System reliability analysis of soldier-piled excavation in unsaturated soil by combining random finite element and seque
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ORIGINAL PAPER
System reliability analysis of soldier-piled excavation in unsaturated soil by combining random finite element and sequential compounding methods A. Johari 1
&
A. R. Kalantari 1
Received: 20 May 2020 / Accepted: 22 October 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The stability of excavation in unsaturated soil is closely related to the variation of soil properties and matric suction. Determination of different failure modes and identifying the contribution of each one in an unsaturated soldier-piled excavation are the vital aspects of system reliability analysis. To address these issues, this paper provided a stochastic framework with a random elasto-plastic finite element–based program coded in MATLAB to evaluate the reliability indices of individual failure modes with considering the inherent uncertainty of real site soil properties and unsaturated state. In the next step, the sequential compounding method (SCM) was utilized to obtain the system reliability index by compounding the reliability indices of individual failure modes. Numerical results of a case study showed that in all failure modes, considering unsaturated state not only increases the mean value of factor of safety (FS) but also decreases the related standard deviation, which can be counted as a goal of reliability analysis. Among the reliability indices of the components, the most critical one is attributed to the lateral displacement. Furthermore, the safety ratio concerning the shear force has the maximum reliability index compared to the others. Moreover, based on the coefficient of variation (COV) of the components, it was found that the uncertainty of the soil parameters has the most significant effect on the global safety factor of the excavation. Keywords Random finite element method . Unsaturated soil . System reliability analysis . Soldier-piled excavation
Introduction Soldier piles are widely used in urban and industrial areas as a temporary or permanent retaining system for constructing the underground structures. The major advantages of this retaining wall system are its relatively low cost and fast construction. For these reasons, the soldier piles are a popular topic and have attracted the attention of researchers (e.g., Zhang 2009). To evaluate the performance of soldier-piled excavation, considering not only multiple failure modes but also soil properties uncertainties and the unsaturated state are crucial. However, some studies have been presented in the literature for stability analysis of retaining wall in the unsaturated state (e.g., Vo and Russell 2014), but there is still a need for
* A. Johari [email protected] 1
Department of Civil and Environmental Engineering, Shiraz University of Technology, Shiraz, Iran
the implementation of this state in stability analysis of soldierpiled excavation. Sahoo and Ganesh (2018) investigated the distribution of active earth pressure against the face of retaining wall with unsaturated backfill. The results showed that the resultant a
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