Fig 1.
Mineral distribution of the schist sample.
Fig 2.
Micro morphology of fracture surface under ESEM, (a) stacked flaky mica and (b) smooth fracture plane.
Fig 3.
Grayscale images obtained by ESEM and the relevant statistical graph, (a) long cracks in the schist sample, (b) rose diagram of flaky minerals orientation and (c) microcracks and micropores in the schist sample.
Fig 4.
Stress-strain curves of specimens subjected to uniaxial compression.
Fig 5.
Mechanical indicators of the tested schist subjected to uniaxial compression.
Table 1.
Mechanical parameter values of specimens subjected to triaxial compression.
Fig 6.
Stress-strain curves of specimens subjected to triaxial compression, (a) α = 90°, (b) α = 30° and (c) α = 0°.
Fig 7.
Variation of compressive strength with confining pressure.
Fig 8.
Variation of shear stress with normal stress on the sliding failure plane.
Fig 9.
Comparison of influence coefficients at different orientation angles.
Fig 10.
Effect of confining pressure on strength anisotropy for rocks with weak planes.
Fig 11.
Response of critical ratio () to the most representative uniaxial compressive strength (
) and strength anisotropy degree under uniaxial compression (
).
Fig 12.
Failed schist specimens subjected to triaxial compression.
Fig 13.
CT scanning images, (a) α = 0° at the confining pressure of 5 MPa, (b) α= 90° at the confining pressure of 10 MPa and (c) α = 30° at the confining pressure of 5 MPa.
The vertical direction in each image corresponds to the specimen axial direction.
Fig 14.
Localized kinking revealed by CT scanning.
Fig 15.
Diagrammatic drawing of failure modes of schist under the condition of low confining pressure, (a) schist containing high content and aggregation degree of mica and (b) schist containing low content and aggregation degree of mica.
In the drawing, represents the flaky mica cluster and represents a weak layer including multiple mica clusters. represents the strong mineral phase composed of granular minerals.