Experimental and Numerical Simulation Study on Shear Strength and Secondary Particle Breakage of Coarse Sand with Different Dry Densities

In order to guarantee perpendicularity of rotary cast-in-place pile in Karst areas, filling, like sand, etc., is commonly used between the inner steel casing and outer sleeve; while sleeve pulled out or a vertical load applied on top pile, sand will move, contact, push against each other, which leads recrushing; therefore, shear characteristics secondary breakage are meaningful problem study with regard influence different densities. Through experimental direct tests, dry densities, stress versus displacement curves obtained internal friction angles analyzed. The results show that increase along increment densities; more interesting ratio also increases. A comparative numerical 2D model set up using PFC2D, lower porosity simulate large density, similar obtained, say, increase.