【作者】 卢海峰；

【导师】 陈从新；

【作者基本信息】 中国科学院研究生院（武汉岩土力学研究所） ， 岩土工程， 2010， 博士

【摘要】 本文以依托工程—沪蓉西高速公路为研究背景,从巴东组软岩边坡岩体结构特点入手,通过一系列室内和现场试验对巴东组软岩边坡岩体的工程特性进行了系统的分析和研究,在此基础上分别对巴东组软岩两种典型的破坏形式边坡—缓倾顺层边坡和反倾边坡的破坏机理进行了分析探讨,得出了巴东组软岩边坡岩体的工程特性方面规律,提出了两类典型边坡的主要破坏机理和破坏模式。论本文主要内容和结论如下：(1)通过对依托工程全线巴东组软岩破坏边坡的统计,得出该区域巴东组软岩边坡的主要破坏模式可分为顺层滑动破坏和反倾破坏两种,顺层破坏边坡的岩层倾角主要集中在10～20°之间,属于缓倾顺层滑动破坏；而反倾破坏边坡的岩层倾角主要在50～70°之间。针对两类主要破坏模式,通过对典型破坏边坡调查分析,发现无论是缓倾顺层边坡还是反倾边坡,其稳定性及破坏模式与巴东组软岩特殊的岩体结构和力学特性密切相关,尤其是岩层中普遍存在的软弱夹层,是边坡稳定性的控制因素。(2)依据孙广忠岩体结构分类方案,结合巴东组软岩自身特点,将巴东组软岩边坡结构定为层状板裂结构,并将其岩体细化为碎裂结构、断续结构和散体结构三个亚类,对各亚类基本特征进行相关的试验分析。通过试验分析,对碎裂结构紫红色粉砂质泥岩和断续结构青灰色泥岩的崩解特性及崩解机理进行了探讨,指出两种岩体分属“吸附—楔裂性崩解”和“水化—分散(膨胀)性软化、崩解”,并对散体结构层间错动带的膨胀特性进行研究,研究表明该层膨胀特性不是特别明显,在边坡稳定性分析中可以不予考虑。(3)进行了室内三轴压缩试验,试验结果表明水的介入对巴东组软岩强度和变形特性有显著影响,选用孙广忠提出的弹性碎裂结构岩体变形本构模型对破坏前岩体的应力—应变规律进行拟合分析,分别得到了自然状态和饱水状态下考虑结构面闭合变形的弹性本构方程。通过原位压缩试验,得到了不同矿物组成的巴东组软岩变形特性以及循环荷载作用下的残余变形特性,并对荷载作用下岩体内部弹性应力分布及位移影响深度进行了探讨,得出了相关结论,为边坡破坏机理及加固处置技术研究提供理论依据。在原位压缩模量试验的基础上对巴东组软岩进行了现场压缩流变试验,试验结果显示巴东组软岩流变变形较明显,在边坡长期稳定性研究中不容忽视,为此,以孙广忠提出的粘弹性碎裂岩体本构模型为基础,得到了巴东组软岩考虑结构面闭合变形的流变本构模型,为边坡长期稳定性研究提供了理论支持。(4)通过室内直剪试验对巴东组软岩边坡岩体中普遍存在的泥化夹层的剪切强度特性进行了分析,结果表明随着含水率的增加,泥化夹层的抗剪强度明显降低,其中内摩擦角φ值降低尤为明显。结构面室内夹泥试验表明,随着泥化夹层厚度的增加,含泥结构面的抗剪强度指标逐渐降低。(5)基于独立块体安全系数表达式和考虑结构面闭合变形的自定义本构模型,对巴东组软岩缓倾顺层边坡破坏机理进行了分析,得出巴东组软岩缓倾顺层边坡的破坏是从坡脚开挖开始到软弱结构面由等速蠕变到加速破坏的渐进过程,期间伴随着坡脚岩体的崩解软化、节理裂隙的扩展延伸和地表水沿裂隙下渗软化潜在滑动面等多方面因素共同作用的结果。从破坏模式来看,该类边坡属于“推动—牵引组合”破坏,坡前一般处于推动区,坡脚对推动区起到一定阻挡作用,一旦坡脚被开挖或者长期风化崩解使其丧失抗滑作用,边坡将发生推动滑移,而且后缘牵引区也将出现新的稳定性问题,可见其破坏过程是前缘和后缘块体共同作用相互协调的结果。(6)在D.P.Adhikary和A.V. Dyshin悬臂梁弯曲极限平衡分析模型的基础上,经过分析推导,对其折裂面形式、层间粘聚力的影响和各层岩体重度等方面问题进行修正,得到了改进的悬臂梁极限平衡模型,提出了以各层位剩余不平衡力作为分析反倾边坡稳定性标准的新方法,并对边坡稳定性各影响因素进行了分析研究,得出的结论和规律更符合工程实际,对该类边坡的设计施工具有指导意义。(7)基于改进的悬臂梁极限平衡模型计算和离散元数值模拟分析,对依托工程中典型反倾高边坡破坏过程进行了分析探讨,结合边坡开挖影响分析和层间错动带影响分析,得出巴东组软岩反倾边坡的破坏模式为“倾倒—滑移—弯曲”模式,层间错动带以及边坡中部岩体是边坡破坏的起始点,坡脚对边坡稳定性具有十分重要的作用,这三部分在巴东组软岩反倾边坡加固和防护过程中应重点对待。更多还原

