Analysis of Undrained Shear Characteristics and Structural Damage of Granite Residual Soil

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Analysis of Undrained Shear Characteristics and Structural Damage of Granite Residual Soil

Yin, Song / Liu, Pengfei / Yan, Pan / Zhang, Xianwei / Li, Xinming

Three-dimensional consolidation testing, scanning electron microscopy, and undrained triaxial testing of granite residual soil (GRS) in Shenzhen, China, were conducted. The effect of the structural strength of GRS was quantitatively analyzed using the method of comprehensive structure potential parameter description. The failure strength ratio of the soil decreases with increasing confining pressure, and it is approximately 1 when the confining pressure is higher than the yield stress (σ_s). The undrained shear strength (S_u) of the undisturbed soil varies in stages with confining pressure σ₃. The relationship between S_u and σ₃ for the reconstituted soil is approximated as a straight line through the origin. The soil’s comprehensive structure potential parameters (the structural contribution rates of the tangential shear modulus, m_E, and the deviatoric stress, m_d) decrease linearly with increasing σ₃. The m_E and m_d sample values are similar under the same confining pressure. It is reasonable to use structure potential parameters to quantitatively evaluate the structure contribution rate of GRS. The microstructure is constantly adjusted, and the soil microstructure form for different confining pressures strongly correlates with its shear characteristics.