【作者】 崔杰；

【导师】 王兰生；

【作者基本信息】 成都理工大学 ， 岩土工程， 2009， 博士

【摘要】 当今人类地下工程活动与山坡地质环境关系日益紧密,山坡结构对地下工程则起到控制性影响。由于山坡自然演化过程受许多外部因素影响,在坡体内部形成一些复杂结构与现象。以往工程实践表明,忽略对山坡结构的分析与研究,往往导致严重的工程地质问题甚至灾难性后果。因此,开展地下工程活动必须重视对坡体内部结构的分析,将地下工程活动与山坡地质环境有机地结合起来。研究区暨美姑河流域坪头电站厂区岸坡,是由厚层灯影组白云岩构成的典型层状结构顺向坡,但在隧洞开挖中却揭示出岸坡内部存在一系列特殊地质现象,由此引发重大工程地质问题,对该电站地下工程的安全与施工造成明显不利的影响。本文将其分为顺层岸坡深部变形破坏现象与深部白云岩岩溶砂化现象,并针对两类特殊地质现象进行系统研究:利用岸坡内多条已开挖硐室的调查,一方面对特殊岩溶砂化结构类型、空间展布特征与宏观演化模式进行了调查与论述,通过试验手段阐述岩溶砂化作用的微观机理与演化模式;另一方面,通过对岸坡深部变形破坏现象的空间结构进行了分析,论证了顺层结构岸坡产生深部滑坡的成因模式,分析其稳定性;通过对岸坡特殊地质现象的系统研究,与地下工程与相互作用的阐述,提出该水电地下工程的可行性要求。对本文主要研究工作与取得的成果论述如下:(1)以大量已开挖硐室的调查统计为基础,分析了白云岩岩溶砂化现象的发育特征,将白云岩宏观岩溶砂化结构进行了划分,提出了岩溶砂化岩体结构分级的概念,将宏观岩溶砂化结构演化过程定义为轻微→中等→强烈→破坏四阶段演化模式;通过分析岸坡岩溶砂化作用的空间展布规律,阐述了岩溶砂化现象与岩性、地下水、岸坡地质构造及区域河谷地貌等影响因素的相关性;(2)对岩溶砂化物质结构与组分分析,认为岩溶砂化具有典型的基岩—砂化溶虑层—粘土层的物质结构;通过地球化学方法,选取各分层进行岩溶砂化过程中的化学组分迁移规律分析,认为白云岩的岩溶砂化演化过程,首先是从基岩溶蚀形成白云岩砂开始,之后是富Si、Al、Fe、Mn的地下水直接沉淀生成粘土矿物或者交代白云石矿物形成粘土矿物并最终形成粘土夹层的发展过程;(3)在对宏观岩溶砂化现象研究的基础上,通过白云岩岩溶砂化结构微观试验研究,发现白云岩微观溶蚀特征主要受白云石成岩类型与矿物微结构所控制,认为原生白云石及其构成的岩石微观结构类型,其岩溶砂化发育程度明显低于次生白云石矿物及其构成的岩石微观结构类型;(4)利用高压岩石渗透试验研究,阐述了灯影组主要白云岩类型的岩石渗透性规律,表明白云石矿物类型与微结构特征控制了岩石的孔隙结构及其渗透性的大小;通过分析与对比显示,矿物组分均一的粒状结构、砂屑结构、微晶结构,其岩石渗透性大小依此降低;模拟了在岸坡卸荷条件下的白云岩渗透性规律,并阐述了岸坡内部的宏观岩溶砂化发育的基本分布规律及其影响控制机理;(5)对岸坡深部变形破坏现象进行了详细调查分析,从滑坡内部破坏结构、物质组成、滑坡空间形态等方面,阐述了岸坡深部古滑坡的基本特征;通过三维楔形体计算方法,反演分析了造成岸坡破坏的水动力条件和边界条件,推断该滑坡为发生顺向结构岸坡深部的后缘拉裂充水型暴雨式滑坡的破坏模式;(6)分析了岸坡深部滑坡形成的主要影响与控制因素,尤其是末次冰期气候条件下,岸坡表部深厚的冰水成因堆积层的形成演化对岸坡体结构演化的意义;并且对岸坡岩体的岩溶作用与滑坡破坏的关系进行了阐述,认为岸坡深部变形破坏过程中,冰期气候、地下水与岩溶砂化作用对岸坡深部变形破坏形成演化具有重要的意义;由于白云岩在我国南方地区分布广泛,对白云岩构成的不同结构类型岸坡来说,美姑河坪头电站厂址区岸坡深部出现的两类特殊地质现象绝非是孤立存在的,应该与区域性的构造背景与古气候特征的演化相一致,具有代表性和典型的研究意义,因此本论文为在类似条件下的山区地质环境中开展人类工程活动,提供了一个可供借鉴与参考的典型实例。更多还原

