【作者】 周立荣；

【导师】 周德培；

【作者基本信息】 西南交通大学 ， 岩土工程， 2011， 博士

【摘要】 红层是一种具有特殊地质力学性质的岩体,强度低、易变形,抗风化能力差、遇水易崩解、软化等。在红层地区开挖边坡,若不采取坡面防护措施,极易造成边坡水土流失及风化剥落、崩塌、落石、浅层滑坡等各种浅层地质灾害。而红层在我国的分布相当广泛,随着基础设施建设进程的加快,大量高等级公路、铁路通过红层地区,因此开展红层边坡浅层破坏机理及防护措施的研究十分必要。鉴于上述原因,本文通过参与西部交通建设科技项目“红层软岩地区公路修建技术研究”,采用野外调研、现场试验、室内试验、理论分析多种手段和方法,对红层软岩边坡浅层破坏类型、浅层破坏机理、可植被性相关参数、可植被性评价方法、生态防护方法及防护效果等方面进行了系统研究与分析。论文主要内容及结论如下：1.总结红层边坡浅层破坏类型,并对影响浅层破坏的因素进行探讨,为红层边坡浅层破坏机理的研究提供依据。在广泛的资料调研和野外调查的基础上,总结提出红层边坡浅层破坏类型主要有风化剥落、落石、崩塌、溜坍、滑塌、浅层滑坡六大类和十四个亚类,并对各种破坏形式发生的条件及特点进行分析。研究结果表明,红层边坡浅层破坏与红层自身的结构及其独特的物理力学性质有关,尤其是红层的水理性和易风化性是造成红层边坡浅层破坏的主要因素,为红层边坡浅层破坏机理的研究提供依据。2.针对红层边坡浅层破坏的主要因素风化进行原位监测研究,揭示了红层边坡浅层破坏机理。通过红层边坡风化剥落的原位监测,研究温度和水分变化对红层岩体快速风化的影响。监测结果表明,单纯温度或水环境的改变不能引起红层软岩的快速风化崩解,高温下强降雨是导致红层软岩快速风化的重要原因。3.采用数学物理方程和mathematica软件,对红层裸露边坡浅层风化破坏机理进行深入的理论研究。采用数学物理方程建立红层边坡处于高温时突遇强降雨,急剧降温的热传导方程,利用mathematica软件,求解红层裸露边坡处于高温状态时降雨的急剧降温过程和日常缓慢温度变化过程的温度场,对比分析两种情况下温度场的分布特征,进一步印证了红层边坡风化原位监测的结论,红层表层处于高温状态时降雨是导致其快速风化剥落的重要原因,并通过温差的变化值确定红层边坡快速风化范围。4.采用现场模拟降雨试验,研究裸露红层坡面的冲刷性质。降雨对红层边坡风化起重要作用,它不仅使岩石快速降温,而且使表层已风化崩解的红层碎屑在雨水的作用下冲刷,暴露出下面的新鲜岩石,使风化加深。5.在对红层边坡生态防护相关参数进行研究的基础上,建立红层边坡表土和客土可植被性模糊综合评价方法,为红层边坡生态防护设计提供指导。通过红层地区生态防护的调研,总结红层边坡生态防护存在的问题,提出红层边坡浅层岩土样及客土的可植被性评价指标,并对红层生态防护相关的参数进行试验和隶属度研究,建立红层边坡表上及客土可植被性模糊综合评价方法,这些参数及模糊评价结果可为植被护坡设计中土质改良、植物选型等提供参考,结合边坡的稳定状态可指导边坡生态防护设计6.通过生态防护对红层边坡浅层稳定的防护效果的系统研究,证明了生态防护能有效阻止红层坡面的风化和冲刷,提高红层边坡浅层稳定性。通过红层边坡生态防护前后的降雨冲蚀试验、边坡浅层温度场和水分场的长期监测,以及红层有无植物根系的力学试验,系统研究生态防护对红层边坡浅层稳定的影响。生态防护通过消除表层风化碎屑的冲蚀、改变红层坡体浅层的温度场和水分场极大地减缓红层边坡的风化进程,基本消除因高温、降雨共同作用引发的浅层快速风化崩解,并通过植物根系的力学效应提高了根系范围内浅层坡体(包括客土层)的抗剪强度,从而提高了浅层坡体的稳定性。更多还原

