1、Designation: D6918 09Standard Test Method forTesting Vertical Strip Drains in the Crimped Condition1This standard is issued under the fixed designation D6918; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisio
2、n. 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 test method is a performance test that measures theeffect crimping has on the ability of vertical strip drains totransmit wat
3、er parallel to the plane of the drain.1.2 This test method is applicable to all vertical strip drains.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard does not purport to address all of thesafety concerns, i
4、f 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. Referenced Documents2.1 ASTM Standards:2D4354 Practice for Sampling of Geosynthetics f
5、or TestingD4439 Terminology for Geosynthetics3. Terminology3.1 Definitions:3.1.1 For general geosynthetics terms used in this standard,refer to Terminology D4439.3.2 Definitions: Definitions of Terms Specific to This Stan-dard:3.2.1 vertical strip drain, na geocomposite consisting of ageotextile cov
6、er and drainage core installed vertically into soilto provide drainage for accelerated consolidation of soils.4. Summary of Test Method4.1 This test method presents two methods for determiningthe effect of a crimp forming in the vertical strip drain due theconsolidation of soils around it in the fie
7、ld.4.1.1 A vertical strip drain is sealed in a waterproof mem-brane to prevent any water from escaping out through thegeotextile during the test.4.1.2 The sealed vertical strip drain is placed in the appro-priate crimping device and water is allowed to pass through itunder a constant head of water.4
8、.1.3 A crimp is placed on the specimen, and water allowedto pass through it under a constant head in the crimpedcondition.4.1.4 The flow rate of water along the plane of the un-crimped vertical strip drain is compared to the flow rate in thecrimped condition.5. Significance and Use5.1 This test meth
9、od is considered satisfactory for theacceptance of commercial shipments of vertical strip drains.5.1.1 In case of dispute arising from differences in reportedtest results when using this test method for acceptance testingof commercial shipments, the purchaser and the suppliershould conduct comparati
10、ve tests to determine if there is anystatistical bias between their laboratories. Competent statisticalassistance is recommended for the investigation of bias. As aminimum, the two parties should take a group of test speci-mens that as homogenous as possible, and that are from a lot ofmaterial of th
11、e type in question. The test specimens should berandomly assigned in numbers to each laboratory for testing.The average results from the two laboratories should becompared using Students t-test for unpaired data and anacceptable probability level chosen by the two parties beforethe start of testing.
12、 If a bias is found, either its cause must befound and corrected, or the purchaser and the supplier mustagree to interpret future test results in light of the known bias.5.2 Vertical strip drains are installed in areas where it isdesired to increase the rate of soil consolidation. It has beenshown t
13、hat as the soil around the vertical strip drain consoli-dates, a crimp may form in the vertical strip drain due to themovement of the drain in the area of soil consolidation.5.3 This test method can be used to evaluate if there is anyreduction in flow rate of water through the drain due to thecrimpi
14、ng, and what effect, if any, this crimping may have onthe rate of consolidation of the soil.1This test method is under the jurisdiction of ASTM Committee D35 onGeosynthetics and is the direct responsibility of Subcommittee D35.03 on Perme-ability and Filtration.Current edition approved Nov. 1, 2009.
