Different filter design criteria and their applications to reservoir design in mountainous areas of southern Ningxia
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摘要: 渗流作用是引起土石坝破坏的主要原因之一,合理设置反滤层能有效控制土体发生渗透破坏。为评价不同反滤准则在以黄土为筑坝材料的土坝中的效果,探讨黄土丘陵山区水利工程反滤系统适宜的设计准则,结合宁夏南部山区乔家沟水库土坝反滤系统设计案例,在反滤料级配曲线的上、下包线范围内平行选取4条不同的级配曲线,通过理论计算得出不同反滤准则所需的反滤料和被保护土料的特征粒径,对比分析了国内外7种反滤准则在该工程中的适用性。结果表明:当被保护土料为粉质黏性黄土时,我国现行碾压式土石坝设计规范(SL 274—2001)反滤准则在该工程反滤料级配曲线的上下包线内适用范围大、效果好,能同时满足滤土与排水条件。Abstract: Seepage is one of the main causes of embankment dam failures, whereas the seepage failures in hydraulic structure can be prevented by reasonable installation of filter layers. For the purpose of evaluating the effectiveness of protective filters for the loess base soils by using different filter design criteria, and finding out an appropriate one for the hydraulic structures in the loess hilly mountainous area, this paper takes the embankment dam filter system of Qiaojiagou reservoir in the mountainous area of southern Ningxia as an example. Four different grading curves were chosen from those paralleled grading curves within the upper and lower envelope of the actual filter material grading curves, whereby the characteristic particle sizes of the these curves and base soil curves were calculated. Then seven filter design criteria were applied to these grading curves and their applicability to the project was analyzed. The results show that with respect to the silty clayey loess acting as protected base soil, the current Chinese filter design criteria Design Code for Rolled Earth-Rock Fill Dams (SL 274—2001) has a broad application range and an excellent performance within the upper and lower envelope of the grading curve of the filter material in Qiaojiagou reservoir project, meanwhile the filtering and draining conditions are satisfied well.
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Key words:
- filter design criteria /
- filter layer /
- filling material /
- grading curve /
- loess
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表 1 美国水土保持局反滤准则
Table 1. Filter criteria of NRCS
分类 被保护土料① 反滤料② 名称 d<0.075 mm颗粒质量分数/% 1 细砂、黏土 >85 ${D_{{\rm{15}}}} \leqslant {\rm{9}}{d_{85}}$③ 2 砂、粉砂、粉
质黏土、粉质砂40~85 ${D_{ {\rm{15} } } } \leqslant {\rm{0} }{\rm{.7\; mm} }$ 3 砂、粉质砂、
砂砾石15~39 ${D_{ {\rm{15} } } } \leqslant \left( {\dfrac{ { {\rm{40 - } }A} }{ { {\rm{40 - 15} } } }} \right)\left( {4{d_{85} } - 0.7} \right) + {\rm{0} }{\rm{.7} }$④⑤ 4 砂和砂砾石 <15 ${D_{{\rm{15}}}} \leqslant {\rm{4}}{d_{85}}$⑥ 注:反滤层应满足排水条件:D15≥4d15;①~⑥相关含义及用法具体参见文献[14]。 表 2 碾压式土石坝设计规范(SL 274—2001)反滤准则(黏性土)
Table 2. Design code for rolled earth-rock fill dams (cohesion soil)
被保护土为黏性土① d<0.075 mm颗
粒质量分数/%第一层反滤级配 滤土准则 排水准则 >85 ${D_{{\rm{15}}}} \leqslant {\rm{9}}{d_{85}}$② ${D_{{\rm{15}}}} \geqslant {\rm{4}}{d_{15}}$⑤ 40~85 ${D_{ {\rm{15} } } } \leqslant {\rm{0} }{\rm{.7\;mm} }$ <15 ${D_{ {\rm{15} } } } \leqslant \left( {\dfrac{ { {\rm{40 - } }A} }{ { {\rm{40 - 15} } } }} \right)\left( {4{d_{85} } - 0.7} \right) + 0.7$③④ 注:①~⑤相关含义及用法与表1稍有区别,具体参见文献[17]。 表 3 太沙基、IWHR、威特反滤准则应用到乔家沟水库反滤设计的结果
Table 3. Results of Terzaghi, IWHR and Witt filter criteria applied to the filter design of Qiaojiagou reservoir
填筑土