【Abstract】 Nowadays, with the increasingly close relationship between underground engineering of human beings activities and the geological environment of slope, the structure of slope has a significant impact on the underground engineering. As the process of the natural evolution of the slope is affected by many external factors, some complex structure and phenomenon are formed in the internal slope. The past engineering practice shows that neglect of the slope analysis and research about structure of projects often leads to serious engineering geological problems and even catastrophic consequences. Therefore, the activities carried out underground engineering must pay attention to the analysis of the internal structure of slope, combining with underground engineering activities and the geological environment of slope.The study area is located in the slope of Pingtou Hydropower Station lied in the Meigu valley, where a typical forward and layer structure slope consists of the thick Dengying Formation dolomite. However, during the excavation of the tunnel, it reveals the existence of a series of special geological phenomenon in the internal structure of slope, leading to a major engineering geological problem and a significant adverse effect of the underground engineering during the safe construction of the works. This paper is divided it into two parts, the deformation and failure phenomenon of the deep bedding bank slope and the deep karst sandification of dolomite. Moreover, the two types of special geological phenomenon are systematically studied.Based on the investigation of a number of chambers excavated in the bank slope, on the one hand, the structural type, spatial distribution characteristics and macro evolution model of the karst sandification of dolomite are investigated and discussed, and the micro mechanism and evolution of model are also described by test. On the other hand,by the analysis of the deformation and failure phenomenon of deep space structure of the bank slope, not only the genetic model of the deep landslide brought by bedding structure of the bank slope is demonstrated but also the stability of the present situation is analyzed. In addition, through systematic research of the special geological phenomenon and the interaction with the underground engineering, the feasibility of the requirements of underground engineering of the hydropower station is proposed. The research work on this paper and results achieved are as follows:(1) Based on a survey of a large number of excavation chamber, the development characteristics of the karst sandification of dolomite is analyzed. The macro structure of dolomite sandification is compartmentalized. The concept of the rock structure classification of dolomite sandification is put forward. Macro evolution of it as light-middle-strong-destructive the four-stage evolution model is defined. Furthermore, by analyzing the law of spatial distribution of karst sandification phenomenon, the relativity between the dolomite sandification phenomenon and the influencing factors is discussed,such as lithology, groundwater, geological structure of bank slope, the regional valley geomorphology and so on.(2) By analyzing of the structure and composition of karst sandification material, the article considers that it has a typical structure of matter as bedrock - dissolution layer of sandification– clay. Based on geochemical method, each layer is selected to analyze migration regularity of chemical composition during the karst sandification. It is considered that during the karst sandification of dolomite, the evolution process begins from forming of dolomite sand because of bedrock dissolution. Then a direct sedimentation of clay mineral formed by the groundwater rich in Si、Al、Fe、Mn forms or by the metasomatic dolomite, finally resulting in the clay soil interlayer.(3) Base on the study of macroscopic karst sandification phenomenon and the study of microcosmic-test about the structure of karst sandification of dolomite, the characteristics of microcosmic corrosion about dolomite are controlled by the types of dolomite diagenesis and mineral microstructure of dolomite. It is considered that development degree of karst sandification about primary dolomite and its constructive classification of microstructure is obviously lower than that of secondary dolomite’s.(4) By using high rock pressure permeability test, the regularity of rock permeability about the types of dolomite in the Dengying Formation is described. It also demonstrates that the rock pore structure and its permeability is controlled by mineral type of dolomite and its microstructure features. Through analysis and comparison, it is showed that the rock permeability gradually decreases by the variation of the granular structure, sand cutting texture and microcrystalline structure which mineral composition is homogeneous. Regularity of permeability about dolomite is simulated under the condition of bank slope is unloaded. Moreover, the basic distribution regularity of macroscopic karst sandification and its impact of the control mechanism are described.(5) The detailed investigation and analysis on the interior deformation and damage of bank slope, and the basic character of interior ancient landslide is described based on the damage presentation, material composition and space shape, etc. Furthermore, the hydraulic and boundary conditions causing bank slope fail are inverted by analyzing the 3D wedges. It is inferred that the slope fails along the deep slope by heavy storm, with tailing edge cracked.(6) The main influence and controlling factors on the deep bank slope landslide’s formation is analyzed. The bank slope’s evolutionary significance about thick overburden layers of bank slope’s surface is analyzed under the glacial periods climate. The bank rock mass’s karstification and the landslide damage’s relationship are described. During the process of deeply deformation damage about bank slope, it is considered that the glacial periods climate, the groundwater and the karstification are important influence of the land slope’s evolutionary.Due to the wide distribution of dolomite in the southern region of China, the special geological phenomenon occurred within the internal bank slope of the research area is not isolated, as for the different structure types of bank slope composed of dolomite. It should be consistent to regional structure and quaternary climate evolution of the background, and may have some representative characteristics and typical significance. Therefore, it provides useful experience and reference for developing human engineering activities in the similar geological environment of the slope. So it provided a reference for reference example works for the human condition developments in the similar geological environment of the slope.更多还原