# Research on the Early Warning Model for Pipelines Due to Landslide Geohazards under Multiple Influencing Factors

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## Abstract

**:**

## 1. Introduction

## 2. Site Survey

## 3. Numerical Simulation

#### 3.1. Simulation of Working Conditions

#### 3.2. Simulation Parameters

^{2}is applied to all the elements. The pressure inside the pipeline is 2.4 MPa. The z-direction displacement of the left and right planes of the soil is fixed. The x-direction displacement in front and back and all displacement of the bottom of the soil are fixed. At the same time, the z-direction displacement of the pipeline is fixed.

#### 3.3. Simulation Results

#### 3.3.1. The Pipeline Crossing Landslide Laterally

#### 3.3.2. The Pipeline Crossing Landslide Longitudinally

#### 3.4. Discussion of Simulation Results

- Whether the pipe crosses the landslide laterally or longitudinally, the effects of landslide slope, landslide thickness, and landslide length on pipeline deformation are consistent with the same trend, which means that the degree of pipeline deformation is increasing with those variables. It is because both the mass of the unstable soil above the pipe and the unbalance force become larger as these quantities become larger. Thus, the deformation of the pipeline becomes larger.
- When the pipeline crosses the landslide laterally, it is noticed that the pipeline deformation decreases with the increasing width of the landslide body. The smaller the landslide width is, the more concentrated the strain is, and, therefore, the larger the pipeline deformation is.
- When the pipeline crosses the landslide laterally, the pipelines are relatively safe at the leading edge of the landslide body, followed by the trailing edge of the landslide body, and are most dangerous in the middle of the landslide body. The unbalanced force is the slightest because the soil at the front edge of the landslide body is supported by the stable soil below. Thus, the deformation of pipelines is minor when the pipeline is located at the front edge of the landslide body. Furthermore, the unstable soil mass carried in the middle of the landslide body is more significant than that at the back edge of the landslide body. Therefore, the pipeline in the middle of the landslide body shows the most significant deformation.

## 4. Quantitative Impact of Influencing Factors and Early Warning Models

#### 4.1. Quantitative Impact of Influencing Factors

_{n}denotes the influence factors, f(x

_{n}) is the influence function, the subscript n is the total number of factors, and K is the benchmark data.

#### 4.2. Discussion of the Early Warning Models

_{S}< 1.05). At this moment, the pipeline performs a recognizable degree of deformation along with the deformation of landslide soil. Damage and leakage are less likely to occur. Therefore, the warning level is the caution level at this stage. (3) With the normalized soil displacement continuously increasing to 0.65, the safety coefficient of the landslide is lower than 1.05, and the landslide is in an unstable state. The ovality of the pipeline is close to the threshold. However, the maximum strain of the pipeline is still under the set threshold value. Thus, the warning level is the alarm level. (4) As the normalized soil displacement remains increasing to 1.3, the landslide is in the unstable stage (F

_{S}< 1.05). At this time, the ovality of the pipeline has gone beyond the set threshold value, and the max strain of the pipeline also exceeds over 3% of the threshold of strain with an accelerating trend. According to the “Gas Transmission Pipeline Engineering Design Regulations” in China, the pipeline is currently in an unstable and damaged state; there is a huge possibility that the damage leads to leakage of the pipeline located in the landslide zone; meanwhile, various short-term precursor features are apparent. Naturally, the warning level is the catastrophe level.

## 5. Conclusions

- Through a field investigation, we found that the scale of landslides, including the length, width, slope, and thickness, and the relative position of the pipeline landslide are the main factors determining the deformation of pipelines induced by landslides. The degree of the pipeline’s deformation was determined by the relative position between the pipeline’s location and the landslide and the landslide scale.
- Based on numerical simulation, no matter whether the pipeline crosses the landslide laterally or longitudinally, with the increase of the landslides’ angles, thicknesses, and lengths, the deformation characteristic of pipelines appears almost identical. The deformation of pipelines keeps continues to increase. The smaller the landslide width is, the more concentrated the strain is, and therefore, the larger the pipeline deformation is.
- When the pipelines cross the landslides laterally, the deformation of pipelines reduces with the broadening of the width of landslides, it is safer for the pipelines buried in the leading edge of landslides than the tail edge, and it is most dangerous when the pipelines are located in the middle of landslides.
- Considering the variation of the scale, a piecewise forewarning model including multiple parameters was established based on the influence function for crossing pipelines in landslides.

## Author Contributions

## Funding

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## Abbreviations

InSAR | Interferometric synthetic aperture radar |

FBG | Fiber Bragg grating |

SSAW | Steel pipe of spiral seam submerged arc welded |

ILDTs | In-line device technologies |

TTBTs | Transient test-based techniques |

ρ | Density |

E | Elastic modulus |

φ | Internal friction |

C | Cohesive force |

D | Outside diameter of the pipeline |

T | Thickness of pipeline |

μ | Poisson’s ratio |

σ_{S} | Minimum yield strength |

d | Deformation of pipeline |

x_{n} | Influence factor |

f(x_{n}) | Influence function |

K | Benchmark data |

A | Slope of the landslide body |

w | Width of the landslide body |

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**Figure 1.**One example of the field survey of a landslide along the pipeline in the southeast areas of China.

