Basal stability analysis of braced excavations in anisotropic and non-homogeneous undrained clay using streamline veloci
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RESEARCH PAPER
Basal stability analysis of braced excavations in anisotropic and nonhomogeneous undrained clay using streamline velocity fields Maosong Huang1,2 • Hongyu Wang1,2 • Zhen Tang1,2 • Jian Yu1,2 Received: 11 December 2019 / Accepted: 29 July 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract A basal heave stability analysis in anisotropic and non-homogeneous undrained clay by using the kinematic approach of limit analysis is presented. The proposed failure mechanism consists of four translational rigid blocks and a streamlinebased shear zone. The velocity field for the shear zone, formulated by a streamline solution in a polar coordinate system, is a supplement to the previous streamline solution in rectangular coordinates. The present study is first verified by comparison with other existing solutions in homogeneous and isotropic soils. It is found that the streamline solution can produce sufficiently accurate upper-bounds compared with the multi-block mechanism, the finite element limit analysis and the shear strength reduction finite element method. Subsequently, validation of the streamline solution on basal stability in anisotropic and non-homogeneous clay is carried out by discussion on a well-documented case study. Keywords Anisotropic clay Basal stability Limit analysis Streamline velocity field
1 Introduction Recent years have witnessed the rapid development of underground engineering around the world due to the limited space available, especially in urban areas [22]. As the excavation depth keeps rising, it is of great significance to investigate the factor of safety against basal heave failure for braced excavations in soft clay. In current practice, there are generally three methods available for performing stability evaluation on braced excavations: (1) limit equilibrium method, (2) finite element method and (3) limit analysis method. Most of the existing basal heave stability analyses are carried out by using the limit equilibrium method. The significance of basal stability was first recognized by Terzaghi [30]. By analogy to the failure of wide footings, Bjerrum and Eide [1] examined the factor of safety against & Jian Yu [email protected] 1
Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China
2
Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092, China
basal heave failure by introducing bearing capacity solutions. Later, Eide et al. [10] further proposed a method to account for the wall embedded depth in assessing basal stability. Goh et al. [16] investigated the effect of soil resistance along the embedded part of the supporting wall on basal stability by using a modified Terzaghi method. It should be noted that the limit equilibrium method may not produce rigorous solutions due to its inherent limitations [24, 25]. Another commonly used approach to address basal stability problem is the finite element method
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