Effect of interparticle behavior on the development of soil arching in soil-structure interaction

Direct shear tests have been commonly used to study the frictional stresses during pipe-jacking. Particle angularity and mineralogy will influence the shear strength with apparent cohesion contributing to the arching effect during soil-structure interaction via pipe-jacking. Past researchers found it challenging to physically study particle behavior along the shear band during shearing due to the opaque nature of the equipment. This study used an original transparent shear box to conduct direct shear tests on tunneling rock spoils of sandstone and shale. Sequential images were captured during shearing and analyzed using GeoPIV software to demonstrate localized activities which were found to influence the apparent cohesion. Furthermore, the findings were successfully used to assess the arching phenomenon observed during pipe-jacking and other established pipejacking case studies. Rounded particles with strong mineralogy were found to be more likely to produce an arching effect as compared to angular particles with weaker minerals.