砂土最大最小孔隙比测定及其影响因素分析
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摘要
相对密实度是影响砂土力学性质的重要指标,密实的砂土呈现强度软化,松散的砂土却呈现强度硬化,而测定最大、最小孔隙比是计算相对密实度的前提。砂土的最小及最大孔隙比是通过直接测定的相应最大、最小干密度换算得到的,但目前常忽略了试验方法对其试验结果的影响,也忽略了黏粒含量对砂样密实度的影响。现取细、中、粗砂3种砂样,进行了干密度测试试验并测定了不同黏粒及黏粒掺量下砂样的最大、最小孔隙比。研究结果表明:采用量筒慢转法测量砂土最小干密度较为合理;采用振动锤击法测定砂土最大干密度时,建议细砂采用容积为250 m L击实筒,中、粗砂采用1000 m L击实筒;掺入粉粒、黏粒后砂样的最小孔隙比均随黏粒掺量(≤30%)增加而减小,且两者之间存在一定的线性关系;砂样最大孔隙比随粉粒、黏粒掺量增加逐渐减小,而随高岭土黏粒掺量增加呈缓慢增大趋势。
The mechanical behaviors of sand are heavily dependent on its relative density: the dense sand exhibits softening strength; on the contrary, the loose one displays hardening strength. Furthermore, the relative density is determined based on the maximum and minimum void ratios. The maximum and minimum void ratios are commonly obtained by using the maximum and minimum densities, ignoring the effects of test methods and clay contents in sand. The maximum and minimum void ratios are tested by considering three different sized groups of sands with various clay contents. It is shown that the minimum dry density can be attained in a measuring cylinder with low rotation speed. In addition, it is suggested that the maximum dry density of fine sands should be measured with the 250 m L compaction cylinder combining vibration with hit, while the 1000 m L compaction cylinder is suitable for medium and coarse sands. The results also show that the void ratio decreases with the increase in clay contents(less than 30%), while there is a linear relationship between the clay contents and the void ratio of sands. However, the maximum void ratio of sand decreases with increasing content of silty clay and clay, and increases with increasing content of kaolin clay.
The mechanical behaviors of sand are heavily dependent on its relative density: the dense sand exhibits softening strength; on the contrary, the loose one displays hardening strength. Furthermore, the relative density is determined based on the maximum and minimum void ratios. The maximum and minimum void ratios are commonly obtained by using the maximum and minimum densities, ignoring the effects of test methods and clay contents in sand. The maximum and minimum void ratios are tested by considering three different sized groups of sands with various clay contents. It is shown that the minimum dry density can be attained in a measuring cylinder with low rotation speed. In addition, it is suggested that the maximum dry density of fine sands should be measured with the 250 m L compaction cylinder combining vibration with hit, while the 1000 m L compaction cylinder is suitable for medium and coarse sands. The results also show that the void ratio decreases with the increase in clay contents(less than 30%), while there is a linear relationship between the clay contents and the void ratio of sands. However, the maximum void ratio of sand decreases with increasing content of silty clay and clay, and increases with increasing content of kaolin clay.
引文
[1]TAVENAS F,ROCHELLE P.Accuracy of relative density measurements[J].Géotechnique,1972,22(4):549–562.
[2]DAS B,SOBHAN K.Principles of geotechnical engineering[M].7th ed.New York:Cengage Learning,2010:51–72.
[3]GB/T 50123—1999土工试验方法标准[S].1999.(GB/T50123—1999 Standard for soil test method[S].1999.(in Chinese))
[4]HUMPRHES H W.A method for controlling compaction of granular materials[J].Highway Research Board Bulletin,1957,159:41–57.
[5]郭庆国,刘贞草.确定大径粒粗粒土最大密度的近似方法[J].西北水资源与水工程,1992,3(1):12–21.(GUO Qing-guo,LIU Zhen-cao.Approximation of maximum density of coarse-grained soils[J].Water Resources&Water Engineering,1992,3(1):12–21.(in Chinese))
[6]李细荣.基于激光图像土的压实度检测方法的研究[D].西安:长安大学,2013.(LI Xi-rong.Research on detection method of compaction degree based on laser image of soil[D].Xi'an:Chang'an University,2013.(in Chinese))
[7]邹峰.基于数字图像处理技术的砂土干密度评价研究[D].镇江:江苏科技大学,2015.(ZOU Feng.Based on digital image processing technology of sandy soil compactness appraisal research[D].Zhenjiang:Jiangsu University of Science and Technology,2015.(in Chinese))
[8]CUBRINOVSKI M,ISHIHARA K.Maximum and minimum void ratio characteristics of sand[J].Japanese Geotechnical Society,2002,42(6):65–78.
[9]MUSZYNSKI M R.Determination of maximum and minimum density of poorly graded sands using a simplified method[J].Geotechnical Testing Journal,2006,29(3):263–272.
[10]范孟华,邹正伟.改进砂的相对密度试验方法的建议[J].路基工程,2007(5):67–68.(FAN Meng-hua,ZOU Zheng-wei.Suggestions on improving testing method for relative density of sand[J].Subgrade Engineering,2007(5):67–68.(in Chinese))
[11]范孟华,孔德志.砂相对密度试验方法的改进[J].岩矿测试,2007,26(5):428–430.(FAN Meng-hua,KONG De-zhi.Improvement on method for relative density of sand experiments[J].Rock&Mineral Analysis,2007,26(5):67–68.(in Chinese))
[12]DAS B,SOBHAN K.Principles of geotechnical engineering[M].8th ed.New York:Cengage Learning,2014.
