1、BRITISH STANDARD BS EN ISO 12957-1:2005 Geosynthetics Determination of friction characteristics Part 1: Direct shear test The European Standard EN ISO 12957-1:2005 has the status of a British Standard ICS 59.080.70 BS EN ISO 12957-1:2005 This British Standard was published under the authority of the
2、 Standards Policy and Strategy Committee on 8 March 2005 BSI 8 March 2005 ISBN 0 580 45585 8 National foreword This British Standard is the official English language version of EN ISO 12957-1:2005. It is identical with ISO 12957-1:2005. The UK participation in its preparation was entrusted to Techni
3、cal Committee B/553, Geosynthetics, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this document may be fo
4、und in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are res
5、ponsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep
6、 the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the EN ISO title page, pages 2 to 11 and a back cover. The BSI copyright notice displayed in this document
7、 indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsEUROPEANSTANDARD NORMEEUROPENNE EUROPISCHENORM ENISO129571 February2005 ICS59.080.70 Englishversion GeosyntheticsDeterminationoffrictioncharacteristicsPart1: Directsheartest(ISO129571:2005) Gosynt
8、htiquesDterminationdescaractristiquesde frottementPartie1:Essaidecisaillementdirect(ISO 129571:2005) GeokunststoffeBestimmungderReibungseigenschaften Teil1:Scherkastenversuch(ISO129571:2005) ThisEuropeanStandardwasapprovedbyCENon18November2004. CENmembersareboundtocomplywiththeCEN/CENELECInternalReg
9、ulationswhichstipulatetheconditionsforgivingthisEurope an Standardthestatusofanationalstandardwithoutanyalteration.Uptodatelistsandbibliographicalreferencesconcernings uchnational standardsmaybeobtainedonapplicationtotheCentralSecretariatortoanyCENmember. ThisEuropeanStandardexistsinthreeofficialver
10、sions(English,French,German).Aversioninanyotherlanguagemadebytra nslation undertheresponsibilityofaCENmemberintoitsownlanguageandnotifiedtotheCentralSecretariathasthesamestatusast heofficial versions. CENmembersarethenationalstandardsbodiesofAustria,Belgium,Cyprus,CzechRepublic,Denmark,Estonia,Finla
11、nd,France, Germany,Greece,Hungary,Iceland,Ireland,Italy,Latvia,Lithuania,Luxembourg,Malta,Netherlands,Norway,Poland,Portugal, Slovakia, Slovenia,Spain,Sweden,SwitzerlandandUnitedKingdom. EUROPEANCOMMITTEEFORSTANDARDIZATION COMITEUROPENDENORMALISATION EUROPISCHESKOMITEEFRNORMUNG ManagementCentre:rued
12、eStassart,36B1050Brussels 2005CEN Allrightsofexploitationinanyformandbyanymeansreserved worldwideforCENnationalMembers. Ref.No.ENISO129571:2005:EEN ISO 12957-1:2005 (E) 2 Contents page Foreword3 1 Scope.4 2 Normative references.4 3 Terms and definitions 4 4 Principle.5 5 Test specimens.5 6 Condition
13、ing.5 7 Apparatus6 8 Procedure8 9 Calculations9 10 Test report.10 EN ISO 12957-1:2005 (E) 3 Foreword This document (EN ISO 12957-1:2005) has been prepared by Technical Committee CEN/TC 189 “Geosynthetics“, the secretariat of which is held by IBN, in collaboration with Technical Committee ISO/TC 221
14、“Geosynthetics“. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by August 2005, and conflicting national standards shall be withdrawn at the latest by August 2005. According to the CEN/CENELEC Inter
15、nal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Nether
16、lands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EN ISO 12957-1:2005 (E) 4 1 Scope This document describes an index test method to determine the friction characteristics of geotextiles and geotextile-related products in contact with a standard sand,
17、 i.e. with a specified density and moisture content, under a normal stress and at a constant rate of displacement, using a direct shear apparatus. The procedure can also be used for testing geosynthetic barriers. When geogrids are tested with a rigid support, the results are dependent on the frictio
18、n with the support and the results are not necessarily realistic. The accuracy of the test should be verified by calibration tests. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies.
