德州地区土体固结过程微观结构的显微观测分析
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摘要
土体的宏观工程力学性质受土体微细结构状态和变化规律的影响,其复杂的物理力学特性是微细结构特性的本质体现。为探明宏观土体沉降现象背后的本质机理,对德州地区沉降中心附近土体进行钻孔取芯,对五组不同深度土体试样进行不同荷载下的固结试验与SEM电镜扫描试验,探讨不同深度粘性土随着固结压力变化,土体压缩性及其微观结构的变化规律,总结土体微结构特征与微观参数变化特征,以期从细观本质机理上解释德州地区地面沉降的宏观现象。结果表明,随着固结压力的变化,土体的平均颗粒面积呈增大趋势,土体颗粒扁圆度提高。单元体排列概率熵均呈明显下降趋势,土体颗粒与土内孔隙分布定向性提高。不同深度的五组土体孔隙分布分维数均呈下降趋势且最终趋于稳定,颗粒分布分维数则明显上升,土体密实程度提高。
The macroscopic engineering mechanical properties of soil are influenced by the state and variation of soil microstructure,and its complex physical and mechanical properties are the essential embodiment of microstructure characteristics.In order to find out the essential mechanism behind the macroscopic soil subsidence phenomenon,the core of soil is drilled near the settlement center of Dezhou area,and consolidation experiment and SEM observation were carried out for five groups of soil samples with different depth and subjected to different loads.The change of soil compressibility and its microstructure with consolidation pressure in different depth are discussed,and the characteristics of microstructure and parameters of soil are summarized.The aim is to explain the macroscopic phenomenon of land subsidence in Dezhou area from the mesoscopic essential mechanism of.Results show that with the change of consolidation pressure,the average particle size of soil is increasing and the soil particles have a higher degree of flatness.The probability entropy of the soil particle arrangement was significantly decreased,and the distribution of soil particles was more targeted.The distribution fractal dimension of the five groups of soil in different depths falls down and remains stable ultimately,while the fractal dimension of particle distribution increases obviously,and the soil compaction degree increases.
The macroscopic engineering mechanical properties of soil are influenced by the state and variation of soil microstructure,and its complex physical and mechanical properties are the essential embodiment of microstructure characteristics.In order to find out the essential mechanism behind the macroscopic soil subsidence phenomenon,the core of soil is drilled near the settlement center of Dezhou area,and consolidation experiment and SEM observation were carried out for five groups of soil samples with different depth and subjected to different loads.The change of soil compressibility and its microstructure with consolidation pressure in different depth are discussed,and the characteristics of microstructure and parameters of soil are summarized.The aim is to explain the macroscopic phenomenon of land subsidence in Dezhou area from the mesoscopic essential mechanism of.Results show that with the change of consolidation pressure,the average particle size of soil is increasing and the soil particles have a higher degree of flatness.The probability entropy of the soil particle arrangement was significantly decreased,and the distribution of soil particles was more targeted.The distribution fractal dimension of the five groups of soil in different depths falls down and remains stable ultimately,while the fractal dimension of particle distribution increases obviously,and the soil compaction degree increases.
引文
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[16]施斌.粘性土微观结构研究回顾与展望[J].工程地质学报,1996,4(1):39-44(SHI Bin.Review and prospect on the microstructure of clayey soil[J].Journal of Engineering Geology,1996,4(1):39-44(in Chinese))
[17]王来贵,张红记,张春会,等.含水率和围压对安家岭泥岩峰后力学特性影响的试验研究[J].实验力学,2016,31(5):683-693(WANG Laigui,ZHANG Hongji,ZHANG Chunhui,et al.Experimental investigation on the effects of confining pressure and moisture content on post-peak mechanical behavior of anjialing mudstone[J].Journal of Experimental Mechanics,2016,31(5):683-693(in Chinese))
[18]王怀文,周宏伟,谢和平,等.扫描电镜下断口表面的三维重建及分形维数的测量[J].实验力学,2008,23(2):118-124(WANG Huaiwen,ZHOU Hongwei,XIE Heping,et al.3Dreconstruction and fractal dimension measurement of a fracture surface under SEM[J].Journal of Experimental Mechanics,2008,23(2):118-124(in Chinese))
[19]马莉英,肖树芳,王清.黄土的流变特性模拟与研究[J].实验力学,2004,21(2):178-182(MA Liying,XIAO Shufang,WANG Qing.Simulation and study on rheological behavior of loess[J].Journal of Experimental Mechanics,2004,21(2):178-182(in Chinese))
[20]周晖.珠江三角洲软土显微结构与渗流固结机理研究[D].华南理工大学,2013(ZHOU Hui.Study on soft soil microstructure and mechanism of seepage and consolidation in Pearl River Delta(PRD)[D].South China University of Technology,2013(in Chinese))
