非饱和黄土震陷物理力学机制与主导影响因素
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摘要
通过分析黄土震陷的物理过程及其力学机制,指出非饱和黄土震陷实质上是土体广义固相介质响应外部动荷载作用的再固结过程。将影响黄土震陷的主导因素归纳为两方面,即土体广义固相介质的强度、体积特征和外部动荷载特征。介质的强度特征可通过引入土工试验获取的参数(粘聚力和内摩擦角)来宏观表征;体积特征可由能够反映土体欠压密程度的孔隙比描述。与非饱和黄土震陷的宏观物理力学机制相适应,粘聚力与内摩擦角主要反映土体的结构性强度(黄土强度特征),孔隙比则反映了土体再固结的潜在性态(黄土沉降量值特征);黄土强度特征对应土体抵御外部载荷的能力,黄土沉降量值特征对应外部载荷作用下的土体沉降能力。
Based on the comprehensive analysis of physical process and mechanical mechanism of loess seismic subsidence,the seismic subsidence of unsaturated loess could be described as a consolidation response of generalized solid-phase-media of soil mass under external dynamic loading.The dominant influence factors of loess seismic subsidence should include two aspects,which are the strength and volume characteristics of generalized solid-phase-media of soil mass and external dynamic loading features.The strength characteristic of the media could be figured by the cohesion and internal friction angle,both obtained expediently through laboratory geotechnical tests,while the volume feature of the media could be described by the void ratio.By the view of the macro physical-mechanical mechanism of seismic subsidence in unsaturated loess,the factors of cohesion and internal friction angle briefly represent the characteristics of soil structure strength,and the factor of void ratio influences the final seismic subsidence magnitude of soil mass.In fact,the strength feature of loess shows the endurance capacity of soil mass to resist the external dynamic loading meanwhile,the subsidence magnitude characteristic of loess describes the settlement capacity of soil mass under the external dynamic loading.
Based on the comprehensive analysis of physical process and mechanical mechanism of loess seismic subsidence,the seismic subsidence of unsaturated loess could be described as a consolidation response of generalized solid-phase-media of soil mass under external dynamic loading.The dominant influence factors of loess seismic subsidence should include two aspects,which are the strength and volume characteristics of generalized solid-phase-media of soil mass and external dynamic loading features.The strength characteristic of the media could be figured by the cohesion and internal friction angle,both obtained expediently through laboratory geotechnical tests,while the volume feature of the media could be described by the void ratio.By the view of the macro physical-mechanical mechanism of seismic subsidence in unsaturated loess,the factors of cohesion and internal friction angle briefly represent the characteristics of soil structure strength,and the factor of void ratio influences the final seismic subsidence magnitude of soil mass.In fact,the strength feature of loess shows the endurance capacity of soil mass to resist the external dynamic loading meanwhile,the subsidence magnitude characteristic of loess describes the settlement capacity of soil mass under the external dynamic loading.
引文
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[2]《地球科学大辞典》编委会.地球科学大辞典(基础学科卷)[M].北京:地质出版社,2006.
[3]雷祥义.中国黄土的孔隙类型与湿陷性[J].中国科学(B),1987,(12):1309-1316.
[4]高国瑞.黄土显微结构分类与湿陷性[J].中国科学,1980,(12):1203-1208.
[5]王永焱,滕志宏.中国黄土的显微结构及其在时代上和区域上的变化[J].科学通报,1982,27(2):102-105.
[6]王兰民.黄土动力学[M].北京:地震出版社,2003.
[7]苗天德,刘忠玉,任九生.湿陷性黄土的变形机理与本构关系[J].岩土工程学报,1999,21(4):783-787.
[8]Rogers C D F,Dijkstra T A,Smalley I J.Hydroconsolidation and subsidence of loess:studies from China,Russia,North America and Europe[J].Engineering Geology,1994,37(2):83-113.
[9]Feda J.Structural stability of subsident loess soils from Praha-Dejvice[J].Engineering Geology,1966,1(3):201-219.
[10]杨运来.黄土湿陷机理的研究[J].中国科学(B辑),1988,(7):754-766.
[11]高国瑞.我国黄土湿陷性质的形成研究[J].南京建筑工程学院学报,1994,(2):1-8.
[12]谢定义.试论我国黄土力学研究中的若干新趋向[J].岩土工程学报,2001,23(1):3-13.
[13]甘肃省质量技术监督局,甘肃省建设厅.兰州市区建筑抗震设计规程(DB62/T25-3037-2006)[S].北京:中国建筑工业出版社,2007.
[14]王兰民,张振中.地震时黄土震陷量的估算方法[J].自然灾害学报,1993,2(3):85-94.
[15]邓津,王兰民,张振中.黄土显微结构特征与震陷性[J].岩土工程学报,2007,29(4):542-548.
[16]邓津.黄土微观结构的区域成土环境与震害机理研究[D].兰州:兰州大学.2009.
[17]Ayman A Abed,Pieter A,Vermeer.Numerical simulation of unsaturated soil behaviour[J].International Journal of Computer Applications in Technology,2009,34(1):2-12.
[18]沈珠江.广义吸力和非饱和土的统一变形理论[J].岩土工程学报,1996,18(2):1-9.
[19]孙军杰.黄土场地震陷与桩基负摩阻力现场试验研究[D].兰州:兰州大学,2010.
[20]《工程地质手册》编写委员会.工程地质手册[M].北京:中国建筑工业出版社,2004.
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