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

作　　者：Fengwen Lai Fuquan Chen Songyu Liu Suraparb Keawsawasvong Jim Shiau 

机构地区：[1]Institute of Geotechnical Engineering,Southeast University,Nanjing 211189,China [2]Faculty of Civil Engineering and Geosciences,Delft University of Technology,PO-box 5048,2628 CN Delft/2600 GA Delft,The Netherlands [3]College of Civil Engineering,Fuzhou Univ,Fuzhou 350116,China [4]Department of Civil Engineering,Thammasat School of Engineering,Thammasat Univ,Pathumthani 12120,Thailand [5]School of Engineering,University of Southern Queensland,Toowoomba,QLD,4350,Australia

出　　处：《Underground Space》2022年第6期1139-1155,共17页地下空间（英文）

基　　金：financially supported by the National Natural Science Foundation of China(Grant No.41972269);Fundamental Research Funds for the Central Universities of China(Grant No.2242022 k30055);Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX20_0118);Scientific Research Foundation of Graduate School of Southeast University(Grant No.YBPY2041);CSC Scholarships.

摘　　要：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.

关 键 词：Pit-in-pit excavation Hydraulic uplift Undrained stability Finite element limit analysis Multivariate adaptive regression splines 

分 类 号：TU473.1[建筑科学—结构工程]