# Experimental Study on the Deformation and Mechanical Properties of Bamboo Forest Slopes

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## Abstract

**:**

## 1. Introduction

^{2}) of landslide disaster points in various vegetation types, the highest distribution of landslide density is bamboo forest, fir forest, and pine forest. Therefore, it is important to study the instability laws of the slopes of bamboo forest areas for disaster prevention.

## 2. Materials and Methods

#### 2.1. Similarity Ratio Design

#### 2.2. Test Material

^{2}were selected to be excavated to a depth of 25 cm. After removing the soil containing the bamboo rhizomes, the two were separated to obtain complete bamboo rhizomes. The mass ratio of root to dry soil was defined as root content [20], and the average root content in these three areas was calculated to be 0.53%. In the model tests, appropriate lengths and weights of bamboo rhizomes were selected and buried into the model slopes, where the root content was controlled to be around 0.53%. The morphology of the bamboo rhizomes is shown in Figure 2. The parameters of the bamboo rhizomes are shown in Table 3.

#### 2.3. Testing Device

- (1)
- Model box. The L × W × H was 360 cm × 150 cm × 200 cm. Both sides of the model box were made of transparent acrylic plates. The interior was taped with yellow tape to outline the dimensional edges of the designed slope to facilitate subsequent filling and comparison of the displacement changes in the soil before and after the test. To miniaturize the boundary effect of the sidewalls of the model box on the soil, Vaseline was uniformly applied to the interior of the box walls before each slope filling.
- (2)
- Slope top loading system. This system included a jack, a pull pressure sensor, a ball seat, a distribution beam, an iron plate, and a wedge block. To simulate the sliding process of the slope, wedge blocks were buried at the top of the slope to increase the sliding thrust transmitted to the outside of the slope by the jack above. The ball seat placed under the sensor can keep the force of the jack vertically downward to the distribution beam, and then the distribution beam and iron plate would convert the force into a uniform load applied to the upper surface of the wedge block to achieve the loading of the slope top.
- (3)
- Rainfall simulation system. This included angle steels, a water supply piping system, rainfall nozzles, and a flowmeter. The spraying diameter of each rainfall nozzle was 1 m, and the spraying flow rate was 0.8 L/h. There were eight nozzles in total, which were connected through the water supply pipeline. Two rainfall nozzles were fixed on each angle steel, and the angle steels were spaced 60 cm apart and evenly arranged above the model box. A flowmeter was connected to the delivery pipe and was able to measure the amount of liquid passing at a rate of 1–40 L/min. The rainfall system was able to simulate an effective rainfall area of 5 m
^{2}, the rainfall intensity could be controlled at 0–20 mm/h, and the average rainfall uniformity was 82%. - (4)
- Measurement system. The data acquisition system included an IMC_CRFX_400 dynamic data collector and a DH3821 data collector. The displacement and earth pressure sensors adopted the YWD-100-type strain displacement sensor and DMTY-type earth pressure cell, respectively.

#### 2.4. Test Program

## 3. Results

#### 3.1. Deformation Failure Characteristics Analysis

#### 3.2. Slope Horizontal Displacement Analysis

#### 3.3. Slope Earth Pressure Analysis

#### 3.3.1. Horizontal Earth Pressure Analysis along the Slope Direction

#### 3.3.2. Horizontal Earth Pressure Analysis along the Bottom of the Slope

## 4. Discussion

## 5. Conclusions

- (1)
- The bamboo rhizomes could change the failure mode of the slope and make the slope change from block sliding failure to progressive backward failure. Their intertwined root system forms a net-like structure, which will drive more surface soil to slide down during the sliding process of the slope.
- (2)
- In the process of applying the slope top load step-by-step, the horizontal displacement of the slope shows a trend that the top of the slope was large and the foot of the slope was small. Compared with the plain soil slope, the sliding area of the bamboo-rooted slope was significantly increased. Under rainfall conditions, the displacement of the bamboo root slope increased significantly. With the large deformation, the restraint effect of bamboo rhizomes on the soil gradually appeared. The displacement of each measuring point increased nearly linearly with the increase in slope top load.
- (3)
- The bamboo rhizomes could better limit the deformation of the soil at the foot of the slope and improve the compactness of the soil behind the root. The increase in soil pressure at the foot of the slope was larger under the top load of the slope. However, the influence range of bamboo rhizomes on soil was limited, mainly concentrated in the area within 40 cm near the roots. Beyond this area, the reinforcement effect of bamboo rhizomes on soil was not obvious.
- (4)
- Rainfall had a greater impact on the soil in the area closer to the slope surface, and the infiltration of rainwater reduced the effective stress between the soil particles. In the process of loading step-by-step, the slope deformed more, the soil was uncompacted, and the rise in earth pressure was smaller with the increase in load.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 6.**Slope failure after loading in each group of tests. (

