NRC Publications Archive Archives des publications du CNRC

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1 NRC Publications rchive rchives des publications du CNRC Triaxial tests on Leda clay Crawford, C.. For the publisher s version, please access the DOI link below./ Pour consulter la version de l éditeur, utilisez le lien DOI cidessous. Publisher s version / Version de l'éditeur: Internal Report (National Research Council Canada. Division of uilding Research), NRC Publications Record / Notice d'rchives des publications de CNRC: ccess and use of this website and the material on it are subject to the Terms and Conditions set forth at RED THESE TERMS ND CONDITIONS CREFULLY EFORE USING THIS WESITE. L accès à ce site Web et l utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS TTENTIVEMENT VNT D UTILISER CE SITE WE. Questions? Contact the NRC Publications rchive team at PublicationsrchiverchivesPublications@nrccnrc.gc.ca. If you wish to the authors directly, please see the first page of the publication for their contact information. Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n arrivez pas à les repérer, communiquez avec nous à PublicationsrchiverchivesPublications@nrccnrc.gc.ca.

2 NTIONL RESERCH COUNCIL CND DIVISION OF UILDING RESERCH TRIXIL TESTS ON LED CLY by C.. Crawford Internal Report No. 269 of the Division of uilding Research OTTW pril 1963

3 PREFCE It has not been possible in papers published by the Division on its shear research on Leda alay to include a complete record of all tests. Several workers who wanted to make a detailed study of the tests have asked for more complete information. This report provides supplementary information on the more important tests and should therefore be used together with the quoted references. 'Phe author, a civil engineer, is Read of the Soil Mechanics Section, D R/NRC. Ottawa pril 1963 R. F. Legget Direct or

4 TRIXIL TESTS ON LED CLY C.. Crawford General engineering properties of Leda clay have been recorded (1) but this record is far from complete. Detailed studies of shear strength have been confined to samples from the Ottawa area. Earlier tests on tube samples indicated the need for fundamental studies on good undisturbed block samples. t every opportunity, therefore, block samples have been obtained from deep excavations. To date it has been possible to carry out comprehensive tests on specimens cut from relatively uniform layers of undisturbed block samples obtained from three locations. The average properties o? the soil in these blocks are given in Table I. ll specimens were saturated and undisturbed. TESTS ND TEST RESULTS The first series of consolidated undrained (CU) tests, designed to investigate the influence of rate of strain on test results, has been published (2). Detailed supplementary information on each test is given in Table I1 of this present report. Consolidated drained (CD) tests with increasing axial stress resulted in such distortion of the soil that the tests were judged to be unsatisfactory. Detailed information for each consolidated drained test specimen is,given in Table I11 and the stressstrain curves are shown in Figure 10 of Reference (2). The second series of consolidated undrained tes' designed to investigate the infl.uence of axia 1 strain on test results and interpretation, ha s been pub lished (3). Further detailed infor.&ation on each test is given in Tables IV and V. The consolidated drained tests on this soil have not been published and are reported in Table VI and Figures 1 to 8. These consolidated drained tests were considered to confirm the earlier interpretation that the ordinary consolidated drained test with axial loading is an unsatisfactory test method. Figures 1 to 4 show the normal trend of continuing increase in deviator stress at strains in excess of 20 per cent. This may prove to be a test of the

remoulded soil but cannot be considered to represent the performance of the undisturbed soil. Figures 5 and 6 illustrate similar performance of specimens from an adjacent block.

5 remoulded soil but cannot be considered to represent the performance of the undisturbed soil. Figures 5 and 6 illustrate similar performance of specimens from an adjacent block. Consolidated drained tests with axial stress decreasing may be better suited to this material; Figures 7 and 8 show results of such tests. Each specimen was first consolidated and then the lateral stress was decreased in stages while the axial stress remained constant. In these cases, it was possible to apply about 3/4 of the ultimate shear stress under fully drained conditions while axially straining the specimen by only 1 per cent. Further increases in the shearing stress would cause much reater axial strain until the last increment causes failure probably under only partially drained conditions). 7 The volume changes noted on Figures 7, and 8 are probably unreliable. Due to the long duration of the test the independently estimated magnitude of membrane leakage is of the same order as the measured volume change. ssessment of membrane leakage is difficult but in the average stress v range these tests it may amount to about 0.1 cm3 2 or 1.5 cm' during the period of shear. Membrane leakage may in fact account for most of the measured volume change during the long shearing period of tests 9633 and Since volume change during the consolidation stage is computed by subtracting volume change during the period of shear from total volume change this may account for the lower than average avc recorded for these two tests. third series of tests, designed to investigate shear at low effective stress levels, has been completed and is in process of publication (4). This series, primarily on block sample 9421, includes unconfined compression, consolidated undrained tests, and consolidated drained tests at constant volume, This report was intended to supplement published information by giving detailed test results. It includes the results of a number of consolidated drained tests which have not been published, These tests round out the test series but are not considered to be sufficient for a general assessment of shear strength of Leda clay.

