1、Designation: D6747 04D6747 12Standard Guide forSelection of Techniques for Electrical Detection of PotentialLeak Paths Leaks in Geomembranes1This standard is issued under the fixed designation D6747; the number immediately following the designation indicates the year oforiginal adoption or, in the c
2、ase of 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 This standard guide is intended to assist individuals or groups in assessing different op
3、tions available for locating potentialleak paths leaks in installed geomembranes through the use of using electrical methods. For clarity, this document uses the termpotential leak path to mean holes, punctures, tears, knife cuts, seam defects, cracks and similar breaches over the partial or entirea
4、rea of through an installed geomembrane.1.2 This guide does not cover systems that are restricted to seam testing only, nor does it cover systems that may detect leaksnon-electrically. It does not cover systems that only detect the presence, but not the location of leaks.1.3 WarningThe electrical me
5、thods used for geomembrane leak location could use high voltages, resulting in the potentialfor electrical shock or electrocution. This hazard might be increased because operations might be conducted in or near water. Inparticular, a high voltage could exist between the water or earth material and e
6、arth ground, or any grounded conductor. Theseprocedures are potentially very dangerous, and can result in personal injury or death.The electrical methods used for geomembraneleak location should be attempted only by qualified and experienced personnel. Appropriate safety measures must be taken topro
7、tect the leak location operators as well as other people at the site.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the
8、applicability of regulatoryrequirements prior to use.2. Referenced Documents2.1 ASTM Standards:2D4439 Terminology for GeosyntheticsD7002 Practice for Leak Location on Exposed Geomembranes Using the Water Puddle SystemD7007 Practices for Electrical Methods for Locating Leaks in Geomembranes Covered w
9、ith Water or Earth MaterialsD7240 Practice for Leak Location using Geomembranes with an Insulating Layer in Intimate Contact with a Conductive Layervia Electrical Capacitance Technique (Conductive Geomembrane Spark Test)3. Terminology3.1 For general definitions used in this document, refer to D4439.
10、3.2 Definitions:Definitions of Terms Specific to This Standard:3.2.1 electrical leak location, nanya method which uses electrical current or electrical potential to detect and locate potentialleak paths.leaks.3.1.2 geomembrane, nan essentially impermeable membrane used with foundation, soil, rock, e
11、arth or any other geotechnicalengineering related material as an integral part of a manmade project, structure, or system.3.1.3 geosynthetic, na planar product manufactured from polymeric material used with soil, rock, earth, or other geotechnicalengineering related material as an integral part of a
12、 manmade project, structure, or system.1 This guide is under the jurisdiction of ASTM Committee D35 on Geosynthetics and is the direct responsibility of Subcommittee D35.10 on Geomembranes.Current edition approved Nov. 1, 2004Feb. 15, 2012. Published November 2004February 2012. Originally approved i
13、n 2002. Last previous edition approved in 2002 asD67470204.e1 DOI: 10.1520/D6747-04.10.1520/D6747-12.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Do
14、cument Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM
15、 recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.2 po
16、tential leak paths, leak, nfor the purposes of this document, a potential leak path is any unintended opening,perforation, breach, slit, tear, puncture, crack, or seam breach. Significant amounts of liquids or solids may or may not flow througha leak. Scratches, gouges, dents, or other aberrations t
17、hat do not completely penetrate the geomembrane are not considered. Leakpaths considered to be leaks. Leaks detected during surveys have been grouped into five categories: (1) Holesround shaped voidswith downward or upward protruding rims, (2) Tearslinear or areal voids with irregular edge borders,
18、(3) Linear cutslinearvoids with neat close edges, (4) Seam defectsarea of partial or total separation between sheets, and (5) Burned throughzonesareas where the polymer has been melted during the welding process.3.2.2.1 holesround shaped voids with downward or upward protruding rims.3.2.2.2 tearslin
19、ear or areal voids with irregular edge borders.3.2.2.3 linear cutslinear voids with neat close edges.3.2.2.4 seam defectsarea of partial or total separation between sheets.3.2.2.5 burned through zonesvoids created by melting polymer during welding.4. Significance and Use4.1 Types of potential leak p
