Factors affecting the stability of deep excavations in clay with consideration of a full elastoplastic support system

  • Tuan-Nghia Do
  • Chang-Yu OuEmail author
Review Paper


This study investigates the stability of internally braced excavations in thick, saturated clay using a finite element method with reduced shear strength. The support system was fully modeled using elastoplastic structural elements, including struts, walls, and center posts. Effects of the ratio of the wall embedded depth to the excavation depth (Hp/He), the excavation width (B), the wall thickness (tw), the strut capacity, and the normalized undrained shear strength (\(s_{\text{u}} /\sigma_{\text{v}}^{\prime }\)) of soil were studied. Results showed that when the Hp/He ratio increased, the stability of excavations first improved and then remained unchanged with increasing Hp/He. An increase in the excavation width did not influence the stability of excavations. The wall bending moment capacity had a more pronounced effect on the stability of excavations than the strut capacity. Additionally, the stability of excavations was most affected by \(s_{\text{u}} /\sigma_{\text{v}}^{\prime }\). Finally, a simplified method was proposed to estimate the factor of safety of excavations without performing numerical analysis.


Deep excavations Finite element method Stability analysis 

List of symbols


Excavation width


Factor of safety by finite element method

Fsc (R)

Factor of safety by slip circle method using the numerical failure surface

Fsc (toe)

Factor of safety by slip circle method using the failure surface passing through wall toe


Factor of safety by Terzaghi’s method


Ratio of wall embedded depth to excavation depth


Strut capacity multiplier


Wall thickness



The authors gratefully acknowledge financial support of the National Science Council, Taiwan, R.O.C., under Grant NSC 101-2221-E-011-110-MY3.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of Construction EngineeringNational Taiwan University of Science and Technology (Taiwan Tech)TaipeiTaiwan
  2. 2.Faculty of Civil EngineeringThuyloi UniversityHanoiVietnam
  3. 3.Department of Civil and Construction EngineeringNational Taiwan University of Science and Technology (Taiwan Tech)TaipeiTaiwan

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