Feasibility study on dam and reservoir construction in the catchment area of complex karst water system: Taking Pucha Reservoir of Beipan River as an example
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摘要: 北盘江流域沿线山高谷深，岩溶水文地质条件复杂，局部区域水资源短缺，岩溶渗漏问题成为水利水电工程建设的瓶颈。文章综合地质调查测绘、钻探及物探、水文地质试验、岩溶水系统分析、地下水均衡分析等方法，论证了PCH水库不会发生邻谷渗漏及绕坝基深部的岩溶管道型渗漏，但发生溶隙型渗漏的可能性较大。采用有限元法模拟溶隙渗漏显示：随着T1yn1-1灰岩溶蚀率的增大，坝基抗滑稳定系数稍有降低，潜在失稳模式为后缘剪断T1yn1-2岩体，前缘沿T1yn1-2层内岩屑夹泥型软弱结构面剪出；坝基渗漏量呈线性增加，T1yn1-1灰岩溶隙密集带为坝基主要渗漏区。当溶隙密集带沿T1yn1-1灰岩与T1yn1-2泥灰岩接触带水平发育且集中分布时，坝基抗滑稳定系数将明显减小，坝基渗漏量将明显增大；当溶隙密集带垂直发育、分散发育或主要分布于坝后区域时，其对坝基抗滑稳定及坝基渗漏量影响微弱。岩溶水文地质分析及数值模拟均显示，复杂岩溶水系统势汇区下游区域多以溶隙渗漏为主，其工程影响有限，具备建坝成库条件。Abstract: The topographic and geological conditions in the basin of Beipan River are complex with high mountains and deep valleys on both banks, strong karst development and deeply buried groundwater.Consequently, water resources are in great shortage in this area. The construction of water conservancy projects can effectively solve the problem of water shortage. However, karst leakage has become a difficult problem restricting the construction. By comprehensively using the methods of geological survey and mapping, drilling and geophysical exploration, hydrogeological test, karst water system analysis and groundwater balance analysis, this paper demonstrates that a leakage to the adjacent valley or along the karst pipeline deep under the dam foundation will not occur in the Pucha reservoir, but the possibility of solution crack leakage is great. The finite element method is used to simulate the solution crack leakage and analyze the engineering impact. Results show that with the increase of the dissolution rate of T1yn1-1 limestone, the anti-sliding stability coefficient of the dam foundation decreases slightly, and there is an inverse correlation between them. The regression equation is y1=−0.081x +2.678. The potential instability mode of the dam foundation is that the T1yn1-2 marl rock mass is sheared at the upstream, and the bottom is sheared along the gently inclined upstream with weak structural plane of rock debris mixed with mud in T1yn1-2 layer. With the increase of dissolution rate of T1yn1-1 limestone, the leakage of dam foundation increases significantly, and there is a positive correlation between them. The regression equation is y2=120.3x+224.8. The concentrated belt of solution crack is the main leakage area of dam foundation. When the concentrated belt develops horizontally and distributes intensively along the contact belt between T1yn1-1 limestone and T1yn1-2 marl, the anti-sliding stability coefficient of dam foundation will significantly reduce and the leakage of dam foundation will significantly increase.Therefore, the concentrated belt should be treated as a key area. When the concentrated belt is vertically developed, dispersed or mainly distributed in the area behind the dam, it has little impact on the anti-sliding stability and leakage of the dam foundation, and can be used as a secondary treatment area. Karst hydrogeological analysis and numerical simulation show that in complex karst areas, after groundwater is discharged from the surface in the potential catchment area, it mainly influxes in the form of runoff to the downstream river channel, and the vertical infiltration of water flow is relatively weak, so it is difficult to form karst pipelines bypassing the anti-seepage curtain and connecting the upstream and downstream in the deep part of the riverbed. The leakage form of dam foundation is mainly solution crack leakage, and its engineering impact is limited. Therefore, the catchment area of karst groundwater is suitable for dam and reservoir construction. In addition, according to the spatial distribution characteristics of the concentrated belt of solution crack, the targeted treatment of zoning grouting can improve the treatment efficiency and save investment.
