(3)

The shear stress-shear displacement relationship and shear strength parameters at the pipe-soil interface are crucial for calculating jacking force. To investigate these properties, a series of tests were performed using a large-scale direct shear device to examine the shear mechanics of the steel-sand interface under various conditions. The effects of particle size, normal stress, and slurry concentration on shear performance were analyzed macroscopically. Additionally, the evolution of interface micro-behavior was studied using discrete element software PFC 2D. The experimental results indicate that the particle size of the sand has a significant impact on the shear stress-shear displacement curve of the interface, with smaller particle sizes requiring greater shear stress to achieve stability during shear. The strain-softening degree of sand is affected by normal stress. The shear stress-shear displacement curve is more significantly affected by particle size with the increase of normal stress. By considering different slurry concentrations, it is observed that both the shear stress and the sliding friction coefficient reached a minimum value at a concentration of 14%. The numerical simulation results indicate that particle motion causes changes in the distribution of particle structures. The distribution of particle force chains is relatively dispersed before shear. Particles move vigorously toward the shear interface, and force chains primarily concentrate on the shear interface during shear. Shear stress is transmitted through particle movement, and particle displacement causes shear dilation within the contact zone. Particles essentially cease moving toward the shear interface, and the force chains no longer change once the shear band is formed.

来源平台：INDIAN GEOTECHNICAL JOURNAL