止水帷幕缝隙渗漏变化过程试验研究
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摘要
由于施工工艺的原因,止水帷幕一般存在缝隙。在长期渗流的作用下,带缝隙的止水帷幕渗漏量如何发展需要进一步研究。因此,作者自行设计并制作了砂槽模型模拟带裂缝的止水帷幕,并开展了一系列的渗流试验。试验考虑了水力条件、砂样级配和缝隙尺度因素的影响。结果表明,在水头不变的情况下,各试验中均出现了渗漏量下降的现象,但水头升高则会破坏这一现象。缝隙渗漏量下降的实质是砂颗粒移动和聚集导致淤堵的产生,淤堵位置可能在上下游缝口、缝隙进出口或缝隙内。当砂样粒径较细时,缝隙渗漏量下降效果最为显著;当下游回填级配不稳定的砂样时,缝隙渗漏量下降效果不佳。
Generally, there are cracks in the cut-off wall because of the defects in construction craft.Therefore,it is necessary to further study the water interception capacity of the cut-off wall with cracks in the long term of seepage. The authors designed and made a sand box to simulate the cut-off wall with cracks, and carried out a series of seepage tests. Hydraulic conditions, gradation of soil specimens and crack size were considered in the tests. The results showed that,under the condition of constant head,the total flow rate of leakage decreased in each test,but the flow rate increased again when the head rose.The essence of the decrease of leaking flow rate is that the movement and aggregation of sand particles lead to the formation of clogging,which may be formed in the area near the inlet and outlet of the crack,or within the crack. When the particle size of sand is fine,the effect of leaking flow rate drop is most significant. However,when unstable sand is backfilled in the downstream,the effect of crack leakage reduction is poor.
Generally, there are cracks in the cut-off wall because of the defects in construction craft.Therefore,it is necessary to further study the water interception capacity of the cut-off wall with cracks in the long term of seepage. The authors designed and made a sand box to simulate the cut-off wall with cracks, and carried out a series of seepage tests. Hydraulic conditions, gradation of soil specimens and crack size were considered in the tests. The results showed that,under the condition of constant head,the total flow rate of leakage decreased in each test,but the flow rate increased again when the head rose.The essence of the decrease of leaking flow rate is that the movement and aggregation of sand particles lead to the formation of clogging,which may be formed in the area near the inlet and outlet of the crack,or within the crack. When the particle size of sand is fine,the effect of leaking flow rate drop is most significant. However,when unstable sand is backfilled in the downstream,the effect of crack leakage reduction is poor.
引文
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[2] SHERARD J L. Trends and debatable aspects in embankment dam engineering[J]. Water Power and Dam Construction,1984,36(12):26-32.
[3]刘杰,罗玉再.高土石坝心墙裂缝的自愈机理与反滤层的防护作用[J].水利学报,1987(7):20-29.
[4]党进谦,马晓婷,孙仲林,等.分散性对心墙土料裂缝冲刷影响的试验研究[J].水利学报,2012,43(9):1103-1107.
[5] SHERARD J L,DUNNIGAN L. Filters and leakage control in embankment dams[C]//Proc. Symposium on Seepage and Leakage from Dams and Impoundments,R. L. Volpe and W. E. Kelly eds.,ASCE,1985.
[6]毛昶熙.渗流计算分析与控制[M]. 2版.北京:中国水利水电出版社,2002.
[7]朱丹,毛昶熙.闸基板桩缝对渗流影响的计算[J].人民黄河,1997(2):15-19.
[8]曹洪,罗彦,周红星.新光大桥桥墩钢板桩围堰抗渗问题分析[J].岩石力学与工程学报,2006(1):152-157.
[9]罗彦.钢板桩接缝-自愈过程研究[D].广州:华南理工大学,2006.
[10]丁留谦,周晓光,杨凯虹,等.超高面板坝淤填自愈型止水结构可行性的初步研究[J].水利学报,2001(1):76-80.
[11] SIVAKUMAR Babu G L,SRIVASTAVA A. A procedure for the design of protective filters[J]. Canadian Geotechnical Journal,2007,44:490-495.
[12]徐鹏,邱淑霞,姜舟婷,等.各向同性多孔介质中Kozeny-Carman常数的分形分析[J].重庆大学学报,2011,34(4):78-82.
[13] NOMURA S,YAMAMOTO Y,SAKAGUCHI H. Modified expression of Kozeny-Carman equation based on semilog-sigmoid function[J]. Soils and Foundations,2018,58:1350-1357.
[14] VALDES J R,SANTAMARINA J C. Clogging:bridge formation and vibration-based destabilization[J]. Canadian Geotechnical Journal,2008,45:177-184.
[15] RAUT A K. Mathematical modelling of granular filters and constriction-based filter design criteria[D]. Ph. D.,Univ. of Wollongong,Wollongong,Australia,2006.