Transverse Cracks Cause Analysis on Rock-Anchored Beam During the Construction Process of Hydropower Station Underground Powerhouse

The different size of transverse cracks was appeared on the upper surface of rock-anchored beam in the process of excavation of underground powerhouse of hydropower station. Detailed cause analysis of these cracks was made based on the in situ geological condition, construction process, monitoring data, geophysical survey and numerical simulation. The results showed that the layered rock and faults are the premise of differential deformation of surrounding rock. Monitoring data and geophysical test results indicated that sidewall surficial surrounding rock was cracked by the blasting excavation which promoted the differential deformation of surrounding rock, easy to the generation of transverse crack on rock-anchor beam. Numerical analysis results revealed that differential vertical deformation of surrounding rock is the most important reason for the rock-anchored beam transverse cracks while the lithological differences as well as the existence of the faults are the main reason for the differences on the vertical deformation. The procedure of excavation and the nearby cavern excavation which resulted stress redistribution and differences on the deformation also leaded to another cause of rock-anchored beam transverse crack.