# A Method for Predicting the Load Interaction between Reinforced Thermoplastic Pipe and Sandy Soil Based on Model Testing

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## Abstract

**:**

## 1. Introduction

## 2. Experimental System and Content

#### 2.1. Experimental Configuration

- (1)
- Experimental system: In a rectangular soil box, two parallel tracks with a length of 1.5 m were built, and a connection structure with a flexible pipeline was designed to connect the pipe to the motive force transmission device and install it on the soil box. The motive force transmission device was connected to the pressure sensor, and the pipeline was driven horizontally in the soil sample to obtain the relationship curve between the pipe displacement and the soil resistance force.

- A connecting rod: It provides the structural connection between different parts of the mechanism;
- A connecting outer circle: Its diameter is equal to the outer diameter of the pipeline. It ensures the connection between the mechanism and the outer surface of the pipeline;
- A connecting inner embedded circle: Its diameter is equal to the inner diameter of the pipeline. It ensures the connection between the mechanism and the inner surface of the pipeline;
- An anti-rotation latch: It is embedded in the gap of the pipeline to prevent circumferential movement during horizontal motion of the pipeline.

- (2)
- Experimental equipment: The main instruments and components used in this experiment included the following: a soil box size whose length × width × depth = 1.5 m × 1.0 m × 1.0 m, an LTR-1 tension–compression load, sensor, a sliding rail, a pipeline anti-roll and translation device, a motor, etc.
- (3)
- Experimental samples: Flexible, non-metallic pipes with a diameter of 76 mm and sandy soil from the seabed.

#### 2.2. Experiment Content

#### 2.3. Tests Pipe

#### 2.4. Test Soil

#### 2.5. Experimental Process

- Soil shear strength test:

- 2.
- Pipe–soil interaction experiment:

## 3. Numerical Method

#### 3.1. CEL Theoretical Approach

#### 3.2. Modeling Criteria

- Constitutive Model

- b.
- Pipe–Soil Interaction

- c.
- Modeling Dimension Verification

## 4. Results and Discussion

#### 4.1. The Results of the Soil Shear Strength Test

#### 4.2. Pipe-Soil Interaction Experiment Results

- (1)
- Experimental phenomena:

- (2)
- Experimental data

## 5. Conclusions

- (1)
- Within the lateral displacement range of 0.5D, the lateral soil resistance increases rapidly. As the lateral displacement of the pipe increases, the soil climbs along the circumferential direction of the pipe, increasing the load-bearing capacity of the pipe and the accumulated soil resistance. The accumulation of soil leads to a larger range of soil failure.
- (2)
- With an increase in the burial depth, the ultimate soil resistance exhibits an increasing sequence, and the final uplifted height of the soil reaches a critical state. A larger initial burial depth allows for a quicker attainment of the critical soil resistance state. The differences in the final soil resistance among different burial depths decrease gradually, and this conclusion was validated through data calculations.
- (3)
- The CEL method successfully addresses the issue of grid distortion caused by soil deformation and effectively simulates the pipe–soil interaction forces under large lateral displacements. The results of the simulation align well with the experimental findings, demonstrating the effectiveness of this method from both qualitative and quantitative perspectives.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 1.**Sketch of the experimental device. 1—soil box; 2—flexible pipe; 3—anti-roll linkage mechanism; 4—tension–compression load sensor; 5—slide (with wiping lubricant); 6—steel wire; and 7—electric motor.

**Figure 2.**Schematic diagram of the pipe connection. 1—connecting rod, 2—connecting outer circle, 3—connecting inner embedded circle, and 4—anti-rotation latch.

Property | Value |
---|---|

Pipe diameter (mm) | 76 |

Internal friction angle (degrees) | To be tested |

Cohesive strength (Pa) | To be tested |

Soil density (kg·m^{−3}) | 1560 |

Horizontal displacement (mm) | 760 (10 times the pipe diameter) |

Initial embedment | 0.1D, 0.2D, and 0.3D |

No. | Normal Pressure (kPa) | Load Coefficient (kPa·mm ^{−1}) | Load Measurement (mm) | Shear Pressure (kPa) |
---|---|---|---|---|

1 | 100 | 1.572 | 34.72 | 54.58 |

2 | 150 | 1.558 | 70.69 | 110.13 |

3 | 200 | 1.572 | 83.18 | 130.76 |

4 | 250 | 1.585 | 98.69 | 156.42 |

5 | 300 | 1.585 | 122.29 | 193.83 |

6 | 350 | 1.558 | 141.50 | 220.46 |

7 | 400 | 1.558 | 166.90 | 260.03 |

No. | Initial Embedment | Soil Resistance/N | Difference/N |
---|---|---|---|

1 | 0.1D | 160.38 | —— |

2 | 0.2D | 252.69 | 92.30 |

3 | 0.3D | 315.77 | 63.07 |

No. | Initial Embedment | Numerical Simulation/N | Tests/N | Difference/N |
---|---|---|---|---|

1 | 0.1D | 138 | 160.38 | 13.9% |

2 | 0.2D | 231 | 252.69 | 8.6% |

3 | 0.3D | 289 | 315.77 | 8.5% |

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## Share and Cite

**MDPI and ACS Style**

Wang, C.; Liu, L.; Zhang, Y.; Lou, M.
A Method for Predicting the Load Interaction between Reinforced Thermoplastic Pipe and Sandy Soil Based on Model Testing. *J. Mar. Sci. Eng.* **2023**, *11*, 2353.
https://doi.org/10.3390/jmse11122353

**AMA Style**

Wang C, Liu L, Zhang Y, Lou M.
A Method for Predicting the Load Interaction between Reinforced Thermoplastic Pipe and Sandy Soil Based on Model Testing. *Journal of Marine Science and Engineering*. 2023; 11(12):2353.
https://doi.org/10.3390/jmse11122353

**Chicago/Turabian Style**

Wang, Chuan, Lianghai Liu, Ya Zhang, and Min Lou.
2023. "A Method for Predicting the Load Interaction between Reinforced Thermoplastic Pipe and Sandy Soil Based on Model Testing" *Journal of Marine Science and Engineering* 11, no. 12: 2353.
https://doi.org/10.3390/jmse11122353