**Figure 2.**Model configuration: (

**a**) pipeline crossing landslide laterally; (

**b**) pipeline crossing landslide longitudinally.

**Figure 3.**The influences of relative locations between landslide and pipeline (laterally): (

**a**) the maximum strain; (

**b**) the variation of ovality.

**Figure 4.**The influences of thickness of the main landslide body (laterally): (

**a**) the maximum strain; (

**b**) the variation of ovality.

**Figure 5.**The influences of the width of the main landslide body (laterally): (

**a**) the maximum strain; (

**b**) the variation of ovality.

**Figure 6.**The influences of the length of landslide the main body (laterally): (

**a**) the maximum strain; (

**b**) the variation of ovality.

**Figure 7.**The influences of the slope of landslide (laterally): (

**a**) the maximum strain; (

**b**) the variation of ovality.

**Figure 8.**The influences of thickness of landslide (longitudinally): (

**a**) the maximum strain; (

**b**) the variation of ovality.

**Figure 9.**The influences of the length of landslide (longitudinally): (

**a**) the maximum strain; (

**b**) the variation of ovality.

**Figure 10.**The influences of the slope of landslide (longitudinally): (

**a**) the maximum strain; (

**b**) the variation of ovality.

**Figure 11.**Schematic diagram of early warning model: (

**a**) pipeline crossing landslide horizontally; (

**b**) pipeline crossing landslide vertically.

Category | Value | |
---|---|---|

landslide | width (m) | 30/40/50 |

thickness (m) | 3/4.5/6 | |

slope (°) | 20/30/40 | |

length (m) | 30/60/90 | |

relative location of the pipeline | pipeline crossing landslide laterally | leading edge/middle/tail edge |

pipeline crossing landslide longitudinally | middle |

Materials | State | Density ρ (kg/m³) | Elastic Modulus E (MPa) | Poisson’s Coefficient μ | Internal Friction φ (°) | Cohesive Force C (kPa) |
---|---|---|---|---|---|---|

Landslide body | saturated | 2360 | 20 | 0.35 | 15.0 | 13.0 |

Support area | natural | 1980 | 20 | 0.3 | 18.0 | 25.0 |

Basement of slope | / | 2600 | 5.56 × 10^{4} | 0.23 | 35.0 | 26.0 |

Item | Value | Item | Value |
---|---|---|---|

Steel types | L320 | Outside diameter D (mm) | 610 |

Elastic modulus E (MPa) | 2.1 × 10^{5} | Thickness T (mm) | 7.9 |

Poisson’s ratio μ | 0.25 | Minimum yield strength σ _{S} (MPa) | 320 |

Density ρ (kg/m ^{3}) | 7800 |

**Table 4.**The influence function of impact factors when the pipeline crosses the landslide laterally.

Category | Function |
---|---|

Relative location | Not considering other influence factors, the deformation degree of the pipeline in the middle of the landslide is 1.6 times at the leading edge of the landslide, and the deformation degree of a pipeline at the tail edge is 1.4 times at the leading edge |

Slopes of landslide | $0.6+0.01\times A$ |

Thickness of landslide | $0.1+13.05\times \frac{D}{W}-40.05\times {(\frac{D}{W})}^{2}$ |

Lengths of landslide | $0.7+0.1\times \frac{L}{W}$ |

Global influence function | $(0.6+0.01\times A)\times (0.1+13.05\times \frac{D}{W}-40.05\times {(\frac{D}{W})}^{2})\times (0.7+0.1\times \frac{L}{W})\times \frac{K}{W}=\frac{d}{W}$ |

**Table 5.**The influence function of impact factors when the pipeline crosses the landslide longitudinally.

Category | Function |
---|---|

Slopes of landslide | $0.45A+5\times {10}^{-4}{A}^{2}$ |

Thickness of landslide | $0.475-0.25\frac{D}{W}$ |

Lengths of landslide | $0.7+6\times {10}^{-3}\frac{L}{W}-2.8\times {10}^{-5}{(\frac{L}{W})}^{2}$ |

Global influence function | $(0.45A+5\times {10}^{-4}{A}^{2})\times (0.475-0.25\frac{D}{W})\times (0.7+6\times {10}^{-3}\frac{L}{W}-2.8\times {10}^{-5}{(\frac{L}{W})}^{2})\times \frac{K}{W}=\frac{d}{W}$ |

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## Share and Cite

**MDPI and ACS Style**

Ning, P.; Jiang, Y.-j.; Tang, J.-j.; Xie, Q.-j.
Research on the Early Warning Model for Pipelines Due to Landslide Geohazards under Multiple Influencing Factors. *Water* **2023**, *15*, 693.
https://doi.org/10.3390/w15040693

**AMA Style**

Ning P, Jiang Y-j, Tang J-j, Xie Q-j.
Research on the Early Warning Model for Pipelines Due to Landslide Geohazards under Multiple Influencing Factors. *Water*. 2023; 15(4):693.
https://doi.org/10.3390/w15040693

**Chicago/Turabian Style**

Ning, Po, Yuan-jun Jiang, Jun-jie Tang, and Qi-jun Xie.
2023. "Research on the Early Warning Model for Pipelines Due to Landslide Geohazards under Multiple Influencing Factors" *Water* 15, no. 4: 693.
https://doi.org/10.3390/w15040693