Stability Analysis of Jinchuan Hydropower Station Hydraulic Tunnels during Excavation and Unloading
Abstract
:1. Introduction
2. Engineering Background
3. Study of the MS Activity of the Surrounding Rock
3.1. Temporal Evolution Characteristics of MS Events
3.2. Spatial Evolution Characteristics of MS Events
4. Numerical Modeling of the Excavation of Adjacent Tunnels
4.1. FLAC3D Finite-Difference Software
4.2. Modeling
4.3. Constitutive Model and Parameters
4.4. Mechanical Response of the Surrounding Rock during Step-by-Step Excavation
4.4.1. Deformation Characteristics of the Surrounding Rock
4.4.2. Stress Characteristics of the Surrounding Rock
4.5. Comparison between Numerical Modeling and Monitoring Results
4.6. Comparison between Numerical Modeling and Site Surveys
5. Conclusions
- (1)
- The study focused on the temporal and spatial evolution characteristics of MS events brought on by the excavation and unloading of the spillway tunnel. When the causes of MS event concentration under various working conditions were combined with the site construction conditions, it was determined that the main causes of MS events were construction disturbance and an unfavorable geological structure, which damaged the surrounding rock and made it vulnerable to macroscopic deformation.
- (2)
- In the tunnel at shallow burial depths, there was only a slight stress concentration at some right-angle intersections of the free face due to the low level of ground stress, and the minimum principal stress of the shallow surrounding rock was directed at the free face, while the direction of the maximum principal stress was parallel to that of the tunnel axis, thus helping ensure tunnel stability. In the deeper part of the tunnel, the stress concentration became obvious due to the increased level of ground stress, and the maximum principal stress was nearly perpendicular to the tunnel axis, thus undermining the stability of the tunnel surrounding rock.
- (3)
- By comparing microseismic monitoring results, numerical simulation, and conventional monitoring, it is found that there is a good spatial correspondence between microseismic monitoring and numerical simulation results, as well as good temporal correspondence between numerical simulation results and changes in stress gauges, which proves the feasibility of the comprehensive research method of microseismic monitoring combined with numerical simulation. It can provide reliable technical support for assessing the stability of the surrounding rock.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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Rock | Deformation Modulus | Elastic Modulus | Poisson’s Ratio | Rock/Rock | Allowed Bearing Capacity | |||
---|---|---|---|---|---|---|---|---|
Shearing Strength | Shear Strength | |||||||
E0 (GPa) | ES (GPa) | μ | f | c (MPa) | f | c (MPa) | [R] (MPa) | |
4–5 | 4.5–6 | 0.30–0.35 | 0.65–0.70 | 0.30–0.40 | 0.55–0.60 | 0 | 2.0–3.0 |
Structural Plane Type | f′ | c′ (MPa) | |
---|---|---|---|
f31 | Debris with mud | 0.35–0.40 | 0.05–0.07 |
f27 | Debris with mud | 0.35–0.40 | 0.05–0.07 |
f54 | Debris with mud | 0.35–0.40 | 0.05–0.07 |
Excavation Steps | Excavation Position |
---|---|
Step 1 excavation | Adits and adjacent main tunnels at the inlet and outlet |
Step 2 excavation | Stakes 0 + 160 m to 0 + 240 m and 0 + 724 m to 0 + 824 m in the first layer |
Step 3 excavation | Stakes 0 + 240 m to 0 + 340 m and 0 + 655 m to 0 + 724 m in the first layer |
Step 4 excavation | Stakes 0 + 630 m to 0 + 655 m in the first layer |
Step 5 excavation | Stakes 0 + 323 m to 0 + 414 m and 0 + 530 m to 0 + 630 m in the first layer, and stakes 0 + 724 m to 0 + 824 m in the second layer |
Step 6 excavation | Stakes 0 + 464 m to 0 + 530 m in the first layer |
Step 7 excavation | Stakes 0 + 160 m to 0 + 240 m in the second layer, and stakes 0 + 414 m to 0 + 424 m in the first layer |
Step 8 excavation | Stakes 0 + 424 m to 0 + 464 m in the first layer |
Step 9 excavation | \ |
Step 10 excavation | \ |
Excavation Steps | Excavation Position |
---|---|
Step 1 excavation | Adits and adjacent main tunnels at the inlet and outlet |
Step 2 excavation | Stakes 0 + 165 m to 0 + 290 m and 0 + 790 m to 0 + 890 m in the first layer |
Step 3 excavation | Stakes 0 + 780 m to 0 + 790 m in the first layer |
Step 4 excavation | Stakes 0 + 690 m to 0 + 780 m in the first layer, and stakes 0 + 790 m to 0 + 890 m in the second layer |
Step 5 excavation | Stakes 0 + 590 m to 0 + 690 m in the first layer |
Step 6 excavation | Stakes 0 + 570 m to 0 + 590 m in the first layer |
Step 7 excavation | Stakes 0 + 290 m to 0 + 390 m in the first layer |
Step 8 excavation | \ |
Step 9 excavation | Stakes 0 + 490 m to 0 + 570 m in the first layer |
Step 10 excavation | Stakes 0 + 390 m to 0 + 490 m in the first layer |
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Zhang, Y.; Mao, H.; Li, B.; Sun, Y. Stability Analysis of Jinchuan Hydropower Station Hydraulic Tunnels during Excavation and Unloading. Appl. Sci. 2022, 12, 11660. https://doi.org/10.3390/app122211660
Zhang Y, Mao H, Li B, Sun Y. Stability Analysis of Jinchuan Hydropower Station Hydraulic Tunnels during Excavation and Unloading. Applied Sciences. 2022; 12(22):11660. https://doi.org/10.3390/app122211660
Chicago/Turabian StyleZhang, Yan, Haoyu Mao, Biao Li, and Yuepeng Sun. 2022. "Stability Analysis of Jinchuan Hydropower Station Hydraulic Tunnels during Excavation and Unloading" Applied Sciences 12, no. 22: 11660. https://doi.org/10.3390/app122211660
APA StyleZhang, Y., Mao, H., Li, B., & Sun, Y. (2022). Stability Analysis of Jinchuan Hydropower Station Hydraulic Tunnels during Excavation and Unloading. Applied Sciences, 12(22), 11660. https://doi.org/10.3390/app122211660