Currently, tion projects in urban areas are frequently reported in China.The due to a lack of approaches for basal-heave analysis of pit-in-pit formsofbracedexcavationsarediverseduetovariousfactorssuch braced excavations, basal-heave failures of pit-in-pit braced as geological conditions and client needs.Theleft surface depends on the bottom strut level and wall length.The boundary is the centerline of the braced excavation.One venientforpracticalapplicationsandhasbeenwidelyadopted. For challenge is that the basal-heave failure surface depends on many the slip circle method, the FS is deﬁned as: factors—such as the spacing between the inner and outer braced M R excavations (W) and the embedment depths of inner and outer FS ¼ ð1Þ M D in which M and M are the resisting moment and the driving ⇑ R D Corresponding author. Based on the limit equilibrium method and E-mail addresses: sunyuyong2126(Y. Asimpliﬁedapproachforbasal-heavestability FS ¼ R ¼ ð2Þ f S e analysis of pit-in-pit is developed based on the limit equilibrium method, and this simpliﬁed approach is also compared with in which S and S are original soil shear strength and reduced soil a e numerical analysis results and the results of a slip circle method shear strength in the critical state, respectively.R is the shear f based on a single braced excavation.
the simpliﬁed approach is applicable and is expected to err on Compared with the limit equilibrium method and the limit the conservative side.
Limit equilibrium methods can the pit-in-pit braced excavations will become more frequently be divided into two categories: the bearing capacity method adoptedinmetropolitanareasworldwide.
Failureorunsatisfactory 1,3,30,31and the slip circlemethod 14,16,19,25,29. In the limit performanceoftheseexcavationsin acitywouldhavedevastating equilibrium method, a failure surface of soil is ﬁrst assumed, and social, economic and environmental consequences. Sun et al./Computers and Geotechnics 81 (2017) 294–306 295 Museum of Natural History braced excavation Strut 1 Strut 2 Strut 3 Strut 4 Strut 5 Metro Line 13 braced excavation Strut 6 Outer diaphragm wall Diaphragm wall (0.8 m thickness) Inner diaphragm wall Diaphragm wall (1.0 m thickness) Fig. The elevation view of co-construction engineering of Shanghai Museum of Fig. The excavation depths and wall embedded depths for inner and outer Natural History and Metro Line 13. have been developed 5,17,20,35,37,38 that use reliability theory 0 (H ).
Stress dependent stiffness according to a power law (m) 1.0 There is a trade-off between mesh size and computational effort, Lateral pressure coefﬁcient (K ) 0.557 0 as further reﬁnement can reduce the shear band size but will Strut bending stiffness (EI) 26,224 k Nm require much more computation time.
The left and right vertical boundariesare restrainedfrom movinginthehorizontaldirection, and the bottom is restrained from both vertical and horizontal Fortheshearstrengthreductiontechnique,somefailurecriteria movement.