# Numerical Analysis of Mechanical Characteristics of Constant-Resistance, Energy-Absorbing and Anti-Scour Bolts

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Design of Constant-Resistance Energy-Absorbing Anti-Scour Anchor

#### 2.1. Design of Constant Resistance Anti-Impact Device

#### 2.2. The Composition of a Constant-Resistance Energy-Absorbing Anti-Scour Anchor

#### 2.3. The Working Principle of a Constant Resistance Energy-Absorbing Anti-Scour Anchor

## 3. Analysis of Mechanical Properties of an Anchor under Static Load

#### 3.1. Model Building and Parameter Setting

^{3}, the modulus of elasticity was 210 GPa, Poisson’s ratio was 0.3, and the plasticity parameters were taken from the data obtained from the laboratory anchor tensile test, and the yield strength of the material was 600 MPa and the tensile strength was 810 MPa after conversion. The rod was set up with flexible damage in ductile metal damage. The model’s boundary conditions are the left end of the rod is completely fixed, and only the axial displacement of the shaped nut end is allowed. A rigid plate with a diameter larger than the diameter of the rod with holes is used to displace 500 mm from the left side of the pallet to the right. in the mesh module, C3D8R cells are used for each component, the mesh shape is hexahedral, the pallet and rod mesh size are set to 5, the thin-walled circular tube mesh size is set to 2, and the cell type of the rod is set hourglass control for stiffness, and the cell is set to delete [35,36,37].

#### 3.2. Comparative Analysis of Mechanical Properties with Conventional Anchor

## 4. Analysis of Mechanical Properties of Anchor under Impact Load

#### 4.1. The Law of Impact Energy on The Mechanical Properties of Anchor

- (1)
- When the impact energy of the surrounding rock is 25 kJ, both conventional anchor rod and constant resistance energy-absorbing impact anchor rod are not broken; when the impact energy of the surrounding rock is 50 kJ, the conventional anchor rod is broken and the constant resistance energy-absorbing impact anchor rod is not broken; when the impact energy of the surrounding rock is 80 kJ, both the conventional anchor rod and constant resistance energy-absorbing impact anchor rod are broken. It shows that the constant resistance energy-absorbing impact anchor has good mechanical properties of impact resistance;
- (2)
- Under static load and 50 kJ and 80 kJ impact energy dynamic load, the yield load of the rod is 178, 183 and 183 kN, the breaking load is 226, 227 and 224 kN, the absorbed energy is 43, 41 and 43 kJ, and the yield distance is 240, 233 and 237 mm respectively. Compared with the static load, the yield load of the rod slightly increases, the yield distance slightly decreases, and the breaking load and absorbed energy remain the same. The effect of impact energy on the mechanical properties of conventional anchor rods can be ignored;
- (3)
- Under static load and 80 kJ impact energy dynamic load, the yield load of the rod is 178 and 184 kN, the breaking load is 226 and 224 kN, the absorbed energy is 66 and 60 kJ, the yield distance is 375 and 370 mm, and the load capacity of the impact prevention device is 162 and 156 kN. Compared with the static load, the yield load of the rod increased slightly, the breaking load was basically unchanged, and the absorbed energy, the yield distance and the load carrying capacity of the anti-squeezer decreased by 9%, 3% and 4%, respectively;
- (4)
- With the increase in impact energy, the bearing capacity of the deformation phase of the anti-puncher is 152~156 kN, which indicates that the anti-puncher has a more constant bearing capacity and deformation load threshold;
- (5)
- When the impact energy of the surrounding rock is 80 kJ, the yield load of the rod is 183 and 184 kN, the breaking load is 228 and 227 kN, the impact resistance time is 35 and 65 ms, the absorbed energy is 43 and 60 kJ, and the yield distance is 229 and 370 mm for the conventional anchor rod and the constant resistance energy-absorbing impact anchor rod, respectively. The impact resistance time, absorbed energy and yield distance are 1.86, 1.40 and 1.61 times of conventional anchor rods, respectively, which means that the impact resistance mechanical performance of constant resistance energy-absorbing anchor rods is significantly better than that of conventional anchor rods.

