【作者】 郭健；

【导师】 许模；

【作者基本信息】 成都理工大学 ， 地质工程， 2010， 硕士

【摘要】 座落于雅砻江中游河段第五个梯级的杨房沟水电站,位于四川省凉山州木里县境内。根据工程预可行性研究成果,杨房沟水电站推荐坝型为混凝土双曲拱坝,最大坝高158米,正常蓄水位2092米,相应库容4.442亿立方米。坝址区为高山峡谷地貌,雅砻江流向S30~40°E,枯水期江面宽50~100m,水位高程1984~1985m。两岸地形陡峭,基岩裸露。拟建大坝区内出露地层主要为燕山期花岗闪长岩,岩质坚硬,岩体较完整,岩性条件较好,仅右岸引水隧洞及地下厂房分布变质粉砂岩,局部夹含炭质板岩。两岸山体雄厚,河谷狭窄,两岸地形基本呈对称的“V”型,河床覆盖层24~30m。坝区未见区域性大断层,工程地质条件总体较好,适于修建双曲拱坝。对于装机容量达百万千瓦的电站而言,其坝体工程建设往往涉及到深切河谷地区,考虑到现阶段经济发展和社会投资水平,决定了工程对岩土体的改造利用只能局限于地表浅表层数十米至数百米的范围之内。而坝区浅表层出露岩石作为大坝工程围岩的物质基础,主要接受风化作用与卸荷作用两种重要的外生营力的改造,因此研究风化、卸荷岩体,对于工程设计、岩体开挖、岩体质量分级以及建基面选取等具有非常重要的意义。尽管岩体(或岩石)风化、卸荷的研究已经是一个被讨论了数十年的老课题,但将这些新成果转化为指导工程实践的行业规范却很滞后,有鉴于此,本文针对杨房沟水电站花岗闪长岩地区的岩体风化、卸荷的特征进行量化研究,同时对风化、卸荷之间的关系做一些尝试性的探索分析,以丰富该研究领域内对不同岩性的岩体风化、卸荷的细化研究。在对岩体风化的机理进行分析后,对杨房沟坝区岩体风化特征进行初步调查,总结了坝区岩体风化的三种特征。紧接着开始对岩体风化的量化进行研究,可以表征岩体风化程度的因素很多,把这些因素都用来划分岩体的风化是不太现实的,从岩体工程地质和现场工作条件出发,本次杨房沟水电站岩体风化特征指标主要选取了:岩石点荷载强度(PLS)、岩石变形性能回弹值(Re)、岩石质量指标(RQD)、岩体弹性波和声波的纵波波速(Vp)、完整性系数(Kv)。这些指标在勘探平硐,地表露头等地可以通过现场测量获得,而在勘探钻孔中则不易取得,钻孔中较易取得的是岩石质量指标(RQD)以及钻孔声波的纵波波速(Vp)、完整性系数(Kv)。通过对各特征指标之间的关系分析,确立各指标的相关性与可靠度,进而对岩体风化的渐进性进行分析,然后综合考虑国内外多个岩浆岩坝基的水电站的风化带量化参数取值,再考虑到杨房沟坝区花岗闪长岩岩体各代表性指标的渐进性特征,建立起杨房沟坝区花岗闪长岩岩体风化带划分的量化标准。通过确立的量化指标对坝区岩体风化带进行定量划分,在岩体风化带的最终综合判定中,加入岩体结构类型作为一项考虑指标进行综合划分。最后展示出杨房沟坝区岩体风化的空间分布特征。在对坝址区岩体卸荷开始研究前,同样先对岩体卸荷的机理进行分析,通过现场调查,得出岸坡卸荷大多以整体松弛为主,并且以2100m高程作为界限存在不同的卸荷特征。岩体卸荷带划分采用定性与定量相结合,其中定性以地表调查与平硐调查为主,定量划分则主要从张开裂隙数量的增多、裂隙张开宽度的变化以及岩体结构的松弛等方面入手。结合杨房沟水电站实测平硐资料,本次卸荷带的划分以裂隙率(单位长度上张开裂隙的条数)和裂隙张开度(单位长度上裂隙的累计隙宽)作为主要量化指标进行岩体卸荷定量化研究,并结合各平硐和钻孔的波速资料,运用纵波波速作为对所划分卸荷带的验证。综合考虑国内外多个岩浆岩坝基的水电站的卸荷带量化参数取值,再考虑到杨房沟坝区花岗闪长岩岩体各代表性指标的具体规律,建立起杨房沟坝区花岗闪长岩岩体卸荷带划分的量化标准。通过确立的量化指标对坝区岩体卸荷带进行定量划分,最后展示出杨房沟坝区岩体卸荷的空间分布特征。文中用同样的模式对研究区岩体的风化与卸荷分别进行了量化研究,然而岩体的风化与卸荷事实上是存在着密不可分的联系的。根据坝区岩体弱卸荷下限深度与弱风化上段下限深度的比拟,发现两者之间存在某种耦合关系。为了进一步探索两者之间的联系,本文通过现场实测的坝区地应力状态,用数值模拟的方法反演整个河谷的应力场的分布;分别建立两种不同的概化模型,一种考虑了坝区不同风化程度岩体对河谷应力场分布的影响;而另一种则不考虑岩体的风化,均作为新鲜岩体对待。运用两种概化模型得出的河谷应力场大小的分布划分出岩体的弱卸荷深度,并用两者作对比得出结论,说明岩体的风化可以影响岩体的卸荷深度,特别是增大岩体弱卸荷的深度。更多还原

