IIT Gandhinagar  ajanta@iitgn.ac.in  ap@iitgn.ac.in
Soil Testing Lab

Introduction Experimental Setup Data Analysis Results Theory

Unconsolidated Undrained (UU) Triaxial Test

Need and Scope:

To find the shear strength of soil by Unconsolidated Undrained Triaxial test. In UU test, soil specimen is not consolidated and thus drainage is not allowed either during application of cell pressure (confining pressure) or shearing. UU triaxial test is the fastest triaxial test to obtain shear strength parameters (c,Φ) of soil.


A cylindrical soil specimen is subjected to three compressive stresses in mutually perpendicular directions and one of these three stresses being increased until specimen fails in shear. Initially, a confining pressure (σ3) is applied through water around the specimen in an impermeable membrane. The vertical stress becomes major principal stress (σ1) while the confining pressure σ3 acts in other two principal directions. The intermediate principal and minor principal stresses are equal to each other. Deviator stress (σd) is the difference of σ1 and σ3, acts on specimen while its shear deformation.

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