Study on the mechanical properties and particle breakage of geogrid-reinforced tunnel spoil

The use of tunnel spoil as subgrade filler can save resources and promote the sustainable and low-carbon development of transportation infrastructure. To investigate the mechanical properties evolution law of tunnel spoil as subgrade filler, SEM and large-scale triaxial tests were conducted to analyze its macroscopic and microscopic characteristics, and particle breakage behavior. The study focuses on the impact of geogrid on the shear strength, deformation, and particle breakage of tunnel spoil and its working mechanism. The results indicate that an increase in soft rock content reduces the shear strength and weakens its shear induced dilatancy. The average peak shear strength of tested geogrid reinforced dense specimens can be increased by 10%, and the residual shear strength can be increased by about 30%. The relative breakage index increases in an S-shaped pattern with increase in soft rock content. Higher confining pressure and soft rock content lead to more particle breakage, however, particle breakage in the reinforced specimens can be significantly reduced. The research findings contribute to the enhanced design and implementation of waste material repurposing, thereby advancing the sustainable development of traffic infrastructure.