大石峡砂砾石坝料渗透特性及其影响因素研究

Experimental study on permeability and its influencing factors for sandy gravel of Dashixia dam

利用试样截面尺寸为1000 mm×1000 mm的超大型渗透仪和Φ300 mm的常规大型渗透仪,针对大石峡面板坝筑坝砂砾石料的渗透特性开展了较为系统的试验研究。结果表明:砂砾石料小于5 mm细粒含量对其渗透系数、抗渗透破坏能力及其破坏模式均具有重要影响;经过缩尺的砂砾石料渗透特性试验结果将高估原型料的排水性能和抗渗透破坏能力;试样尺寸越大,在振动压实制样过程中,砂砾石料中细颗粒离析至试样表面的现象越严重,为提高试验结果的可靠性,利用超大尺寸渗透仪开展试验时,应模拟现场砂砾石料实际振动碾压过程进行制样;大石峡高面板坝筑坝砂砾石料小于5 mm细颗粒含量较高,渗透系数偏小,有必要在垫层区和主堆砂砾料区之间设置过渡反滤区,以提高垫层区料的抗渗透破坏能力。

A super-large cubic permeability meter(1000 mm×1000 mm) and a traditional cylindrical large-scale permeability meter(Φ300 mm) are used to conduct systematic experiments on the permeability characteristics of gravel materials to be used in Dashixia concrete face gravel dam(CFGD). It is found that the content of fine particles smaller than 5 mm has important effects on the permeability coefficient, the seepage failure resistance and the relevant failure modes. Scaling of specimens tends to result in an overestimation of the drainage behavior and seepage failure resistance of the test gravel. Evident particle segregation phenomenon is observed in compacted and prepared specimens, particularly in those prepared in the super-large cubic permeability meter. Therefore, to improve the reliability of the test results, the in-situ compaction condition should be taken into account carefully. The test results also show that the content of particles smaller than 5 mm is high in the gravel materials to be used in Dashixia CFGD, which is responsible for the low permeability measured in the tests. It is necessary to set a transition and filter zone between the main gravel zone and the cushion so as to enhance the seepage failure resistance of the cushion materials.