【Abstract】 As the fifth cascade station in the middle reach of Yalong River, Yangfanggou hydropower station is located in Muli County, Liangshan Prefecture in Sichuan. According to the pre-feasibility study results, the dam in Yangfanggou hydropower station is recommended as concrete double-curvature arch dam, with the maximum height of 158 meters, normal water level of 2092 meters, and total capacity of 444.2 million cubic meters. Dam site belongs to landforms of highland and ravine. Yalong River flows in the direction of S30 ~ 40°E with water level elevation of 1984 ~1985m, and is usually 50~100m wide in dry season. Terrain on two banks is steep with exposed rock. Emergence stratum in the dam area is mainly hard and intact Yanshanian granodiorite. There is metamorphic siltstone with carbonaceous slale interbeds distributed only in derivation tunnel and underground powerhouse on left bank. Terrain beside the narrow valley basically assumes symmetrical type "V", and the covering layer on riverbed is 24-30m thick. Engineering geological condition in dam site is quite good overall with no regional faults, so it is suitable for building double-curvature arch dam.For the plant of 1000mw installed capacity, the dam construction often involves deep valley area. The current level of economic development and social investment determines the engineering reconstruction of rock and soil is confined to the near-surface tens to hundreds meters. As the foundation of dam project, surface rock in dam area is mainly reformed by two important exogenic forces of weathering and unloading effects. So the study of weathering and unloading rock mass has extremely vital significance for engineering design, rock excavation, rock quality grading and bearing surface selection etc. Research on rock mass (or rock) weathering and unloading has been an old task discussed for decades. Although progress and achievements on rock weathering and unloading research have been made in recent years through a large number of projects, translation of these new achievements to the guidance of engineering practice is quite lagging behind. According to this, quantitative characteristics of rock weathering and unloading in Yangfanggou hydropower station granodiorites area were researched. Besides, some tentative exploration of relationship between weathering and unloading was tried to enrich the refined research of weathering and unloading research in different lithology.On the analysis of rock weathering mechanisms, rock weathering features in Yangfanggou dam area were preliminary investigated, and three kinds of weathering patterns were summarized. Then rock weathering in quantity was studied. Rock weathering degree can be characterized through many factors, the main indexes were selected as follows in Yangfanggou station according to the rock engineering geology and site conditions: rock point load strength (PLS), rock deformation performance rebound value (Re), rock quality designation (RQD), p-wave velocity of rock mass elastic waves and sound wave (Vp), integrity index (Kv). These indicators can be obtained in exploration adits, surface occurrences by field measurement. Rock quality designation (RQD), borehole p-wave velocity (Vp) and integrity index (Kv) can be easily obtained from boreholes. Based on the analysis of correlation and reliability of feature indexes, the progressive rock weathering was then analyzed. Rock weathering quantitative criteria of Yangfanggou dam granodiorites was established, considering comprehensively of the quantitative selection of weathered zone parameters in multiple magmatic-foundation dams, and progressive feature of representative index in Yangfanggou dam granodiorites. The dam rock was classified according to the established quantitative indexes, and rock mass structure type was added as an index in final integrated judgment of rock weathering zones. Finally spatial distribution features of rock weathering in Yangfanggou station were shown out.The rock mass unloading mechanism was analyzed similarly before the study of rock mass unloading in dam area. The field investigation indicates that bank slope unloading is mainly Overall Relaxation, and 2100m elevation is a boundary of different unloading characteristics. Mass unloading zone is partitioned using qualitative and quantitative method. Qualitative investigation includes the surface survey and adit survey; while quantitative division are mainly obtained from the number increase and open width change of open fractures, rock structure relaxation, etc. Fissure rate (number of open fractures of unit length) and fracture apertures (accumulative total gap width of unit length) got from field adits measurement were chosen as major indicators for quantitative study of rock mass unloading in Youngfanggou station. Speed of longitudinal wave from drilling was used to verify the unloading zones dividing. Rock weathering quantitative criteria of Yangfanggou dam granodiorites was established, considering comprehensively of the quantitative selection of weathered zone parameters in multiple magmatic-foundation dams, and progressive feature of representative index in Yangfanggou dam granodiorites. The dam rock was classified according to the established quantitative indexes. Finally spatial distribution features of rock weathering in Yangfanggou station was shown out.Rock’s weathering and unloading were studied quantitatively in the same pattern. However, there is an inseparable connection between weathering and unloading actually. The comparison of weak unloading maximum depth and weak weathering maximum depth of rock mass shows a coupling relationship between them. In order to further explore the connection between unloading and weathering, numerical simulation was used to converse stress distribution of the whole valley on the basis of the field observation. Two different kinds of generalized model were established respectively, the first of which considered the influence of different-degree weathering rock mass on the valley stress distribution, while the other treated rock fresh without considering the weathering. Depth of weak unloading was divided according to the valley stress distribution obtained from two generalized models. After comparing the two models, conclusion was drawn that rock weathering can affect the rock mass unloading depth, especially the weak unloading depth.更多还原