# Why use finite element analysis for slope stability?

February , 16th 2024 | Author: Mariele Oliveira (@Prontubeam_en) Read: 917 times

Why use finite element analysis for slope stability?

Natural and man-made slopes are found in various environments worldwide, serving critical roles in mining, highway construction, and other industries. Understanding the geotechnical properties of slopes and implementing appropriate engineering measures is essential for maximizing their benefits while mitigating associated risks. Therefore, analyzing the stability of slopes is essential to guarantee the safety of the structure. In this article, we will explore the importance of Finite Element Analysis (FEA) as a powerful tool for evaluating and understanding slope stability.

According to Matsui and San (1992)[1], the principle behind the shear strength reduction technique in the finite element slope stability analysis is to reduce c and tan f until slope failure occurs, where slope failure is defined as the development of shear strain from the toe to the top of the slope. The authors highlight that in finite element analysis, it is difficult to trace the failure slip surface of a slope, as it is based on the stress failure criterion.

In the SRM (FEA), the critical slip surface is found automatically from the increase in the shear strain due to the reduction of the shear strength. In many cases, the location of the critical slip surface defined by the SRM (e.g., the contour of the equivalent plastic strain) is unclear (Liu, Shao, Li, 2015)[2].

Limit methods are well established for the latter, but can in certain situations be misleading. Also, they may not provide sufficient information. Another and more obvious limitation of limit methods is that they provide no information about the development of failure. They do not indicate where yield initiates (Naylor, 1982)[3].

Griffiths and Lane (1999)[4] outline the advantages of the FE approach to slope stability analysis over traditional limit equilibrium methods, which can be summarized as follows: (i) no assumption needs to be made in advance about the shape or location of the failure surface; (ii) since there is no concept of slices in the FE approach, there is no need for assumptions about slice side forces. The FE method preserves global equilibrium until "failure" is reached; (iii) if realistic soil compressibility data are available, the FE solutions will give information about deformations at working stress levels; (iv) the FE method is able to monitor progressive failure up to and including overall shear failure.

However, the finite element method has not become widely adopted for slope stability studies due to intense computational requirements and difficulties in assessing the stress versus strain characteristics of the soils. In addition, affordable and user-friendly limit equilibrium methods have provided factors of safety that appear to represent failure conditions in the field in most situations (Fredlund and Scoular, 1999)[5].

In conclusion, the use of finite element analysis (FEA) for evaluating slope stability presents significant advantages and challenges. While FEA offers a powerful and versatile approach to understanding the complex behaviour of slopes, including the ability to analyze progressive failure and consider realistic soil properties, it also comes with computational demands and challenges in assessing soil stress-strain characteristics. Despite these hurdles, the benefits of FEA, such as its ability to model failure surfaces without pre-assumptions and monitor progressive failure, make it a valuable tool for engineers and researchers in the field of geotechnical engineering. However, traditional limit equilibrium methods still hold relevance. Ultimately, the choice between FEA and traditional methods depends on the specific requirements of the analysis and the available resources, highlighting the importance of understanding and considering the strengths and limitations of each approach in slope stability studies.

References

[1] Matsui, T., & San, K. C. (1992). Finite element slope stability analysis by shear strength reduction technique. Soils and foundations, 32(1), 59-70.

[2] Liu, S. Y., Shao, L. T., & Li, H. J. (2015). Slope stability analysis using the limit equilibrium method and two finite element methods. Computers and Geotechnics, 63, 291-298.

[3] Naylor, D. J. (1982). Finite elements and slope stability. In Numerical Methods in Geomechanics: Proceedings of the NATO Advanced Study Institute, University of Minho, Braga, Portugal, held at Vimeiro, August 24–September 4, 1981 (pp. 229-244). Dordrecht: Springer Netherlands.

[4] Griffiths, D. V., & Lane, P. A. (1999). Slope stability analysis by finite elements. Geotechnique, 49(3), 387-403.

[5] Fredlund, D. G., & Scoular, R. E. G. (1999). Using limit equilibrium concepts in finite element slope stability analysis. In Proceedings of the International Symposium on Slope stability Engineering-IS Shikoku (Vol. 99, pp. 31-47)

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Mariele Oliveira. Slope Stability | LEM | FEM | Geotechnical Software Analysis
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