Abstract: This paper presents the conventional triaxial consolidation test results on Guiyang red clay by using SLB-1 triaxial shearing and osmotic apparatus.  The evolution of the pore water pressure of soil samples during the consolidation and shearing stages, the value of the test failure stress, the relationship between the total stress path and the effective stress path are observed and evaluated. Meanwhile, the deformation failure mechanism of samples is analyzed from the effective stress principles. The test result show that, the pore water pressure is an important parameter of triaxial test, which controls the effective stress intensity of soil sample. Specifically, in the consolidation stage, with the compression of the pore volume, the excess pore water pressure gradually dissipates to zero. In the shear stage, after the soil particles are rearranged, the excess pore water pressure is generated and increases with the increase of strain. At this stage, the effective stress decreases. In the stress space, the effective stress trajectory is on the left side of the total stress trajectory, which is reverse bending. The variation of the pore water pressure is the fundamental factor that causes the characteristics of the two different stress paths. Under the action of the pore water pressure, the change process of points in the stress space can be divided into the total stress path and the effective stress path, but both stress states can be represented by Mohr circles, and the two Mohr circles are on the horizontal axis. The interval is the excess static pore water pressure.

Key words: Red Clay, Consolidate Undrained, Pore Water Pressure, Effective Stress, Total Stress, Failure Mechanism