19、For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 554, Standard atmospheres for conditioning and/or testing - Specifications. ISO 6344-2, Coated abrasives Grain size analysis Part 2: Determination of grain size distribution of macrogrits P
20、12 to P 220. EN ISO 9862, Geotextiles Sampling and preparation of test specimens (ISO 9862:2005). 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 relative displacement (s) displacement of the sand relative to the specimen during shearing, in
21、millimetres 3.2 normal force (N) constant vertical force applied to the specimen, in kilonewtons 3.3 shear force (S) horizontal force, measured during shearing at a constant rate of displacement, in kilonewtons 3.4 normal stress ( ) normal force divided by the contact area of the specimen, in kilopa
22、scals 3.5 shear stress ( ) shear force along the sand/geotextile interface, divided by the contact area of the specimen, in kilopascals 3.6 maximum shear stress ( max ) maximum value of shear stress developed in a shear test, in kilopascals 3.7 angle of friction ( sg ) (between geosynthetic and sand
23、) slope of the “best fit straight line“, through the plot of maximum shear stress, in degrees EN ISO 12957-1:2005 (E) 5 3.8 apparent cohesion (c sg ) (between geosynthetic and sand) calculated value of the shear stress on the “best fit straight line“ corresponding to zero normal stress, in kilopasca
24、ls 3.9 maximum shear stress in sand ( s max ) maximum shear stress developed during a shear test on sand alone, in kilopascals 3.10 maximum shear stress sand/support ( sup max ) maximum shear stress developed during the shearing along the sand/support interface (without geosynthetic), in kilopascals
25、 3.11 friction ratio (f g ( ) ratio of the maximum shear stress max(friction test sand/geosynthetic) to the maximum shear stress s max(shear test on sand alone) for the same normal stress 4 Principle A geosynthetic is submitted to direct shear at its contact surface with standard sand in a shear box
26、 or similar apparatus. The angle of friction at the sand/geosynthetic interface is determined. 5 Test specimens 5.1 Sampling Take specimens in accordance with EN ISO 9862. 5.2 Number and dimensions of test specimens Cut four specimens from the test sample for each direction to be tested. The size of
27、 the specimens shall suit the dimensions of the apparatus. If the two faces of the sample are different, both faces shall be tested; four specimens shall be tested for each face. 6 Conditioning Condition the test specimens and conduct the tests in the standard atmosphere for testing, defined in ISO
28、554, i.e. at a temperature of (20 + 2) C and a relative humidity of (65 + 2) %, until the change in mass between successive readings made at intervals of not less than two hours does not exceed 0,25 % of the mass of the test specimens. NOTE Conditioning and/or testing at a specified relative humidit
29、y may be omitted if it can be proved that the results are not affected by this omission. EN ISO 12957-1:2005 (E) 6 7 Apparatus 7.1 Shearing apparatus 7.1.1 Constant contact area shear box (schematically represented in Figure 1) The shear box shall be divided into upper and lower sections. The appara
30、tus shall be sufficiently rigid to resist distortion under the loads applied. It shall be possible to lift the upper part of the shear box from the lower part. The upper part of the shear box shall have internal dimensions of not less than 300 mm 300 mm, the width of both boxes being not less than 5
31、0 % of their length. The box shall be sufficiently deep to accommodate the sand layer and the loading system. For the testing of geogrids the minimum dimensions of the shear box shall be such that at least two full longitudinal ribs and three transverse bars are contained within the length of both t
32、he upper and lower box throughout the test. The lower part of the shear box shall contain the support of the specimen and any clamping arrangements to prevent the specimen from slipping during the test. The lower part of the shear box shall be sufficiently long to maintain full contact between speci
33、men and sand over a relative shear displacement of at least 16,5 % of the internal length of the top box. 7.1.2 Reducing contact area shear box (schematically represented in Figure 2) Alternatively a standard soil shear box with equally sized (300 mm 300 mm minimum) upper and lower halves can be use