#### 4.2. The Law of Impact Velocity on The Mechanical Energy Absorption of Anchor

- (1)
- At impact velocities of 2, 4, 6 and 8 m/s, the rod yield load is 181, 181, 182 and 183 kN, the breaking load is 228, 228, 227 and 224 kN, the absorbed energy is 44, 43, 44 and 43 kJ, the yield distance is 242, 239, 245 and 237 mm, and the impact resistance time is 139, 69, 48 and 35 ms. It shows that the impact velocity has a small effect on the rod yield load, breaking load, absorbed energy and yield distance of conventional anchor rods, and the impact time decreases non-linearly with the increase in impact velocity;
- (2)
- When the impact velocity of constant resistance energy-absorbing anti-shock anchor is 2, 4, 6 and 8 m/s, the yield load of rod is 181, 181, 184 and 184 kN, the breaking load is 227, 226, 228 and 224 kN, the absorbed energy is 66, 64, 65 and 60 kJ, and the yield distance is 377, 377, 375 and 370 mm, respectively. The impact resistance time was 258, 144, 101 and 65 ms, respectively, indicating that the impact speed had a small effect on the rod yield load, breaking load, absorbed energy and yield distance of the constant resistance energy-absorbing anchor, and the impact resistance time decreased non-linearly with the increase in impact speed;
- (3)
- The bearing capacity of the impact prevention device in the deformation phase at the impact speed of the surrounding rock is 2, 4, 6, and 8 m/s is 156, 149, 153, and 155 kN, the impact resistance time is 79, 39, 27, and 20 ms, and the yielding distance is 134, 132, 132, and 135 mm, indicating that the impact prevention device at different impact speeds has a more constant bearing capacity and a higher stroking efficiency;
- (4)
- Under the same impact velocity, the three indexes of constant resistance energy-absorbing anti-impact anchor rods, such as yielding distance, impact resistance time and energy absorption, are significantly better than those of conventional anchor rods.

## 5. Field Applications

#### 5.1. Site Overview

#### 5.2. Field Test Results

## 6. Conclusions

- (1)
- Based on the requirements that the anchor rod anti-scouring device should have a reasonable deformation load threshold, high stroke efficiency, a constant reaction force and stable repeatable deformation damage mode, a constant resistance anti-scouring device is designed. Additionally, a constant-resistance energy-absorbing anti-stroke anchor rod consisting of rod body, tray, anti-stroke and profiled nut is designed, and the working principle of constant-resistance energy-absorbing anti-stroke anchor rod is given;
- (2)
- The constant resistance energy-absorbing anti-stroke anchor has a stable and repeatable deformation damage mode under both static and impact loads. The impact energy and impact velocity have less influence on the load carrying capacity and stroke efficiency of the constant resistance anti-impact device;
- (3)
- The impact velocity has a small effect on the indices of rod yield load, breaking load, absorbed energy and yield distance of conventional anchor rods and constant resistance energy-absorbing anti-shock anchor rods, and the impact resistance time all decreases non-linearly with the increase in impact velocity;
- (4)
- Under static and impact loads, the three indexes of constant resistance energy-absorbing anti-shock anchor rods, such as yielding distance, impact resistance time and energy absorption, are significantly better than those of conventional anchor rods.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

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**Figure 1.**Constant resistance anti-impact device. (

