Bedding effect on sandstone stability using three-point loading: Implication of Longyou Grottoes caves

Weak bedding planes have a negative impact on the mechanical properties of rocks, which greatly affects the stability of underground caves in Longyou Grottoes. In this work, the Weibull-based finite-discrete element method (FDEM) is utilized to investigate the stability of Longyou bedded sandstone using three-point loading (TPL). Firstly, the input parameters in FDEM are calibrated based on existing laboratory tests. Subsequently, the FDEM model and parameter calibration are validated. Finally, a series of TPL numerical models of bedded sandstones is established. Effects of the bedding strength reduction coefficient ( f ), orientation ( θ ) and spacing ( s ) on the failure characteristics, bending strength (BS), acoustic emission (AE) events, crack number and energy evolution are discussed. Results indicate that the reduction of bedding strength leads to a sharp drop in BS except for a θ of 0°. Crack number decreases quickly as f increases from 0.1 to 0.3, but remains unchanged with further increase of f . The BS decreases first and then increases as θ increases and has the smallest value with an f of 0.1 and θ of 90°. Generally, more shear cracks develop along the bedding plane and make the interlayer peeling with a small f . Besides, s has little effect on fracture morphology, but an initial increase in s leads to a sharp decrease in crack numbers. Additionally, implications of Longyou Grottoes caves are discussed. The results of this study are expected to provide theoretical support for the stability evaluation of Longyou Grottoes and other underground caves composed of bedded sandstone. • A Weibull-based FDEM approach is first adopted to study the stability of Longyou bedded sandstone under three-point loading. • The input parameters in FDEM are calibrated by the uniaxial tensile and compression numerical tests on complete sandstone. • Effects of bedding strength, orientation and spacing on failure mode and bending strength are discussed. • Energy evolution and AE events of bedded sandstone during TPL are revealed. • Implications for the instability of Longyou Grottoes caves are discussed.