Abstract：The optimal algorithm is applied to determine the initial stress field of rock mass according to the stress changes around tunnel after excavation. The inverse problem of parameter identification is formulated as optimal problem，which is solved with BFGS algorithm. The best estimation of stress field is determined by comparing measured and predicted stress changes. The measurement errors are taken into account in the identification of the initial stress parameters of rock mass. The values and direction of the principal stresses can be accurately identified by using proposed inversion algorithm. The computational results show that the proposed identification algorithm is effective for determining the initial stress parameters and has strong ability against the measurement noises.
