Analysis and Practicality of a Plate Wall and Prestressed Steel Struts in the Interstage Backfill Construction of Deep Foundation Pits

Abstract

Based on the phase II project of Block 07, District 14 of Shanggang, Baoshan New City SB-A-4, Shanghai, the underground three-layer foundation pits were excavated to the basement at one time. Due to project needs, the backfill construction progress of specific super high-rise building areas needed to be excavated significantly in advance. The calculation method of an elastic ground slab combined with a space frame beam was used to establish an integrated coupling analysis model for the foundation pit and the main structure in the incomplete state and to calculate the interaction mechanism and load distribution between the foundation pit and the main structure under a specific state. Under the premise of non-zoned excavation of the foundation pit, the preliminary removal of the supports in the specific area and the backfill construction of the main structure were achieved. The actual measurement data verify that, as a type of strut structure with a large bearing capacity and high structural stiffness, a plate wall combined with prestressed steel di-agonal braces can ensure that the plate wall has better lateral stiffness and overturning resistance through the application of matching prestresses. This meets the conditions of an interstage support replacement system for deep foundation pits. The successful implementation of the project provides certain reference value for deep foundation pits that need backfill construction in advance.

Keywords

elastic ground slab / space frame / finite element analysis / support replacement

References

[[1]] Zhu X. Design of Support Replacement for Controlling Deformtion Caused by Support Dismantling of Deep Foundation Pits in Soft Ground. Chinese Journal of Geotechnical Engineering 2010, 32, 256-260.

[[2]] Liu Y.; Liu J.; Xin Z.; Shen H. Support Replacement Technology of Bracing System with Oblique Bracing + Piles in Row. Chinese Journal of Geotechnical Engineering 2010, 306-311.

[[3]] Wu J.; Zhang B.; Mao K.; Meng S. Application of Steel Structure Changing Beams in Inner Supporting Founda-tion Pit Engineering. Architecture Technology 2020, 51, 1055-1059, doi:10.3969/j.issn.1000-4726.2020.09.008.

[[4]] Liu Y.; Liu J.; Wang H. Removing First and Supporting Then Method for Diagonal Bracing System. Chinese Jour-nal of Geotechnical Engineering 2010, 77-80.

[[5]] Shen X.; Zhang J.; Xu X.; Wang Z. Optimization and Construction of Bracing Substitution of Deep Foundation Excavation Support by Stage Construction. Construction Technology 2014, 43, 45-47, doi:10.7672/sgjs2014010045.

[[6]] Fang H.; Chai Y.; An W.; Xu X. Numerical Simulation Study on Brace Replacement of Standard Station of Tianjin Metro. Low Temperature Architecture Technology 2013, 35, 122-123, doi:10.3969/j.issn.1001-6864.2013.12.047.

[[7]] Zhou S.; Qiu C.; Zhou J.; Yu A.; Sun Y. Construction Technology of Support Replacement by Rib Wall in Deep Foundation Pit. Building Construction 2020, 42, 329-331, doi:10.14144/j.cnki.jzsg.2020.03.010.

[[8]] Shen J.; Wang W.; Weng Q. Analytic Method of Diaphragm Walls of Circular Foundation Pits. Chinese Journal of Geotechnical Engineering 2008, 280-285.

[[9]] American Concrete Institute. ACI 318: American Code for Design of Concrete Structures. 2014.

[[10]] Li M.; Xu Y.; Zhang B. Research on Lateral Stiffness of Strutted Retaining Structure for Deep Excavation. Journal of Engineering Geology 2020, 28, 1116-1122, doi:10.13544/j.cnki.jeg.2020-430.

[[11]] Weng Z. Discussion on the Control of Interstory Displacement Angle Limit Value of High-Rise Building Struc-ture. Master, South China University of Technology, 2015.