15、 Published January 2010. Originallyapproved in 2003. Last previous edition approved in 2007 as D691803(2007).DOI: 10.1520/D6918-09.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume informa
16、tion, 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.6. Apparatus6.1 Method A:6.1.1 The test device must be capable of maintaining aconstant head of water on the vertic
17、al strip drain being tested.The apparatus consists of a water chamber assembly, a speci-men holder, and a crimping wedge, all of which are attached toa holding stand. See Fig. 1 and Fig. 2.6.1.2 Container, for collecting the water as it flows throughthe vertical strip drain.6.1.3 Stopwatch or Electr
18、onic Timing Device, connected tothe collection container, for timing the flow of water throughthe vertical strip drain.6.1.4 Blow Dryer, used for applying heat to the heatshrink-wrap that is placed around the test specimen prior totesting.6.2 Method B:6.2.1 Discharge Capacity TesterThe discharge cap
19、acitytester may be pressured by earth pressure when the verticalstrip drains are mounted vertically within the ground to serveas discharging interstitial water. The apparatus in use for theprinciple illustrated in the following Fig. 3 is used for moni-toring the variation of the discharge capacity o
20、f the verticalstrip drains in the event of the earth pressure.6.2.2 The discharge capacity tester is mainly comprised of asample mounting portion, a pressure controller, water supply,and a flow-rate measurement portion.6.2.3 The sample mounting portion must maintain all ver-tically mounted vertical
21、strip drains. The length of the verticalstrip drain exposed to external pressure must be (300 6 10)mm.6.2.4 The mounted sample is covered by a cylinder, and airpressure or hydraulic pressure must be applied to the internalcomponent of the cylinder in order to model the pressurearising from the earth
22、 mass.6.2.5 The pressure controller should be provided for con-trolling the pressure applied to the mounted sample.6.2.6 The water supply for adjusting height is required.6.2.7 The flow-rate measurement portion measures theamount of water passing through the mounted sample.6.2.8 Rubber Membranea cyl
23、inder-shaped rubber mem-brane, of a thickness of 0.35mm, and formed with synthesizedrubber latex6.2.9 StopwatchSee Section 6.3.6.2.10 Thermometera thermometer with an accuracylevel to 0.26.2.11 Flowmeteran instrument capable of measuring theamount of water with an accuracy level of 10, or a gaugerev
24、ised with an accuracy of 5% for enabling the directmeasurement of the flow velocity.7. Materials7.1 Method A:7.1.1 Heat Shrink Plastic WrapThe heat shrink plasticwrap, of the type used in homes for sealing windows fromwind drafts, is used to seal the vertical strip drain so that waterdoes not flow o
25、ut through the geotextile wrap on the core. Thewater is to flow in a parallel plan to the fabric, along the corematerial of the drain.7.1.2 Bathtub Caulkthe caulk is used to seal the testspecimen into the water chamber assembly as directed in12.1.1.7.2 Method B:7.2.1 Test Water7.2.2 Water ranging fr
26、om 18 to 22 is used for the test water.NOTE 1 The temperature correction, (referring to an accompanyingdocument A), is in relation only to streamline flow, and thus, where theflow of water is not the streamline flow, the water temperature should bemaintained close to a temperature of 20 in order to
27、minimize anyinaccuracies caused by the inappropriate correction coefficient.7.2.3 If the test water is directly provided from the watersupply, air bubbles may be generated in the internal construc-tion of the test specimens. Therefore, the test water should beprovided from a distillation tank in a b
28、ubble-removed state.7.2.4 Where the test water includes solids or substancesapparent to the naked eye, or where the passage amount of thewater is gradually reduced due to a stacked solid or substanceson the test specimens, the water should be filtered.8. Hazards8.1 There are no known hazards either
29、with the materials, orin performing this test.9. Sampling, Test Specimens, and Test Units9.1 Division into Lots and Lot SamplesDivide the mate-rial into lots and take a lot sample as directed in PracticeD4354. Rolls of prefabricated vertical strip drains are theprimary sampling unit.FIG. 1 Complete
30、Crimp Test Apparatus for Method AD6918 0929.2 Laboratory SampleRemove the outer wrap of drainmaterial from the roll to avoid sampling and testing anymaterial, which may have been damaged during storage. Takefor the laboratory sample a 1830 mm (6 ft) length of the drainmaterial.9.3 Test SpecimensFrom
31、 the laboratory sample takenfrom each lot, cut test specimens as directed in 10. Each testspecimen shall be 610 mm (2 ft) long.10. Number of Specimens (Methods A and B)10.1 Unless otherwise agreed upon, as when provided in anapplicable material specification, take a number of test speci-mens per lab
32、oratory sample such that the user may expect the95 % probability level that the test result is no more than 5 %above the average for each laboratory sample.10.1.1 Reliable Estimate of vWhen there is a reliableestimate of v based upon extensive test records for similarmaterials in the users laborator
