延安Q_3原状黄土渗透各向异性及微结构分析
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摘要
为研究原状马兰黄土的渗透各向异性,以延安削山造地重大工程开挖所揭露的完整黄土剖面中的马兰黄土层为研究对象,采用室内变水头渗透试验获取不同埋深不同渗流时长原状黄土垂直向和水平向的渗透系数,并对试验前后黄土试样垂直向和水平向SEM(scanning electron microscope)电镜扫描结果进行分析,从微观结构上揭示原状马兰黄土结构各向异性的原因。结果表明:原状黄土垂直向和水平向饱和渗透系数具有显著各向异性,且垂直向和水平向渗透系数都随渗流时间的持续而减小,各向异性渗透性能在时间尺度上具有某种衰减关系;同时,原状黄土各向异渗透性能随埋深的增大而逐渐减弱;土颗粒结构的接触、排列方式是导致黄土原生各向异性的根本原因,也是导致渗流初始阶段渗透系数各向异性的原因,而渗流作用产生的次生结构各向异性则使渗透系数各向异性在时间尺度上表现得更为明显。
In order to study the anisotropic permeability of undisturbed loess, Yan'an Q_3 loess with obvious anisotropy was chosen as the research object. The vertical and horizontal permeability coefficients of different deep-buried undisturbed loess were measured by variable water head permeability tests in laboratory. The results showed that the vertical permeability coefficient of undisturbed loess was larger than the horizontal permeability coefficient of the same horizon. In addition, both vertical and horizontal permeability coefficients of undisturbed loess decreased with the increase of burial depth of loess, and the anisotropy of undisturbed loess was weakened as the burial depth increased, which indicates that anisotropic undisturbed loess gradually become isotropic with the increase of buried depth. Furthermore, in order to investigate the anisotropy of undisturbed loess from microstructure, the longitudinal and transversal sections of undisturbed loess in different buried depths were characterized by SEM(scanning electron microscopy). It was found that the contact and arrangement of soil particles are the fundamental factors resulting in the anisotropic loess.
In order to study the anisotropic permeability of undisturbed loess, Yan'an Q_3 loess with obvious anisotropy was chosen as the research object. The vertical and horizontal permeability coefficients of different deep-buried undisturbed loess were measured by variable water head permeability tests in laboratory. The results showed that the vertical permeability coefficient of undisturbed loess was larger than the horizontal permeability coefficient of the same horizon. In addition, both vertical and horizontal permeability coefficients of undisturbed loess decreased with the increase of burial depth of loess, and the anisotropy of undisturbed loess was weakened as the burial depth increased, which indicates that anisotropic undisturbed loess gradually become isotropic with the increase of buried depth. Furthermore, in order to investigate the anisotropy of undisturbed loess from microstructure, the longitudinal and transversal sections of undisturbed loess in different buried depths were characterized by SEM(scanning electron microscopy). It was found that the contact and arrangement of soil particles are the fundamental factors resulting in the anisotropic loess.
引文
[1] Chan H T,Kenney T C.LaboratoryInvestigation of Permeability Ratio of New Liskeard Varved Soil[J].Canadian Geotechnical Journal,1973,10(3):453-472.
[2] Kenney T C,Chan H T.Field Investigation of Permeability Ratio of New Liskeard Varved Soil[J].Canadian Geotechnical Journal,1973,10(3):473-488.
[3] 张宗祜,姚足金,王开申.中国黄土的主要工程地质问题[J].地质学报,1973(2):255-269.Zhang Zonghu,Yao Zujin,Wang Kaishen.Main Engineering Geological Problems of Chinese Loess[J].Acta Geologica Sinica,1973(2):255-269.
[4] 关文章.湿陷性黄土工程性能新篇[M].西安:西安交通大学出版社,1992.Guan Wenzhang.New Engineering Characteristics of Collapsible Loess[M].Xi’an:Xi’an Jiaotong University Press,1992.
[5] 郝君任,李大可.用一个试样测定黄土各向渗透系数的方法[J].大坝观测与土工测试,1988(2):37-41.Hao Junren,Li Dake.An Improvment for the Determination of Permeability Coefficient of Loess in Different Directions[J].Dam Observation and Geotechnical Tests,1988(2):37-41.
