A great number of numerical simulations of multiple schemes were conducted to investigate the stability of underground cavern complexes in three representative hydropower stations in China. The purpose was to study the displacement law of side walls of underground openings under different conditions. In the calculation, four major typical rocks, four overburden thicknesses, and five geo-stress conditions were taken into account. The best-fit formulae to predict the displacement of key points on the side walls of underground openings were obtained by using the dimension less technique. The formulations can describe the effects of rock quality, overburden thickness, horizontal in Situ stress, the height of the power house and the spacing between openings. The formulation/methodology was used to predict the side wall displacements of nine underground complexes in China. A comparison analysis showed that the predicted values were in close agreement with those obtained by field measurements and by back analysis. (C) 2008 Published by Elsevier Ltd.