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一、前言丹江口枢纽的河床混凝土坝位于侵入的火成岩上,构造现象极为严重,构造破碎带和构造裂隙甚为发育,裂隙宽度大都在1公厘以下,并充填有薄膜状的钙质、方解石及挤压变质矿物等。倾角较陡,一般在60°—70°以上,由于相互交截的缘故,伸延不远;构造破碎带的规模,以顺河向的较大,如开挖后发观的 F_(16)、F_(204)、F_(241)等几条。破碎带本身胶结不牢固,两侧影响带节理发育,常为地下水通道。由于破碎带和裂隙的发育,将岩石切割成大小不等的碎块,尤其在节理密集带和破碎带的交会地区,因相互交截的缘故,使交会点附近的岩石破碎程度更为严重。其水文地质的特征是透水性不均一,随裂隙的发育程度和充填物的不同而异。一般说来:闪长玢岩的透水性大于闪长岩;基岩面以下25—30公尺的范围内,岩层的单位吸水量(ω)大于0.01公升/分者较多,但是,透水性较大的地区往往成透镜体状和带状分布,在破碎带中,由于胶结物和带中产物性质的不同,有时透水性反而不大,如 F_(204)及 F(16)破碎带的ω值都在0.002公升/分以下。
I. INTRODUCTION The riverbed concrete dam at the Danjiangkou junction is located on invaded igneous rocks and has a very serious tectonic phenomenon. The structural belt and structural fractures are well developed. Most of the fractures are below 1 mm in width and are filled with film-like calcareous, calcite and Extruded metamorphic minerals. Inclination angle steep, generally above 60 ° -70 °, due to the mutual intercept of the reason, not far; structure of the scale of the broken belt to the river along the larger, such as the excavation of the F12 (16) F_ (204), F_ (241) and so on. Fragmentation itself is not solidified cement, both sides affect the joint development, often for groundwater channel. Due to the development of fractured zone and fracture, the rock is cut into fragments of different sizes, especially in the intersection areas where the dense belts and fractures are intersected. Due to the mutual interception, the rock near the rendezvous point is more severely crushed. Its hydrogeology is characterized by a heterogeneous water permeability that varies with the degree of fissure development and fillings. In general, the permeability of diorite porphyrite is greater than that of diorite; within 25-30 meters below bedrock, water absorption per unit area (ω) is greater than 0.01 liters / min, but water permeability Larger areas tend to be lens-like and ribbon-like distributions. In the fractured zone, due to the different nature of the products in the cements and belts, the water permeability is sometimes rather small, as in F 204 and F 16 The values of ω are both 0.002 L / min or less.