[Abstract]：The coarse-grained content of sandy cobbled soil has a great influence on the stability of the foundation pit and tunnel surrounding rock, But the macroscopic and micromechanical properties of sand and gravel with different coarse contents are not clear. The macroscopic and meso-mechanical properties of different coarse-grained sand-pebbled soils were studied using a combination of a large-scale coarse-grained soil triaxial test and a numerical triaxial test. Research indicates: With the increase of coarse-grain content, the stress-strain curve of sand-pebble soil shows strain softening; When the confining pressure is constant, the sand pebble soil increases with the increase of coarse grain content, and the stress peak value increases, and the strain at the peak value gradually decreases; The functional relationship between the coarse-grained content and the internal friction angle and cohesion of sand-pebble soil was established. With the increase of coarse-grain content, the internal friction angle and cohesion of sand-pebble soil increased linearly; The parameters such as the contact modulus, friction coefficient, particle stiffness ratio, and contact bonding strength of different coarse-grained sand-pebble soils were proposed. The research results provide theoretical support for the refinement design and construction of sand and gravel strata.