Coupling Relationship Between Seepage and Stress of Purple Soil in Three Gorges Reservoir Area

Abstract

[Objective] The permeability and shear strength characteristics of purple soil in the Three Gorges reservoir area under the coupling effect of seepage and stress were studied, and the coupling relationship between stress and seepage of purple soil was deeply explored, in order to provide theoretical reference for practical engineering applications such as agricultural engineering, slope engineering and soil and water conservation. [Methods] Changes in shear strength and permeability of purple soil under multi-factor coupling were analyzed using an SLB-1A stress-strain controlled triaxial shear permeability tester. [Results] The influence of water content on cohesion (c) and internal friction angle (φ) of purple soil in the Three Gorges reservoir area was different, and the peak value was obtained at the water content of 11%. The internal friction angle decreased linearly with increasing water content. The permeability of purple soil varied greatly among different water content gradients, and the differences were relatively obvious when the water contents were between 11% and 13%. With the permeability pressure equal to the critical value of 40 kPa, the permeability reduction forms of purple soil were different. The greater the control value of the principal stress difference, the lower the permeability of purple soil with different moisture contents. [Conclusion] Water content and confining pressure greatly affected the shear strength of purple soil under the action of seepage-shear. Cohesion reached a peak value at 11% water content, and the changes of cohesion and internal friction angle were linear. Under the same conditions, the influence of water content and principal stress difference on the permeability coefficient of purple soil with axial stress followed a cubic relationship. The contribution rates of various factors to the permeability of purple soil from high to low followed the order of permeability pressure > principal stress difference > confining pressure > water content.

Keywords

• purple soil
• water content
• permeability-shear
• permeability
• shear strength