【Abstract】 Taking HuRongxi expressway as the research background, considering the characteristics of rock mass structure of the soft-rock slope in Badong formation, a series of laboratory and in situ tests are carried out in order to study the engineering characteristics of rock mass in Badong formation. Based on these systematic researches, the failure mechanism of two typical failure soft-rock slopes containing gently inclined consequent slope and counter-tilt slope in Badong formation is studied here, the law about engineering properties of soft-rock slope in Badong is gained. At the same time, the failure mechanism and failure mode are put forward. The main contents of this paper are stated as follows:(1) Based on statistical analysis on the failure of many soft-rock slopes in Badong formation during construction, it can be found that there are mainly two major failure patterns that are consequent slide and counter-tilt failure. The dip angle of rock stratum for consequent slope is mainly between 10～20°, which belongs to gently inclined consequent slide failure. While the dip angle of counter-tilt slope is mainly between 50～70°. According to the two typical failures, investigations and analyses are carried out on those typical failure slopes. It can be found that the failures of the slopes are close related with the special rock mass structure and mechanical behavior of soft-rock slope in Badong formation, especially the weak intercalation which is the controlling factor for slope stability.(2) Based on classification scheme of rock mass structure by Sun GZ, the rock mass structure of soft-rock slope in Badong formation is considered as layered slab-rent structure according to its self-characteristics, and three subclasses containing cataclastic texture, intermittent texture and scattering texture are classified. According to these classifications, analyses on basic characteristics by laboratory test are carried out, and conclusions on the disintegration and expansibility of the rock are obtained.(3) The laboratory triaxial test results show that water influence the characteristics of rock intensity and deformation obviously. Based on constitutive model gave by Sun GZ, considering the close of structural surface, elastic constitutive model for natural and saturated state is established here. By doing load-bearing plate test, under different argillaceous content, the deformation characteristics of two kinds of soft rock in Badong formation are analyzed here. The rock characteristics containing stress and displacement distribution and the influence range of depth under cycling load are also studied here. On the basis of researches above, we totally understand the deformation behavior of soft rock in Badong formation. Advices to the design of soft-rock slopes in Badong formation are given. It can also offer references to the research on reinforcement effect of pre-stressed cable. According to the rheological test, rheological constitutive equation considering the closure of structural surface is established. It can offer theoretical support to research on long-term stability of slope.(4) By doing direct shear laboratory test, we analyzed the shear characteristics of intercalation existing widely in the soft rock in Badong formation. The results show that the shear intensity reduced significantly as the increase of water content and thickness of intercalation, especially the shear friction angle.(5) Based on the method of safety factor for independent blocks and user-defined constitutive model considering the closure of structural surface, further analysis on the failure mechanism of gently inclined consequent soft-rock slopes in Badong formation are carried out. Conclusions on the failure of mentioned slope type above are:the failure start from excavation of toe and come with intercalation failure from constant rate creep to acceleration creep. From the view of failure mode, the failure belongs to the mode of disintegration, expansion of cracks, infiltration of surface water and so on. The failure model is motivation and traction combination model, the frontal slope is the motivation area and the toe can countercheck the slide of this area.(6) Based on the cantilever beam limiting equilibrium model by D.P.Adhikary and A.V. Dyshin, the article made some improvements mainly on the form of fracture plane and influences of cohesion and severe by different layers, at the same time, an improved cantilever beam limiting equilibrium model is proposed. A new method taking residual unbalance force as standard is used to analyze the stability of counter-tilt rock slopes, and the influence factors of counter-tilt rock slopes are further studied. Conclusions and laws useful for design and construction of these slope types are suggested.(7) Based on improved cantilever beam limiting equilibrium model and numerical simulation by UDEC, combining with the influence of excavation and intercalation, analysis on a typical counter-tilt slope are carried out. The main failure pattern of counter-tilt soft-rock slopes in Badong formation is toppling-sliding-bending. Rocks in the middle of slopes and intercalations are the beginning point of the slope failure, and the toe of slopes is very important in stability analyses which need to be mainly considered during the construction. These three points are the most important part for the reinforcement and protection of counter-tilt soft-rock slopes in Badong formation.更多还原