压实黄土(Q_2)溶滤变形特性研究
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摘要
为探究压实黄土(Q_2)溶滤变形特性,开展12种应力组合条件下的宏观溶滤试验及不同浸水时长的微观电镜扫描试验。宏观试验结果表明,溶滤应变及强度参数变化具时效性;其中,溶滤轴、体应变及应变率近似自然指数变化,黏聚力随浸水时长增加而减小,内摩擦角变化不大。围压应力对溶滤变形有阻碍作用,湿化应力水平s对溶滤应变有促进作用,并决定其量级。微观参数定量分析表明,随浸水时长增加,微观孔隙的孔径、概率熵和分形维数减小,团粒概率熵和分形维数增大,团粒粒径和曲率系数变小,微观孔隙比和连接系数分别减小和增大。孔径与粒径均减小的现象表明,溶滤变形是浸水和压力共同作用下的压密过程。其次,试样粒径变化率随s减小趋于降低,表明微结构破坏重组程度与s成正比。此外,通过KPCA法确定了影响溶滤体应变的3个主要参数为孔径、孔隙分形维数和曲率系数;影响黏聚力的2个主要参数为孔隙概率熵和团粒分形维数。
In order to explore the leaching deformation characteristics of compacted loess(Q_2),macroscopic leaching tests with 12 kinds of stress combinations and SEM tests with different immersion times were carried out. The results indicate that the changes of leaching strain and strength parameters have timeliness characteristics. The leaching axis,bulk strain and strain rate vary with the immersion time in a natural exponential function. The cohesive force decreases with increasing the duration of immersion but the internal friction angle changes little. For test control variable,the confining pressure has a hindering effect on the leaching deformation,and the slaking stress promotes the process of the leaching strain and determines the magnitude of the leaching strain. The quantitative analysis of microscopic parameters shows that,with increasing the immersion time,the pore size,the probability entropy and the fractal dimension of micro pores decrease while the probability entropy and fractal dimension of the cluster increase,and that the microscopic void ratio,the cluster size and curvature coefficient of the cluster decrease as the immersion time increases but the connection coefficient increase. The decreases of the pore size and the particle size indicate that the leaching deformation is a compaction process under the combined action of the immersion and the pressure. The change rate of the cluster size decrease with decreasing the slaking stress,which indicates that the degree of microstructure failure and recombination is proportional to the slaking stress. Three main microscopic parameters affecting the leaching volumetric strain such as the pore size,the fractal dimension of pores and the microscopic curvature coefficient,and two parameters influencing the cohesion including the pore probability entropy and the cluster fractal dimension were determined by KPCA method.
In order to explore the leaching deformation characteristics of compacted loess(Q_2),macroscopic leaching tests with 12 kinds of stress combinations and SEM tests with different immersion times were carried out. The results indicate that the changes of leaching strain and strength parameters have timeliness characteristics. The leaching axis,bulk strain and strain rate vary with the immersion time in a natural exponential function. The cohesive force decreases with increasing the duration of immersion but the internal friction angle changes little. For test control variable,the confining pressure has a hindering effect on the leaching deformation,and the slaking stress promotes the process of the leaching strain and determines the magnitude of the leaching strain. The quantitative analysis of microscopic parameters shows that,with increasing the immersion time,the pore size,the probability entropy and the fractal dimension of micro pores decrease while the probability entropy and fractal dimension of the cluster increase,and that the microscopic void ratio,the cluster size and curvature coefficient of the cluster decrease as the immersion time increases but the connection coefficient increase. The decreases of the pore size and the particle size indicate that the leaching deformation is a compaction process under the combined action of the immersion and the pressure. The change rate of the cluster size decrease with decreasing the slaking stress,which indicates that the degree of microstructure failure and recombination is proportional to the slaking stress. Three main microscopic parameters affecting the leaching volumetric strain such as the pore size,the fractal dimension of pores and the microscopic curvature coefficient,and two parameters influencing the cohesion including the pore probability entropy and the cluster fractal dimension were determined by KPCA method.
