# Numerical Simulation Study on the Distribution Characteristics of Precipitation Seepage Field in Water-Rich Ultra-Thick Sand and Gravel Layer

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## Abstract

**:**

## 1. Introduction

## 2. Methods of Analysis

#### 2.1. Universal Model

#### 2.2. Calculation Model

## 3. Distribution Characteristics of Seepage Field in Foundation Pits

#### 3.1. Distribution Characteristics of Seepage Field under the Influence of Precipitation Depth

#### 3.1.1. Effect on Pore Water Pressure

#### 3.1.2. Effect on Flow Velocity

#### 3.1.3. Effect on Water Inflow

#### 3.2. Distribution Characteristics of Seepage Field under the Influence of Aquifer Thickness

#### 3.2.1. Effect on Pore Water Pressure

#### 3.2.2. Effect on Flow Velocity

#### 3.2.3. Effect on Water Inflow

## 4. Model Validation

## 5. Conclusions

- (1)
- Under the condition of the suspended water-stop curtain, the pore water pressure on the outer side of the water-stop curtain is greater than that on the inner side of the foundation pit. It increases linearly with an increase in the precipitation depth. As the aquifer thickness increases, it increases. The pore water pressure distribution characteristics deeply influence the dynamic water level curve.
- (2)
- Under the condition of the suspended water-stop curtain, the maximum seepage flow velocity occurs at the position where the curtain’s bottom leans towards the inner side of the foundation pit. The maximum seepage flow velocity increases linearly with an increase in the precipitation depth, and there is a threshold value for the aquifer thickness, which is five times the precipitation depth.
- (3)
- Under the condition of the suspended water-stop curtain, the relationship between the precipitation depth and water inflow can be described by a linear or parabolic function; the relationship between the aquifer thickness and water inflow can be described by a logistic function.
- (4)
- The calculation results are compared with the measured water level measurements. The average error of the water level drop in the pit and precipitation well under the suspended water-stop curtain condition is 11.7%, indicating that the established numerical model can meet the calculation requirements.

## Author Contributions

## Funding

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 4.**Transverse section velocity distribution and seepage path at different precipitation depths (i.e., y = 105) (m/s).

**Figure 10.**Transverse section velocity distribution and seepage path at different aquifer thicknesses (i.e., y = 105) (m/s).

Soil Layer Number | Soil Layer | Thickness | Physical and Mechanical Parameters | ||||||
---|---|---|---|---|---|---|---|---|---|

Poisson’s Ratio | Density (kg/m^{3}) | Elastic Modulus (MPa) | Permeability Coefficient (m/d) | Internal Friction Angle (°) | Cohesive Force (MPa) | Void Ratio | |||

1 | Miscellaneous fill, loess- shaped silty clay | 2 | 0.35 | 1750 | 15.4 | 6 | 20 | 0.022 | 0.9 |

2 | Fine sand | 6 | 0.30 | 1850 | 24 | 15 | 20 | 0 | 0.46 |

3 | Loose to slightly dense sandy and gravel | 6 | 0.25 | 2100 | 46 | 60 | 30 | 0 | 0.42 |

4 | Medium-dense to dense sand and gravel | 16 | 0.25 | 2200 | 120 | 80 | 35 | 0 | 0.39 |

5 | Dense sand and gravel | 70 | 0.22 | 2200 | 120 | 60 | 42 | 0.36 | |

6 | Impermeable bedrock | 20 | 0.20 | 2500 | 1500 | - | - | - | 0.2 |

7 | Enclosure structure | - | 0.20 | 2500 | 3100 | 80 | - | - | 0.2 |

**Table 2.**Calculation conditions and parameter settings for the influence of precipitation depth on the seepage field.

Calculation Conditions | Parameter Setting Values | |||||
---|---|---|---|---|---|---|

