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

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 (H-p/H-e), the excavation width (B), the wall thickness (t(w)), the strut capacity, and the normalized undrained shear strength (su/sigma v ') of soil were studied. Results showed that when the H-p/H-e ratio increased, the stability of excavations first improved and then remained unchanged with increasing H-p/H-e. 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 su/sigma v '. Finally, a simplified method was proposed to estimate the factor of safety of excavations without performing numerical analysis.