Abstract: It is a good choice for applying the multi-block upper bound method to the stability analysis of geotechnical problems. This method is simple, highly effective and based on rigorous theory basis. The multi-block upper bound method is used to solve the basal stability of deep excavations. According to the disciplines in China, the consolidated-undrained strength parameters are always employed to design the excavations. Simplification is taken to apply the consolidated-undrained strength parameters to the calculation in the upper bound method. Several excavation cases are calculated by the multi-block upper bound method, and the results are compared with those of the bearing capacity method and the circular slip method. The reasonable criterion is discussed when the safety factor for basal stability analysis is obtained from the multi-block upper bound method.