34、d. 7.2 Specimen support The specimen shall be placed on a rigid, horizontal support in the lower part of the shear box. The specimen shall be fixed to prevent, as far as possible, any relative displacement between the specimen and the support. The geosynthetic should be clamped at the front part out
35、side the shear area. Inside the friction area, it should be fixed by gluing or with a standard friction suppport, e.g. an aluminium oxide abrasive sheet (P 80 type in accordance with ISO 6344-2). When using a rigid plate as support for geogrids (or geotextiles) with a high percentage of openings, fr
36、iction tests between sand and the support shall be performed and the maximum shear stress ( sup max ) related to every normal stress shall be evaluated. NOTE For geogrids with large apertures ( 15 mm) and a high percentage of openings ( 50 % of the overall surface of the specimen), a sand support ma
37、y be used, i.e. by filling the lower box with standard sand at the specified density. 7.3 Rigid carriage The shear box shall be supported on the machine bed on low friction bearings, which allow movement in the longitudinal direction. 7.4 Loading device The loading device shall be capable of applyin
38、g a horizontal shear force to the shear box at a constant rate of displacement of (1 0,2) mm/min. EN ISO 12957-1:2005 (E) 7 7.5 Application of the normal force The normal force can be applied using any type of fluid filled soft membrane which ensures that the normal force is applied uniformly over t
39、he whole area of the specimen. The normal force shall be measured to a precision of 2 %. 7.6 Measurement of shear force and displacement The shear force shall be measured to a precision of 2 %. The relative displacement shall be measured to a precision of 0,02 mm. NOTE 1 The design of the apparatus
40、should allow for the dilatation of the sand, i.e. a gap, equal to the thickness of the specimen plus 0,5 mm, should be left between the upper and lower parts of the apparatus. NOTE 2 The upper box should be fitted with a rigid confinement system to prevent sand particles blocking the space between t
41、he upper part of the shear box and the geotextile or geogrid support. The sand in contact with the specimen shall be a natural siliceous sand, consisting preferably of rounded particles and with a silica content of at least 98 %. The moisture content, determined as the loss of mass after 2 h drying
42、at 105 C, shall be less than 0,2 %, expressed as a percentage by mass of the dried sample. The grading is defined in Table 1. Table 1 - Grading of standard sand Sieve size (in mm) Cumulative sieve residue (in %) 2,00 0 1,60 7 5 1,00 33 5 0,50 67 5 0,16 87 5 0,08 99 1 If loss of fine particles is obs
43、erved during a test, the grading of the sand shall be checked. The amount of sand entrapped shall be determined by re-weighing the specimen and reported. NOTE 3 A visual check may be adequate to verify whether the grading has changed. Water may be added to the sand to avoid particle segregation but
44、the moisture content should not exceed 2 %. The internal angle of friction of the sand shall be measured in a common direct shear box. The same equipment as used for the friction test may be used if it satisfies the requirements of the common direct shear box. EN ISO 12957-1:2005 (E) 8 8 Procedure T
45、he specimen shall be flat, free from folds and wrinkles. Fix the specimen to the support system. In the reducing contact area apparatus the top surface of the specimen shall be flush with the lower part of the shear box. Assemble the upper section of the box. Fill the upper part of the shear box wit
46、h the standard sand to a compacted thickness of 50 mm. The sand shall be compacted to a dry density of 1 750 kg/m. Fill the upper part of the box with a pre-weighed mass of sand, such that, when compacted, the material has the required density and occupies the required volume. Assemble the loading d
47、evices and displacement measuring devices (transducers or dial gauges). Apply the normal force to obtain one of the following pressures: 50 kPa, 100 kPa or 150 kPa. Measurements of the shear force shall be taken continuously or at intervals which correspond to displacements of 0,2 mm or 12 second ti
48、me intervals. The actual relative displacement shall be recorded at the same time, and the plate (used to apply the vertical load) lift and rotation should be measured at the end of the test. The test is terminated when the relative displacement reaches 50 mm for a shear surface length of 300 mm (or 16,5 % of the shear surface length in other cases). Dismantle the apparatus, carefully remove the sand, inspect the specimen and record any stretching, wrinkles or damage. Carry out the test t
