklocation method for a geomembrane covered with water andfor a geomembrane covered with earthen materials respec-tively. One output of an electrical excitation power supply isconnected to a current source electrode placed in the
28、 materialcovering the geomembrane. The other output of the powersupply is connected to an electrode in contact with electricallyconductive material under the geomembrane.5.2.2 When there are leaks, electrical current flows throughthe leaks, which produces high current density and a localizedanomaly
29、in the voltage potential distribution in the materialabove the geomembrane. Electrical measurements are made tolocate those areas of anomalous signal at the leaks.5.2.3 Measurements are made using a dipole or pole mea-surement configuration. Various types of data acquisition areused, including audio
30、 indications of the signal level, manualmeasurements with manual recording of data, and automateddigital data acquisition.FIG. 1 Diagram of the Electrical Leak Location Method for Surveys with Water Covering the GeomembraneD7007 1525.2.4 Direct current and alternating current excitation powersupplie
31、s and potential measurement systems have been usedfor leak location surveys.5.3 Leak Location Surveys of Geomembranes Covered withWater:5.3.1 Leak location surveys for geomembranes coveredwith water can be conducted with water on the geomembraneor with water covering a layer of earthen materials on
32、thegeomembrane.5.3.2 For leak location surveys with water on thegeomembrane, usually a dipole probe is systematically scannedthrough the water covering the geomembrane to locate thepoints of anomalous potential distribution. The dipole spacingis typically 0.2 to 1 m.5.3.3 Various types of probes can
33、 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.5.3.4 The probe is typically connected to an electronicdetector assembly that con
34、verts the electrical signal from theprobe to an audible signal that increases in pitch and amplitudeas the leak signal increases.5.3.5 When a leak signal is detected, the point with themaximum signal is then determined. This point of maximumsignal corresponds to the location of the leak. The locatio
35、n ofthe leak is then marked or measured relative to fixed points.5.3.6 The leak detection distance depends on the leak size,the conductivity of the materials within, above, and below theleak, the electrical homogeneity of the material above the leak,the output level of the excitation power supply, t
36、he design ofthe measurement probe, the sensitivity of the detectorelectronics, the distance away from the leak, and the surveyprocedures. Leaks as small as 1 mm in diameter have beenroutinely found, including tortuous leaks through welds in thegeomembrane. Leaks larger than 25 mm in diameter canusua
37、lly be detected from several metres away.5.3.7 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.5.4 Leak Location Surveys of Geomembranes Covered withEarthen Materials:5.4.1 For leak location
38、 surveys with earthen materials cov-ering the geomembrane, point-by-point measurements aremade on the earthen material using either dipole measurementsor pole measurements. Dipole measurements are typicallymade with a spacing of 0.5 to 3 m. Measurements are typicallymade along parallel survey lines
39、or on a grid pattern.5.4.2 The survey procedures are conducted by systemati-cally taking measurements of voltage potential in a gridpattern. Leaks can be located during the performance of thevoltage measurements, but the voltage data must be collectedfor post-survey evaluation. The measurements and
40、positionscan be recorded manually or using a digital data acquisitionsystem. Appendix X1 details the two main methods of dataanalysis and the advantages and disadvantages of each.5.4.3 The data is typically downloaded or manually enteredinto a computer and plotted. Sometimes data is taken alongsurve
41、y lines and plotted in graphical format. Sometimes data istaken in a grid pattern and plotted in two-dimensional contour,shade of gray, or color contour plots, or in three-dimensionalrepresentations of the contours. The data plots are examined forcharacteristic leak signals.5.4.4 The approximate loc
42、ation of the leak signal is deter-mined from the data plots and additional measurements aremade on the earthen material in the vicinity of the detected leaksignal to more accurately determine the position of the leak.5.4.5 The leak detection distance depends on the leak size,the conductivity of the
43、materials within, above, and below theleak, the electrical homogeneity of the material above the leak,the design of the measurement electrodes, the output level ofthe excitation power supply, the sensitivity of the detectorelectronics, the distance away from the leak, the surveyprocedures, and data
44、interpretation methods and expertise.Usually leaks as small as 5 mm in diameter can be locatedunder 600 mm of earthen material. Leaks larger than 25 mm indiameter can usually be detected from several metres away.5.4.6 The survey rate depends primarily on the spacingbetween the measurement points, th
45、e 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.FIG. 2 Diagram of the Electrical Leak Location Method for Surveys with Earthen Material C
46、overing the GeomembraneD7007 1536. General Leak Location Survey Procedures6.1 The following measures shall be taken to optimize theleak location survey:6.1.1 Conductive paths such as metal pipe penetrations,pump grounds, and batten strips on concrete should be isolatedor insulated from the water or
47、earthen material on the geomem-brane whenever practical. These conductive paths conductelectricity and mask nearby leaks from detection, as well ascompromising the overall survey quality.6.1.2 In applications where a single geomembrane is cov-ered with earthen materials that overlap the edges of the
48、geomembrane, if practical, measures should be taken to isolatethe edges. If earthen materials overlap the edges of the surveyarea to earth ground, electrical current will flow from theearthen material to earth ground, causing a large signal that willmask small leak signals near the edges of the surv
49、ey area.Isolation can be accomplished by either: performing the leaklocation survey before the edges of the geomembrane arecovered; removing the earthen materials from a narrow patharound the perimeter of the geomembrane; or allowing theedge of the geomembrane to protrude above the earthenmaterials.6.1.3 There must 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
