Understanding the shear behaviors of expansive soils under a wide range of confining pressures 6 3 is crucial for effectively managing their shallow hazards, especially at low 6 3 values. The shear behaviors of expansive soils under the low 6 3 values exhibit significant differences with those under the high 6 3 values, which have been inadequately addressed in existing research. This paper investigated the shear behaviors of two expansive soils across a wide range of 6 3 values (i.e., 15-400 kPa) through consolidated undrained triaxial tests. The results showed a significant nonlinear relationship between the shear strength and 6 3 , particularly at the low 6 3 values. The nonlinearity of shear strength versus 6 3 in shallow expansive soils was described by a modified power function. As 6 3 decreased, both the brittleness index 7 and curvature K increased nonlinearly. Comparisons between the tangent method, based on the modified power function, and the K f method, based on the Mohr- Coulomb criterion, suggested that neglecting the nonlinearity of shear strength versus 6 3 led to overestimations of the cohesion and underestimations of the internal friction angle at low 6 3 values, and the reverse trend was observed at high 6 3 values. The magnitude of these deviations depended on both the shear strength nonlinearity and the selected 6 3 values. The findings presented herein are helpful for the mitigation of shallow hazards in roadbeds, slopes, and foundation engineering associated with expansive soils.

来源平台：TRANSPORTATION GEOTECHNICS