叶巴滩水电站坝址区深部变形破裂特征

Characteristics of deep-seated crack in dam site of Yebatan Hydropower Station

深入研究叶巴滩水电站坝址区对称发育的深部变形破裂的分布规律、地质特征、类型和控制因素,为进一步评价深部变形破裂岩体质量及可利用性奠定基础。基于野外调查、地震层析成像(CT)、平硐波速测试(Vp)和工程地质类比等方法,揭示深部变形破裂分布规律与宏观地质特征,划分深部变形破裂类型,探讨对称分布的深部变形破裂的控制因素。研究表明:深部变形破裂分布于距边坡表面水平深度约80~140 m范围,具有随高程的升高水平分布深度逐渐增加的规律,两岸均未形成贯通性破裂面;深部变形破裂大多继承早期构造节理形成,具有明显的张性特征,局部受地下水影响,破裂面表层风化加剧;深部变形破裂类型可分为轻微松弛型、中等松弛型和强烈松弛型;地壳抬升、河谷演化和高地应力等区域因素与边坡形态、边坡物质基础及微地貌共同控制深部变形破裂的形成和分布。

There is a series of symmetric deep-seated cracks（DSC） in the abutment slope of Yebatan Hydropower Station. The special geological phenomenon is analyzed to provide a scientific basis for a comprehensive analysis on rock mass quality and availability evaluation. Through particular field survey, seismic tomography（CT） and sonic wave testing（Vp）, the spatial distribution characteristics and macroscopic geological features of DSC are summarized. Additionally, DSC is divided into different types. According to these analyses, the controlling factors of DSC are studied completely by using the engineering geologic analogy method. The spatial distribution range of DSC ranges between 80 m and 140 m in horizontal direction from the surface of rock slope. The horizontal depth of DSC is positively correlated with the elevation of abutment slope, but there are not any connected cracks at two sides. The majority of DSC inherits early tectonic joint formation with tensile characteristics, and the weathering of rock is strengthened because of underground water. The slackness extent of DSC can be divided into three types： slightness, medium and severity. The formation and distribution of DSC are controlled by the regional factors and other factors such as the slope shape, the material foundation of the slope and the micro topography. The crust upward, incised valley and magnitude of the tectonic stress are the prerequisite for DSC. Furthermore, the rock property and complex slope structure provide material foundation for DSC. These are reasons for the symmetric distribution of DSC.