The Degenerate Mechanism of Sand-Concrete Interface under Cyclic Loading

Abstract

The sliding interaction between the sand and the surface of the structure is involved in many aspects of geotechnical engineering and is particularly important for the derivation of the shaft capacity of piles. A constant normal stiffness direct shear apparatus is designed and applied herein to research the soil-structure interface weakening mechanism under cyclic loading. The test results show that the sand-concrete shear stress and normal stress change in the "Hysteresis loop" and "Butterfly" trends with shear displacement respectively in a complete shear cycle. The difference of adjacent "Hysteresis loop" or "Butterfly" is evident in the initial stage of cyclic shear, but tends to gentle after 15 cycles. The evident decays of both the shear stress and the maximum normal stress take place during cyclic shearing, which is approximately logarithmically with the shear cycles. The shear strength of the interface is approximately linear with the normal stress under different cycles. The percentage of particle breakage is between 5.5% and 6% of the original sand after 20 shearing cycles. The percentage of particle breakage and the degeneration rate of shear stress and normal stress increase with the increase of the initial normal stress and the amplitude of shear displacement.