【作者】 张强；

【导师】 黄润秋；

【作者基本信息】 成都理工大学 ， 地质工程， 2010， 博士

【摘要】 中国岩溶地区面积广阔,岩溶发育类型多样,与岩溶有关的工程、环境问题涉及广泛而复杂。受区域构造、地下水、古地理环境以及古气候环境等综合作用,在金沙江观音岩水电站枢纽区分布的红色侏罗系陆相碎屑岩地层中,发育着大量溶蚀现象并形成规模尺度不一的溶蚀空间。这种溶蚀现象与传统意义上的碳酸盐岩岩溶有所差异,并且与红层中普遍存在的盐岩、膏岩在地下水作用下的溶解淋滤有本质区别。作为一种极为特殊岩溶现象,这类发育于陆相红色碎屑岩地层中的红层岩溶,因砾岩溶蚀和砂岩钙质流失形成的大规模溶蚀孔洞,对水电工程坝基防渗和工程渗透稳定存在重大不利影响。论文在研究金沙江观音岩水电站区域地质构造背景、区域侏罗纪以来岩相古地理演化史及其地层特征、坝段金沙江河谷演化史的基础上,通过对枢纽区钙质砂(砾)岩的溶蚀类型、空间展布特征、岩石学性质及其溶蚀作用特征进行描述,总结其岩溶发育规律、分析钙质砂(砾)岩溶蚀形成机理,并以溶蚀条件下的钙质砂(砾)岩岩体质量分级、钙质砂(砾)岩渗透能力分级为核心,对坝基岩体渗透变形及工程影响进行分析研究。论文在红层类岩溶的形成机理、发育特征及其对溶蚀工程特性研究方法方面具有一定的创新,主要成果如下:(1)综合分析坝基钙质砂(砾)岩体的宏观与微观岩溶发育特征,对红层溶蚀现象进行定位。通过对钙质砂(砾)岩的溶蚀形态、溶蚀类型、空间展布特征、岩石学性质、微观溶蚀作用特征描述、溶蚀能力计算和溶蚀对比试验研究,对观音岩水电站枢纽区坝基中的砾岩溶蚀、砂岩钙质流失问题进行定量分析,对钙质溶蚀现象进行了定位,认为:发育于攀西地区侏罗系中统蛇店组地层中的红层岩溶,是介于碎屑岩和碳酸盐岩岩溶间的一种特殊的类岩溶现象—其溶蚀强度介于两者之间,而溶蚀行为类似于灰岩;并与其他红层地层中盐岩、膏岩在地下水作用下的溶解淋滤存在根本区别;(2)系统分析溶蚀形成机理和发育历史。基于构造控制下地下水循环体系分析,综合采用水化学、同位素、水化学热力学和ESR测年方法,恢复地下水循环历史和钙质溶蚀史并结合金沙江河谷地貌和河谷演化史,系统分析了其溶蚀形成机理,推演钙质砂(砾)岩的溶蚀过程,认为:金沙江全线贯通进入现代河谷发展阶段以后,在区域循环系统控制下,受近浅表地下水循环系统和地表水流的作用影响,枢纽区钙质砂(砾)岩溶蚀时间在5.8~12.5×104a之间,对应金沙江河谷发育历史,该时段介于金沙江中下游河谷阶地中的Ⅱ、Ⅲ阶地发育期之间。并进一步计算分析其溶蚀潜力;(3)针对溶蚀条件下的岩体质量进行综合分级评价。结合平硐、钻孔波速、RQD等综合指标与其他单项指标,通过水电工程围岩工程地质分类、工程岩体分级以及RMR系统分类三种分类分级方法,对溶蚀条件下的坝基岩体质量,对比分析溶蚀作用对岩体质量的控制作用:①由于岩石胶结物的溶蚀,使得其岩体质量有较明显的减弱,总体上可减小一个量级;②提出不同溶蚀程度的钙质砂(砾)岩波速值溶蚀损伤折减率,其中砾岩为12.73~68.45%,砂岩为9.54~30.66%; (4)研究选取不同溶蚀程度的岩样进行渗透试验,获得其渗透性能与溶蚀程度间的内在关系,得出溶蚀钙质砂岩岩体渗透性能与岩石孔隙度间的关系式:K = 2×10-5e0.3298x(R2 = 0.9596)。同时,对于枢纽区钙质砾岩、钙质砂岩、粉砂岩、泥岩的互层结构地层,差异性溶蚀效应表现尤为显著,由此带来岩体渗透性能的复杂多样性。基于统计分析,提出观音岩电站枢纽区差异性溶蚀效应下岩体渗透系数,对钙质砂(砾)岩渗透能力的空间分布特征进行预测评价;(5)对工程条件下坝基岩体的渗透稳定性进行深入研究。通过对工程区地下水渗流场在天然条件和工程条件下的对比模拟计算,预测评价工程防渗措施效果。在此基础上,进行坝基岩体渗透变形判别,分析其在高水头压力下的渗透破坏模式(将以管涌为主)。并总结国内外红层区水利水电工程经验,对于存在大量溶蚀现象和较强的溶蚀发育潜力的枢纽区钙质砂(砾)岩坝基,建议采用防渗系统和排水系统并重的工程措施,重视加强排水设施,对提高软岩坝基的渗透稳定最为关键。更多还原

