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1、 1 AS 1289.3.2.12009 Standards Australia Australian Standard Methods of testing soils for engineering purposes Method 3.2.1: Soil classification tests Determination of the plastic limit of a soil Standard method 1 SCOPE This Standard sets out a method for determining the plastic limit of a soil (the
2、 moisture content at which a soil passes from the semi-solid to the plastic state). 2 REFERENCED DOCUMENTS The following documents are referred to in this Standard: AS 1289 Methods of testing soils for engineering purposes 1289.1.1 Method 1.1: Sampling and preparation of soilsPreparation of disturbe
3、d soil samples for testing 1289.2.1.1 Method 2.1.1: Soil moisture content testsDetermination of the moisture content of a soilOven drying method (standard method) 3 APPARATUS The following apparatus shall be used: (a)A thick, flat, rigid mixing plate of suitable size, made of non-absorbent material.
4、 (b)A mixing bowl of convenient size with a suitable close-fitting lid. (c)Palette knives of convenient size. (d)Frosted glass plate of suitable size on which to roll the threads. (e)A rod 3 mm in diameter and about 100 mm long. (f)Small containers with close-fitting lids. (g)A wash bottle or beaker
5、 containing potable water. NOTE: Some types of clay may be affected by poor or marginally potable water. In such cases, and when testing for reference purposes, distilled, demineralized or deionized water should be used. 4 PROCEDURE The procedure shall be as follows: (a)Obtain a sample of about 40 g
6、 of soil from the material passing the 425 m sieve which has been prepared in accordance with the procedure prescribed in AS 1289.1.1. Alternatively, when practically all soil passes a 425 m sieve the material may be used in the natural state without further preparation. AS 1289.3.2.12009 AS 1289.3.
7、2.12009 2 Standards Australia www.standards.org.au If the plasticity index is to be calculated using the results from this test, the same method of preparation shall be used for both liquid limit and plastic limit tests. NOTE: If stones are present, only the material passing the 425 m sieve should b
8、e used for the test. This can be achieved by rubbing the wet soil through the sieve until a sufficient quantity is obtained. The sieve used for this process should not be one of a set used for a particle size analysis, as the rubbing of wet soil through a sieve results in rapid wear of the sieve. Th
9、is wear, however, will not have any appreciable effect on the plastic limit obtained for the sample under test. Then proceed as follows: (i)Record the method of preparation. (ii)Thoroughly mix the soil with the water on the glass mixing plate or in the bowl, and knead until it becomes homogeneous an
10、d plastic enough to be shaped into a ball. (iii)Cover the soil and allow to cure for at least 12 h at room temperature. NOTE: Prior to testing, some clayey soils may require to stand for 24 h to allow thorough permeation of the water through the soil. (b)Take a ball of soil of about 8 g and mould it
11、 between the fingers. Then roll the ball between the palms of the hands until slight cracks appear on its surface. (This is to ensure that the soil has dried sufficiently.) Roll the ball between the hands and the glass plate, or between two glass plates, using sufficient pressure to form the soil in
12、to a thread of about 3 mm diameter. (c)If the soil thread crumbles before the diameter reaches 3 mm, add more potable water to the whole soil mass, re-mix on the glass plate, and knead thoroughly. (d)If the soil thread rolls down to 3 mm diameter without crumbling, gather up the soil, knead it toget
13、her again, and re-roll a thread. The rod shall be used for comparison as a guide to the correct thread diameter. (e)Repeat Step (d) until the thread crumbles when it becomes 3 mm in diameter. Gather the portions of the crumbled thread into the container and cover the container. When threads of at le
14、ast 3 mm in diameter cannot be rolled owing to the lack of cohesion of the soil (a true crumbling point), the plastic limit cannot be determined and shall be reported as such. NOTE: Determination of crumbling point is as follows: With some soils the threads become extremely tough and it is difficult
15、 to determine the end point, since it is not possible to fully knead together the portions of the previously rolled thread, and the thread tends to split back into the unkneaded portions. Whether a true thread crumbling has taken place can be tested by trying to roll the crumbs. If they immediately
16、break up, the plastic limit has been reached; but if they continue to roll down, then a true crumbling point has not been reached. (f)Roll further threads until between 5 g and 20 g of crumbled threads are produced and place them into the container. NOTE: The quantity of 5 g to 20 g, which is taken
17、as the moisture content sample, is less than that recommended in AS 1289.2.1.1; however, because of the homogeneity of the soil which constitutes the sample, it is considered to be a satisfactory quantity. (g)Determine the moisture content of the soil in the container in accordance with AS 1289.2.1.
18、1. (h)Make two completely separate determinations as described in Steps (b) to (f) above. If the results from the two determinations differ by more than 2% moisture content, repeat the test. 3 AS 1289.3.2.12009 www.standards.org.au Standards Australia 5 CALCULATION Determine the average of the moist
19、ure contents obtained in Clause 4 as the plastic limit (wP) of the soil. 6 TEST REPORT The following shall be reported: (a)The plastic limit (wP) of the soil, in percent, to the nearest whole number. (b)The history of the sample, i.e., natural state, air-dried, oven-dried or unknown. (c)The method o
20、f preparation, i.e., wet-sieved or dry-sieved. (d)Reference to this test method, i.e., AS 1289.3.2.1. AS 1289.3.2.12009 4 This Australian Standard was prepared by Committee CE-009, Testing of Soils for Engineering Purposes. It was approved on behalf of the Council of Standards Australia on 9 Decembe
21、r 2008 and published on 6 February 2009. The following are represented on Committee CE-009: AUSTROADS Association of Geotechnical Testing Authorities (Qld) Australian Building Codes Board Australian Chamber of Commerce and Industry Australian Geomechanics Society Australian Stabilisation Industry As
22、sociation Cement Concrete and Aggregates Australia Engineering and Construction Laboratories Association Engineers Australia National Association of Testing Authorities Australia University of Melbourne University of Sydney Victorian Construction Materials Laboratories Association Keeping Standards
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26、 476, Sydney, NSW 2001. Originated as AS A891966. Revised and redesignated as AS 1289.C2.11977. Revised and redesignated as AS 1289.3.2.11995. Second edition 2009. This Standard was issued in draft form for comment as DR 06692. COPYRIGHT Standards Australia All rights are reserved. No part of this w
27、ork may be reproduced or copied in any form or by any means, electronic or mechanical, including photocopying, without the written permission of the publisher. Published by Standards Australia Limited GPO Box 476, Sydney, NSW 2001, Australia ISBN 0 7337 9005 4 Printed in Australia This page has been left intentionally blank.