乌东德水电站右岸地下厂房随机块体特征研究

随机块体的几何特征和稳定性是水利水电工程中地下厂房支护设计的重要依据。对乌东德水电站右岸地下厂房随机块体的特征进行了深入研究。对研究区域内实测的裂隙参数进行了分组统计，确定了各组裂隙产状、迹长等参数的分布形式和大小。利用逆建模方法建立了三维裂隙网络模型，获取了各组裂隙的直径和三维密度。采用一般块体方法对地下厂房进行随机块体的识别和稳定性分析，利用GeneralBlock软件进行了10次随机实现，对10次计算结果进行了统计分析和讨论。研究结果表明，结构面与开挖面形成的随机块体集中在地下厂房的顶拱部位，10次随机实现中，地下厂房全长范围内平均每次形成的随机块体为414个；随机块体的平均体积为2.9 m³，最大块体的体积达152.0 m³；可移动块体中，大部分为稳定块体，不稳定块体均以坠落形式破坏；构成可移动块体的结构面多为3~4条，最多可达12条，其中倾W向的中等倾角裂隙是构成块体并可能造成块体失稳的最危险结构面；随机块体的平均深度为1.2 m，最大深度为8.8 m。建议支护锚杆应尽量穿透倾W向中等倾角的长大裂隙，且锚杆支护长度大于8.8 m。

Characteristics of Stochastic Blocks in Underground Powerhouse on the Right Bank of Wudongde Hydropower Station

The geometry and stability of stochastic blocks are fundamental to support design of underground powerhouse of Wudongde hydropower station.In this paper,the characteristics of stochastic blocks in the underground powerhouse on the right bank of Wudongde hydropower station are studied in detail.Firstly,measured fractures in the study area were grouped and statistically analyzed to determine the distribution type and magnitude of orientation,trace length and some other parameters of each fracture set.Three-dimensional fracture network is subsequently built by an inverse method in order to determine the diameter and volumetric density of each fracture set.A general block method was employed to detect stochastic blocks and evaluate the stability of blocks.Ten implementations were conducted and the results were analyzed and discussed.Results of the study show that stochastic blocks formed by discontinuities and excavations are located in the vault of the powerhouse.The average number of stochastic blocks formed in entire powerhouse of ten implementations is 414;the average volume of stochastic blocks is 2.9 m3 and the maximum block is 152.0 m3 in volume;most removable blocks are stable while unstable blocks collapse under the gravitational loading;most removable blocks have 3 or 4 discontinuities and the maximum value is 12.Fractures with west dip direction and medium dip are the most dangerous discontinuities in forming blocks and making them unstable;the average depth of stochastic blocks is 1.2 m and the maximum depth can be up to 8.8 m.It is suggested that the anchor bolts should go through the large fractures with west dip direction and medium dip as far as possible and their lengths should be greater than 8.8 m.