STABL is a computer program written for the general solution of slope-stability problems using a two-dimensional limiting equilibrium method. The original program was developed by Ronald A. Siegel at Purdue University in 1975. STABL was placed on line for routine use in 1976 by the Indiana Department of Highways, and after being reported in the open literature, the program was adopted by many agencies.

The extensive use of STABL for academic purposes originated requests from users to introduce many improvements to the original STABL program since its introduction. Most of the current versions can handle tieback loading, reinforced-earth layers in embankment, and Spencer's method of analysis.STABL programs feature unique, random techniques for generation of potential failure surfaces and the most critical surface is shown in the output as the one with the lowest factor of safety.


Program STABLPRO was developed to improve the user-friendly features for Program STABL. STABLPRO was written for Windows platforms and uses a graphics interface for data entry. The user may read the screen information, then type the data at the specified entry field. The entered data can be changed freely by moving the mouse to the field location on the screen.

STABLPRO integrates the input modules, main-computation module, and graphics module into one system. Therefore, the user may freely call on each module inside Windows for operation. In general, after entering the input data , the user may use the computation module to execute the input data. The user may also call on the graphics module to plot the computed potential failure surfaces.

Program STABL features unique random techniques for generation of potential failure surfaces for subsequent determination of the most critical surfaces and their corresponding factors of safety. One technique generates circular failure surface, another technique generates general, irregular surfaces of random shape. While the latest versions of the STABL group of programs are more versatile than the earlier versions, all of the versions of Program STABL adopt the original command-line type of input format which is inconvenient to infrequent users.

The current version of STABLPRO can handle tieback loading, reinforced-earth layers in embankment, and Spencer’s method of analysis.