Influence of the initial hydrostatic pressure on contact area coefficient under drainage condition

¹ The Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education, Beijing University of Technology, 100124 Beijing, China
² School of Civil and Transportation Engineering, Beijing University of Civil Engineering and Architecture, 102616 Beijing, China
³ Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China

^* Corresponding author: xuchengshun@bjut.edu.cn

Abstract

The expression of effective stress proposed by Terzaghi has always been questioned. Many correction formulas are modification of pore pressure term. The pore pressure factor is related to porosity, contact area and other factors. When the particles are in point contact, the expression of the effective stress is that proposed by Terzaghi, while for the surface contact particles, the actual effective stress increases the stress produced by pore pressure passing through the contact surface based on the Terzaghi effective stress. There are many factors that affect the development of contact area and pore pressure, therefore, a series of the drained triaxial tests were carried out on four groups of sand samples with different initial hydrostatic pressures to study the influence of different initial hydrostatic pressures on the effective stress due to the term of contact area (σ_α). The test results show that the shear strength is increases with the initial hydrostatic pressure under the same effective confining pressure, which indirectly indicates that the initial hydrostatic pressure increases the contact area stress.