Formation mechanism of deep fractures in near-dam slope of Jinping I Hydropower Station and their influence on long-term slope deformation

WEI Chengyao; ZHUANG Wenyu; WANG Tao; GAO Chenfeng; LIU Yaoru; YANG Qiang

doi:10.16511/j.cnki.qhdxxb.2024.26.044

PDF(16108 KB)

Journal of Tsinghua University(Science and Technology) ›› 2024, Vol. 64 ›› Issue (11) : 1944-1954. DOI: 10.16511/j.cnki.qhdxxb.2024.26.044

SPECIAL SECTION: WATER ENGINEERING AND GEOTECHNICS

Formation mechanism of deep fractures in near-dam slope of Jinping I Hydropower Station and their influence on long-term slope deformation

{{article.zuoZhe_EN}}

Author information +

History +

Abstract

[Objective] There have been numerous cases of dam failures caused by slope instability in water conservancy projects domestically and internationally, leading to significant casualties and property losses. Therefore, the stability of the slopes near the river banks is crucial for the operational safety of dams and hydropower stations. The Jinping Dam, features a massive engineering slope on its left bank. For approximately 10 years following the commencement of operations at the Jinping I Hydropower Station, certain areas near the dam on the left bank have exhibited persistent deformation, and the underlying mechanisms are still not fully understood. The presence of deep cracks on the left bank significantly influences the selection of the arch dam axis during the design phase. [Methods] This paper utilizes numerical simulation to analyze the variation characteristics of in-situ stress during the evolution of the river valley, aiming to clarify the influencing factors and mechanical mechanisms behind the formation of deep fractures. Additionally, by leveraging monitoring data on slope deformation and conducting a creep analysis of river valley evolution, this paper examines the relationship between deep fractures and the continuous deformation of the slope during operation. [Results] This study found that the formation of deep fractures was closely related to valley incision, the complex geological conditions, and the tectonic stress of the valley slope. Owing to these factors, the unloading depth gradually decreased with a decrease in elevation. Consequently, when the rock mass at higher elevations experienced unloading at greater depths, the rapid release of strain energy occurred during the later stages of valley incision, which led to the unloading failure of the deep rock mass and the formation of deep fractures. Moreover, although the rock mass at lower elevations only experienced surface unloading failure, as the depth increased, the ratios of principal compressive stress and principal tensile stress decreased and the former remained at a high value. This resulted in compressive shear failure and the formation of deep fractures in the deep rock mass. Monitoring data showed that the arch thrust of the dam body hindered deformation in the empty direction, and displacement at high elevations was mainly due to gravity-driven tipping deformation. A comparison of apparent and deep deformation revealed that lamprophyre dikes, faults, and other weak zones were the main factors affecting slope deformation during operation, while the influence of deep fractures was not significant. Additionally, the tectonic stress of the mountain on the left bank had minimal impact on slope deformation. The results of the creep calculations were consistent with the observed deformation patterns of the slope during operation, further confirming that the influence of tectonic stress on slope deformation had dissipated. [Conclusions] In summary, this paper identifies the causes and mechanical mechanisms of deep fractures through finite element calculations and analysis of measured monitoring data, enhancing the engineering understanding of such slope issues. Compared with weak zones such as faults, deep fractures have less influence on the long-term deformation of the slope. The influence of tectonic stress on slope deformation has dissipated, which provides a foundation for further studies on the left bank slope of Jinping I Hydropower Station.

Key words

Jinping I / rock slope / deep fractures / evolution of river valley / creep

Cite this article

EndNote

Ris (Procite)

Bibtex

Download Citations

WEI Chengyao, ZHUANG Wenyu, WANG Tao, GAO Chenfeng, LIU Yaoru, YANG Qiang. Formation mechanism of deep fractures in near-dam slope of Jinping I Hydropower Station and their influence on long-term slope deformation[J]. Journal of Tsinghua University(Science and Technology). 2024, 64(11): 1944-1954 https://doi.org/10.16511/j.cnki.qhdxxb.2024.26.044

