水的作用下黄土崩塌形成的机理研究

发布时间：2018-04-13 02:25

本文选题：黄土崩塌 + 工程特性　；参考：《西安科技大学》2015年硕士论文

【摘要】：黄土崩塌是西北黄土高原地区最常见、最严重的一种地质灾害。黄土是一种松散沉积物,是在第四纪特殊的气候条件下形成的,具有大孔隙、垂直节理发育等特殊性质,在水的作用、切坡卸载、地震等外在触发因素作用下黄土高原地区崩塌灾害频繁发生。在水的作用下,黄土崩塌的形成,首先是由于土体内裂隙的发育、发展以及贯通;其次由于边坡坡脚发生破坏从而失去支撑力,最终在其共同的作用下导致崩塌的形成。因此开展水的作用下黄土体的节理裂隙的发育以及物理力学性质的变化规律等方面的机理研究,对治理防护黄土地区崩塌等灾害具有重要的指导意义。在收集已有黄土地区崩塌灾害的研究成果以及对黄土地区黄土崩塌灾害进行补充调查的基础上,以延安市洛川塬边缘为典型研究场地,通过野外踏勘、测绘以及相关资料的收集,总结阐述了水的作用对黄土体自身表现出的工程特性具有重要影响,研究分析了黄土体的工程特性对于导致黄土崩塌灾害具有一定内在联系;通过干湿循环试验,利用CT扫描研究水的物理作用—干湿循环对黄土内部结构劣化的影响规律;针对干湿循环后土样的强度力学试验,研究干湿循环次数、干湿循环幅度与土体强度劣化等相关参数的关系;通过室内物理力学试验,研究在水的化学作用—溶蚀作用对黄土体的物理力学性质的影响;并利用Abaqus软件,结合理论分析与数值模拟等方法,对黄土边坡形成崩塌机理进行数值模拟分析。研究表明:由于黄土边坡的开挖,坡体内垂直节理的张开,形成的拉张裂隙促进水的入渗,在水的物理化学作用以及黄土的水理特性等共同作用下,使得黄土体的物理力学性质发生了改变,黄土体的强度降低,导致黄土边坡发生塑性变形,由局部破坏发展为整体破坏,最终造成不同类型的崩塌破坏模式。总之,黄土边坡在切坡卸荷引起垂直裂隙发育的基础上,解释了在干湿循环以及水的化学溶蚀的综合作用下造成垂直节理裂隙扩展变形,黄土体内部应力分布不均匀以及土体自身的物理力学性质的劣化,导致边坡整体变形,最终形成崩塌灾害的力学机制,认为水的作用是黄土崩塌形成的主导因素。
[Abstract]:Loess collapse is the most common and serious geological hazard in the Northwest Loess Plateau.Loess is a loose sediment formed under the special climatic conditions of the Quaternary. It has special properties such as macroporosity, vertical joint development, and so on.Collapses occur frequently in the Loess Plateau under the action of external triggering factors such as earthquakes.Under the action of water, the formation of loess collapse is firstly due to the development, development and penetration of cracks in the soil; secondly, the failure of the foot of the edge slope leads to the formation of the collapse.Therefore, it is of great significance to study the mechanism of the development of joints and fissures of loess body under the action of water, as well as the change law of physical and mechanical properties, which is of great significance for the prevention and control of disasters such as collapse in loess area.On the basis of collecting the research results of the collapse disaster in loess area and the supplementary investigation of loess collapse disaster in loess area, taking the edge of Luochuan tableland of Yan'an city as the typical research site, through field exploration,Surveying and mapping and the collection of relevant data, summarized and expounded the role of water on the yellow soil itself showed an important impact on the engineering characteristics, research and analysis of the loess body of engineering characteristics for the cause of loess collapse disaster has a certain internal relationship;Through dry and wet cycle test, CT scanning was used to study the physical action of water, the effect of dry and wet cycle on loess internal structure deterioration, the strength and mechanics test of soil sample after dry and wet cycle, the number of dry and wet cycles,The relationship between dry-wet cycle amplitude and soil strength deterioration and other related parameters; through indoor physical and mechanical tests, the influence of water chemical action-dissolution on the physical and mechanical properties of loess body is studied; and the physical and mechanical properties of loess body are studied by Abaqus software.Combined with theoretical analysis and numerical simulation, the formation and collapse mechanism of loess slope is numerically simulated.The results show that because of the excavation of loess slope and the opening of vertical joints in the slope, the tensile fissure formed promotes the infiltration of water.The physical and mechanical properties of loess body have been changed, and the strength of loess soil has been reduced, which leads to plastic deformation of loess slope, from local failure to whole failure, and finally to different collapse failure modes.In a word, on the basis of vertical fracture development caused by cutting slope unloading, it is explained that vertical joint crack expansion deformation is caused by the combined action of dry and wet cycle and chemical dissolution of water.The uneven distribution of internal stress and the deterioration of physical and mechanical properties of the loess soil resulted in the deformation of the slope and the formation of the mechanical mechanism of the collapse disaster. It is considered that the action of water is the leading factor in the formation of loess collapse.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU444

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