[2]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(4):560-565(TANG Chaosheng,SHI Bin,WANG Baojun.Factors affecting analysis of soil microstructure using SEM[J].Chinese Journal of Geotechnical Engineering,2008(4):560-565(in Chinese))
[3]周建,邓以亮,曹洋,等.杭州饱和软土固结过程微观结构试验研究[J].中南大学学报(自然科学版),2014,45(6):1998-2005(ZHOU Jian,DENG Yiliang,CAO Yang,et al.Experimental study of microstructure of Hangzhou saturated soft soil during consolidation process[J].Journal of Central South University(Science and Technology),2014,45(6):1998-2005(in Chinese))
[4]冯德銮,房营光,侯明勋.土体力学特性颗粒尺度效应的理论与试验研究[J].岩土力学,2015,36(S1):209-214(FENG Deluan,FANG Yingguang,HOU Mingxun.Theoretical and experimental studies of particle size effect of mechanical properties of soil[J].Rock and Soil Mechanics,2015,36(S1):209-214(in Chinese))
[5]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):1497-1502(XU Riqing,DENG Yiwen,XU Bo,et al.Calculation of three-dimension porosity of soft soil based on SEM image[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(7):1497-1502(in Chinese))
[6]方庆军,洪宝宁.岩土体微细结构研究进展[J].科学技术与工程,2014,14(17):143-149(FANG Qingjun,HONG Baoning.Research progress at geotechnical micro and mesostructure[J].Science Technology and Engineering,2014,14(17):143-149(in Chinese))
[7]尹振宇.土体微观力学解析模型:进展及发展[J].岩土工程学报,2013,35(6):993-1009(YIN Zhenyu.Micromechanics-based analytical model for soils:review and development[J].Chinese Journal of Geotechnical Engineering,2013,35(6):993-1009(in Chinese))
[8]周晖,房营光,禹长江.广州软土固结过程微观结构的显微观测与分析[J].岩石力学与工程学报,2009,28(S2):3830-3837(ZHOU Hui,FANG Yingguang,YU Changjiang.Microstructure observation and analysis of Guangzhou soft soil during consolidation process[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(2):3830-3837(in Chinese))
[9]施斌,姜洪涛.粘性土微观结构分析技术研究[J].岩石力学与工程学报,2001,20(6):864-870(SHI Bin,JIANG Hongtao.Research on the analysis techniques for clayey soil microstructure[J].Chinese Journal of Rock Mechanics and Engineering,2001,20(6):864-870(in Chinese))
[10]汤强,刘春,顾颖凡,等.土体SEM图像微观结构的识别和统计方法[J].桂林理工大学学报,2017,37(3):547-552(TANG Qiang,LIU Chun,GU Yinfan,et al.Microstructure identification and statistical method of the soil SEM image[J].Journal of Guilin University of Technology,2017,37(3):547-552(in Chinese))
[11]孟庆山,杨超,许孝祖,等.动力排水固结前后软土微观结构分析[J].岩土力学,2008,29(7):1759-1763(MENG Qingshan,YANG Chao,XU Xiaozu,et al.Analysis of microstructure of soft clay before and after its improvement with dynamic consolidation by drainage[J].Rock and Soil Mechanics,2008,29(7):1759-1763(in Chinese))
[12]孔令荣,黄宏伟,张冬梅,等.不同固结压力下饱和软黏土孔隙分布试验研究[J].地下空间与工程学报,2007,3(6):1036-1040(KONG Lingrong,HUANG Hongwei,ZHANG Dongmei,et al.Experiment study on relationship between pore distribution and different stress levels due to consolidation of soft clays[J].Chinese Journal of Underground Space and Engineering,2007,3(6):1036-1040(in Chinese))
[13]陈嘉鸥,叶斌,郭素杰.珠江三角洲黏性土微结构与工程特性初探[J].岩石力学与工程学报,2000,19(5):132-136(CHEN Jiaou,YE Bin,GUO Sujie.Detecting clay′s micro-structure and engineering properties of PRD[J].Chinese Journal of Rock Mechanics and Engineering,2000,19(5):132-136(in Chinese))
[14]白冰,周健.扫描电子显微镜测试技术在岩土工程中的应用与进展[J].电子显微镜学报,2001,20(2):154-155(BAI Bing,ZHOU Jian.The applications and advances of SEM in geotechnical engineering[J].Journal of Chinese Electron Microscopy Society,2001,20(2):154-155(in Chinese))
[15]施斌.黏性土微观结构定向性的定量研究[J].地质学报,1997,71(1):36-44(SHI Bin.Quantitative research of clay microstructure orientation characteristics for clay[J].Geological Journal,1997,71(1):36-44(in Chinese))
[16]施斌.粘性土微观结构研究回顾与展望[J].工程地质学报,1996,4(1):39-44(SHI Bin.Review and prospect on the microstructure of clayey soil[J].Journal of Engineering Geology,1996,4(1):39-44(in Chinese))
[17]王来贵,张红记,张春会,等.含水率和围压对安家岭泥岩峰后力学特性影响的试验研究[J].实验力学,2016,31(5):683-693(WANG Laigui,ZHANG Hongji,ZHANG Chunhui,et al.Experimental investigation on the effects of confining pressure and moisture content on post-peak mechanical behavior of anjialing mudstone[J].Journal of Experimental Mechanics,2016,31(5):683-693(in Chinese))
[18]王怀文,周宏伟,谢和平,等.扫描电镜下断口表面的三维重建及分形维数的测量[J].实验力学,2008,23(2):118-124(WANG Huaiwen,ZHOU Hongwei,XIE Heping,et al.3Dreconstruction and fractal dimension measurement of a fracture surface under SEM[J].Journal of Experimental Mechanics,2008,23(2):118-124(in Chinese))
[19]马莉英,肖树芳,王清.黄土的流变特性模拟与研究[J].实验力学,2004,21(2):178-182(MA Liying,XIAO Shufang,WANG Qing.Simulation and study on rheological behavior of loess[J].Journal of Experimental Mechanics,2004,21(2):178-182(in Chinese))
[20]周晖.珠江三角洲软土显微结构与渗流固结机理研究[D].华南理工大学,2013(ZHOU Hui.Study on soft soil microstructure and mechanism of seepage and consolidation in Pearl River Delta(PRD)[D].South China University of Technology,2013(in Chinese))