Abstract: Based on the theory of slip line field, this paper proposes a limit curve method of slope stability according to the deformation situation; the method is the inverse process for computing a heavy slope ultimate load and the dual process of strength reduction method. Defines two evaluation indexes: the degree of safety(DOS) and the degree of failure(DOF) according to the deformation failure criterion of the limit stable slope curve and the slope surface intersection computed by characteristic line difference method(SCM) and the slope limit experimental approximate formula(CCM). The method does not require assuming and searching critical slip surface. Classic examples and typical examples show that with the increase of nodes, the accuracy of SCM increases; when boundary step is constant, the judgment value obtained by three spline interpolation are unchanged, which proves the stability of SCM. Typical examples show that the larger the slope angle becomes, the lower the slope stability is; limit slope curve and slope is from without intersection to intersection, which proves that the correctness of the deformation failure criterion. Comparing the results from the two examples show that the safety factor is large and SCM, CCM results are comparable; this paper increases external load relative to the original boundary conditions; so the safety factor becomes smaller; SCM, CCM is conservative. To calculate the correct rate, this paper uses 34 samples: safety factor method is 67.7%, the stress state method is 73.5%, CCM is 79.4% and SCM is 70.6%, which indicates that SCM, CCM correct rate is higher. The conclusions of SCM, CCM factor sensitivity analysis and safety coefficient method are completely consistent. By analyzing and computing the slope stability and the ultimate slope angle of open pit mining, the report about SCM, CCM is the same as the original; when the parameter variable is smaller, CCM is more conducive to practice, which indicates that the method has a certain value in engineering applications.

Key words: limit curve method, deformation failure criterion, degree of safety, degree of failure