# Permeability Tests and Numerical Simulation of Argillaceous Dolomite in the Jurong Pumped-Storage Power Station, China

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Case Study

#### 2.1. Project Overview

^{3}. The normal storage level of the lower reservoir is 81 m with a total storage capacity of 20.35 million m

^{3}. The power station consists of the upper and lower reservoirs, dams, water conveyance systems, underground powerhouses, and permanent flood discharge structures (Figure 1) [26]. The upper reservoir is located on the southwest side of the main peak of Lunshan Mountain and is formed by excavating and filling the valleys of the main peak of Lunshan Mountain. The lower reservoir is formed by damming at the Zimei Bridge, which is mainly located at the tail of Lunshan Reservoir. It is equipped with drainage holes and a spillway. Within the main peak of Lunshan Mountain, the water conveyance system and underground powerhouses are placed with a total length of approximately 1400 m. The underground powerhouse area is mainly located at elevations of 30 m to 40 m.

#### 2.2. Stratal and Distribution Characteristics of Argillaceous Dolomite

_{2}dn) mainly consists of fine crystal dolomite and internal clastic dolomite with a thickness of 150–227 m. The Cambrian Guanyintai Group (∈

_{2–3}gn) is mainly composed of chert-bearing nodules or chert-banded dolomite mixed with argillaceous and calcareous dolomite with a thickness of 150–210 m. Baotaishan Group (∈

_{1}p) mainly consists of a thin (less than 10 cm) to medium (10–50 cm) layer of argillaceous dolomite, siliceous dolomite, and cataclastic dolomite with an exposed thickness of 39–78 m. The argillaceous dolomite is thin, and the surface is strongly weathered. The upper section of the Mufushan Group (∈

_{1}m

^{2}) is mainly composed of phosphorous siliceous rock, phosphorous limestone dolomite, phosphorite, thick-bedded. Permian Longtan Group (P

_{2}l) comprises carbonaceous mudstone and argillaceous siltstone, which is distributed around the water inlet or outlet of the lower reservoir with a thickness of about 100 m.

## 3. Methods

#### 3.1. Water Pressure Test

#### 3.2. Seepage Failure Test

#### 3.3. Variable Head Permeability Test

_{1}and h

_{2}represent the water head values in the variable head pipe at t

_{1}and t

_{2}, respectively.

#### 3.4. Numerical Simulation Method

_{m}is the liquid source or sink term, D represents the position head, ρ is the fluid density, i.e., the density of water, g is gravitational acceleration, η is the fluid viscosity, C

_{m}is the water capacity, S

_{e}denotes the saturation, S is the water storage coefficient, k

_{r}is the relative hydraulic conductivity, κ

_{s}is the saturation hydraulic conductivity, and p refers to the pressure. The mixed boundary conditions in COMSOL can be expressed as

_{b}is the external conductivity, when R

_{b}= 0, the mixed boundary is the second type of boundary condition, and when R

_{b}approaches infinity, it is the first type of boundary condition, n is the direction of the normal outside the boundary plane, z is the axis coordinate, N

_{0}is the inward flux, H

_{b}represents the external total head, z

_{b}is the external elevation, p

_{b}is the external pressure, and H is the total hydraulic head.

## 4. Analysis of Results and Discussion

#### 4.1. Permeability Tests

^{−6}to 1.0 × 10

^{−4}cm/s, among which the hydraulic conductivity of argillaceous dolomite is 1.55 × 10

^{−5}to 4.54 × 10

^{−5}cm/s. Some 34 sections of water pressure tests were conducted on the underground powerhouse, and the results showed that the permeability of rock masses in different layers did not differ significantly, mainly in weakly permeable rock layers. The permeability of most test sections was 5–7 Lu; however, dissolution fractures were relatively well developed near the groundwater level, and the permeability of rock masses below the groundwater level was 4.44–6.3 Lu. The water pressure test did not reveal the existence of large karst leakage channels. According to Equation (2), the hydraulic conductivity of the rock strata in the underground powerhouse area is calculated to be between 1.0 × 10

^{−6}to 1.0 × 10

^{−4}cm/s.