References

[1] 王小群, 王兰生, 沈军辉, 等. 西南某电站坝址区岸坡深裂缝分布规律 [J]. 重庆大学学报(自然科学版), 2003, 26(9): 14-17. WANG X Q, WANG L S, SHEN J H, et al. Disquisition on distributing law of bank slope deep fracture of an electricity station dam site section at southwest [J]. Journal of Chongqing University (Natural Science Edition), 2003, 26(9): 14-17. (in Chinese)
[2] 陈鸿. 大渡河中下游典型岸坡深部裂缝形成机制及工程效应研究 [D]. 成都: 成都理工大学, 2005. CHEN H. A study on the formation mechanic and engineering effect of deep crack in typical slopes of middle and lower reaches of the Dadu River [D]. Chengdu: Chengdu University of Technology, 2005. (in Chinese)
[3] 黄润秋, 王士天, 张倬元, 等. 中国西南地壳浅表层动力学过程及其工程环境效应研究 [M]. 成都: 四川大学出版社, 2001. HUANG R Q, WANG S T, ZHANG Z Y, et al. The dynamic process of earth's superficial crust and its engineering environmental effects in southwestern of China [M]. Chengdu: Sichuan University Press, 2001. (in Chinese)
[4] 韩文峰. 黄河黑山峡大柳树松动岩体工程地质研究 [M]. 兰州: 甘肃科学技术出版社, 1993. HAN W F. Engineering geological research on the loose rock mass at Daliushu of Heishan Gorge in Yellow River [M]. Lanzhou: Gansu Science & Technology Press, 1993. (in Chinese)
[5] 杨永明. 苗家坝水电站坝区加坡典型楔形体的变形破坏特征 [J]. 甘肃电力, 1995(2): 28-33, 51. YANG Y M. The deformation and damage character of typical wedge in abutment slope at Miaojiaba Hydropower Station [J]. Gansu Electric, 1995(2): 28-33, 51. (in Chinese)
[6] 韩刚, 赵其华, 彭社琴. 白鹤滩水电站坝区深部破裂岩体地应力演化特征 [J]. 岩土力学, 2011, 32(S1): 583-589. HAN G, ZHAO Q H, PENG S Q. In-situ stress field evolution of deep fracture rock mass at dam area of Baihetan Hydropower Station [J]. Rock and Soil Mechanics, 2011, 32(S1): 583-589. (in Chinese)
[7] 梁靖, 裴向军, 罗路广, 等. 锦屏一级水电站左岸高边坡变形监测及稳定性分析 [J]. 水利水电技术(中英文), 2021, 52(4): 180-185. LIANG J, PEI X J, LUO L G, et al. Deformation monitoring and stability analysis of left bank highslope at Jinping I Hydropower Station [J]. Water Resources and Hydropower Engineering, 2021, 52(4): 180-185. (in Chinese)
[8] 周绿, 刘明昌. 锦屏一级水电站运行期左岸边坡稳定性分析 [J]. 水利水电快报, 2021, 42(6): 26-30. ZHOU L, LIU M C. Stability analysis of slope on left bank of Jinping I Hydropower Station during operation period [J]. Express Water Resources & Hydropower Information, 2021, 42(6): 26-30. (in Chinese)
[9] 梁瑶. 深切河谷地区的地应力场研究和高边坡稳定性评价 [D]. 成都: 西南交通大学, 2009. LIANG Y. The study of in situ stress and rock slope stability analysis in deep-incised valley [D]. Chengdu: Southwest Jiaotong University, 2009. (in Chinese)
[10] SHAN Z G, NI W D, LIU A. Numerical simulation of in-situ stress field characteristics about the dam site area of Baihetan Hydropower Station [J]. Journal of Physics: Conference Series, 2022, 2202(1): 012008.
[11] 梁瑶, 赵刚, 杨涛. 考虑侵蚀下切作用的深切河谷岩体地应力场回归 [J]. 西南交通大学学报, 2009, 44(4): 569-573. LIANG Y, ZHAO G, YANG T. Multi-regression analysis of in-situ stress field in deep river valley [J]. Journal of Southwest Jiaotong University, 2009, 44(4): 569-573. (in Chinese)
[12] 周勇, 李啟常, 潘兵, 等. 杨房沟水电站深切河谷地应力场反演分析 [J]. 人民长江, 2018, 49(24): 44-48, 71. ZHOU Y, LI Q C, PAN B, et al. Back analysis of initial geostress field in deep-cut valley of Yangfanggou Hydropower Station [J]. Yangtze River, 2018, 49(24): 44-48, 71. (in Chinese)
[13] 祁生文, 伍法权, 兰恒星. 锦屏一级水电站普斯罗沟左岸深部裂缝成因的工程地质分析 [J]. 岩土工程学报, 2002, 24(5): 596-599. QI S W, WU F Q, LAN H X. Study on the mechanism of the deep fractures of the left abutment slope at the Jinping First Stage Hydropower Station [J]. Chinese Journal of Geotechnical Engineering, 2002, 24(5): 596-599. (in Chinese)