**a**) Test G1 plain soil slope. (

**b**) Test G2 bamboo-rooted slope. (

**c**) Test G3 rainfall bamboo-rooted slope.

**Figure 7.**Variation of horizontal displacement in the slope with a slope top load. (

**a**) Test G1 plain soil slope. (

**b**) Test G2 bamboo-rooted slope. (

**c**) Test G3 rainfall bamboo-rooted slope.

**Figure 8.**Displacement of representative measurement points in each group of tests. (

**a**) Measurement point D4. (

**b**) Measurement point D3.

**Figure 9.**Variation of horizontal earth pressure at measured points along the slope with the slope top load (

**a**) Test G1 plain soil slope. (

**b**) Test G2 bamboo-rooted slope. (

**c**) Test G3 rainfall bamboo-rooted slope.

**Figure 10.**Earth pressure of representative measurement points in each group of tests. (

**a**) Measurement point S2. (

**b**) Measurement point S4.

**Figure 11.**Variation of horizontal earth pressure at measured points along the bottom of the slope with the slope top load (

**a**) Test G1 plain soil slope. (

**b**) Test G2 bamboo-rooted slope. (

**c**) Test G3 rainfall bamboo-rooted slope.

**Figure 12.**Earth pressure at representative measurement points in each group of tests. (

**a**) Measurement point S6. (

**b**) Measurement point S7.

Type | Physical Quantities | Dimension | Similarity Relation | Similarity Ratio |
---|---|---|---|---|

Material properties | Stress $\sigma $ | $F{L}^{-2}$ | ${C}_{\sigma}={C}_{E}{C}_{\epsilon}$ | 7 |

Strain $\epsilon $ | — | ${C}_{\epsilon}={C}_{E}{}^{-1}{C}_{l}{C}_{\rho}$ | 1 | |

Elastic modulus $E$ | $M{L}^{-1}{T}^{2}$ | ${C}_{E}$ | 7 | |

Poisson’s ratio $\mu $ | — | ${C}_{\mu}$ | 1 | |

Density $\rho $ | $M{L}^{-3}$ | ${C}_{\rho}$ | 1 | |

Cohesion $C$ | $M{L}^{-1}{T}^{2}$ | ${C}_{C}={C}_{E}{C}_{\epsilon}$ | 7 | |

Internal friction angle $\phi $ | — | — | 1 | |

Geometric properties | Geometrical length $L$ | $L$ | ${C}_{l}$ | 7 |

Displacement $u$ | $L$ | ${C}_{u}={C}_{l}{C}_{\epsilon}{}^{-1}$ | 7 | |

Boundary Condition | Rainfall intensity $q$ | $L{S}^{-1}$ | ${C}_{q}=\sqrt{{C}_{l}}$ | $\sqrt{7}$ |

Time $t$ | $S$ | ${C}_{t}=\sqrt{{C}_{l}}$ | $\sqrt{7}$ |

Soil Type | Unit Weight/ (kN/m ^{3}) | Maximum Dry Density /(g/cm ^{3}) | Poisson’s Ratio | Cohesion/ kPa | Internal Friction Angle/(°) | Optimum Water Content/(%) |
---|---|---|---|---|---|---|

Clay soil | 18.37 | 1.85 | 0.32 | 12 | 18.5 | 14.5 |

Barite powder | 21.58 | 1.94 | 0.38 | 18 | 22.5 | — |

Material Name | Elastic Modulus/ (kPa) | Tensile Strength /(MPa) | Poisson’s Ratio | Volume Weight/(kN/m^{3}) |
---|---|---|---|---|

Bamboo rhizome | 322.3 | 23.06 | 0.28 | 7.8 |

Water Content ω | Depth of Soil Layer | ||||
---|---|---|---|---|---|

5 cm | 10 cm | 15 cm | 20 cm | 25 cm | |

Measuring point 1 | 26.05% | 24.16% | 27.13% | 16.70% | 13.35% |

Measuring point 2 | 23.14% | 24.14% | 24.52% | 23.13% | 17.81% |

Measuring point 3 | 21.95% | 22.87% | 24.88% | 23.88% | 23.50% |

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**MDPI and ACS Style**

Yang, H.; Cao, Z.; Jiang, X.; Wang, Y. Experimental Study on the Deformation and Mechanical Properties of Bamboo Forest Slopes. *Appl. Sci.* **2023**, *13*, 470.
https://doi.org/10.3390/app13010470

**AMA Style**

Yang H, Cao Z, Jiang X, Wang Y. Experimental Study on the Deformation and Mechanical Properties of Bamboo Forest Slopes. *Applied Sciences*. 2023; 13(1):470.
https://doi.org/10.3390/app13010470

**Chicago/Turabian Style**

Yang, Hui, Zhengyi Cao, Xueliang Jiang, and Yixian Wang. 2023. "Experimental Study on the Deformation and Mechanical Properties of Bamboo Forest Slopes" *Applied Sciences* 13, no. 1: 470.
https://doi.org/10.3390/app13010470