Mechanism Analysis of Surrounding Rock Mass Failure Induced by the Multi-Cavern Effect in a Large-Scale Underground Powerhouse

The underground powerhouse of a hydropower station, in the form cavern group, is generally characterized by large scale and complicated spatial structure. During construction phase, extensive excavation limited space may cause multi-cavern effect between adjacent caverns thus lead to deformation failure surrounding rock mass, which undoubtedly compromises stability safety. This paper takes drainage gallery LPL5-1 Baihetan (adjacent main powerhouse) as case study. powerhouse, shotcrete at upstream arch cracked, ballooned peeled off. After field investigation numerical simulations, stress evolution induced studied mechanism analyzed. results indicate that led mass failures LPL5-1, related continuous resultant adjustment. excavation, concentration zone was generated intensified with progressed. expanded affected made its split, causing cracking.