are too close to the structure being analyzed, the program likely will not identify the critical failure surface and factor of safety. To ensure the critical failure surface is not overlooked, the model extents should be at least two times the width of the structure. Refinement of model size and extents can be performed only after the engineer is confident the analysis is capturing the critical failure surfaces and factor of safety (Figure 3). Software Model Verification Model verification is a critical aspect for all engineering analyses, but is particularly important when using commercially available software packages. When performing GSAs, a prudent approach is to verify the reasonableness of the results for a simple case or to use a previously validated problem to assist in validating the results. Typically, the model validation uses the same inputs and analysis methodologies, and if the results are inconsistent, the engineer should evaluate the differ- ences and update the analysis. Closing Remarks Global stability analyses are commonly encountered within the geo- technical engineering industry. Background and knowledge of typical analysis methodologies and commonly utilized commercially available software packages are required to achieve reliable results. Unexpected movements or catastrophic failures can occur if these analyses are performed incorrectly. While recognizing and avoiding common pitfalls aid in achieving successful GSA performance, the authors recommend the following
fundamental strategies, 1) utilize LEMs that are considered complete equilibrium procedures (e.g., Spencer, and Morgenstern and Price), 2) use site-specific information for the subsurface and loading conditions, 3) check the model extents, and 4) verify the analysis software. Follow - ing these approaches provides greater reliability in the analysis results.
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March 2023
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