粗粒土渗透试验边壁孔隙特征及处理层最优厚度研究
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摘要
室内渗透试验的边壁效应对粗粒土渗透系数的测定影响显著。从颗粒与边壁间孔隙的组成特征出发,根据边壁孔隙体积V_b与构成边壁孔隙的颗粒关联体积V_s之比,定义了试样边界孔隙比e_b。基于等直径圆堆积原理,确立了边壁颗粒的堆积模式,构建了考虑边壁处理层厚度的边界孔隙比平面几何计算模型,并通过空间和颗粒级配修正导出了e_b表达式;以e_b与试样孔隙比e相等为原则,提出了确定边壁处理层最优厚度h_(opt)的等效孔隙比法,探讨了渗透仪直径D与边壁效应的关系。研究表明:边壁引起的多余孔隙将提高边壁处的渗流速度;边壁颗粒存在两颗粒、三颗粒锐角以及三颗粒钝角3类典型平面堆积模式,与此对应的e_b依次增加;h_(opt)由试样级配、密实程度、颗粒密度、边壁颗粒堆积模式以及D等因素决定,其估算值与试验结果吻合;D超过8倍试样最大粒径后边壁效应对渗透试验结果的影响不再显著。
Boundary effect has a significant influence on the permeability coefficient measurement of coarse grained soil in laboratory seepage tests. Based on the composition characteristics of the pore V_b between soil particles and the seepage equipment wall, a parameter called boundary pore ratio of the soil sample e_b was defined according to the ratio of the volume of boundary pore Vb to the particle volume Vs which concerns the constitution of boundary pore. Furthermore, based on the uniform circle packing principle, the boundary particle accumulation patterns were established, and a plane geometric calculation model of boundary pore ratio considering the wall treatment layer thickness was proposed. The expression of e_b was finally derived through space and particle gradation correction.Based on the principle of the equality of e_b and sample pore ratio e, a criterion called ‘equivalent pore ratio method' for confirming the optimal thickness of the wall treatment layer hopt was presented. At last, the relationship between the seepage equipment diameter D and the boundary effect was discussed. The researches indicate that the redundant pore caused by the boundary effect would raise the seepage velocity near the seepage boundary. There are three typical plane accumulation patterns of the boundary particles,including two particles pattern, three particles with acute packing angle pattern and three particles with obtuse packing angle pattern,of which the corresponding e_b increases accordingly. Furthermore, hopt is comprehensively determined by sample gradation,compression degree, particle density, boundary particle accumulation pattern and D. The estimate value of hopt agrees well with the test result. The influence of the boundary effect on the seepage test result becomes less significant as D exceeds eight times of the maximum particle size of soil sample.
Boundary effect has a significant influence on the permeability coefficient measurement of coarse grained soil in laboratory seepage tests. Based on the composition characteristics of the pore V_b between soil particles and the seepage equipment wall, a parameter called boundary pore ratio of the soil sample e_b was defined according to the ratio of the volume of boundary pore Vb to the particle volume Vs which concerns the constitution of boundary pore. Furthermore, based on the uniform circle packing principle, the boundary particle accumulation patterns were established, and a plane geometric calculation model of boundary pore ratio considering the wall treatment layer thickness was proposed. The expression of e_b was finally derived through space and particle gradation correction.Based on the principle of the equality of e_b and sample pore ratio e, a criterion called ‘equivalent pore ratio method' for confirming the optimal thickness of the wall treatment layer hopt was presented. At last, the relationship between the seepage equipment diameter D and the boundary effect was discussed. The researches indicate that the redundant pore caused by the boundary effect would raise the seepage velocity near the seepage boundary. There are three typical plane accumulation patterns of the boundary particles,including two particles pattern, three particles with acute packing angle pattern and three particles with obtuse packing angle pattern,of which the corresponding e_b increases accordingly. Furthermore, hopt is comprehensively determined by sample gradation,compression degree, particle density, boundary particle accumulation pattern and D. The estimate value of hopt agrees well with the test result. The influence of the boundary effect on the seepage test result becomes less significant as D exceeds eight times of the maximum particle size of soil sample.
引文
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[14]陈坚,罗强,张良,等.高速铁路基床表层级配碎石填料土体结构类型试验分析[J].铁道学报,2015,37(11):82-88.CHEN Jian,LUO Qiang,ZHANG Liang,et al.Experimental analysis on soil structure type of graded gravelly soil filling surface layer of subgrade of high-speed railway[J].Journal of the China Railway Society,2015,37(11):82-88.
[15]杨启贵,刘宁,孙役,等.水布垭面板堆石坝筑坝技术[M].北京:中国水利水电出版社,2010.YANG Qi-gui,LIU Ning,SUN Yi,et al.Construction technology for Shuibuya concrete face rock fill dam[M].Beijing:China Water and Power Press,2010.
[16]李广信,张丙印,于玉贞.土力学(第2版)[M].北京:清华大学出版社,2013.LI Guang-xin,ZHANG Bing-yin,YU Yu-zhen.Soil mechanics(the 2nd edition)[M].Beijing:Tsinghua University Press,2013.
