以澜沧江某水电站左坝肩边坡为研究对象,通过野外调查发现,坡体广泛发育一类同时具有碎裂结构和显著松动变形的特殊岩体,由此提出了碎裂松动岩体的概念。对其发育特征进行研究后发现,碎裂松动岩体不仅具有从坡表往里依次呈现出散体-碎裂-块裂的结构特征,而且其发育深度与极强卸荷带也具有较好的对应关系。鉴于此,提出了其划分标准:将具有散体-碎裂-块裂结构的岩体深度作为其结构上的发育深度,而极强卸荷带发育深度则作为其卸荷上的发育深度,取二者的平均值作为最终的发育深度。为了验证利用该标准划分的结果能够指导边坡开挖,采用UDEC进行模拟,结果表明:边坡开挖后,整体变形小、稳定性较好,仅局部开挖面附近出现小规模的危岩体。建议沿划分的碎裂松动岩体发育深度对该边坡进行开挖,2 880 m高程上、下开挖坡比分别为1∶1.5和1∶1。通过碎裂松动岩体的划分,能够为此类特殊的边坡岩体合理的开挖深度的确定提供参考。

Field survey on the left abutment slope of a hydropower station on the Lancang River reveals a type of special rock mass with fragmented structure and significant loosening deformation synchronously. On this basis, we put forward the concept of cataclastic loose rock mass. Study on its development characteristics unveils that the cataclastic loose rock mass features with granular structure, cataclastic structure, and block structure from the slope surface to the interior, and its development depth corresponds well to the extremely-strong unloading zone. In view of this, we put forward the division standard: the depth of the rock mass with granular structure, cataclastic structure and block structure is regarded as the development depth of cataclastic rock mass, while the depth of the extremely-strong unloading zone is the depth of its unloading zone; and the average value of the two is determined as the ultimate development depth. In order to prove that the result acquired by this standard can be used to guide the excavation of the slope, we performed simulations using UDEC. Results demonstrated that after the excavation of the slope, besides the dangerous rock in a small scale near the excavation face, the overall deformation is small, and the stability is good. Therefore, we recommend to excavating the slope along the division depth of the cataclastic rock mass, and the excavation slope ratio above and below 2 880 m height is 1∶1.5 and 1∶1, respectively.The results prove that the division of cataclastic loose rock mass provides reasonable reference for the excavation depth in such special slope rock mass.