Experimental Investigation of Consolidated Undrained Shear Behavior on Peaty Soil in Dian-Chi, China

Peat deposits are extensively distributed worldwide, and the various common engineering-failure problems involving peat have attracted greater attention from researchers in regard to understanding the mechanical behavior of peat. This study investigated extensive index and consolidated undrained triaxial compression tests applied to the peaty soils of Dian-Chi Lake, located in Yunnan, China. A series of consolidated undrained triaxial compression tests on peat specimens were carried out in this study, and the influences of confining pressure, organic matter content and strength parameters were investigated. The test results indicate that, to obtain a B-value greater than 0.98, the average back pressure of the Dian-Chi Lake peaty soil should be at least 150 kPa, with organic matter contents N ranging from 30% to 85%. Compared with the existing oedometer consolidation results of the research team, the values of compressibility and permeability behavior under the oedometer and isotropic consolidation conditions are not significantly different. In addition, the average failure strain, ε f , ranged from 9% to 15% for the investigated normally consolidated specimens, and the average effective angle of internal friction was 43.8°, which is greater than the maximum internal friction angle of 35° for typical soft clay and silt soils. A correlation was proposed by curve fitting the experimental data to better capture the nonlinear relationship between φ ′ and N . Furthermore, the values of the normalized undrained strength, S u / σ c ′, varied from 0.56 to 0.84, which is larger than that of the inorganic soft clay and silt deposits.