【作者】 魏玉峰；

【导师】 聂德新；

【作者基本信息】 成都理工大学 ， 地质工程， 2010， 博士

【摘要】 白鹤滩水电站层位众多、岩性复杂,建基岩体直接利用层位包含亚层9层、岩性小层50层,主要岩性有:斜斑玄武岩、含斑玄武岩、隐晶玄武岩、微晶玄武岩、柱状节理玄武岩、杏仁玄武岩、含杏仁玄武岩、角砾熔岩、凝灰岩等近11种,介质类型体系复杂。不同岩性岩体在表观块度、纵波波速、力学性质等多个方面出现非常明显的差异,最为明显的是柱状节理玄武岩和角砾熔岩,表观结构与力学属性反差巨大,按现行规范或通用方法划分岩体结构和岩体质量,力学属性最好的柱状节理玄武岩被判定为坝基最差的岩体,而力学性质最差的角砾熔岩却成为坝基最好的岩体,划分结果不能反映岩体真实的工程地质性质。同时,众多的层位、复杂的岩性、不同岩性岩体各方面性质明显的差异,使坝基岩体在岩体结构划分、岩体质量评价及力学参数取值等方面遇到了较大的难题和挑战,对这种多层位、多岩性复杂坝基岩体开展工程地质评价,准确表征表观结构与力学性质反差巨大的岩体真实的工程地质条件,研究在理论和工程实践上均具有重要意义。论文以白鹤滩水电站多层位、多岩性的坝基岩体为研究对象,重点开展复杂坝基岩体岩体结构划分和岩体质量评价的研究,主要取得了以下成果:(1)通过分析坝基多层位、复杂岩性、结构体特性与结构面发育程度差异明显的岩体基本特征,在现场大量结构面调查、声波测试、现场及室内试验的基础上,论述分析了当前单一块度指标划分岩体结构的有关问题,以及结构体性质和结构面效应对岩体结构的影响,确定了岩体结构划分的参评因素和主要指标,并针对坝址区岩体岩性多样、结构体性质差异明显、本底波速不同的典型特征,创新性的提出了完整程度划分指标—同质完整性系数和不同结构类型的统一比较指标—标准结构系数,建立了考虑结构体性质和结构面效应的岩体结构划分方案,划分结果能够准确体现表观结构与力学性质反差巨大的岩体真实的工程地质条件。(2)对坝基岩体风化、卸荷特征进行了研究,采用波速比、单元面积裂隙总条数和现场判断等定性定量指标对坝基岩体水平和铅直两个方向进行了风化分带,分析了不同岩性岩体的风化特点;利用张开结构面数量和钻孔吕荣值对坝基岩体开展了卸荷带划分。(3)现场开展了数量较多的岩体变形试验,重点研究了柱状节理玄武岩变形特征,并综合不同岩性岩体中开展的原位波速同步、应力同向变形试验,获得了相关性良好的岩体纵波波速与模量的关系式。(4)统计分析结构体性质、岩体纵波波速、结构面间距、单元面积裂隙条数等岩体特征指标,对特征指标一致或接近的岩体视为有效相近岩体,据此对坝基11种岩性进行综合处理,合并为杏仁玄武岩、隐晶玄武岩、柱状节理玄武岩和角砾熔岩这四个类似岩性层。(5)根据坝基岩体的典型特征,确定了岩体质量分级的主要参评因素及量化指标为岩体结构、风化、卸荷、结构体强度、刚度、岩体纵波波速、洞壁地震波纵波波速、变形及强度参数,建立了岩体质量划分方案。(6)采用类似岩性层资料共享和联用的方法,根据岩级划分方案对坝基50层小层(岩性层)岩体岩级进行了划分,在此基础上对小层岩体进行并层处理,利用理论公式计算获得了并层后大层(岩流层亚层)岩体的综合模量和综合波速,最终对大层岩体开展了岩级划分。(7)论文通过建立的相关关系式对各小层不同岩级的岩体力学参数进行了取值,并根据理论公式对并层后大层岩体不同岩级开展了力学参数取值研究。(8)从岩体结构、风化、卸荷、岩体质量等多个方面对坝基岩体工程地质条件进行评价,并按岩体质量分级结果确定了建基面位置。更多还原

