# Study on Crack Propagation of Rock Bridge in Rock-like Material with Fractures under Compression Loading with Sudden Change Rate

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## Abstract

**:**

## 1. Introduction

## 2. Test Scheme

#### 2.1. Test Materials and Specimen Preparation

#### 2.2. Spatial Distribution of Crack

#### 2.3. Test Equipment and Test Methods

## 3. Crack Evolution and Failure Characteristics of Rock Bridge Specimen at Sudden Change Loading Rate

#### 3.1. Analysis of the Corresponding Relationship between Crack Propagation and Stress–Strain Curve under Uniform Loading

_{c}and maximum strain ε

_{c}(that is, the strain corresponding to the peak axial stress) of the specimen at the corresponding loading rate.

#### 3.2. Analysis of Crack Propagation and Failure Modes of Specimens under Sudden Change Loading Rate Loading

#### 3.3. Correspondence of AE Information under Sudden Change Loading Rate

^{6}aJ. ② Linear elastic stage, AE signals are inactive, amplitudes mainly distribute in the range of 30~50 dB, occasionally 69 dB AE, and the absolute energy is mostly less than 1 × 10

^{6}aJ. ③ Stable crack propagation stage, acoustic emission signals are fast and active, and accumulated energy increases rapidly. Amplitude distribution is between 50 and 80 dB, and amplitude is 97 dB in the middle stage. ④ Unstable crack propagation stage, the signal surges, and the accumulated energy increases rapidly, with the amplitude distribution between 70 and 80 dB. The absolute energy is mostly less than 2 × 10

^{8}aJ. ⑤ Post-peak stage, when the stress drops, the amplitude of acoustic emission signal decreases immediately within 30–40 dB, and the absolute energy is less than 1 × 10

^{6}aJ.

^{6}aJ. ② Linear elastic stage, a relatively high acoustic emission signal peak appears, and the amplitude is distributed in the range of 50~80 Db. The acoustic emission of 96 dB appears in the sudden change loading rate, and the absolute energy is mostly less than 1 × 10

^{7}aJ. ③ Stable crack propagation stage, and the AE signal responds with high value and gradually increases, with the amplitude ranging from 65 to 90 dB. The absolute energy is mostly less than 1 × 10

^{8}aJ. ④ Unstable crack propagation stage, the stress reaches the peak, the amplitude is between 80 and 100 dB, and the absolute energy is less than 1 × 10

^{8}aJ. ⑤ Post-peak stage, the stress drops precipitously, with the amplitude of 30–50 dB, and the absolute energy is less than 1 × 10

^{6}aJ.

^{8}aJ. ② Linear elastic stage, the AE signal is always at a low level, the amplitude is between 30 and 45 dB, and the absolute energy is mostly less than 1 × 10

^{6}aJ. ③ Stable crack propagation stage, the acoustic emission signals are dense, and the response begins to be dense. The amplitude distribution is between 50 and 70 dB, and the absolute energy is mostly less than 1 × 10

^{7}aJ. ④ Unstable crack propagation stage, the acoustic emission detection signal surges, with the amplitude between 70 and 90 dB, and the absolute energy mostly less than 1 × 10

^{8}aJ. ⑤ Post-peak stage; the AE signal drops, the amplitude distribution is 30~50 dB, and the absolute energy is less than 1 × 10

^{5}aJ.

## 4. Discussion on the Mechanism of Crack Evolution Influenced by Sudden Change Loading Rate

## 5. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## References

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**Figure 1.**Rock mechanics test, acoustic emission system, and schematic diagram of prefabricated double fissure rock specimen.

**Figure 6.**Correspondence relationship between crack propagation and stress–strain curve of typical specimen.

**Figure 10.**Comparison diagram of stress–strain in elastic stage of velocity line after same sudden change speed.

Loading Rate v/(mm/min) | Peak Strength q_{c}/mpa | Peak Strain ε_{c}/10^{−3} | Elastic Modulus/GPa |
---|---|---|---|

0.5 | 9.70 | 11.37 | 1.20 |

1 | 9.96 | 10.70 | 1.41 |

3 | 10.81 | 10.39 | 1.42 |

5 | 11.11 | 10.30 | 1.79 |

Specimen Number | Realistic Graph | Sketch | Failure Mode Diagram |
---|---|---|---|

0.5-1 | |||

0.5-3 | |||

0.5-5 | |||

1-3 | |||

3-5 | |||

5-0.5 | |||

5-1 |

Specimen Number | Realistic Graph | Sketch | Failure Mode Diagram |
---|---|---|---|

0.5-1 | |||

0.5-3 | |||

0.5-5 | |||

1-3 | |||

3-5 | |||

5-0.5 | |||

5-1 |

Rate of Loading | fv 0.5 mm/min | fv 1 mm/min | fv 3 mm/min | fv 5 mm/min |
---|---|---|---|---|

iv 0.5 mm/min | T | M | T | S |

iv 1 mm/min | \ | M | M | \ |

iv 3 mm/min | \ | \ | M | M |

iv 5 mm/min | T | S | \ | S |

Rate of Loading | fv 0.5 mm/min | fv 1 mm/min | fv 3 mm/min | fv 5 mm/min |
---|---|---|---|---|

iv 0.5 mm/min | T | T | T | S |

iv 1 mm/min | \ | T | M | \ |

iv 3 mm/min | \ | \ | M | M |

iv 5 mm/min | T | T | \ | S |

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**MDPI and ACS Style**

Huang, X.; Wan, W.; Wang, M.; Zhou, Y.; Liu, J.; Chen, W. Study on Crack Propagation of Rock Bridge in Rock-like Material with Fractures under Compression Loading with Sudden Change Rate. *Appl. Sci.* **2023**, *13*, 4354.
https://doi.org/10.3390/app13074354

**AMA Style**

Huang X, Wan W, Wang M, Zhou Y, Liu J, Chen W. Study on Crack Propagation of Rock Bridge in Rock-like Material with Fractures under Compression Loading with Sudden Change Rate. *Applied Sciences*. 2023; 13(7):4354.
https://doi.org/10.3390/app13074354

**Chicago/Turabian Style**

Huang, Xuanqi, Wen Wan, Min Wang, Yu Zhou, Jie Liu, and Wei Chen. 2023. "Study on Crack Propagation of Rock Bridge in Rock-like Material with Fractures under Compression Loading with Sudden Change Rate" *Applied Sciences* 13, no. 7: 4354.
https://doi.org/10.3390/app13074354