Precipitation depth (m) | 4 | 6 | 8 | 10 | 12 | 14 |

Groundwater level (m) | 104 | 106 | 108 | 110 | 112 | 114 |

Silty clay bottom (m) | 114 | |||||

Medium-dense to dense pebble bottom (m) | 24 | 26 | 28 | 30 | 32 | 34 |

Impermeable bedrock (m) | 0~24 | 0~26 | 0~28 | 0~30 | 0~32 | 0~34 |

The bottom of the suspended water-stop curtain (m) | 86 |

Precipitation Depth (m) | Projected Area (m^{2}) | Maximum Seepage Flow Velocity (mm/s) | |||
---|---|---|---|---|---|

>0.1875 mm/s | >0.375 mm/s | >0.5625 mm/s | >0.75 mm/s | ||

4 | 0 | 0 | 0 | 0 | 0.18 |

6 | 31.1 | 0 | 0 | 0 | 0.28 |

8 | 174.66 | 2 | 0 | 0 | 0.38 |

10 | 194 | 4 | 0 | 0 | 0.45 |

12 | 238.39 | 8 | 0 | 0 | 0.54 |

14 | 273.928 | 84 | 4 | 0 | 0.66 |

**Table 4.**Calculation conditions and parameter settings for the influence of aquifer thickness on seepage field.

Calculation Conditions | Parameter Setting Values | ||||
---|---|---|---|---|---|

Precipitation depth (m) | 8 | ||||

Groundwater level (m) | 108 | ||||

Silty clay bottom (m) | 114 | ||||

Medium-dense to dense gravel bottom (m) | 88 | 68 | 48 | 28 | 8 |

Impermeable bedrock (m) | 0~88 | 0~68 | 0~48 | 0~28 | 0~8 |

The bottom of the suspend water-stop curtain (m) | 92 |

Aquifer Thickness (m) | Projected Area (m^{2}) | Maximum Seepage Flow Velocity (mm/s) | |||
---|---|---|---|---|---|

>0.1875 mm/s | >0.375 mm/s | >0.5625 mm/s | >0.75 mm/s | ||

20 | 24.33 | 0 | 0 | 0 | 0.37 |

40 | 50.66 | 0 | 0 | 0 | 0.32 |

60 | 115.05 | 2 | 0 | 0 | 0.40 |

80 | 128.00 | 4 | 0 | 0 | 0.44 |

100 | 136.00 | 4 | 0 | 0 | 0.46 |

**Table 6.**Measurement and calculation results of water level drop in foundation pit ends and dewatering wells.

Position | Measurement Value | Calculated Value of Water Level Drop (m) | |
---|---|---|---|

Elevation (m) | Water Level Drop Value (m) | ||

B8 | 112.50 | 1.78 | 1.53 |

J6 | 101.78 | 12.50 | 13.9 |

J9 | 112.38 | 1.90 | 2.01 |

J70 | 112.39 | 1.88 | 1.98 |

J72 | 109.45 | 4.83 | 5.08 |

West End Head | 105.9 | 8.38 | 9.02 |

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## Share and Cite

**MDPI and ACS Style**

Li, D.; Cheng, S.; Liu, N.; Liu, Z.; Sun, Y.
Numerical Simulation Study on the Distribution Characteristics of Precipitation Seepage Field in Water-Rich Ultra-Thick Sand and Gravel Layer. *Water* **2023**, *15*, 3720.
https://doi.org/10.3390/w15213720

**AMA Style**

Li D, Cheng S, Liu N, Liu Z, Sun Y.
Numerical Simulation Study on the Distribution Characteristics of Precipitation Seepage Field in Water-Rich Ultra-Thick Sand and Gravel Layer. *Water*. 2023; 15(21):3720.
https://doi.org/10.3390/w15213720

**Chicago/Turabian Style**

Li, Da, Shukai Cheng, Ningyi Liu, Zhongxin Liu, and Yinghao Sun.
2023. "Numerical Simulation Study on the Distribution Characteristics of Precipitation Seepage Field in Water-Rich Ultra-Thick Sand and Gravel Layer" *Water* 15, no. 21: 3720.
https://doi.org/10.3390/w15213720