[13]SAMARASINGHE M,HUANG Y,DRENEVICH P.Permeability and consolidation of normally consolidated soils[J].Journal of the Geotechnical Engineering Division,ASCE,1982,108(6):835–850.
[14]YILMAZ Y.A study on the limit void ratio characteristics of medium to fine mixed graded sands[J].Engineering Geology,2009,104(3):290–294.
[15]LADE P V,YANAMURO J A,LIGGIO G D.Effects of fines content on void ratio,compressibility,and static liquefaction of silty sand[J].Geomechanics and Engineering,2009,1(1):1–15.
[16]CHANGA C S,WANGB J Y,GEB L.Modeling of minimum void ratio for sand-silt mixtures[J].Engineering Geology,2015,196:293–304.
[17]CHANGA C S,WANGB J Y,GEB L.Maximum and minimum void ratios for sand-silt mixtures[J].Engineering Geology,2016,211:7–18.
[18]YANG S,LACASSE S R.Determination of the transitional fines content of mixtures of sand and non-plastic fines[J].Geotechnical Testing Journal,2006,29(2):102–107.
[19]DASH H K,SITHARAM T G,BAUDET B A.Influence of non-plastic fines on the response of a silty sand to cyclic loading[J].Soils and Foundations,2010,50(5):695–704.
[20]ANTHI P,THEODORA T.The effect of fines on critical state and liquefaction resistance characteristics of non-plastic silty sands[J].Soils and Foundations,2008,48(5):713–725.
[2]DAS B,SOBHAN K.Principles of geotechnical engineering[M].7th ed.New York:Cengage Learning,2010:51–72.
[3]GB/T 50123—1999土工试验方法标准[S].1999.(GB/T50123—1999 Standard for soil test method[S].1999.(in Chinese))
[4]HUMPRHES H W.A method for controlling compaction of granular materials[J].Highway Research Board Bulletin,1957,159:41–57.
[5]郭庆国,刘贞草.确定大径粒粗粒土最大密度的近似方法[J].西北水资源与水工程,1992,3(1):12–21.(GUO Qing-guo,LIU Zhen-cao.Approximation of maximum density of coarse-grained soils[J].Water Resources&Water Engineering,1992,3(1):12–21.(in Chinese))
[6]李细荣.基于激光图像土的压实度检测方法的研究[D].西安:长安大学,2013.(LI Xi-rong.Research on detection method of compaction degree based on laser image of soil[D].Xi'an:Chang'an University,2013.(in Chinese))
[7]邹峰.基于数字图像处理技术的砂土干密度评价研究[D].镇江:江苏科技大学,2015.(ZOU Feng.Based on digital image processing technology of sandy soil compactness appraisal research[D].Zhenjiang:Jiangsu University of Science and Technology,2015.(in Chinese))
[8]CUBRINOVSKI M,ISHIHARA K.Maximum and minimum void ratio characteristics of sand[J].Japanese Geotechnical Society,2002,42(6):65–78.
[9]MUSZYNSKI M R.Determination of maximum and minimum density of poorly graded sands using a simplified method[J].Geotechnical Testing Journal,2006,29(3):263–272.
[10]范孟华,邹正伟.改进砂的相对密度试验方法的建议[J].路基工程,2007(5):67–68.(FAN Meng-hua,ZOU Zheng-wei.Suggestions on improving testing method for relative density of sand[J].Subgrade Engineering,2007(5):67–68.(in Chinese))
[11]范孟华,孔德志.砂相对密度试验方法的改进[J].岩矿测试,2007,26(5):428–430.(FAN Meng-hua,KONG De-zhi.Improvement on method for relative density of sand experiments[J].Rock&Mineral Analysis,2007,26(5):67–68.(in Chinese))
[12]DAS B,SOBHAN K.Principles of geotechnical engineering[M].8th ed.New York:Cengage Learning,2014.
[13]SAMARASINGHE M,HUANG Y,DRENEVICH P.Permeability and consolidation of normally consolidated soils[J].Journal of the Geotechnical Engineering Division,ASCE,1982,108(6):835–850.
[14]YILMAZ Y.A study on the limit void ratio characteristics of medium to fine mixed graded sands[J].Engineering Geology,2009,104(3):290–294.
[15]LADE P V,YANAMURO J A,LIGGIO G D.Effects of fines content on void ratio,compressibility,and static liquefaction of silty sand[J].Geomechanics and Engineering,2009,1(1):1–15.
[16]CHANGA C S,WANGB J Y,GEB L.Modeling of minimum void ratio for sand-silt mixtures[J].Engineering Geology,2015,196:293–304.
[17]CHANGA C S,WANGB J Y,GEB L.Maximum and minimum void ratios for sand-silt mixtures[J].Engineering Geology,2016,211:7–18.
[18]YANG S,LACASSE S R.Determination of the transitional fines content of mixtures of sand and non-plastic fines[J].Geotechnical Testing Journal,2006,29(2):102–107.
[19]DASH H K,SITHARAM T G,BAUDET B A.Influence of non-plastic fines on the response of a silty sand to cyclic loading[J].Soils and Foundations,2010,50(5):695–704.
[20]ANTHI P,THEODORA T.The effect of fines on critical state and liquefaction resistance characteristics of non-plastic silty sands[J].Soils and Foundations,2008,48(5):713–725.