Test and prediction for the shear behavior of the sand–irregular concrete interface under constant and dynamic normal loading

Abstract

Pile foundations commonly withstand dynamic loading, which calls for a detailed analysis of cyclic shear properties at the pile–soil interface. This research entailed a sequence of direct shear tests on sand and concrete with irregular surface under both constant and dynamic normal loading, employing joint roughness coefficients (JRC) of 0.4, 5.8, 9.5, 12.8, and 16.7, and varying initial normal loading of 100, 150, and 200 kPa. Results showed that dynamic normal loading diminished the shear strength at the sand–concrete interface and hastened the onset of shear displacement at peak shear stress. Increased surface roughness and initial normal loading mitigated the detrimental effects of dynamic normal loading on this interface. A specific surface roughness was identified as critical for maximizing shear stress under both constant and dynamic normal loading conditions. Furthermore, an increase in the initial normal loading enhanced the interface shear strength. Dynamic normal loading also reduced the interface dilatancy, which could be further influenced by changes in surface roughness and initial normal loading. Notably, dynamic normal loading caused a phase shift in shear stress relative to normal stress, lessened by increased surface roughness. The study introduced a shear strength prediction method for the sand–irregular concrete interface under dynamic normal loading, validated through comparison with experimental data.