Main engineering geological problems and treatment measures of large underground cavern rock beams during excavation

In order to study the main engineering geological problems and treatment measures of underground cavern rock beams, by analysing the geological conditions, failure characteristics, influencing factors and adverse consequences of the rock beams of Baihetan Hydropower Station, the main geological problems of rock beams are classified, the causes are discussed, and the treatment measures are summarized. The study indicates the main geological problems of rock beams in the clued deformation of surrounding rock, unloading rebound, breakage, relaxation failure, block failure, influence of the slightly inclined weak layer, and influence of high dip angle fissure. In order to greatly avoid the influences of unfavorable geological conditions, full consideration should be given to the site selection and layout of caverns. Before excavation, the excavation plans of rock beams should be worked out in detail, and the pretreatment measures should be taken if necessary. For the failure of surrounding rock after excavation, the relevant measures such as mechanical excavation, pre-stressed reinforcement, additional reinforcement, concrete repair, supporting wall, consolidation grouting and reinforcement prestressed anchor cables should be adopted.