[14] 祁生文, 伍法权, 丁振明, 等. 从工程地质类比的角度看锦屏一级水电站左岸深部裂缝的形成 [J]. 岩石力学与工程学报, 2004, 23(8): 1380-1384. QI S W, WU F Q, DING Z M, et al. Study on mechanism of deep fractures of Jinping First Stage Hydropower Station by engineering geology analogy [J]. Chinese Journal of Rock Mechanics and Engineering, 2004, 23(8): 1380-1384. (in Chinese)
[15] 荣冠, 朱焕春, 王思敬. 锦屏一级水电站左岸边坡深部裂缝成因初探 [J]. 岩石力学与工程学报, 2008, 27(S1): 2855-2863. RONG G, ZHU H C, WANG S J. Primary research on mechanism of deep fractures formation in left bank of Jinping First Stage Hydropower Station [J]. Chinese Journal of Rock Mechanics and Engineering, 2008, 27(S1): 2855-2863. (in Chinese)
[16] 徐佩华, 黄润秋, 陈剑平, 等. 高地应力区复杂结构河谷应力场特征：以锦屏Ⅰ级水电站为例 [J]. 吉林大学学报(地球科学版), 2013, 43(5): 1523-1532. XU P H, HUANG Y Q, CHEN J P, et al. Stress field characteristics of a valley slope with complex geological structure in high geo-stress area: A case of Jinping I Hydropower Station [J]. Journal of Jilin University (Earth Science Edition), 2013, 43(5): 1523-1532. (in Chinese)
[17] 黄润秋. 论中国西南地区水电开发工程地质问题及其研究对策 [J]. 地质灾害与环境保护, 2002, 13(1): 1-5. HUANG R Q. Discussion on the main engineering geological problems in hydropower development in southwestern China and their research strategies [J]. Journal of Geological Hazards and Environment Preservation, 2002, 13(1): 1-5. (in Chinese)
[18] 黄润秋. 中国西南岩石高边坡的主要特征及其演化 [J]. 地球科学进展, 2005, 20(3): 292-297. HUANG R Q. Main characteristics of high rock slopes in southwestern China and their dynamic evolution [J]. Advances in Earth Science, 2005, 20(3): 292-297. (in Chinese)
[19] 王运生, 罗永红, 吴俊峰, 等. 中国西部深切河谷谷底卸荷松弛带成因机理研究 [J]. 地球科学进展, 2008, 23(5): 463-468. WANG Y S, LOU Y H, WU J F, et al. Study on the genetic mechanism of unloaded and relaxed zone in the deep river valley bottom, West of China [J]. Advances in Earth Science, 2008, 23(5): 463-468. (in Chinese)
[20] 侯孝东. 河流快速下切对岸坡岩体卸荷深度的影响研究 [D]. 成都: 成都理工大学, 2021. HOU X D. Study on the influence of rapid river undercutting on unloading depth bank slope rock mass [D]. Chengdu: Chengdu University of Technology, 2021. (in Chinese)
[21] 柴建峰, 祁生文, 滕开永, 等. 高山峡谷地区高陡边坡深部裂缝一般特征分析 [J]. 工程地质学报, 2007, 15(6): 730-738. CHAI J F, QI S W, TENG K Y, et al. Spectial characteristics of deep fractures in high and steep slopes in southwestern of China [J]. Journal of Engineering Geology, 2007, 15(6): 730-738. (in Chinese)
[22] 钟传贵. 库水作用下锦屏一级坝区左岸工程边坡稳定性研究 [D]. 成都: 成都理工大学, 2018. ZHONG C G. Under the action of reservoir water kam screen level in the left bank of the reservoir engineering slope stability research [D]. Chengdu: Chengdu University of Technology, 2018. (in Chinese)
[23] 赵德军, 陈洪德, 吴德超. 雅砻江锦屏一级水电站左岸深部裂缝成因机制探讨 [J]. 水文地质工程地质, 2011, 38(6): 102-107. ZHAO D J, CHEN H D, WU D C. Discussion of the formation of deep fractures on the left bank of the Jinping I Hydropower Station of the Yalong River [J]. Hydrogeology & Engineering Geology, 2011, 38(6): 102-107. (in Chinese)
[24] 周维垣. 岩体工程结构的稳定性 [J]. 岩石力学与工程学报, 2010, 29(9): 1729-1753. ZHOU W Y. Structure stability of rock mass engineering [J]. Chinese Journal of Rock Mechanics and Engineering, 2010, 29(9): 1729-1753. (in Chinese)
[25] LIU Y R, WU Z S, YANG Q, et al. Dynamic stability evaluation of underground tunnels based on deformation reinforcement theory [J]. Advances in Engineering Software, 2018, 124: 97-108.
[26] ZHANG L, LIU Y R, YANG Q. A creep model with damage based on internal variable theory and its fundamental properties [J]. Mechanics of Materials, 2014, 78: 44-55.