Abstract：The improved genetic algorithm is proposed to identify the elastic constants of rock foundation of concrete arch dams according to the measured displacements. Considering the premature phases of genetic algorithms，niche technology and method of adaptive probabilities of crossover and mutation are both introduced into the classical simple genetic algorithm to carry out the displacement back analysis which is based on the displacements measured in the model experiments and 3D FEM. In a case study on the practical engineering，the elastic modulus and Poisson′s ratio are obtained. The study shows that this method is suitable for the displacement back analysis of arch dams. It can also avoid premature phases that often happen in simple genetic algorithms，and a good convergence is achieved.
