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| A ''' direct shear test''' is a laboratory or field test used by [[geotechnical engineering|geotechnical engineers]] to measure the [[shear strength]] properties of [[soil]]<ref name=Bardet1997/><ref name=Price2009/> or [[Rock (geology)|rock]]<ref name=Price2009/> material, or of [[Discontinuity (geotechnical engineering)|discontinuities]] in soil or rock masses.<ref name=Price2009/><ref name=ISRMbluebook2007/> A detailed description of the testing equipment and procedure can be also found on [http://www.geotechdata.info/geotest/direct-shear-test.html geotechdata.info direct shear test] page.
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| The U.S. and U.K. standards defining how the test should be performed are [[ASTM]] D 3080 and [[British Standards|BS]] 1377-7:1990, respectively. For rock the test is generally restricted to [[Rock (geology)|rock]] with (very) low shear strength. The test is, however, standard practice to establish the [[Shear strength (Discontinuity)|shear strength properties of discontinuities]] in rock.
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| The test is performed on three or four specimens from a relatively undisturbed soil sample.<ref name=Bardet1997/><ref name=Texaslecnotes/> A specimen is placed in a ''shear box'' which has two stacked rings to hold the sample; the contact between the two rings is at approximately the mid-height of the sample. A ''confining stress'' is applied vertically to the specimen, and the upper ring is pulled laterally until the sample fails, or through a specified [[Strain (materials science)|strain]]. The load applied and the strain induced is recorded at frequent intervals to determine a [[stress-strain curve]] for each confining stress.
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| Several specimens are tested at varying confining stresses to determine the shear strength parameters, the soil cohesion (c) and the angle of internal friction (commonly ''[[Friction#Angle of friction|friction angle]]'') (<math>\phi</math>). The results of the tests on each specimen are plotted on a graph with the peak (or residual) stress on the x-axis and the confining stress on the y-axis. The y-intercept of the curve which fits the test results is the cohesion, and the slope of the line or curve is the friction angle.
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| Direct shear tests can be performed under several conditions. The sample is normally saturated before the test is run, but can be run at the in-situ moisture content. The rate of strain can be varied to create a test of ''undrained'' or ''drained'' conditions, depending whether the strain is applied slowly enough for water in the sample to prevent pore-water pressure buildup.
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| The advantages of the direct shear test over other shear tests are the simplicity of setup and equipment used, and the ability to test under differing saturation, drainage, and consolidation conditions. These advantages have to be weighed against the difficulty of measuring pore-water pressure when testing in undrained conditions, and possible spuriously high results from forcing the failure plane to occur in a specific location.
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| The test equipment and procedures are slightly different for test on discontinuities.<ref name=HencherRichards1989/>
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| ==See also==
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| *[[Geotechnical investigation]]
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| *[[Shear strength (Discontinuity)]]
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| *[[Tilt test (Geotechnical engineering)]]
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| *[[Triaxial shear test]]
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| *[[Shear vane test]]
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| ==References==
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| <references>
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| <ref name=Bardet1997>{{cite book |last1= Bardet |first1= J.-P. |year= 1997 |title= Experimental Soil Mechanics |publisher= [[Prentice Hall]] |isbn= 978-0-13-374935-9}}</ref>
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| <ref name=Price2009>{{Cite book | last1 = Price | first1 = D.G. | editor1-last = De Freitas | editor1-first = M.H. | year = 2009 | title = Engineering Geology: Principles and Practice | publisher = [[Springer Science+Business Media|Springer]] | page = 450 | ISBN = 3-540-29249-7 }}</ref> | |
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| <ref name=ISRMbluebook2007>{{Cite book | last1 = [[ISRM]] | year = 2007 | title = The Blue Book - The Complete ISRM Suggested Methods for Rock Characterization, Testing and Monitoring: 1974-2006 | editor1-last = Ulusay | editor1-first = R. | editor2-last = Hudson | editor2-first = J.A.
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| | publisher = [[ISRM]] & ISRM Turkish National Group | place = Ankara | ISBN = 978-975-93675-4-1 | page = 628 | url = http://www.isrm.net/gca/index.php?id=935 }}</ref>
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| <ref name=Texaslecnotes>{{Cite book |title= Direct shear test from geotechnical lab notes |publisher= University of Texas Arlington |url= http://geotech.uta.edu/lab/Main/DIRECT%20SHEAR%20TEST.pdf }}</ref>
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| <ref name=HencherRichards1989>{{cite journal |first1=S. R. |last1=Hencher |first2=L. R. |last2=Richards |title= Laboratory direct shear testing of rock discontinuities |journal=Ground Engineering |volume=22 |issue=2 |year=1989 |pages=24–31}}</ref>
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| <references/>
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| {{Geotechnical engineering}}
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| [[Category:Soil tests]]
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Alyson is what my husband loves to call me but I don't like when individuals use my full title. Ohio is where his house is and his family members enjoys it. What me and my family members love is to climb but I'm considering on starting something new. I am currently a journey agent.
My web-site ... clairvoyance (http://modenpeople.co.kr)