^{−5}and 3.98 × 10

^{−5}cm/s with an average value of 2.90 × 10

^{−5}cm/s. The hydraulic conductivity of UP1 and UP2 in the underground powerhouse is not significantly different, while the hydraulic conductivity of UP3 is about three to four times that of UP1 and UP2. The hydraulic conductivity of the argillaceous dolomite in the underground powerhouse varies between 0.99 × 10

^{−4}and 5.77 × 10

^{−4}cm/s with an average value of 2.31 × 10

^{−4}cm/s. Both are argillaceous dolomites, and the underground powerhouse area is about eight times larger than the upper reservoir area. Whether in the upper reservoir or underground powerhouse, the test results of hydraulic conductivity by the laboratory tests are consistent with the results of water pressure tests. These parameters are used as the initial values for the parameter inversion of the numerical model.

#### 4.2. Seepage Failure Tests

#### 4.3. Numerical Simulation

#### 4.3.1. Model Area Discretization

#### 4.3.2. Parameter Inversion Results

_{x}, K

_{y}, and K

_{z}, for fractured rocks, are 0.26 m/d, 0.34 m/d, and 0.17 m/d, respectively.

#### 4.3.3. Simulation and Prediction Results of Groundwater

## 5. Conclusions

^{−5}to 3.98 × 10

^{−5}cm/s with an average value of 2.90 × 10

^{−5}cm/s. The hydraulic conductivity of argillaceous dolomite in the underground powerhouse in the underground powerhouse is 0.99 × 10

^{−4}to 5.77 × 10

^{−4}cm/s with an average value of 2.31 × 10

^{−4}cm/s, which provides reliable permeability parameters for numerical modelling. The critical water pressure of argillaceous dolomite without lateral pressure was determined through seepage failure tests. The results showed that the critical water pressure values of UP1 and UP2 were 1.5 MPa and 1.6 MPa, respectively. Due to the normal storage water level of 267 m in the upper reservoir, the maximum static water pressure at the underground powerhouse is about 2.6 MPa, which is greater than the test value associated with argillaceous dolomite, giving rise to the possibility of seepage failure, but when anti-seepage and drainage measures were taken in the underground powerhouse, the maximum calculated water head was 98 m. The value did not reach the critical value of seepage failure for argillaceous dolomite, indicating the importance of anti-seepage and drainage systems in the underground powerhouse area.

## Author Contributions

## Funding

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

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**Figure 3.**Photos of argillaceous dolomite in the study area (

**a**) upper reservoir, and (

**b**) underground powerhouse.

**Figure 4.**The model device for seepage failure test (

**a**) sketch map, and (

**b**) experimental model device.

**Figure 6.**Curves of seepage failure tests for argillaceous dolomite (

**a**) P-Q curve, and (

**b**) Q-t curve.

Number | Distribution Location | Occurrence | Width (mm) | Geological Description | Exposure Length (m) |
---|---|---|---|---|---|

UR1 | Northwest side of the upper reservoir | N75° E SW∠45° | 15–40 | It is yellow-brown and contains mud and rock debris. It is weakly weathered with siliceous material. There is a small leakage at the contact surface of dolomite. | |

UP1 | Right side of underground powerhouse | N75° W SW∠45° | 15–20 | It is grey-yellow, mixes with mud, and is weakly to slightly weathered during excavation. It exhibits complete to strong weathering after exposure to the air. | |

UP2 | N75° W SW∠45° | 15–20 | It is white and greyish-yellow and exhibits weak weathering. | ||

UP3 | N75° E SE∠60° | 15–20 | It is grey-white and yellowish-brown, contains mud, and exhibits slight weathering. |