【Abstract】 Red bed has special geomechanics properties, which strength is low, deformation is easy, weathering resistance is poor, and which is easy to be softened and disintegrated after absorbing water, and so on. Therefore, the excavated slope without slope protection in red bed often occur soil erosion and geological hazards of shallow layer, such as weathering spalling, collapse, rockfall, and shallow landslide etc. Red bed is widely distributed in China. A lot of high-grade highway and railway have been built or will be built in the red bed with infrastructure construction. So it is very essential to study failure mechanism and protection measures of shallow layer of red bed slope. In view of this, combined with the west region communication construction technology project, ’Technology Study on Highway Construction in Red-Bed Soft Rock Area", by the methods of field investigation, field test, laboratory test and theoretical analysis, etc, the contents, such as failure types and failure mechanism of shallow layer, parameters and evaluation method correlated to difficult degree of planting, ecological protection and its effects, are studied and analyzed systematically on red-bed soft rock slope.The main contents and conclusions of the article are summarized as follows.1. The failure types of shallow layer of red bed slope are summarized and the influence factors leading to shallow layer failure are analyzed to provide a basis for failure mechanism study.Based on the widely literature and field investigation, the failure types of shallow layer of red bed slope are divided into six categories, including weathering, spalling, rockfall, collapse, topsoil slip, slump, shallow landslide, and 14 sub-categories. By analyzing the occurrence condition and characteristics of various failure types, the conclusion is drawn that the structure and the special physical and mechanical properties of red bed, especially the properties related to water and weathering are the main factors leading to the shallow layer instability of red bed slope. It provides a basis for failure mechanism study.2. Through in-situ monitoring of weathering, a main factor causing slope instability, instability mechanism and fast weathering range of shallow layer of red bed slope are revealed.The influences of temperature and moisture content change on red bed fast weathering are studied by in-situ monitoring the weathering of red bed slope, the monitoring results show that only the change of water environment or temperature can not causes rapid weathering and collapse, the condition that red bed suddenly meets strong rainfall when it is in high temperature is a main cause of red bed fast weathering.3. Theoretical study on shallow layer instability mechanism and the range of fast weathering of shallow layer of red bed slope are carried on deeply with "Mathematical Physics Equation" and the software MATHEMATICA.Heat conduction equation of red bed slope with high temperature exposed to strong rainfall are presented by "Mathematical Physics Equation", further, the temperature field of rapid decreasing temperature when the red bed slope with high temperature are exposed to strong rainfall suddenly and the slow daily temperature change are solved by the software MATHEMATICA, A comparative analysis of the two kinds of temperature field further proved the conclusion of the weathering in-situ monitoring of red bed slope, the former condition is the main external cause leading to red bed fast weathering.4. The erosion properties of bare red bed slope are studied by rainfall simulation experiment.Rainfall is import to weathering of red bed slope, it not only slow down the temperature of rock significantly, but also erosion the weathered material of red bed therefore, the unaltered rocks are exposed to further weathering.5. On the basis of the parameters study correlated to ecological protection for red bed slope, the method of fuzzy comprehensive evaluation on topsoil and foreign soil correlated to difficult degree of planting are put forward, which provide guidance for slope ecological protection design in red bed.By investigating ecological protection for red bed slope, analyzing and summarying the problems existed in it, evaluation indexes of top soil and foreign soil correlated to difficult degree of planting are proposed. Furthermore, the indexes are tested and their membership grades are studied. Based on the results, the method of fuzzy comprehensive evaluation on topsoil and foreign soil correlated to difficult degree of planting are put forward. These indexes and fuzzy comprehensive evaluation results provide reference for soil improvement and plant choice; moreover, combined with stability state of slope, they provide guidance for slope vegetation protections design in red bed.6. By the systematic study on ecological protection effect to shallow layer stability of red bed slope, it is proved that ecological protection can effectively keep red bed slope from weathering and erosion and can improving stability of red bed slope.The influence of ecological protection to shallow layer stability of red bed slope are systematically studied by the field rainfall tests with the ecological protection and without it, the long-term monitoring tests on the temperature field and the moisture content of the shallow layer of red bed slope and the mechanics experiments on red bed with and without plant roots. It is concluded that the ecological protection can not only slow down significantly the weathering process of red bed slope and basically eliminate the fast weathering of the shallow layer caused by high temperature and rainfall together by eliminating the weathering material erosion and changing the temperature field and the moisture content of the shallow layer of red bed slope, but also increase the shear strength of shallow layer (including guest soil) in the range of plant root. So, the shallow layer stability of slope is improved.更多还原