1、Designation: D6918 09 (Reapproved 2014)1Standard 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 y
2、ear 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.1NOTEEditorial changes were made throughout in March 2014.1. Scope1.1 This test method is a performance test that measures
3、theeffect crimping has on the ability of vertical strip drains totransmit water 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 thisstanda
4、rd.1.4 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. Reference
5、d Documents2.1 ASTM Standards:2D4354 Practice for Sampling of Geosynthetics and RolledErosion Control Products(RECPs) for TestingD4439 Terminology for Geosynthetics3. Terminology3.1 Definitions:3.1.1 For general geosynthetics terms used in this testmethod, refer to Terminology D4439.3.2 Definitions
6、of Terms Specific to This Standard:3.2.1 vertical strip drain, na geocomposite consisting of ageotextile cover 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 determining
7、the effect of a crimp forming in the vertical strip drain due theconsolidation of soils around it in the field.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
8、 in the appro-priate crimping device and water is allowed to pass through itunder a constant head of water.4.1.3 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 vertica
9、l strip drain is compared to the flow rate in thecrimped condition.5. Significance and Use5.1 This test method 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
10、method for acceptance testingof commercial shipments, the purchaser and the suppliershould conduct comparative 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 sho
11、uld take a group of test speci-mens that as homogenous as possible, and that are from a lot ofmaterial of the 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-tes
12、t for unpaired data and anacceptable probability level chosen by the two parties beforethe start of testing. 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 dra
13、ins are installed in areas where it isdesired to increase the rate of soil consolidation. It has beenshown that as the soil around the vertical strip drainconsolidates, a crimp may form in the vertical strip drain dueto the movement of the drain in the area of soil consolidation.5.3 This test method
14、 can be used to evaluate if there is anyreduction in flow rate of water through the drain due to thecrimping, 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 re
15、sponsibility of Subcommittee D35.03 on Perme-ability and Filtration.Current edition approved Jan. 1, 2014. Published March 2014. Originallyapproved in 2003. Last previous edition approved in 2009 as D691809. DOI:10.1520/D6918-09R14E01.2For referenced ASTM standards, visit the ASTM website, www.astm.
16、org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States16. Apparatus
17、6.1 Method A:6.1.1 The test device must be capable of maintaining aconstant head of water on the vertical 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 Co
18、ntainer, for collecting the water as it flows throughthe vertical strip drain.6.1.3 Stopwatch or Electronic Timing Device, a stopwatchwith an accuracy level to 0.1 s, connected to the collectioncontainer, for timing the flow of water through the vertical stripdrain.6.1.4 Blow Dryer, used for applyin
19、g heat to the heat shrink-wrap that is placed around the test specimen prior to testing.6.2 Method B:6.2.1 Discharge Capacity TesterThe discharge capacitytester may be pressured by earth pressure when the verticalstrip drains are mounted vertically within the ground to serveas discharging interstiti
20、al water. The apparatus in use for theprinciple illustrated in Fig. 3 is used for monitoring thevariation of the discharge capacity of the vertical strip drains inthe event of the earth pressure.6.2.1.1 The discharge capacity tester is mainly comprised ofa sample mounting portion, a pressure control
21、ler, water supply,and a flow-rate measurement portion.6.2.1.2 The sample mounting portion must maintain allvertically mounted vertical strip drains. The length of thevertical strip drain exposed to external pressure must be (300 610) mm.6.2.1.3 The mounted sample is covered by a cylinder, andair pre
22、ssure or hydraulic pressure must be applied to theinternal component of the cylinder in order to model thepressure arising from the earth mass.6.2.1.4 The pressure controller should be provided forcontrolling the pressure applied to the mounted sample.6.2.1.5 The water supply for adjusting height is
23、 required.6.2.1.6 The flow-rate measurement portion measures theamount of water passing through the mounted sample.6.2.1.7 Rubber Membranea cylinder-shaped rubbermembrane, of a thickness of 0.35 mm, and formed withsynthesized rubber latex.6.2.1.8 StopwatchSee Section 6.1.3.6.2.1.9 Thermometera therm
24、ometer with an accuracylevel to 0.2C.6.2.1.10 Flowmeteran instrument capable of measuringthe amount of water with an accuracy level of 10 cm3,oragauge revised 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 he
25、at 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 out 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 Batht
26、ub Caulkthe caulk is used to seal the testspecimen into the water chamber assembly as directed in12.1.2.7.2 Method B:7.2.1 Test Water:7.2.1.1 Water ranging from 18 to 22C is used for the testwater.NOTE 1The temperature correction, (referring to an accompanyingdocument A), is in relation only to stre