6 REFERENCES 1. Crawford, C.. Engineering studies of Leda clay. Soils in Canada, Roy. Soc. Can., Special Publications No. 3, 1961, p Crawford, C.. The influence of rate of strain on effective stresses in sensitive clay. Papers on Soils 1959 Meetings, STM STP No. 254, m. Soc. Testing Mats., 1960, p NRC Crawford, C.. The influence of strain on shearing resistance of sensitive clay. Proceedings, S!TM, Vol. 61, 1961, p XRC Crawford, C.. Cohesion in an undisturbed sensitive clay. To be published in Gotechnique, June 1963.

7 TLE I PROPERTIES OF SOILS TESTED Sample Depth, ft Elevation, ft Preconsolidation press, kg/cm water content, $ Liquid limit,.% Plastic limit, $ Liquidity index Clay content, % Specific gravity ctivity Salt content, grams/litre

8 TLE I1 COI?SOLIDTED UNDRINED TESTS ON SMPLE (see also Reference (2)) Strain, $ Specimen No I e G j i = deviator stress, kg/sq cm = pore pressure, kg/sq cm

9 TLE I11 CONSOLIDTED DRINED TESTS ON SMvlPLE 8328 (see also Reference (2)) Specimen No. Water Content, % Initial Final 1 bc, kg/cm2 Tc, min dvc, % VT, $.I Rate of strain, %/b bcl = Effective consolidation stress Tc = Time of consolidation avc = Volume change during consolidation stage V ~ = Total volume change during test

10 TLE IV CONSOLIDTED UNDRINED TESTS OW SMPLE 964 (see also Reference (3)) Sp;cinen IT ~~0.4~~~ ;':0.32% :' z0.57: Strain, % , s a 165) * *14 I o Deviator stress constant (see Figure 2 of Reference 3) = Deviator stress, kg/cm 2 = Pore pressure, kg/cm 2

11 0 L PI 4 cd 0 d M d + h CI) M H m W a, "3: W 4 a I4Hfii P9 m 2 2 F1 W O [I) d E 0 M 0 CV dcvm dcvd mawcucuotro r l l n c n C O C V \ L ) c n m In * & & k? a3*cumwcut NtdtCVawCn F: & < & < I+ 'a k P9 4 m t 0 Ln \O In \O to CV M t ~n a cn t d I 0 CV + Warn t cv t tdd t CV CV dcvm Wo8dWMMCVW 4= m C V W C V O M W M CI) o d & &. dcvm amrl M ~ O tem mt d o 0 Ln. 0 Ln CV 0 \oo F: a, 8 r i 0 O k % + F7 * o a r n e d m ~ n t ddocvdwcvm & < & < CVmCVdcnWod WtcncuWa0t d 0 0 d d I n t I n W M t mcvttm+a3a d & G d MMInMCVOOtroddmdnmtd d d d d d d d COa3Int*LnMa \DCUdtWOCVm d d G S CVMd\OCVMdW t a3 rl rl I d d I 1 Sn, x I d

12 TLE VI CONSOLIDTED DRINED TESTS ON SMPLES 963 ND 964 Specimen No. Water Content, $ Initial Final 1 6,, kg/cm2 Tc, min bvc, % vt9 % I Rate of strain, %fir / c1 = Effective consolidation stress Tc = Time of consolidation dvc = Volume change during consolidation stage avt = Total volume change during test

13 I I I I 1 1 SPECIMEN V /' / / / I STRIN, O/o FIGURE I STRESS STRIN RELTION ( DRINED TEST )

14 1 I I I I I SPECIMEN V To; STRIN, % I I L FIGURE 2 STRESS STRIN RELTION (DRINED TEST) R 28892

15 I I 1 I I q q SPECIMEN > V STRIN, O/o I FIGURE 3 STRESS STRIN RELTION (DRINED TEST)

16 I I I I 1 I SPECIMEN q 3 V STRIN, O/o 1 FIGURE 4 STRESS STRIN RELTION [DRINED TEST)

17 1 I I I I I SPECIMEN 9631 o;0; V STRIN, O/o 1 FIGURE 5 STRESS STRIN RELTION ( DRINED TEST )

18 / I I I I 1 SPECIMEN STRIN, O/o I FIGURE 6 STRESS STRIN RELTION (DRINED TEST ) R 24894

19 I I I I TIME INTERVL w > <> n Cc 1 a 0 V) > 4 0 to > a 0 4 HOURS 4 b 1 c c3. I b / V / cr; I 1 %I= KGICM* / / SPECIMEN I I I I I0 15 STRIN, OIo FIGURE 7 STRESS STRIN RELTION (DRINED TEST WITH DECRESING 6,)

20 I I I I TIME INTERVL V) > a Q In I DY 4 b qq I I ~y 4 / / /' / / / I0 15 STRIN, O/o 0; / / / I 6: = KG/CM~ / SPECIMEN 9634 / / 1 I FIGURE 8 STRESS STRIN RELTION (DRINED TEST WITH DECRESING 6,)

1.8 Unconfined Compression Test

1-49 1.8 Unconfined Compression Test - It gives a quick and simple measurement of the undrained strength of cohesive, undisturbed soil specimens. 1) Testing method i) Trimming a sample. Length-diameter