Based on the algorithm advised by Abdallah I. Husein and his classmates

some improvements have been made as follows: (1) adding several conditions of geometry rationality; (2) developing a technique by controlling the range of slip segments rotation to prevent two adjacent vertices of a slip surface from approaching each other; (3) making the algorithm to be suitable for slip surfaces that are convex upward; (4) adding the changeable vertex count mechanism of a slip surface during the searching procedure in order to make the critical slip surface more smooth. The results show that the modified algorithm is more practical feasibility and stability to aim at searching the critical slip surface

preserving the advantages of the original algorithm. The algorithm is also adopted by the slope stability analysis software named ZSlope developed by the authors.