薄喷涂层(TSL)包覆支护对砂岩剥落破坏特性的影响
抽象
关键字
1. 引言

Fig. 1. (a) Supporting properties of TSL (b) Supporting properties of thickly coated concrete.
2. Test scheme
2.1. Specimen preparation
Table 1. Mortar mixture ratio.
Sand/(kg) | Cement/(kg) | Water/(kg) | Water cement ratio |
---|---|---|---|
534 | 170 | 107 | 0.63 |
Table 2. Basic physical-mechanical parameters of material.
Material | Density/(kg/m3) | Elastic modulus/(GPa) | Compressive strength/MPa | Tensile strength/MPa | Wave velocity/(m/s) |
---|---|---|---|---|---|
Sandstone | 2326 | 20.00 | 67 | 5.5 | 3000 |
TSL | 1365 | 1.0 | 6.54 | 8 | 1419 |
Mortar | 2150 | 7.2 | 37 | 4.75 | 1800 |

Fig. 2. Coating specimen and strain gauge pasting position (a) Sandstone specimen (b) Size of coating specimen (b) Schematic diagram of strain gage placement (d) Specimen preparation process (e) TSL-coated specimen (f) Mortar-coated specimen.
2.2. Test method

Fig. 3. SHPB experimental device schematic diagram.
3. Test results
3.1. Adhesion calculation

Fig. 4. Loading waveform diagram of sandstone and TSL-coated specimen.

Fig. 5. Reflected tensile stress and bonding of TSL-coated specimens.
Table 3. The spalling test results of TSL coating specimen.
Numbering | Strain gage placement | ||
---|---|---|---|
Empty Cell | B | C | Empty Cell |
Reflection stress/MPa | Reflection stress/MPa | Adhesive force/kN | |
T-1-3 | 5.54 MPa | 3.12 MPa | 2.964 kN |
T-1-5 | 5.81 MPa | 4.2 MPa | 1.972 kN |
TL-1-3 | 6.35 MPa | 4.31 MPa | 2.499 kN |
TL-1-5 | 6.44 MPa | 4.6 MPa | 2.254 kN |
3.2. Spalling strength and failure characteristics of TSL-coated specimens
Table 4. Spalling results of different TSL coating specimens.
Numbering | Spalling strength/MPa | Layer number of spalling | Distance from each spalling surface to the free end/cm |
---|---|---|---|
S-1 | 13.0 | 1 | 13.3 |
T-1-3 | 5.54 | 1 | 15.2 |
T-1-5 | 5.81 | 1 | 15.3 |
TL-1-3 | 6.35 | 1 | 20.1 |
TL-1-5 | 6.44 | 1 | 20.3 |

Fig. 6. Spalling failure characteristics of TSL-coated specimens.
3.3. Spalling strength and failure characteristics of mortar-coated specimens
Table 5. Spalling strength of different mortar coating specimens.
Numbering | Spalling strength/MPa | Layer number of spalling | Distance from each spalling surface to the free end/cm |
---|---|---|---|
S-1 | 13.0 | 1 | 13.3 |
S-1-3 | 11.8 | 1 | 15.3 |
S-1-5 | 11.3 | 2 | 15.2, 17.1 |
SL-1-3 | 8.84 | 1 | 20.0 |
SL-1-5 | 7.47 | 1 | 20.1 |

Fig. 7. Loading waveform diagram of mortar-coated specimen.

Fig. 8. Spalling failure characteristics of mortar-coated specimens.
4. Numerical simulation
4.1. PFC3D built-in model and parameter calibration

Fig. 9. Numerical simulation results in uniaxial compression (a) Stress-strain curve (b) Failure characteristics.
Table 6. Micro-parameters in numerical simulation.
Parallel bond model | Flat-joint model | |||
---|---|---|---|---|
Micro-parameters | Sandstone | Mortar | Micro-parameters | TSL |
Particle density (kg/m3) | 2700 | 2150 | Particle density (kg/m3) | 1365 |
Minimum radius of particle (mm) | 1.3 | 1.3 | Minimum radius of particle (mm) | 1.2 |
Maximum radius of particle (mm) | 1.8 | 1.8 | Maximum radius of particle (mm) | 1.6 |
Effective modulus of both bond and particle (GPa) | 16 | 7 | Effective modulus of both bond and particle (GPa) | 1 |
Frictional angle (°) | 45 | 30 | Frictional angle (°) | 30 |
Stiffness ratio of both and parallel-bond and particle | 2.0 | 2.0 | Stiffness ratio of both and parallel-bond and particle | 2.0 |
Shear strength of parallel-bond (MPa) | 30 ± 2 | 18 ± 2 | Shear strength of bond (MPa) | 6 ± 2 |
Tensile strength of parallel-bond (MPa) | 56 ± 2 | 26 ± 2 | Tensile strength of bond (MPa) | 10 ± 2 |
4.2. Modeling of PFC3D-FLAC3D coupling

Fig. 10. Numerical simulation (a) Numerical model of SHPB system (b) FLAC3D-PFC3D coupling numerical simulation flowchart (c) Comparison of simulated and experimental waveform.
4.3. Numerical simulation results and analysis

Fig. 11. Numerical simulation (a) Stress cloud diagram of T-1-5 specimen (b) Spalling failure characteristics of TSL-coated specimens.

Fig. 12. Simulation results of TSL-coated specimens under impact loading.
5. Discussion

Fig. 13. Spalling results of TSL-coated specimens under impact loading (a) Spalling failure characteristics (b) Stress time history curve.

Fig. 14. Spalling results of mortar coating specimens under impact loading (a) Numerical simulation (b) Spalling test.

Fig. 15. Time-history curve of stress (a) Shear stress of mortar coating specimens (b) Shear stress of TSL coating specimens(c) Normal stress of TSL coating specimens.
6. Conclusion
- (1)This paper proposed a method to determine the bond force between TSL and rock under dynamic loading. The results showed that the bond force decreased as the thickness of the TSL increased.
- (2)The excellent adhesion and tensile capacity of TSL effectively prevented tensile damage to the sandstone. Under impact loading (at lower levels), the spalling strength of TSL-coated specimens increased with the TSL's thickness and length. Specimen TL-1-5 exhibited the highest spalling strength among the tested specimens, although its spalling strength was still significantly lower than that of pure rock specimens. In contrast, the strength of sandstone spalling under mortar wrapping decreased as the mortar thickness and length increased, as the mortar primarily prevents sandstone damage through its shear capacity. Consequently, the spalling strength of mortar-wrapped specimens was greater than that of those wrapped in TSL. Furthermore, neither the TSL-coated nor mortar-coated specimens showed initial spalling at the wrapped section, with the first spalling fracture occurring at the second interface.
- (3)The simulation results demonstrated that both tensile and shear capacities were enhanced as the thickness TSL and mortar wrapping increased. As the impact load increased, the tensile properties of TSL were fully utilized, consuming more energy during the tensile and compressive deformation of the specimen, thereby reducing the degree of spalling failure. In contrast, the shear action of the mortar resulted in greater energy dissipation with thicker wrapping, further mitigating spalling failure. Overall, under dynamic loading, the bonding force and tensile ability of TSL significantly outperformed its shear performance when compared to traditional mortar. This improved performance made TSL particularly well-suited for supporting underground roadways subject to frequent dynamic disturbances. TSL not only provided superior support but also adhered firmly to the surrounding rock, effectively safeguarding it from potential damage.
CRediT authorship contribution statement
Declaration of competing interest
Acknowledgements
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