20、aths have been Leaks are typically related to the quality of the sub-grade material, quality of thecover material, care in the cover material installation and quality of geomembrane installation.4.2 Experience demonstrates that geomembranes can have leaks caused during their installation and placeme
21、nt of material(s)on the liner.geomembrane.4.3 The damage to a geomembrane can be detected using electrical leak location systems. Such systems have been usedsuccessfully to locate leak paths leaks in electrically-insulating geomembranes such as polyethylene, polypropylene, polyvinylchloride, chloros
22、ulfonated polyethylene and bituminous geomembranes installed in basins, ponds, tanks, ore and waste pads, andlandfill cells.4.4 The principle behind these techniques is to place a voltage across a synthetic geomembrane liner and then locate areas whereelectrical current flows through discontinuities
23、 in the linergeomembrane (as shown schematically in Fig. 1). Insulation must besecured prior to a survey to Other electrical leak paths such as prevent pipe penetrations, flange bolts, steel drains, and batten stripson concrete to conduct electricity through the liner and mask potential leak paths.
24、The liner must act as an insulator across whichan electrical potential is applied. and other extraneous electrical paths should be electrically isolated or insulated to preventmasking of leak signals caused by electrical current flowing through those electrical paths. The only electrical paths shoul
25、d bethrough leaks in the geomembrane. This electric detection method of locating potential leak paths in a geomembrane leaks ingeomembranes can be performed on exposed liners,geomembranes, on linersgeomembranes covered with water,water or on linerscovered by a protective soilgeomembranes covered wit
26、h an earthen material layer, or both.5. Developed Systems5.1 Electrical leak detection systems were developed in the early 1980s and commercial surveys have been available since1985. A short description of each of these systems is presented in this section.FIG. 1 Schematic of the Electrical Leak Det
27、ection MethodLocation Method (Earthen material-Covered Geomembrane System is Shown)D6747 1225.2 The Water Puddle and Water Lance SystemThe technique is appropriate to survey a dry uncovered geomembrane duringits installation when placed directly on a subgrade that is an electrically conductive layer
28、 below the electrically insulatinggeomembrane. Practice D7002 is a standard practice describing the water puddle method. The lower conductive layermaterial isusually the sub-grade soil and the upper conductive layer being water. A cathode ground is established and an anodethe water ina puddle or a s
29、tream of water. One electrode of a low voltage power supply is placed in contact with the lower conductive materialand another electrode is placed in a water puddle maintained by a squeegee or toin the water stream of a lance (as shownschematically in Fig. 2). and Fig. 3, respectively). Water is usu
30、ally supplied by gravity from a tank truck parked at a higherelevation than the lined area. or other pressurized water source. For this technique to be effective, the leaking water effective inlocating leaks, the water in the puddle or stream must come into contact through the leak with the electric
31、al conducting mediumto which the ground electrode of the 12 or 24 volts dc supply can be connected. Since the geomembrane is not a perfect electricalinsulator, a steady background signal can be audible.As the water flows through a leak path, there is an increase in the signal. Leakpaths material bel
32、ow the geomembrane. This completes an electrical circuit and electrical current will flow. Detector electronicsare used to monitor the electrical current. The detector electronics usually convert a change in the current into a change in an audiotone. Leaks as small as 1 mm in size are then located b
33、y have been identified with this method; typically by listening to an audiosignal or by measuring a current of magnitude related to the size of the leak. It can also be used to search for leak paths ingeomembrane-lined concrete and steel tanks.current.5.2.1 FeaturesThe main advantage of this system
34、is the possibility to detect leak paths detection of leaks in geomembranejointsseams and sheets as while the geomembrane installation work progresses during the construction phase. Larger leak pathsdo not mask smaller ones because this technique locates leak paths independently on uncovered liner. c
