In this study, the elastic modulus and the initial stresses of the rock were calculated through back analysis of in-situ displacements measured during excavation of the underground caverns. Results from back analysis were employed to determine the redistributed stresses the displacements and relaxed zone in the rock around the caverns, which supplement the geological characterization results. To verify the reliability of the back analysis program the elastic modulus and the initial stresses were obtained from inputting the displacements calculated by FEM. These were compared with the assumed normalized stresses in FEM and were in a reasonable agreement with an error of more or less than 3%.