Abstract: Accurate prediction of surrounding rock deformation is one of the important prerequisites for scientific design and safe construction of large underground caverns. Existing prediction methods for surrounding rock deformation of underground cavern are mainly based on the monitoring data of the constructed locations surrounding rock deformation to predict the deformation trend of unconstructed locations. This causes difficulties in meeting the requirement of accurately predicting the total surrounding rock deformation of in engineering survey and design stage. Based on the statistical analysis of measured data from 31 large underground caverns in China, a method for predicting the maximum convergence deformation of underground powerhouse side wall based on multiple indexes was proposed. Firstly, it is found that the ratio of saturated uniaxial compressive strength to ground stress R/?, geological strength index (GSI) and material constant of intact rock mi have great influence on the surrounding rock deformation in the 31 cases. Their calculation methods are also given. Meantime, the ratio of maximum convergence deformation to cavern height (relative deformation value U/H) is used to evaluate the value of surrounding rock deformation. Secondly, through many statistical analyses, the prediction formula between the relative deformation value (U/H) of underground cavern and the three indexes is established. Finally, the method for predicting maximum convergence deformation of underground powerhouse side wall is verified by an engineering example. The results show that the calculated results by this method are very close to the actual results, which indicates the rationality of the proposed method.

Key words: geotechnical engineering, large underground cavern, side wall of underground powerhouse, maximum convergence deformation, statistical analysis, prediction method