【Abstract】 Baihetan Hydropower Station is featured by multiple stratums and complex lithology, whose construction of foundation rock directly applies stratums containing 9 sub-layers and 50 small layers of lithology. The main lithology include nearly 11 species, such as porphyritic basalt, aphanitic basalt, micro-crystalline basalt, columnar joints basalt, amygdaloidal basalt, amygdaloid-contained basalt, breccia lava, tuff, etc. made up of complex media type systems. Such lithology of rock has presented very distinct differences in respect to the apparent lumpiness, longitudinal wave velocity, mechanical property and other aspects. The most obvious presentations have been involved in columnar-jointed basalt and breccia lava, whose apparent structure and mechanical property have presented huge contrast. According to existing norms or general methods for the classification of rock structure and rock mass, the columnar-jointed basalt with the best mechanical property has been judged to be the worst rock mass for the dam foundation while the breccia lava with the worst mechanical property has become the best rock mass of the dam foundation. Therefore, the classification results haven’t reflected the true geological nature of the engineering. Meanwhile, distinct differences in relation to various aspects, such as multiple stratums, complex lithology, different lithology of different rock mass have created problems and challenges faced by the classification of rock structure of dam foundation, the quality classification of rock mass, the evaluation of mechanical parameters, etc. The present research would provide great significance in both theory and engineering practice for the engineering geological evaluation of this kind of complex dam foundation of multi-stratum and multi-lithology and the accurate characterization of the true engineering geological conditions having great contrast between the apparent structure and mechanical property. Taking the Baihetan Hydropower Station’s dam foundation rock mass featured by multi-stratum and multi-lithology as the objective of study and focusing on the classification of the complex structure and the evaluation of of the dam foundation rock mass, the major results have been achieved as follows:(1) By analyzing the basic characteristics of the rock mass featured by multi-stratum, complex lithology, the distinct differences between the textinite characteristics and structural surface developmental extent, based on a large number of onsite structural surface investigations, acoustic measurements as well as field and laboratory tests, related issues on the current classification of rock structure using single lumpiness indicators as well as the textinite nature and structural surface effect impacting the rockmass structure have been discoursed and analyzed. In addition, the factors and key indicators participating in the evaluation of rockmass structure classification have been put forward. Besides, considering the typical characteristics, including the diversity of the rock lithology of dam site, distinct varied structures, different velocity of the background, the integrated extent indicators for classification- identical quality integrality coefficient and the unified indicators for different structural types- normal structure coefficient has been established. and rock mass structure classification schemes based on the consideration of textinite characteristics and structural surface effect have been established, by which the classification result can accurately reflect the true engineering geological conditions of rock featured by huge contrast between the related apparent structure and mechanical property.(2) The weathering and unloading features of dam foundation rock have been studied using velocity ratio, the total number of cracks per element area, on-site judging and other qualitative and quantitative indicators to hold weathering zoning of the dam foundation rock mass in horizontal and vertical directions and to analyze the weathering characteristics of different rock lithology. Besides, the volume of open structural surfaces and the Drilling Lu-Rong Value have been used for the unloading classification of the dam foundation rock.(3) A large number of onsite rock mass deformation tests have been carried out, focusing on the deformation characteristics of columnar joints basalt. Besides, tests of situ velocity synchronization and homonymous stress deformation on rock mass of different lithology have been integrated to obtain the relationship between the longitudinal wave velocity and the modulus by satisfactory correlation.(4) Statistical analysis of textinite characteristics, longitudinal wave velocity , spacing of structural surface, number of structural sruface per element area and other indicators of rock mass characteristics has been conducted, by which those rock mass whose characteristic indicators is identical or similar have been judged as effective similar rockmass. According to the said status, 11 kinds of rockmass of the dam foundation have been comprehensively treated into four similar lithologic layers of amygdaloidal basalt, aphanitic basalt, columnar joints basalt and breccia lava.(5) According to the typical characteristics of dam foundation rock mass, it has determined that the main factors participating and quantitative indicators in the rock quality classification should be include rock mass structure, weathering, unloading, structural strength, stiffness and longitudinal wave velocity, longitudinal wave velocity of seismic wave, deformation and strength parameters. The rock quality classification schemes have been established as well.(6) Methods of sharing and jointly using of information about similar lithologic layers have been applied, according to rock quality classification schemes, the quality of 50 small layers (lithologic layers) of the dam foundation have been classified based on which small layers of rock mass have received a layer-joining treatment. Using the theoretical formula to obtain the comprehensive modulus and integrated velocity of the large layer (sub-layers of rock) after the layer-joining treatment, the large layer of rock has been finally treated with a rock-level classification.(7) The present thesis has established related relationships to take the values of mechanical parameters of rock mass in respect to various small layers of each level and theoretical formula has been used to study the value-taking of mechanical parameters of large layers in different levels after the layer-joining treatment.(8) Evaluation of rock mass of dam foundation in relation to structure, weathering, unloading, rock quality and other aspects of engineering geological conditions has been carried out and rock quality classification has been held for the identification of the basic construction surface location according to the classification results of rock mass.更多还原