Undrained stability of pit-in-pit braced excavations under hydraulic uplift

Lai, Fengwen and Chen, Fuquan and Liu, Songyu and Keawsawasvong, Suraparb and Shiau, Jim ORCID: https://orcid.org/0000-0002-9220-3184 (2022) Undrained stability of pit-in-pit braced excavations under hydraulic uplift. Underground Space. ISSN 2096-2754


Abstract

Pit-in-pit (PIP) excavations in an aquifer–aquitard system likely undergo catastrophic failures under the hydraulic uplift, the associated undrained stability problem, however, has not been well analyzed in the past. To this end, a hypothetical model of PIP braced excavation in typical soil layers of Shanghai, China is developed using the finite element limit analysis (FELA) tool. The FELA solutions of safety factors (FSs) against hydraulic uplift are verified with the results from the finite element analysis with strength reduction technique (SRFEA) and existing design approaches. Subsequently, FELA is employed to identify the triggering and failure mechanisms of PIP braced excavations subjected to hydraulic uplift. A series of parametric studies considering the various geometric configurations of the PIP excavation, undrained shear strengths of aquitard, and artesian pressures are carried out. The sensitivities of relevant design parameters are further assessed using a multivariate adaptive regression splines (MARS) model that is capable of accurately capturing the nonlinear relationships between a set of input variables and output variables in multi-dimensions. A MARS-based design equation used for predicting FS is finally presented using the artificial dataset from FELA for practical design uses.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Faculty/School / Institute/Centre: Current – Faculty of Health, Engineering and Sciences - School of Engineering (1 Jan 2022 -)
Faculty/School / Institute/Centre: Current – Faculty of Health, Engineering and Sciences - School of Engineering (1 Jan 2022 -)
Date Deposited: 25 Jul 2022 03:47
Last Modified: 18 Nov 2022 03:53
Uncontrolled Keywords: Pit-in-pit excavation; Hydraulic uplift; Undrained stability; Finite element limit analysis; Multivariate adaptive regression splines
Fields of Research (2020): 40 ENGINEERING > 4005 Civil engineering > 400502 Civil geotechnical engineering
Identification Number or DOI: https://doi.org/10.1016/j.undsp.2022.04.003
URI: http://eprints.usq.edu.au/id/eprint/50214

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