乌东德地下厂房岩体深部加固及施工程序研究

乌东德水电站右岸地下厂房洞室群赋存于前震旦系褶皱基底,为陡倾下游的层状浅变质岩。主厂房第Ⅵ层大桩号段开挖时,单次长度达35.0 m,由于上游边墙处的施工支洞顶部岩体挖除、侧向约束解除、边墙高度突增,导致主厂房上游边墙岩体深部出现较大范围的沿层面开裂及滑移、围岩变形及锚索受力陡增,危及到主厂房施工及运行期安全。为此,采用三维离散元法对岩体开裂部位加固及第Ⅵ层后续开挖区段长度进行了对比研究,并提出了"锚索+接缝灌浆"的处理方案及"小区段、间隔开挖+及时支护"的施工程序。目前,右岸地下厂房已全部开挖完成,各部位监测项目均已收敛,监测成果验证了加固方案及开挖程序的合理性。相关思路可为后续同类工程的建设提供参考。

Research on reinforcement for deep rock cracking and construction procedure of underground powerhouse of Wudongde Hydropower Station

The right-bank underground powerhouse of Wudongde Hydropower Station is located in the fold basement of pre-Sinian system that is characterized as epimetamorphic rock of steep dip to downstream. The maximum length of a single excavation section reached to 35m in layer Ⅵ of the main powerhouse. In the adit excavation construction on the upstream sidewall, due to the top rock mass was excavated, the lateral constraint was removed and the height of sidewall increased sharply, causing large scale rock cracking, sliding of rock stratum as well as increase of rock deformation and bolt stress, which threatened the safety of construction and operation of the main powerhouse. Therefore, three dimensional discrete element method was used to analyze the deep rock cracking reinforcement solutions and compare the excavated length in the follow-up section of layerⅥ. The solution of "anchor cable with joint grouting" and the construction procedure of "short section, interval excavation and timely support " were provided. At present, the excavation of right bank underground powerhouse is already completed and all monitoring items are convergent, which has proved the rationality of the reinforcing scheme and construction procedure. The train of thought can be referred by other similar projects.