35、onstruction. The systemdoes not require covering the geomembrane with water other than the small puddle of water or stream. Procedures can be usedto differentiate smaller leaks from larger leaks in their vicinity. The electrical survey rate of approximately 500 m2/h per operatordoes not affect the i
36、nstallation work schedule and permits a rapid construction quality control (CQC) of the installer geomembraneinstallers finished work. The approximate setup time varies from 1 to 3 h.5.2.2 LimitationsThis technique cannot be used with a protective layer when an earthen material layer is covering the
37、liner.geomembrane. The presence of wrinkles and waves, steep slopes and lack of contact between the linergeomembrane and theconductive soil at bottom of slopes material underneath inhibits the survey speed. from being performed at those locations unlessspecial measures are undertakingen. This techni
38、que cannot be used during stormyrainy weather or when the membrane is installedon an electrically non-conductive material, typically a desiccated subgrade, or whenever and in the near vicinity of conductivestructures that cannot be fully insulated or isolated. The procedure to detect potential leak
39、paths detection of leaks in seams ofrepair patches is difficult and lengthy time consuming since it requires a certain potential lengthy water infiltration time.5.3 The Water-Covered Geomembrane SystemThe principle behind this This system is to test the geomembrane while it iscovered with water, a t
40、echnique similar to the previous system requiring water , with an electrically conductive layer below(subgrade) and above the liner (water ormaterial below the geomembrane. Practice D7007 saturated drainage layer). A cathodeground is established and an anodecontains a standard practice for this syst
41、em. An electrical power supply is connected to oneFIG. 2 Schematic of Water Puddle and Lance SystemsD6747 123electrode which is put in the water and another electrode is placed in contained water. The voltage impressed across the liner (bya high voltage dc or ac power supply) contact with the electr
42、ically conductive material under the geomembrane. The voltageimpressed across the geomembrane produces a low current flow and a relative uniform voltage distribution in the material abovethe geomembrane. To maximize this current, a high voltage power supply with safety circuits is used that can prov
43、ide up to 400volts DC.Ahand-held probe is then traversed through the water.An electrical current flowsflowing through the potential leak pathscausing leaks causes localized abnormalties in the electrical paths potential at the location of the leak as shown schematically inFig. 34. The typical proced
44、ure is to flood the test area, then locate the potential leak paths, drain the area and perform repairs. Tomaximize the current flowing through the leaks, a high voltage power supply with safety circuits can be used. A hand-held probeor a probe on a long cable is scanned through the water to locate
45、these places where current is flowing through a leak. A typicalprocedure is to flood the test area to a depth of approximately 0.15 to 0.75 m. This technique can locate very small leaks, smallerthan 1 mm. The signal amplitude is proportional to the amount of electrical current flowing through the le
46、ak, so practical measuresshould be taken to maximize the current through the leaks. The signal amplitude is inversely related to the distance from the leak,so the scanning spatial frequency should be designed to provide the desired leak detection sensitivity.5.3.1 FeaturesThis system has the advanta
47、ge of being used to locate potential leak paths in in-service impoundments. Primaryand secondary liners can be tested. leaks in in-service impoundments (assuming the contained liquid is electrically conductive).Primary geomembranes can be tested when a conductive material is available underneath the
48、 geomembrane. Secondarygeomembranes can be tested before the primary geomembranes is installed. The water head on the liner facilitates the survey speedby minimizing the presence of wrinkles and waves, and lack of contact between the liner and the conductive soil at the bottomof slopes. This geomemb
49、rane ensures good electrical contact with the conductive material under the geomembrane through anyleaks, resulting in optimum leak detection sensitivity. While this technique can be used in wet conditions. The main advantage ofthis technique isperformed in rainy conditions, it is never recommended to do a survey during stormy conditions. The system canalso be used for the detection of leak paths with the protective granularleaks with an earthen material layer covering the liner (afterFIG. 3 Schematic of Water-Covered GeomembraneWater Lance SystemFIG. 4 Sch