样编号D15/(4d85)(太沙基) D20/(7d70)(IWHR) 威特 ${D_{ {\rm{10} } } }{\rm{/(2} }{\rm{.5} }{d_{95} )}$ ${D_{\rm{5} } }{\rm{/(2} }{\rm{.5} }{d_{95} )}$ 下 上 平 三 下 上 平 三 下 上 平 三 下 上 平 三 1 3.00 0.64 1.79 1.47 2.57 0.57 1.57 1.24 2.60 0.56 1.58 1.24 — — — — 2 3.00 0.64 1.79 1.47 2.49 0.55 1.52 1.20 2.84 0.61 1.72 1.35 — — — — 3 3.34 0.71 2.00 1.64 3.09 0.69 1.89 1.49 2.84 0.61 1.72 1.35 — — — — 4 3.00 0.64 1.79 1.47 2.49 0.55 1.52 1.20 2.56 0.55 1.55 1.22 — — — — 5 3.08 0.66 1.84 1.51 2.49 0.55 1.52 1.20 2.84 0.61 1.72 1.35 — — — — 6 2.85 0.61 1.71 1.40 2.14 0.48 1.31 1.03 2.84 0.61 1.72 1.35 — — — — 7 3.08 0.66 1.84 1.51 2.66 0.59 1.63 1.28 2.84 0.61 1.72 1.35 — — — — 8 3.08 0.66 1.84 1.51 2.66 0.59 1.63 1.28 — — — — 2.54 0.54 1.54 1.22 9 3.25 0.69 1.94 1.60 2.97 0.66 1.81 1.43 2.84 0.61 1.72 1.35 — — — — 10 3.08 0.66 1.84 1.51 2.49 0.55 1.52 1.20 2.60 0.56 1.58 1.24 — — — — 注:表中下、上、平、三分别为下包线、上包线、平均线和三等分线的简写。 表 4 Indraratna & Raut反滤准则应用到乔家沟水库反滤设计的结果
Table 4. Results of Indraratna & Raut filter criteria applied to the filter design of Qiaojiagou reservoir
填筑土
样编号${D_{{\rm{c35}}}}{\rm{/}}{d_{85{\rm{SA}}}}$ ${D_{{\rm{c}}35}}/d_{85}^*$ 下包线 上包线 平均线 三等分线 下包线 上包线 平均线 三等分线 1 2.39 0.52 1.39 1.12 1.93 0.55 1.18 0.97 2 2.32 0.50 1.35 1.09 2.03 0.52 1.21 1.00 3 2.93 0.63 1.70 1.37 2.19 0.59 1.31 1.09 4 2.32 0.50 1.35 1.09 1.98 0.53 1.18 0.97 5 2.32 0.50 1.35 1.09 2.08 0.52 1.24 1.03 6 2.14 0.46 1.24 1.00 1.88 0.46 1.12 0.93 7 2.55 0.55 1.48 1.19 2.08 0.53 1.24 1.03 8 2.47 0.53 1.44 1.16 2.08 0.53 1.24 1.03 9 2.72 0.59 1.59 1.28 2.19 0.59 1.31 1.09 10 2.32 0.50 1.35 1.09 1.98 0.53 1.18 0.97 表 5 规范、NRCS和Lafleur反滤准则应用到乔家沟水库反滤设计的结果
Table 5. Results of design code for rolled earth-rock fill dams, NRCS and Lafleur filter criteria applied to the filter design of Qiaojiagou reservoir
填筑土
样编号D15/(9d85)(NRCS/规范(本工程)) D15/0.4(Lafleur) 下包线 上包线 平均线 三等分线 下包线 上包线 平均线 三等分线 1 1.33 0.29 0.80 0.66 1.17 0.25 0.70 0.58 2 1.33 0.29 0.80 0.66 1.17 0.25 0.70 0.58 3 1.49 0.32 0.89 0.73 1.17 0.25 0.70 0.58 4 1.33 0.29 0.80 0.66 1.17 0.25 0.70 0.58 5 1.37 0.29 0.82 0.67 1.17 0.25 0.70 0.58 6 1.27 0.27 0.76 0.62 1.17 0.25 0.70 0.58 7 1.37 0.29 0.82 0.67 1.17 0.25 0.70 0.58 8 1.37 0.29 0.82 0.67 1.17 0.25 0.70 0.58 9 1.44 0.31 0.86 0.71 1.17 0.25 0.70 0.58 10 1.37 0.29 0.82 0.67 1.17 0.25 0.70 0.58 表 6 太沙基、NRCS、规范、Lafleur和IWHR反滤准则排水条件应用于乔家沟水库的结果
Table 6. Results of drainage conditions of Terzaghi, NRCS, Design code for rolled earth-rock fill dams, Lafleur and IWHR filter criteria applied to Qiaojiagou reservoir
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样编号${D_{ {\rm{15} } } }{\rm{/(4} }{d_{ {\rm{1} }5} )}$(太沙基、NRCS、规范、Lafleur) ${D_{ {\rm{20} } } }{\rm{/(4} }{d_{ {\rm{20} } } )}$(IWHR) 下包线 上包线 平均线 三等分线 下包线 上包线 平均线 三等分线 1 18.00 3.85 10.77 8.85 16.46 3.66 10.06 7.93 2 19.18 4.10 11.48 9.43 17.31 3.85 10.58 8.33 3 22.50 4.81 13.46 11.06 25.47 5.66 15.57 12.27 4 19.50 4.17 11.67 9.58 15.52 3.45 9.48 7.47 5 15.60 3.33 9.33 7.67 12.27 2.73 7.50 5.91 6 15.60 3.33 9.33 7.67 13.50 3.00 8.25 6.50 7 19.83 4.24 11.87 9.75 22.50 5.00 13.75 10.83 8 24.38 5.21 14.58 11.98 22.88 5.09 13.98 11.02 9 23.88 5.10 14.29 11.74 21.43 4.76 13.10 10.32 10 18.00 3.85 10.77 8.85 15.70 3.49 9.59 7.56 -
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