Fig 1.
Specimen preparation and bolt mechanical testing.
(A) red sandstone specimen with a single hole and bolt anchorage configuration; (B) bolt pull-out test and its corresponding stress-strain curve.
Fig 2.
Experimental loading and data acquisition system.
Fig 3.
Complete and single-hole specimen stress-strain curves under uniaxial compression.
Fig 4.
Stress-strain curves of anchored specimens at different locations.
Table 1.
Uniaxial compressive mechanical parameters of specimens.
Fig 5.
Characteristic laws of mechanical parameters for specimens.
(A) peak strength; (B) peak strain;(C) E; (D) secant modulus.
Fig 6.
AE distribution curves and fracture evolution process of anchored specimen at Position 1#.
(A) Stress-strain behavior and AE characteristics of anchored specimen 1#; (B) Crack propagation and failure mechanism of the anchored sample from position 1#.
Fig 7.
Initial crack initiation stress-strain conditions and methods in specimens.
(A) unanchored; (B) position 1#; (C) position 2#; (D) position 3#; (E) position 4#; (F) position 5#; (G) position 6#; (H) position 7#.
Fig 8.
Trends in specimen crack initiation stress.
Fig 9.
(A) unanchored; (B) position 1#; (C) position 2#; (D) position 3#; (E) position 4#; (F) position 5#; (G) position 6#; (H) position 7#.
Fig 10.
Mechanical model of sliding cracks within the bolted zone.
Fig 11.
Equivalent crack model of wing cracks in the anchored region.
Fig 12.
PFC2D numerical calculation model.
(A) numerical model; (B) contact model.
Table 2.
Microscopic parameters for the PFC2D sandstone specimen simulation.
Table 3.
Mesoscopic parameters for the simulation of bolting materials in PFC2D.
Fig 13.
Flowchart of meso-scale parameter calibration.
Fig 14.
Comparison between physical experiments and numerical simulation results.
(A) uniaxial compression test of intact specimen;(B) uniaxial compression test of specimen with a hole defect;(C) bolt pull-out test.
Fig 15.
Stress-strain curves of numerical specimens containing a hole defect anchored at different positions.
Fig 16.
Variation patterns of peak strength, peak strain, and crack initiation stress in numerical specimens with a hole defect anchored at different positions.
(A) peak strength; (B) peak strain; (C) crack initiation stress.
Fig 17.
Comparison of failure modes between specimens from laboratory tests and numerical simulation.
(A) position 1#;(B) position 2#;(C) position 3#;(D) position 4#;(E) position 5#;(F) position 6#;(G) position 7#.
Fig 18.
Evolution trends of the total number of cracks and bolt axial force in the specimens.
(A) unanchored specimen with a hole defect;(B) position 1#;(C) position 2#;(D) position 3#;(E) position 4#;(F) position 5#;(G) position 6#;(H) position 7#.
Fig 19.
Total numbers of tensile and shear cracks at complete failure of the specimens and the corresponding maximum bolt axial force.
Fig 20.
Energy evolution trends during uniaxial compression of the specimens.
(A) unanchored specimen with a hole defect;(B) position 1#;(C) position 2#;(D) position 3#;(E) position 4#;(F) position 5#;(G) position 6#;(H) position 7#.
Fig 21.
Trend of the maximum elastic energy conversion rate for the specimens.
Fig 22.
Particle displacement vector distribution at complete failure of the specimen.
(A) unanchored speciment;(B) position 1#;(C) position 2#;(D) position 3#;(E) position 4#;(F) position 5#;(G) position 6#;(H) position 7#.