Number of Tests | Hydraulic Conductivity (cm/s) | |||
---|---|---|---|---|

UR1 | UP1 | UP2 | UP3 | |

1 | 2.657 × 10^{−5} | 1.078 × 10^{−4} | 0.987 × 10^{−4} | 5.769 × 10^{−4} |

2 | 3.128 × 10^{−5} | 1.188 × 10^{−4} | 1.130 × 10^{−4} | 4.903 × 10^{−4} |

3 | 2.662 × 10^{−5} | 1.182 × 10^{−4} | 1.203 × 10^{−4} | 3.255 × 10^{−4} |

4 | 2.084 × 10^{−5} | 1.226 × 10^{−4} | 1.428 × 10^{−4} | 3.831 × 10^{−4} |

5 | 3.983 × 10^{−5} | 1.287 × 10^{−4} | 1.457 × 10^{−4} | 4.066 × 10^{−4} |

Number of Boreholes | Measured Groundwater Level (m) | Calculated Groundwater Level (m) | Absolute Error (m) | Relative Error (%) |
---|---|---|---|---|

Z2 | 80.30 | 79.6 | 0.70 | 0.19 |

Z4 | 158.90 | 159.65 | 0.75 | 0.47 |

Z5 | 151.33 | 151.16 | 0.17 | 0.11 |

Z9 | 130.20 | 130.28 | 0.08 | 0.06 |

Z10 | 120.70 | 121.53 | 0.83 | 0.53 |

Z13 | 131.52 | 131.8 | 0.28 | 0.21 |

Z15 | 127.92 | 128.74 | 0.82 | 0.64 |

Z16 | 151.96 | 150.47 | 1.49 | 0.98 |

Z17 | 150.12 | 149.13 | 0.99 | 0.66 |

Z21 | 177.17 | 177.58 | 0.41 | 0.23 |

**Table 4.**Design schemes of anti-seepage and drainage for underground powerhouse area and calculated water pressures.

Number of Schemes | The Upper/Lower Reservoir Water Level (m) | Anti-Seepage and Drainage Measures | Calculated Hydraulic Head (m) | Critical Head for Seepage Failure for UP1 (m) | Critical Head for Seepage Failure for UP2 (m) | Seepage Failure |
---|---|---|---|---|---|---|

1 | 267/81 | Fully enclosed anti-seepage and drainage | 80 | 160 | 150 | No |

2 | 267/81 | Anti-seepage and drainage around the underground powerhouse | 82 | 160 | 150 | No |

3 | 267/81 | No anti-seepage measures | 160 | 160 | 150 | Yes |

4 | 267/81 | Anti-seepage and drainage around the underground powerhouse | 98 | 160 | 150 | No |

5 | 246/81 | Fully enclosed anti-seepage and drainage | 59 | 160 | 150 | No |

6 | 246/81 | Anti-seepage and drainage around the underground powerhouse | 61 | 160 | 150 | No |

7 | 246/81 | No anti-seepage measures | 140 | 160 | 150 | No |

8 | 246/81 | Anti-seepage and drainage around the underground powerhouse | 77 | 160 | 150 | No |

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## Share and Cite

**MDPI and ACS Style**

Zhu, X.; Yang, W.; Zhang, J.; Huang, Y.; Zou, L.
Permeability Tests and Numerical Simulation of Argillaceous Dolomite in the Jurong Pumped-Storage Power Station, China. *Water* **2023**, *15*, 3320.
https://doi.org/10.3390/w15183320

**AMA Style**

Zhu X, Yang W, Zhang J, Huang Y, Zou L.
Permeability Tests and Numerical Simulation of Argillaceous Dolomite in the Jurong Pumped-Storage Power Station, China. *Water*. 2023; 15(18):3320.
https://doi.org/10.3390/w15183320

**Chicago/Turabian Style**

Zhu, Xufen, Wenjie Yang, Jie Zhang, Yong Huang, and Lifang Zou.
2023. "Permeability Tests and Numerical Simulation of Argillaceous Dolomite in the Jurong Pumped-Storage Power Station, China" *Water* 15, no. 18: 3320.
https://doi.org/10.3390/w15183320