Print Email Facebook Twitter Undrained stability of pit-in-pit braced excavations under hydraulic uplift Title Undrained stability of pit-in-pit braced excavations under hydraulic uplift Author Lai, F. (TU Delft Geo-engineering; Southeast University) Chen, Fuquan (Fuzhou University) Liu, Songyu (Southeast University) Keawsawasvong, Suraparb (Thammasat University) Shiau, Jim (University of Southern Queensland) Date 2022 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. Subject Finite element limit analysisHydraulic upliftMultivariate adaptive regression splinesPit-in-pit excavationUndrained stability To reference this document use: http://resolver.tudelft.nl/uuid:095cb1cf-424d-41e1-809b-0006454cc24c DOI https://doi.org/10.1016/j.undsp.2022.04.003 ISSN 2096-2754 Source Underground Space, 7 (6), 1-17 Part of collection Institutional Repository Document type journal article Rights © 2022 F. Lai, Fuquan Chen, Songyu Liu, Suraparb Keawsawasvong, Jim Shiau Files PDF 1_s2.0_S2467967422000605_main.pdf 4.07 MB Close viewer /islandora/object/uuid:095cb1cf-424d-41e1-809b-0006454cc24c/datastream/OBJ/view