1、5.3.2 Principle of the triaxial shear testTriaxial shear test is a method to determine the shearstrength parameters of soil under the three-dimensional stress state, and it is also a relativelycomplete test method to determine the shear strengthof soil.Principle of the triaxial shear test土力学Soil Mec
2、hanicsProf. H.J.Liao Triaxial shear apparatusPressurechamberTriaxial shear apparatusTriaxial shear apparatus土力学Soil MechanicsProf. H.J.LiaoAxial loadThe ways of applying axial load : strain controland stress controlThe strain controlled triaxial shearapparatus, and also known as theconventional tria
3、xial apparatus.The axial pressure is applied at thesame axial strain rate until thefailure of specimen during the test.土力学Soil MechanicsProf. H.J.Liao1-pressure regulating valve； 2-confining pressure gauge； 3-confining pressure valve；4-drainage valve； 5-volumetric change tube； 6-drainage tube； 7-def
4、ormation gauge；8-dynamometer ring； 9-discharge hole； 10-axial load system； 11-pressure chamber；12-burette valve； 13-zero indicator； 14-pore water pressure gauge； 15-burette；16-pore water pressure valve； 17-clutch； 18-handwheel； 19-motor； 20-gearboxThe structure diagram of the straincontrolled triaxi
5、al apparatus. Pressure stabilizing and regulating system Volume change measuring system Pore water pressure measuring systemStrain controlled triaxial shear apparatusBasic principle of conventional triaxial shear test.Cylinder sample3.85.0 cm7.510.0 cmRubber film土力学Soil MechanicsProf. H.J.LiaoValveM
6、etal upper coverRubber filmPlexiglass cylinderAxial compression rodPressure waterVent holeTop hatpressure chamberpermeable stoneDrainpipesampleMeasure volume change or pore pressure c c c-ac c csample土力学Soil MechanicsProf. H.J.LiaoTrue triaxial shear test1 23Conventional triaxial shear test1 2=3 Tri
7、axial shear test 2c 3c=a11、 2 and 3 are used to express the major, intermediate and minor principal stress.Conventional triaxial compression testConventional triaxial shear test土力学Soil MechanicsProf. H.J.Liao13 cThe results of the conventional triaxial shear testo 3 3 1土力学Soil MechanicsProf. H.J.Lia
8、o Effective stress principleThe advantages of the triaxial shear test are that the test cancontrol the drainage condition and measure the change ofpore water pressure u in the process of shear. = - u13 co 3 1uEffective stress circleTotal stress circleThe results of the conventional triaxial shear test土力学Soil MechanicsProf. H.J.LiaoStatement: Thanks for some pictures and materials fromthe Internet used in this courseware only for teaching.