[6] 于欣.陕西省宝鸡地区黄土渗透系数的各向异性和尺度效应研究[D].西安:长安大学,2016.Yu Xin.The Anisotropy and the Scale Effect of Hydraulic Conductivivty for the Loess in Baoji City,Shannxi Province[D].Xi’an:Chang’an University,2016.
[7] 张小筱.泾阳南塬黄土边坡饱和渗透系数特性研究[D].西安:长安大学,2016.Zhang Xiaoxiao.Characteristics of Loess Saturated Hydraulic Conductivity in Landslide of the South Jingyang Plateau[D],Xi’an:Chang’an University,2016.
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[11] 王铁行,杨涛,鲁洁.干密度及冻融循环对黄土渗透性的各向异性影响[J].岩土力学,2016,37(增刊1):72-78.Wang Tiexing,Yang Tao,Lu Jie.Influence of Dry Density and Freezing-Thawing Cycles on Anisotropic Permeability of Loess[J].Rock and Soil Mechanics,2016(Sup.1):72-78.
[12] 杨涛.考虑密度及冻融影响的黄土渗透各向异性研究[D].西安:西安建筑科技大学,2016.Yang Tao.Study on Anisotropic Permeability of Loess Considering Density and Freezing-Thawing Effect[D].Xi’an:Xi’an University of Architecture and Technology,2016.
[13] 土工试验方法标准:GB/T 50123—1999 [S].北京:中国计划出版社,1999.Standard for Soil Test Method:GB/T 50123—1999[S].Beijing:China Planning Press,1999.
[14] 李喜安,洪勃,李林翠,等.黄土湿陷对渗透系数影响的试验研究[J].中国公路学报,2017,30(6):198-208,222.Li Xi’an,Hong Bo,Li Lincui,et al.Experimental Research on Permeability Coefficient Under Influence of Loess Collapsibility[J].China Journal of Highway and Transport,2017,30(6):198-208,222.
[15] 刘杰,傅裕.土的渗透压密性质[J].水利学报,1993(5):76-81.Liu Jie,Fu Yu.The Infiltrating Consolidation Characteristic of Clay[J].Journal of Hydraulic Engineering,1993(5):76-81.
[16] 陈荣波,束龙仓,鲁程鹏,等.含水层压密引起其特征参数变化的实验[J].吉林大学学报(地球科学版),2013,43(6):1958-1965.Chen Rongbo,Shu Longcang,Lu Chengpeng,et al.Experimental Study on the Characteristic Parameters Variation of the Aquifer Caused by Aquifer Compaction[J].Journal of Jilin University (Earth Science Edition),2013,43(6):1958-1965.
[17] 洪勃,李喜安,陈广东,等.重塑马兰黄土渗透性试验研究[J].工程地质学报,2016,24(2):276-283.Hong Bo,Li Xi’an,Chen Guangdong,et al.Experimental Study of Permeability of Remolded Malan Loess[J].Journal of Engineering Geology,2016,24(2):276-283.
[18] 矫德全,陈愈炯.土的各向异性和卸荷体缩[J].岩土工程学报,1994,16(4):9-16.Jiao Dequan,Chen Yujiong.Anisotropy and Volume-Contraction of Soil Due to Axial Unloading in CD Test[J].Chinese Jounal of Geotechnical Engineering,1994,16(4):9-16.
[19] Mast R F,Potter P E.Sedimentary Structures,Sand Shape Fabrics,and Permeability:II[J].The Journal of Geology,1963,71(5):548-565.
[20] 叶为民,杨林德,黄雨,等.上海软土微观空隙各向异性特征及其成因分析[J].工程地质学报,2004,12(增刊1):84-87.Ye Weimin,Yang Linde,Huang Yu,et al.Microstructure and Anisotropy of Seepage of Shanghai Soft Soil[J].Journal of Engineering Geology,2004,12(Sup.l):84-87.