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Key words:
- reservoir leakage /
- concentrated belt of solution crack /
- karst /
- numerical simulation /
- Beipan River
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图 8 稳定系数及渗漏量与溶蚀率关系曲线
Figure 8. Relationship between stability factor, leakage and karst fissure rate
图 9 0%溶蚀率时总水头渗流场云图
Figure 9. Field nephogram of the total head seepage with the karst fissure rate of 0%
图 11 50%溶蚀率时总水头渗流场云图
Figure 11. Field nephogram of the otal head seepage with the karst fissure rate of 50%
图 10 25%溶蚀率时总水头渗流场云图
Figure 10. Field nephogram of the total head seepage with the karst fissure rate of 25%
图 12 稳定系数及渗漏量与溶隙密集形态关系曲线
Figure 12. Relationship between stability factor, leakage and karst fissure forms
表 1 工程区岩溶基本特征统计表
Table 1. Statistics of the basic karst features in the project area
编号 分布位置 出口高程/m 流量/L·s−1 汛期 枯期 极枯 S1 普岔河干支汇合处 990 75 50 17 S2 滴水沟左岸1#冲沟上游 1 017 5 1 0 S3 左岸1号冲沟源头 1 125 2 1 0 S4 坝轴线右岸上游侧 1 019 5 1 0 S5 岩溶盲谷左岸后坡 1 004 15 15 15 KS1 坝轴线右岸 1 130 10 3 0 KS2 滴水沟左岸吊水岩 1 100 50 10 0.5 KS3 坝轴线左岸 1 035 8 3 0 KS4 坝轴线左岸 995 5 2 0 KS7 坝址下游暗河出口 851 300 200 40 KS8 坝址下游岩溶管道出口 900 12 5 1.5 KS9 岩溶盲谷内侧右壁 945 7 2 0 
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表 2 工程区岩溶水系统区划表
Table 2. Division of the karst water system in the project area
编号 地层 岩性 分布位置 发育岩溶统计 Ⅰ T1yn1-1 灰岩 库区 S1、S2、KS2 Ⅱ T1yn1-3+4 泥质灰岩 坝址左岸 S3、S5、KS3、KS4 Ⅲ T1yn1-3+4 泥质灰岩 坝址右岸 S4、KS1 Ⅳ T1yn1-1 灰岩 坝址下游 K5-KS7、K6-KS8 Ⅴ T1yn1-1 灰岩 河床深部 潜在岩溶渗漏通道
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表 3 岩土体物理力学参数建议值表
Table 3. Physical and mechanical parameters of rock and soil
地层 类别 物质成分 密度
/g·cm−3抗剪断强度 渗透系数
/cm·s−1tgϕ c/Kpa T1yn1-1 岩体 灰岩 2.65 1.00 850 10−4 T1yn1-2 岩体 泥灰岩 2.60 0.80 650 10−5 层面 岩屑夹泥 2.15 0.45 50 10−3 T1f 岩体 泥页岩 2.55 0.65 550 10−6 Qal 冲积 砂卵砾石 2.20 0.45 0 10−2 Ql 湖积 淤泥质粉土 2.15 0.25 10 10−5 Qcol 崩积 块碎石土 2.20 0.55 10 10−1
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表 4 溶蚀率模拟计算结果表
Table 4. Simulation results of the karst fissure rate
溶蚀率/% 0 10 20 25 30 40 50 Fs 2.678 2.668 2.663 2.660 2.656 2.643 2.638 Q/m3·d−1 225.0 236.3 248.5 257.0 261.0 275.0 283.5
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表 5 溶隙密集带形态模拟结果表
Table 5. Simulation results with different karst fissure forms
发育
形态水平
分散
坝前垂直
分散
坝前分散
水平
坝前集中
水平
坝前坝前
水平
分散坝后
水平
分散Fs 2.660 2.670 2.665 2.630 2.653 2.698 Q/m3·d−1 257.0 232.0 240.0 291.5 237.5 243.0
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