引文
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[18]徐日庆,邓祎文,徐波,等.基于SEM图像的软土三维孔隙率计算及影响因素分析[J].岩石力学与工程学报,2015,34(7):1 497-1 502.(XU Riqing,DENG Yiwen,XU Bo,et al.Calculation of three-dimensional porosity of soft soil based on SEM image[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(7):1 497-1 502.(in Chinese))
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[21]张尧庭,方开泰.多元统计分析引论[M].北京:科学出版社,1982:322-328.(ZHANG Yaoting,FANG Kaitai.Introduction to multivariate statistical analysis[M].Beijing:Science Press,1982:322-328.(in Chinese))
[2]张秀成,王义重,傅旭东.不同应力路径下某高速公路路基黏性土湿化变形试验研究[J].岩土力学,2010,31(6):1 791-1 796.(ZHANG Xiucheng,WANG Yizhong,FU Xudong.Experimental research on wetting deformation of clayey soil of a freeway subgrade with different stress paths[J].Rock and Soil Mechanics,2010,31(6):1 791-1 796.(in Chinese))
[3]殷宗泽,赵航.土坝浸水变形分析[J].岩土工程学报,1990,12(2):1-8.(YIN Zongze,ZHAO Hang.Deformation analysis of earth dam during reservoir filling[J].Chinese Journal of Geotechnical Engineering,1990,12(2):1-8.(in Chinese))
[4]袁聚云.土工试验与原理[M].上海:同济大学出版社,2008:179-185.(YUAN Juyun.Geotechnical tests and priciples[M].Shanghai:Tongji University Press,2008:179-185.(in Chinese))
[5]方祥位,沈春妮,汪龙,等.Q2黄土浸水前后微观结构变化研究[J].岩土力学,2013,34(5):1 319-1 324.(FANG Xiangwei,SHENChunni,WANG Long,et al.Research on microstructure of Q2 loess before and after wetting[J].Rock and Soil Mechanics,2013,34(5):1 319-1 324.(in Chinese))
[6]李姝,许强,张立展.黑方台地区黄土强度弱化的浸水时效特征与机制分析[J].岩土力学,2017,38(7):2 043-2 058.(LI Shu,XU Qiang,ZHANG Lizhan.Time effect and mechanism of strength weakening of loess soaked in water in Heifangtai area[J].Rock and Soil Mechanics,2017,38(7):2 043-2 058.(in Chinese))
[7]高凌霞.黄土湿陷性的微结构效应及其评价方法研究[博士学位论文][D].大连:大连理工大学,2010.(GAO Lingxia.Study on microstructural effects on collapsibility of loess and its evaluation methods[Ph.D.Thesis][D].Dalian:Dalian University of Technology,2010.(in Chinese))
[8]傅旭东,邱晓红,赵刚,等.巫山县污水处理厂高填方地基湿化变形试验研究[J].岩土力学,2004,25(9):1 385-1 389.(FUXudong,QIU Xiaohong,ZHAO Gang,et al.Experimental research on slaking deformation of high fill of Wushan municipal sewage treatment plant[J].Rock and Soil Mechanics,2004,25(9):1 385-1 389.(in Chinese))
[9]马闫,王家鼎,彭淑君,等.大厚度黄土自重湿陷性场地浸水湿陷变形特征研究[J].岩土工程学报,2014,36(3):537-546.(MAYan,WANG Jiading,PENG Shujun,et al.Immersion tests on characteristics of deformation of self-weight collapsible loess under overburden pressure[J].Chinese Journal of Geotechnical Engineering,2014,36(3):537-546.(in Chinese))
[10]陈正汉,刘祖典.黄土的湿陷变形机理[J].岩土工程学报,1986,8(2):1-12.(CHEN Zhenghan,LIU Zudian.Mechanism collapsible deformation of loess[J].Chinese Journal of Geotechnical Engineering,1986,8(2):1-12.(in Chinese))
[11]中华人民共和国行业标准编写组.GB50025-2004湿陷性黄土地区建筑规范[S].北京:中国建筑工业出版社,2004.(The National Standards Compilation Group of People′s Republic of China.GB50025-2004 Building code for collapsible loess area[S].Beijing:China Architecture and Building Press,2004.(in Chinese))
[12]陈正汉.重塑非饱和黄土的变形、强度、屈服和水量变化特性[J].岩土工程学报,1999,21(1):82-90.(CHEN Zhenghan.Deformation,strength,yield and moisture change of a remolded unsaturated loess[J].Chinese Journal of Geotechnical Engineering,1999,21(1):82-90.(in Chinese))
[13]HICHER P Y,CHANG C S.A microstructural elastoplastic model for unsaturated granular materials[J].International Journal of Solids and Structures,2007,44(7/8):2 304-2 323.
[14]唐朝生,施斌,王宝军.基于SEM土体微观结构研究中的影响因素分析[J].岩土工程学报,2008,30(4):560-565.(TANGChaosheng,SHI Bin,WANG Baojun.Factors affecting analysis of soil microstructure using SEM[J].Chinese Journal of Geotechnical Engineering,2008,30(4):560-565.(in Chinese))
[15]洪宝宁,刘鑫.土体微细结构理论与试验[M].北京:科学出版社,2010:88-94.(HONG Baoning,LIU Xin.Soil micro-structure theory and experiment[M].Beijing:Science Press,2010:88-94.(in Chinese))
[16]LIU C,SHI B,ZHOU J,et al.Quantification and characterization of microporosity by image processing,geometric measurement and statistical methods:application on SEM images of clay materials[J].Applied Clay Science,2011,54(1):97-106.
[17]陈仲颐,周景星,王洪瑾,等.土力学[M].北京:清华大学出版社,2009:125-127.(CHEN Zhongyi,ZHOU Jingxing,WANGHongjin,et al.Soil mechanics[M].Beijing:Tsinghua University Press,2009:125-127.(in Chinese))
[18]徐日庆,邓祎文,徐波,等.基于SEM图像的软土三维孔隙率计算及影响因素分析[J].岩石力学与工程学报,2015,34(7):1 497-1 502.(XU Riqing,DENG Yiwen,XU Bo,et al.Calculation of three-dimensional porosity of soft soil based on SEM image[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(7):1 497-1 502.(in Chinese))
[19]OSIPOV Y B,SOKOLOV B A.Quantitative characteristics of clay fabrics using the method of magnetic anisotropy[J].Bulletin of Engineering Geology and the Environment,1972,5(1):23-38.
[20]SCH?LKOPF B,SMOLA A,MüLLER K R.Nonlinear component analysis as a kernel eigenvalue problem[J].Neural Computation,2014,10(5):1 299-1 319.
[21]张尧庭,方开泰.多元统计分析引论[M].北京:科学出版社,1982:322-328.(ZHANG Yaoting,FANG Kaitai.Introduction to multivariate statistical analysis[M].Beijing:Science Press,1982:322-328.(in Chinese))