[21] Chapuis R P,Gill D E.Hydraulic Anisotropy of Homogeneous Soils and Rocks:Influence of the Densification Process[J].Bulletin of the International Association of Engineering Geology,1989,39(1):75-86.
[22] 张坤勇,殷宗泽,梅国雄.土体两种各向异性的区别与联系[J].岩石力学与工程学报,2005,24(9):1599-1604.Zhang Kunyong,Yin Zongze,Mei Guoxiong.Difference and Connection of Two Kinds of Anisotropy of Soils[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(9):1599-1604.
[23] 殷宗泽,徐志伟.土体的各向异性及近似模拟[J].岩土工程学报,2002,24(5):547-551.Yin Zongze,Xu Zhiwei.Anisotropy of Soils and Its Approximate Simulation[J].Chinese Journal of Geotechnical Engineering,2002,24(5):547-551.
[24] 李瑞.非饱和黄土的次生各向异性及结构性试验研究[D].杨凌:西北农林科技大学,2008.Li Rui.Research on Induced Anisotropy and Structural Characteristic of Unsaturated Loess[D].Yangling:Northwest A&F University,2008.
[2] Kenney T C,Chan H T.Field Investigation of Permeability Ratio of New Liskeard Varved Soil[J].Canadian Geotechnical Journal,1973,10(3):473-488.
[3] 张宗祜,姚足金,王开申.中国黄土的主要工程地质问题[J].地质学报,1973(2):255-269.Zhang Zonghu,Yao Zujin,Wang Kaishen.Main Engineering Geological Problems of Chinese Loess[J].Acta Geologica Sinica,1973(2):255-269.
[4] 关文章.湿陷性黄土工程性能新篇[M].西安:西安交通大学出版社,1992.Guan Wenzhang.New Engineering Characteristics of Collapsible Loess[M].Xi’an:Xi’an Jiaotong University Press,1992.
[5] 郝君任,李大可.用一个试样测定黄土各向渗透系数的方法[J].大坝观测与土工测试,1988(2):37-41.Hao Junren,Li Dake.An Improvment for the Determination of Permeability Coefficient of Loess in Different Directions[J].Dam Observation and Geotechnical Tests,1988(2):37-41.
[6] 于欣.陕西省宝鸡地区黄土渗透系数的各向异性和尺度效应研究[D].西安:长安大学,2016.Yu Xin.The Anisotropy and the Scale Effect of Hydraulic Conductivivty for the Loess in Baoji City,Shannxi Province[D].Xi’an:Chang’an University,2016.
[7] 张小筱.泾阳南塬黄土边坡饱和渗透系数特性研究[D].西安:长安大学,2016.Zhang Xiaoxiao.Characteristics of Loess Saturated Hydraulic Conductivity in Landslide of the South Jingyang Plateau[D],Xi’an:Chang’an University,2016.
[8] 吕敬,柯贤敏,张小筱,等.泾阳南塬黄土边坡饱和渗透系数变异性分析[J].水土保持通报,2017,37(3):254-257.Lü Jing,Ke Xianmin,Zhang Xiaoxiao,et al.Variability of Saturated Permeability Coefficient of Loess Slopes in South Jingyang Tableland[J].Bulletin of Soil and Water Conservation,2017,37(3):254-257.
[9] Wang W,Wang Y,Sun Q,et al.Spatial Variation of Saturated Hydraulic Conductivity of a Loess Slope in the South Jingyang Plateau,China[J].Engineering Geology,2018,236:70-78.
[10] 梁燕,邢鲜丽,李同录,等.晚更新世黄土渗透性的各向异性及其机制研究[J].岩土力学,2012,33(5):1312-1318.Liang Yan,Xing Xianli,Li Tonglu,et al.Study of the Anisotropic Permeability and Mechanism of Q3 Loess[J].Rock and Soil Mechanics,2012,33(5):1312-1318.
[11] 王铁行,杨涛,鲁洁.干密度及冻融循环对黄土渗透性的各向异性影响[J].岩土力学,2016,37(增刊1):72-78.Wang Tiexing,Yang Tao,Lu Jie.Influence of Dry Density and Freezing-Thawing Cycles on Anisotropic Permeability of Loess[J].Rock and Soil Mechanics,2016(Sup.1):72-78.
