不同竖向应力和剪切位移下砂砾石与砂双层土渗透试验
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摘要
目前很多高土石坝直接坐落在覆盖层上,修建坝体后,会使坝基覆盖层产生较大的应力和剪切位移,对覆盖层的渗透稳定有极大的影响。因此有必要开展考虑应力和剪切位移影响的坝基覆盖层渗透特性试验研究。利用粗粒土大型高压水平渗透仪,考虑竖向应力和剪切位移的影响,对砂砾石和砂双层土进行渗透试验研究,探讨了砂砾石和砂双层土试样的渗透性和抗渗坡降随竖向应力和剪切位移的变化规律,将渗透破坏的发生和发展分为稳定、过渡和破坏三个阶段。试验结果表明:随着竖向应力的增大,砂砾石和砂双层土的渗透系数逐渐减小,而细颗粒的启动坡降和试样的破坏坡降则逐渐增大。随着剪切位移的增大,砂砾石和砂双层土的整体渗透系数先减小后增大,破坏坡降先增大,后迅速减小。无剪切位移以及剪切位移较小时,细颗粒的启动坡降和试样的破坏坡降之间的过渡阶段较长;而发生大的剪切位移后,启动坡降和破坏坡降之间的过渡阶段大大缩短,达到启动坡降后很快就会出现渗透破坏。
Many high embankment dams are directly located on the deep overburden layer. After the dam is constructed, large stress and shear displacement will appear in the dam foundation, which has great influence on the seepage stability of the overburden layer. Therefore, it is necessary to carry out the seepage tests on overburden layer considering the influence of stress and shear displacement. Using the large-scale high pressure permeameter, the seepage tests on the double-layer soil composed of sandy gravel and sand are conducted under different vertical stresses and shear displacements to investigate the variation of permeability and seepage resistance gradient with change in vertical and shear displacements. The occurrence and evolution of seepage failure are divided into stable seepage, transitional and failure stages. The test results show that the permeability of the double-layer soils decreases, while the initiated gradient of the fine particles and failure gradient of the soil samples increase with the increasing vertical stress. With the increase in shear displacement, the permeability decreases at first and then increases, while the failure gradient increases at first and then decreases rapidly. When there is no shear displacement and the shear displacement is small, the transitional period between the initiated gradient and the failure gradient is long. After large shear displacement occurs, the transitional period is greatly shortened, and the seepage failure occurs soon after the initiated gradient is reached.
Many high embankment dams are directly located on the deep overburden layer. After the dam is constructed, large stress and shear displacement will appear in the dam foundation, which has great influence on the seepage stability of the overburden layer. Therefore, it is necessary to carry out the seepage tests on overburden layer considering the influence of stress and shear displacement. Using the large-scale high pressure permeameter, the seepage tests on the double-layer soil composed of sandy gravel and sand are conducted under different vertical stresses and shear displacements to investigate the variation of permeability and seepage resistance gradient with change in vertical and shear displacements. The occurrence and evolution of seepage failure are divided into stable seepage, transitional and failure stages. The test results show that the permeability of the double-layer soils decreases, while the initiated gradient of the fine particles and failure gradient of the soil samples increase with the increasing vertical stress. With the increase in shear displacement, the permeability decreases at first and then increases, while the failure gradient increases at first and then decreases rapidly. When there is no shear displacement and the shear displacement is small, the transitional period between the initiated gradient and the failure gradient is long. After large shear displacement occurs, the transitional period is greatly shortened, and the seepage failure occurs soon after the initiated gradient is reached.
引文
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[10]SL 237-1999土工试验规程[S].1999.(SL 237-1999Specification of soil test[S].1999.(in Chinese))
[2]MA D.Experimental investigation of seepage properties of fractured rocks under different confining pressures[J].Rock Mechanics and Rock Engineering,2017,46(5):1135-1144.
[3]凌华,张胜,敖大华,等.复杂应力状态下土料三轴渗透试验[J].河海大学学报(自然科学版),2017,45(5):451-456.(LING Hua,ZHANG Sheng,AO Da-hua,et al.Triaxial test study on the permeability of soil under complex stress state[J].Journal of Hohai University(Natural Sciences),2017,45(5):451-456.(in Chinese))
[4]CHANG D S,ZHANG L M.Critical hydraulic gradients of internal erosion under complex stress states[J].Journal of Geotechnical and Geoenvironmental Engineering,2013,134(1):57-67.
[5]RICHARDS K S,REDDY K R.Experimental investigation of initiation of backward erosion piping in soils[J].Géotechnique,2012,62(10):933-942.
[6]雷红军,卞锋,于玉贞,等.黏土大剪切变形中的渗透特性试验研究[J].岩土力学,2010,31(4):1130-1133.(LEIHong-jun,BIAN Feng,YU Yu-zhen,et al.Experimental study of permeability of clayey soil during process of large shear deformation[J].Rock and Soil Mechanics,2010,31(4):1130-1133.(in Chinese))
[7]雷红军,刘中阁,于玉贞,等.黏土-结构接触面大剪切变形后渗流特性试验研究[J].岩土力学,2011,32(4):1040-1044.(LEI Hong-jun,LIU Zhong-ge,YU Yu-zhen,et al.Experimental study of seepage characteristics of clayey soil-structure interface under large shear deformation[J].Rock and Soil Mechanics,2011,32(4):1040-1044.(in Chinese))
[8]李永辉,王卫东,黄茂松,等.超长灌注桩桩-土界面剪切试验研究[J].岩土力学,2015,36(7):1981-1988.(LIYong-hui,WANG Wei-dong,HUANG Mao-song,et al.Experimental research on pile-soil interface shear behaviors of super-long bored pile[J].Rock and Soil Mechanics,2015,36(7):1981-1988.(in Chinese))
[9]邬俊杰,刘帅君,陈锦剑,等.桩土接触面三轴模拟试验设备研究与应用[J].上海交通大学学报,2014,48(11):1523-1527,1535.(WU Jun-jie,LIU Shuai-jun,CHEN Jin-jian,et al.Development and application of a triaxial model test system for pile-soil interface[J].Journal of Shanghai Jiao Tong University,2014,48(11):1523-1527,1535.(in Chinese))
[10]SL 237-1999土工试验规程[S].1999.(SL 237-1999Specification of soil test[S].1999.(in Chinese))