[17]刘杰.土的渗透破坏及控制研究[M].北京:中国水利水电出版社,2014.LIU Jie.Piping and seepage control of soil[M].Beijing:China Water and Power Press,2014.
[2]刘杰.土的渗透稳定与渗流控制[M].北京:水利电力出版社,1992.LIU Jie.Seepage stability and control of soil[M].Beijing:Water Resources and Electric Power Press,1992.
[3]中华人民共和国水利部.SL237-1999土工试验规程[S].北京:中国水利水电出版社,1999.The Ministry of Water Resources of the People’s Republic of China.SL237-1999 Specification of soil test[S].Beijing:China Water and Power Press,1999.
[4]谢定义,陈存礼,胡再强.试验土工学[M].北京:高等教育出版社,2011.XIE Ding-yi,CHEN Cun-li,HU Zai-qiang.Experimental soil engineering[M].Beijing:Higher Education Press,2011.
[5]朱国胜,张家发,张伟,等.宽级配粗粒料渗透试验方法探讨[J].长江科学院院报,2009,26(增刊1):10-13.ZHU Guo-sheng,ZHANG Jia-fa,ZHANG Wei,et al.Discussion of seepage test method for broadly graded coarse material[J].Journal of Yangtze River Scientific Research Institute,2009,26(Suppl.1):10-13.
[6]张家发,定培中,张伟,等.水布垭面板堆石坝过渡料设计及其渗透变形特性研究[J].长江科学院院报,2009,26(10):1-6.ZHANG Jia-fa,DING Pei-zhong,ZHANG Wei,et al.Study on design requirements and seepage deformation characteristics of transition zone material for Shuibuya concrete face rock fill dam[J].Journal of Yangtze River Scientific Research Institute,2009,26(10):1-6.
[7]INDRARATNA B,ISRAR J,RUJIKIATKAMJORN C.Geometrical method for evaluating the internal instability of granular filters based on constriction size distribution[J].Journal of Geotechnical and Geoenvironmental Engineering,2015,141(10):04015045.
[8]邹玉华,陈群,何昌荣,等.不同应力条件下砾石土防渗料和反滤料联合抗渗试验研究[J].岩土力学,2012,33(8):2323-2329.ZOU Yu-hua,CHEN Qun,HE Chang-rong,et al.Filter tests on gravelly soil and filter material under different stress states[J].Rock and Soil Mechanics,2012,33(8):2323-2329.
[9]谢定松,蔡红,魏迎奇,等.粗粒土渗透试验缩尺原则与方法探讨[J].岩土工程学报,2015,37(2):369-373.XIE Ding-song,CAI Hong,WEI Ying-qi,et al.Scaling principle and method in seepage tests on coarse materials[J].Chinese Journal of Geotechnical Engineering,2015,37(2):369-373.
[10]朱国胜,张家发,陈劲松,等.宽级配粗粒土渗透试验尺寸效应及边壁效应研究[J].岩土力学,2012,33(9):2569-2574.ZHU Guo-sheng,ZHANG Jia-fa,CHEN Jing-song,et al.Study of size and wall effects in seepage test of broadly graded coarse materials[J].Rock and Soil Mechanics,2012,33(9):2569-2574.
[11]邵生俊,李建军,杨扶银.粗粒土孔隙特征及其对泥浆渗透性的影响[J].岩土工程学报,2009,31(1):59-65.SHAO Sheng-jun,LI Jian-jun,YANG Fu-yin.Pore characteristics of coarse grained soil and their effect on slurry permeability[J].Chinese Journal of Geotechnical Engineering,2009,31(1):59-65.
[12]MORACI N,LELO D,MANDAGLIO M C.A new theoretical method to evaluate the internal stability of granular soils[J].Canadian Geotechnical Journal,2012,49(1):45-58.
[13]曾凡,胡永平,杨毅,等.矿物加工颗粒学[M].徐州:中国矿业大学出版社,2001.ZENG Fan,HU Yong-ping,YANG Yi,et al.Particle technology of mineral processing[M].Xuzhou:China University of Mining and Technology Press,2001.
[14]陈坚,罗强,张良,等.高速铁路基床表层级配碎石填料土体结构类型试验分析[J].铁道学报,2015,37(11):82-88.CHEN Jian,LUO Qiang,ZHANG Liang,et al.Experimental analysis on soil structure type of graded gravelly soil filling surface layer of subgrade of high-speed railway[J].Journal of the China Railway Society,2015,37(11):82-88.
[15]杨启贵,刘宁,孙役,等.水布垭面板堆石坝筑坝技术[M].北京:中国水利水电出版社,2010.YANG Qi-gui,LIU Ning,SUN Yi,et al.Construction technology for Shuibuya concrete face rock fill dam[M].Beijing:China Water and Power Press,2010.
[16]李广信,张丙印,于玉贞.土力学(第2版)[M].北京:清华大学出版社,2013.LI Guang-xin,ZHANG Bing-yin,YU Yu-zhen.Soil mechanics(the 2nd edition)[M].Beijing:Tsinghua University Press,2013.
[17]刘杰.土的渗透破坏及控制研究[M].北京:中国水利水电出版社,2014.LIU Jie.Piping and seepage control of soil[M].Beijing:China Water and Power Press,2014.
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