33、y as directed in the method,calculate the required number of specimens using Eq 1 asfollows:n 5 tv / A!2(1)where:n = number of test specimens, rounded upward to a wholenumber,v = reliable estimate of coefficient of variation of indi-vidual observations on similar materials in the userslaboratory und
34、er single operator precision, %.t = the value of Students t for I = one sided limits, at 95 %probability level, and the degrees of freedom associ-ated with the estimate of v, andA = 5.0 % of the average, the value of the allowablevariation.10.1.2 No Reliable Estimate of vWhen there is no reliableest
35、imate of v for the users laboratory, Eq 1 should not be useddirectly. Instead, specify the fixed number of three specimensfor testing.11. Conditioning11.1 Prior to testing, the specimens shall be conditioned atthe standard atmosphere for testing geosynthetics for 24 h priorto testing. If the environ
36、ment of the users laboratory is unableto be maintained at the standard atmosphere for testinggeosynthetics, the specimens shall be conditioned for 24 h inthe environment in which they will be tested.12. Procedure12.1 Method A:FIG. 2 Test Device for Method BFIG. 3 Crimping Wedge for Method AD6918 093
37、12.1.1 Specimen PreparationWrap the full length of eachspecimen with heat shrink plastic. Using the blow dryer, applyheat until the wrap has shrunk tightly around the specimens.NOTE 2The heat shrink wrap seals the geotextile so that water willnot escape through it, but rather flow parallel to the pl
38、ane of the drain forthe full length of the specimen.12.1.1.1 Thread the specimen down through the upper andlower level specimen holders of the test stand, and fasten thebottom plate of the water chamber assembly to the stand.Complete the assembly of the water chamber assembly.Tighten the plates of t
39、he specimen holders snuggly against thespecimen, being careful not to pinch the specimen to tight suchthat the flow of water will be effected.12.1.2 Fill the water chamber to the outlet of the chamber.Adjust the flow to maintain a constant head of 610 mm (24 in.)on the specimen.NOTE 3The head is mea
40、sured from the water chamber outlet pipe tothe point where the water exits the drain.12.1.3 Take and record five flow measurements (Q in mL)over a set time interval (t) in the uncrimped condition.Generally5sisused as the time interval.12.1.4 Following the fifth reading in the uncrimped condi-tion, s
41、hut off the water flow to the water chamber, and allow thechamber to empty.12.1.4.1 Once the water chamber is empty, loosen the lowerspecimen holder. Crimp the specimen by tuning the handle ofthe crimp device until the specimen is crimped to the 90 angleof the crimper. See Fig. 3NOTE 4Extreme care n
42、eeds to be taken when crimping the specimensuch that it is not pinched.12.1.5 Repeat 12.1.2-12.1.4 for the crimped condition.12.1.6 Repeat 12.1-12.1.4.1 for the remaining specimens.12.2 Method B:NOTE 5The measurement of discharge capacity of the prefabricatedstrip drain is carried out under two cond
43、itions, namely, straight line andbending line. Firstly, the measurement of the discharge capacity in thestraight line condition should be performed after the sample is verticallymounted. In the bending line condition, the measurement should beperformed while maintaining the bending state in a fixed
44、format, using thebending state maintaining device while preparing the supplemental lengthin addition to the length required in the straight line condition, dependingon the current bending state.12.2.1 The test specimens are extracted from the sampleexposed to a temperature of 2062for2hbyasufficient
45、lengthrequired for the mounting operation.12.2.2 The sample is wrapped with rubber membrane of athickness of less than 0.35 mm. Herein, the rubber membranemust be smoothly mounted so as to ensure no wrinkles areformed.12.2.3 The sample equipped with the rubber membrane isdigested within the water of
46、 a room temperature, including thehumectants,and is moistened for at least 12 h while slowlybeing stirred to remove any bubbles. The humectants include astrength of 0.1%V/V.12.2.4 The sample of the prefabricated strip drain ismounted on the sample mounting portion in a straight line orbending line s
47、hape so as to be in accordance with the testconditions. See Fig. 412.2.5 In principle, a pressure of 300 kPa should be appliedto the internal of a cylinder.NOTE 6Other pressure levels may be applied with the agreement ofall concerned persons or parties. When pressurized, any sudden increase inpressu
48、re may cause damage to the surface of the rubber membrane.Therefore, pressure should preferably be increased by 50 kPa. In otherwords, a pressure of 50 kPa is firstly applied first thereto, with the pressureof the next step then applied after the water provided by the water supplypasses through the
49、mounted sample. In this regard, the procedure applyingthe pressure at each stage should progress in consideration of thefollowing aspects. After the application of pressure at the first stage, theapplied state should be fixated for more than one minute, and then thepressure of the next stage is applied thereto, meaning that the pressure canbe increased to the finally-settled pressure in sequential order. Herein, itshould be noted that the maximum time required in reaching the presetpressure should not exceed 30 min.12.2.6 If the supplied water is provide
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