白鹤滩拱坝左岸坝基变形特征及机理分析

吴家耀 陈浩 徐建荣 周勇 孟国涛

摘 要：白鹤滩水电站左岸拱坝坝基边坡地质条件复杂，坝基边坡内发育的缓倾坡外的层内错动带、反倾坡内的断层和柱状节理玄武岩是开挖边坡变形响应的重要影响因素。在分析现场监测数据基础上，对白鹤滩左岸拱坝坝基630 m高程以上的剪切变形特征及机理进行了分析研究，采用离散元程序UDEC再现了层内错动带LS3319的剪切变形特征，并对左岸拱坝坝基630 m高程以下的开挖响应特征进行了预测。结果表明：630 m高程以上坝基开挖过程中顺坡向缓倾层内错动带LS3319在开挖面坡脚部位出露前后，对坡脚局部应力场产生较明显的影响，其上下盘岩体表现出不同的变形特征，错动带上盘部分岩体首先出现应力增大或集中现象，随着开挖面下移直至错动带出露，出现开挖卸荷引起的岩体松弛;630 m高程以下受层内错动带LS331影响产生剪切变形，上盘浅层岩体出现卸荷松弛。错动带剪切变形主要发生在错动带的坝基面开挖揭露过程中，变形量值主要受赋存地应力条件、结构面参数和产状等因素控制。

关键词：拱坝坝基;剪切变形;层内错动带;变形机理;白鹤滩水电站

中图分类号：TV642.4+6 文献标志码：A

doi：10.3969/j.issn.1000-1379.2021.05.027

Abstract： The geological conditions of the left bank arch dam foundation of Baihetan Hydropower Station are complex. The dislocation interface with gentle inclination， the anti-dip fault and the columnar jointed basalt are the main important factors which influence the deformation response during excavating the slope. The shear deformation characteristics and mechanism of the left bank of Baihetan arch dam foundation were analyzed based on the monitoring data. The characteristics of shear deformation of the dislocation interface LS3319 was reproduced by UDEC. The calculation results show that during the excavation process of the dam foundation above E.L. 630 m， LS3319 has a significant influence to the local stress status of the slope before and after it's exposed in the excavation surface. The rock mass of the upper and lower parts of LS3319 reveals different deformation characteristics; the stress will be concentrated in the upper part firstly and then unloading and relaxation during the excavation surface bench down. Below E.L.630 m， the shear deformation will also occur due to the influence of dislocation interface LS331， rock mass of the upper part of LS331 will behave as relaxation at the same time. The shear deformation of the dislocation interface mainly occurs during the excavation and exposure process of dam foundation surface and the magnitude of the shear deformation mainly is controlled by in-situ stress conditions， mechanical parameters and occurrence of dislocation interface.

Key words： arch dam foundation; shear deformation; dislocation interface; deformation mechanism; Baihetan Hydropower Station

我國西南地区在近年来有不少大中型水电站项目在建或完建，该地区地形地貌的特殊性以及受青藏高原近百万年来持续隆升的影响，在内外动力地质作用下，河谷下切深度较大[1]。在深切河谷中修建200～300 m级的高坝，对坝基岩体质量的要求非常高，不可避免对边坡开挖，使坝基岩体质量满足设计要求。……