27、amline flow, and thus, where theflow of water is not the streamline flow, the water temperature should bemaintained close to a temperature of 20C in order to minimize anyFIG. 1 Crimping Wedge for Method AFIG. 2 Complete Crimp Test Apparatus for Method AD6918 09 (2014)12inaccuracies caused by the ina
28、ppropriate correction coefficient.7.2.1.2 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 bubble-removed state.7.2.1.3 Where the te
29、st 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 with the materials, orin performing th
30、is test.9. Sampling, Test Specimens, and Test Units9.1 Division into Lots and Lot SamplesDivide the materialinto lots and take a lot sample as directed in Practice D4354.Rolls of prefabricated vertical strip drains are the primarysampling unit.9.2 Laboratory SampleRemove the outer wrap of drainmater
31、ial from the roll to avoid sampling and testing anymaterial, which may have been damaged during storage. Takefor the laboratory sample a 1830 mm length of the drainmaterial.9.3 Test SpecimensFrom the laboratory sample taken fromeach lot, cut test specimens as directed in Section 10. Each testspecime
32、n shall be 610 mm 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 laboratory sample such that the user may expect the95 % probability level that the test result is no more t
33、han 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 laboratory as directed in the method,calculate the required number of specimens using Eq 1 asfollows:n 5 tv/A!2(1
34、)where:n = number of test specimens, rounded upward to a wholenumber,v = reliable estimate of coefficient of variation of individualobservations on similar materials in the users labora-tory under single operator precision, %.t = the value of Students t for I = one sided limits, at 95 %probability l
35、evel, and the degrees of freedom associatedwith 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 reliableestimate of v for the users laboratory, Eq 1 should not be useddirectly. Instead, specify the fixed number of t
36、hree 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 environment of the users laboratory is unableto be maintained at the standard atmosphere for testinggeosynthetics,
37、the specimens shall be conditioned for 24 h inthe environment in which they will be tested.12. Procedure12.1 Method A:FIG. 3 Test Device for Method BD6918 09 (2014)1312.1.1 Specimen PreparationWrap the full length of eachspecimen with heat shrink plastic. Using the blow dryer, applyheat until the wr
38、ap has shrunk tightly around the specimens.NOTE 2The heat shrink wrap seals the geotextile so that water will notescape through it, but rather flow parallel to the plane of the drain for thefull length of the specimen.12.1.2 Place the specimen through the slot in the bottomplate of the water chamber
39、 assembly. The specimen shouldprotrude up into the chamber 6.35 mm. Seal the specimen intothe slot with easily a removable sealant, such as bathtub caulk.12.1.2.1 Thread the specimen down through the upper andlower level specimen holders of the test stand, and fasten thebottom plate of the water cha
40、mber assembly to the stand.Complete the assembly of the water chamber assembly.Tighten the plates of the specimen holders snugly against thespecimen, being careful not to pinch the specimen too tightsuch that the flow of water will be effected.12.1.3 Fill the water chamber to the outlet of the chamb
41、er.Adjust the flow to maintain a constant head of 610 mm on thespecimen.NOTE 3The head is measured from the water chamber outlet pipe tothe point where the water exits the drain.12.1.4 Take and record five flow measurements (Q in mL)over a set time interval (t) in the uncrimped condition.Generally5s
42、isused as the time interval.12.1.5 Following the fifth reading in the uncrimpedcondition, shut off the water flow to the water chamber, andallow the chamber to empty.12.1.5.1 Once the water chamber is empty, loosen the lowerspecimen holder. Crimp the specimen by tuning the handle ofthe crimp device
43、until the specimen is crimped to the 90 angleof the crimper. See Fig. 1.NOTE 4Extreme care needs to be taken when crimping the specimensuch that it is not pinched.12.1.6 Repeat 12.1.3 12.1.5 for the crimped condition.12.1.7 Repeat 12.1.1 12.1.6 for the remaining specimens.12.2 Method B:NOTE 5The mea
44、surement of discharge capacity of the prefabricatedstrip drain is carried out under two conditions, 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 c
45、ondition, the measurement should beperformed while maintaining the bending state in a fixed 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 tes
46、t specimens are extracted from the sampleexposed to a temperature of 20 6 2Cfor2hbyasufficientlength required 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 wrinkl
47、es areformed.12.2.3 The sample equipped with the rubber membrane isdigested within the water of 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 pref
48、abricated strip drain ismounted on the sample mounting portion in a straight line orbending line shape so as to be in accordance with the testconditions. See Fig. 4.12.2.5 In principle, a pressure of 300 kPa should be appliedto the internal of a cylinder.NOTE 6Other pressure levels may be applied wi
49、th the agreement of allconcerned persons or parties. When pressurized, any sudden increase inpressure 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 mounted sample. In this regard, the procedure applyingthe pressure at each stage should progress in consideration of thefollowing aspects. After the
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