爆破荷载下白鹤滩大型地下厂房累积损伤机制研究

Study on cumulative damage mechanisms of Baihetan large underground powerhouse under blasting loads

白鹤滩水电站大型地下厂房爆破开挖过程中脆性破坏频发,采用微震监测、多点位移计、锚杆(索)测力计等多种原位监测设备,全面揭示大型地下厂房爆破开挖卸荷下脆性玄武岩的力学响应行为。原位综合监测结果表明,多次爆破开挖后,围岩破裂、变形和应力均发生了一定程度的增长。进一步分析证实,围岩变形与其内部微破裂具有协调性,即爆破荷载作用下岩体逐步开裂,岩体经历裂纹压密、微破裂萌生、破裂扩展等连续破裂阶段,同时伴随围岩变形的增长。基于能量指数和累积视体积的微震参数预警方法,能够有效预警围岩宏观破坏的风险。研究表明,监测爆破荷载诱发的“破裂-变形-应力”演化信号对高应力硬岩地下工程施工方案优化及地质灾害预警具有重要的指导作用。

Brittle failure of rock masses occurs frequently during blasting excavation of large underground powerhouse of the Baihetan Hydropower Station.In-situ monitoring equipments,such as microseismic(MS)monitoring,multi-point extensometers and rockbolt(cable)dynamometers,are adopted to fully reveal the mechanical responses of basalt under blasting excavation of the large underground powerhouse.The comprehensive monitoring results show that the fracture,deformation and stress of the surrounding rock increase to a certain extent after blasting excavation.Further analysis confirms that the surrounding rock deformation is compatible with the internal micro-fracture.The rock mass of the powerhouse cracks gradually under blasting excavation.The rock mass undergoes continuous fracture stages such as crack compaction,micro-fracture initiation and fracture propagation,accompanied by the growth of surrounding rock deformation.The early warning method of MS parameters based on energy index(EI)and cumulative apparent volume(CAV)can effectively warn the risk of macro-damage of the surrounding rock.It is also shown that monitoring the evolution signals of“fracture-deformation-stress”induced by blasting excavation has an important guiding role in the optimization of construction schemes of underground engineering under high-stresses as well as in the early warning of geological disasters.