**a**) Flared thin-walled round tube, (

**b**) special-shaped nut, (

**c**) constant resistance anti-impact device combination chart, (

**d**) top view of constant resistance anti-impact device.

**Figure 2.**Anchor design drawings. (

**a**) constant resistance energy-absorbing anti-scour anchor, (

**b**) conventional anchors; 1: rod body; 2: tray; 3: anti-punch; 4: special-shaped nut.

**Figure 3.**Deformation process of constant resistance energy-absorbing anti-scouring anchor rod by force, (

**a**) initial stage (

**b**) constant resistance deformation stage (

**c**) yielding stage (

**d**) strengthening and damage stage.

**Figure 4.**Anchor rod deformation by static load. (

**a**) conventional anchors, (

**b**) constant resistance energy-absorbing anti-scour anchor, (

**c**) deformation of constant resistance anti-impact device by force.

**Figure 7.**Deformation diagram of anchor rod subjected to impact load. (

**a**) Conventional anchors, (

**b**) constant resistance energy-absorbing anti-scour anchor.

**Figure 8.**Anchor force–time curve: (

**a**) impact energy 25 kJ; (

**b**) impact energy 50 kJ; (

**c**) impact energy 80 kJ.

**Figure 10.**Deformation of constant resistance energy-absorbing anti-scouring anchor rod by force. (

**a**) Conventional anchor, (

**b**) constant resistance energy-absorbing anti-scour anchor.

**Figure 11.**Anchor force–time curve. (

**a**) Conventional anchor, (

**b**) constant resistance energy-absorbing anti-scour anchor.

**Figure 18.**Specific monitoring scheme of 11303 belt chute monitoring area. (

**a**) Surface displacement monitoring; (

**b**) anchor force monitoring. (

**c**) deep displacement monitoring.

Anchor Rods Type | Yield Load/kN | Breaking Load/kN | Energy Absorption/kJ | Letting Distance/mm | Anti-Scouring Device Bearing Capacity/kN |
---|---|---|---|---|---|

Conventional anchors | 178 | 226 | 43 | 240 | |

Constant resistance energy-absorbing anti-scour anchors | 178 | 226 | 66 | 375 | 160–165 |

Anchor Rods Type | Impact Energy/kJ | Yield Load/kN | Breaking Load/kN | Anti-Impact Time/ms | Energy Absorption/kJ | Letting Distance/mm | Anti-Scouring Device Bearing Capacity/kN |
---|---|---|---|---|---|---|---|

Conventional anchors | 25 | 182 | - | 44 | 24 | 155 | - |

Conventional anchors | 50 | 183 | 227 | 39 | 41 | 233 | - |

Conventional anchors | 80 | 183 | 224 | 35 | 43 | 237 | - |

Constant resistance energy-absorbing anti-scour anchor rods | 25 | - | - | 53 | 23 | 176 | Approx. 152 |

Constant resistance energy-absorbing anti-scour anchor rods | 50 | 183 | - | 77 | 43 | 289 | Approximately 156 |

Constant resistance energy-absorbing anti-scour anchor rods | 80 | 184 | 224 | 65 | 60 | 370 | Approximately 156 |

Anchor Type | Impact Speed/m/s | Yield Load/kN | Breaking Load/kN | Antiflush Time/ms | Rod Impact Resistance Time/ms | Energy Absorption/kJ | Anti-Puncher Give Way Distance/mm | The Distance of the Rod Gives Way/mm | Anti-Scouring Device Bearing Capacity/kN |
---|---|---|---|---|---|---|---|---|---|

Conventional anchors | 2 | 181 | 228 | - | 139 | 44 | - | 242 | - |

Conventional anchors | 4 | 181 | 228 | - | 69 | 43 | - | 239 | - |

Conventional anchors | 6 | 182 | 227 | - | 48 | 44 | - | 245 | - |

Conventional anchors | 8 | 183 | 224 | - | 35 | 43 | - | 237 | - |

Constant resistance energy-absorbing anti-scour anchor rods | 2 | 181 | 227 | 79 | 179 | 66 | 134 | 243 | Approximately 156 |

Constant resistance energy-absorbing anti-scour anchor rods | 4 | 181 | 226 | 39 | 105 | 64 | 132 | 245 | Approximately 149 |

Constant resistance energy-absorbing anti-scour anchor rods | 6 | 184 | 228 | 27 | 74 | 65 | 132 | 243 | Approximately 153 |

Constant resistance energy-absorbing anti-scour anchor rods | 8 | 184 | 224 | 20 | 45 | 60 | 135 | 235 | Approximately 155 |

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**MDPI and ACS Style**

Tang, Z.; Wu, H.; Liu, Y.; Pan, Y.; Lv, J.; Chang, D. Numerical Analysis of Mechanical Characteristics of Constant-Resistance, Energy-Absorbing and Anti-Scour Bolts. *Materials* **2022**, *15*, 3464.
https://doi.org/10.3390/ma15103464

**AMA Style**

Tang Z, Wu H, Liu Y, Pan Y, Lv J, Chang D. Numerical Analysis of Mechanical Characteristics of Constant-Resistance, Energy-Absorbing and Anti-Scour Bolts. *Materials*. 2022; 15(10):3464.
https://doi.org/10.3390/ma15103464

**Chicago/Turabian Style**

Tang, Zhi, Hao Wu, Ying Liu, Yishan Pan, Jinguo Lv, and Dezhi Chang. 2022. "Numerical Analysis of Mechanical Characteristics of Constant-Resistance, Energy-Absorbing and Anti-Scour Bolts" *Materials* 15, no. 10: 3464.
https://doi.org/10.3390/ma15103464