TY - JOUR
T1 - Undrained stability of pit-in-pit braced excavations under hydraulic uplift
AU - Lai, Fengwen
AU - Chen, Fuquan
AU - Liu, Songyu
AU - Keawsawasvong, Suraparb
AU - Shiau, Jim
PY - 2022
Y1 - 2022
N2 - 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.
AB - 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.
KW - Finite element limit analysis
KW - Hydraulic uplift
KW - Multivariate adaptive regression splines
KW - Pit-in-pit excavation
KW - Undrained stability
UR - http://www.scopus.com/inward/record.url?scp=85135389186&partnerID=8YFLogxK
U2 - 10.1016/j.undsp.2022.04.003
DO - 10.1016/j.undsp.2022.04.003
M3 - Article
AN - SCOPUS:85135389186
SN - 2096-2754
VL - 7
SP - 1
EP - 17
JO - Underground Space (China)
JF - Underground Space (China)
IS - 6
ER -