【Abstract】 China has broad karst regions, various types of karst developed, thus involving extensive and complex karst-related engineering and environmental problems. Controlled by the regional structure, groundwater, ancient geography and ancient climate environment, corrosion phenomena was well developed, formed different scales of dissolution space in Jurassic continental red beds clastic rock formation in Guanyinyan Hydropower distribution area, Jinsha River. This dissolution phenomenon different with the carbonate karst erosion in traditional sense, also different with the rock salt, gypsum rock dissolution effect in groundwater. As a special karst phenomena, this kind of karst developed in the red beds of the continental red clastic is due to conglomerate dissolution and calcium loss of the sandstone, formed huge corrosion hole that affects the stability and deformation of the dam foundation as well as the seepage project significantly.Based on the study of the regional geological background, the palaeogeographic evolution history of rock after the Jurassic, the stratigraphic features, and the evolution history of the valley near the dam of the Jinsha River, combined with the description of the rock dissolution type, the spatial distribution characteristics, the properties of rocks and the characteristics of dissolution of calcareous sand (gravel), summarized the karst development pattern, the mechanism of karst erosion of calcareous sand (gravel), take the rock mass classification and the permeability classification of the calcareous sand (gravel) as the main work, analysis the seepage deformation of the dam foundation rock and its influence to the project. This paper proposed some new understandings in the red beds karst formation mechanism analysis, characteristics and research methods as follows:(1) Based on the investigation, described the corrosion morphology of the calcareous sand (conglomerate), corrosion types, spatial distribution characteristics, properties of rocks and characterization of micro-corrosion, calculated erosion capacity and carried out corrosion contrast testing research, analyses the solubility of the calcareous sand (gravel) rock quantitatively of Guanyinyan hydropower dam, orientated the calcium dissolution phenomena developed so deep underground (maximum depth of 150m), with such scale (the largest-diameter 7.91m) that : different from other leaching dissolved effect in red beds formation in the salt rock, gypsum rock in the grounwater, the semi-karst phenomena developed in the Jurassic Panxi Shedian formation is between red beds clastic rocks and carbonate rocks - the dissolution strength is less than carbonate rocks while strong than clastic rocks, the dissolution behavior is similar to limestone.(2) Based on the analysis of the groundwater circulation system under the control of structural, combined with the water chemistry, isotope, water chemical thermodynamics and ESR dating methods, restorated the groundwater circulation and the calcium dissolution history, combined with the valley landscape and valley evolution history of the dam area, Jinsha River, analysis formation mechanism of its dissolution systematically, and deduced the calcareous sand (gravel) rock dissolution process, concluded that: after Jinsha River valley into the modern era, under the control of regional groundwater circulation system, and by the shallow groundwater circulation near the surface and the role of water impact, the erosion time of calcareous sand(gravel)is during 5.8~12.5×104a in study area, corresponding to the historical development of the Jinsha River valley, between the development period of the terraceⅡand terraceⅢ. At last calculated the corrosion potential.(3) Combination with the individual indicators data of the adit, drilling velocity, RQD and other comprehensive index, according to hydroelectric project adjacent geological classification, rock mass classification and RMR classification methods, conducted a comprehensive classification of the dissolution rock under the dam foundation, compared the control role and the weaken effect of the dissolution of the rock mass quality, presented the discount rate of velocity values of corrosion damage for different degrees of calcareous sand (conglomerate).(4) According to the dissolution type, the spatial distribution characteristics and dissolution characteristics of the calcareous sand (gravel) rock, combined with various lithological association of calcareous conglomerate, sandstone, siltstone and mudstone rock, analysis the rock permeability test and field pressure test for four grades erosion degree, the paper proposed the permeability for difference lithologic association under the effect of dissolution of Guanyinyan power project area for the first time, and put up predictive evaluation of the spatial distribution of permeability for the calcareous sand (conglomerate).(5) Study the seepage stability of the rock mass under of dam foundation. Simulation and contrast the groundwater seepage field of project area under natural conditions and under the construction, prediction and evaluation the seepage control measures. On this basis, identified the infiltration deformation of the dam foundation rock mass, analyzed the penetration failure mode under high head pressure. Summarized the domestic and international experience of red beds hydropower project that exist large number of corrosion phenomena and strong dissolution of calcareous sand (gravel) rock foundation, proposed seepage system and the drainage system, the drainage facilities is essential to improve the penetration stability of soft rock foundation.更多还原