[12] 杨涛.考虑密度及冻融影响的黄土渗透各向异性研究[D].西安:西安建筑科技大学,2016.Yang Tao.Study on Anisotropic Permeability of Loess Considering Density and Freezing-Thawing Effect[D].Xi’an:Xi’an University of Architecture and Technology,2016.
[13] 土工试验方法标准:GB/T 50123—1999 [S].北京:中国计划出版社,1999.Standard for Soil Test Method:GB/T 50123—1999[S].Beijing:China Planning Press,1999.
[14] 李喜安,洪勃,李林翠,等.黄土湿陷对渗透系数影响的试验研究[J].中国公路学报,2017,30(6):198-208,222.Li Xi’an,Hong Bo,Li Lincui,et al.Experimental Research on Permeability Coefficient Under Influence of Loess Collapsibility[J].China Journal of Highway and Transport,2017,30(6):198-208,222.
[15] 刘杰,傅裕.土的渗透压密性质[J].水利学报,1993(5):76-81.Liu Jie,Fu Yu.The Infiltrating Consolidation Characteristic of Clay[J].Journal of Hydraulic Engineering,1993(5):76-81.
[16] 陈荣波,束龙仓,鲁程鹏,等.含水层压密引起其特征参数变化的实验[J].吉林大学学报(地球科学版),2013,43(6):1958-1965.Chen Rongbo,Shu Longcang,Lu Chengpeng,et al.Experimental Study on the Characteristic Parameters Variation of the Aquifer Caused by Aquifer Compaction[J].Journal of Jilin University (Earth Science Edition),2013,43(6):1958-1965.
[17] 洪勃,李喜安,陈广东,等.重塑马兰黄土渗透性试验研究[J].工程地质学报,2016,24(2):276-283.Hong Bo,Li Xi’an,Chen Guangdong,et al.Experimental Study of Permeability of Remolded Malan Loess[J].Journal of Engineering Geology,2016,24(2):276-283.
[18] 矫德全,陈愈炯.土的各向异性和卸荷体缩[J].岩土工程学报,1994,16(4):9-16.Jiao Dequan,Chen Yujiong.Anisotropy and Volume-Contraction of Soil Due to Axial Unloading in CD Test[J].Chinese Jounal of Geotechnical Engineering,1994,16(4):9-16.
[19] Mast R F,Potter P E.Sedimentary Structures,Sand Shape Fabrics,and Permeability:II[J].The Journal of Geology,1963,71(5):548-565.
[20] 叶为民,杨林德,黄雨,等.上海软土微观空隙各向异性特征及其成因分析[J].工程地质学报,2004,12(增刊1):84-87.Ye Weimin,Yang Linde,Huang Yu,et al.Microstructure and Anisotropy of Seepage of Shanghai Soft Soil[J].Journal of Engineering Geology,2004,12(Sup.l):84-87.
[21] Chapuis R P,Gill D E.Hydraulic Anisotropy of Homogeneous Soils and Rocks:Influence of the Densification Process[J].Bulletin of the International Association of Engineering Geology,1989,39(1):75-86.
[22] 张坤勇,殷宗泽,梅国雄.土体两种各向异性的区别与联系[J].岩石力学与工程学报,2005,24(9):1599-1604.Zhang Kunyong,Yin Zongze,Mei Guoxiong.Difference and Connection of Two Kinds of Anisotropy of Soils[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(9):1599-1604.
[23] 殷宗泽,徐志伟.土体的各向异性及近似模拟[J].岩土工程学报,2002,24(5):547-551.Yin Zongze,Xu Zhiwei.Anisotropy of Soils and Its Approximate Simulation[J].Chinese Journal of Geotechnical Engineering,2002,24(5):547-551.
[24] 李瑞.非饱和黄土的次生各向异性及结构性试验研究[D].杨凌:西北农林科技大学,2008.Li Rui.Research on Induced Anisotropy and Structural Characteristic of Unsaturated Loess[D].Yangling:Northwest A&F University,2008.
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