Foundation pit excavation engineering is an old subject full of decision making. Yet, it still deserves further research due to the associated high failure cost and the complexity of the geological conditions and/or t...Foundation pit excavation engineering is an old subject full of decision making. Yet, it still deserves further research due to the associated high failure cost and the complexity of the geological conditions and/or the surrounding existing infrastructure around it. This article overviews the risk control practice of foundation pit excavation projects in close proximity to <span style="font-family:Verdana;">existing</span><span style="font-family:Verdana;"> disconnected piled raft. More focus is given to geotechnical aspects. The review begins with achievements to ensure excavation performance </span><span style="font-family:Verdana;">requirements,</span><span style="font-family:Verdana;"> and follows to discuss the complex </span><span style="font-family:Verdana;">soil structure</span><span style="font-family:Verdana;"> interaction involved among the fundamental components</span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">: </span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">the retaining wall, mat, piles, cushion, and the soil. After bringing consensus points to practicing engineers and </span><span style="font-family:Verdana;">decision makers</span><span style="font-family:Verdana;">, it then suggests possible future research directions.</span></span></span></span>展开更多
There is growing engineering concern about the base heave and post uplift phenomena in deep excavation in soft clay,which may pose a risk of instability of retaining systems.The purpose here is to conduct a detailed c...There is growing engineering concern about the base heave and post uplift phenomena in deep excavation in soft clay,which may pose a risk of instability of retaining systems.The purpose here is to conduct a detailed case study on the post uplift observed in a 17.6-meterdeep braced excavation of a subway station in thick soft clay(total thickness up to 42 m)in Shanghai.In this case,a large uplift up to 87 mm unexpectedly developed for the post founded on a 30-meter-long pile foundation.Efforts were first made to examine the complex relationships between the post uplift with the excavation depth(H),Terzaghi’s safety factor against base heave(Fs)and maximum deflection of retaining wall.A simplified approach for soil-post-strut interaction analysis was then proposed and used for quantitative research.The working characteristics of the long pile foundation under low safety factor against base heave(Fs<1.5)are summarized as following:(a)the back-analyzed neutral plane,where soil uplift equals the post uplift,lies at approximately 0.68 times the pile length from the pile top;(b)deep soil movement below the neutral plane results in the observed post uplift;(c)strut reaction plays a minor role in the restriction of post uplift.The influence of base treatment and excavation/construction procedures on post uplift and the principles of pile foundation design are also discussed in this paper.展开更多
文摘Foundation pit excavation engineering is an old subject full of decision making. Yet, it still deserves further research due to the associated high failure cost and the complexity of the geological conditions and/or the surrounding existing infrastructure around it. This article overviews the risk control practice of foundation pit excavation projects in close proximity to <span style="font-family:Verdana;">existing</span><span style="font-family:Verdana;"> disconnected piled raft. More focus is given to geotechnical aspects. The review begins with achievements to ensure excavation performance </span><span style="font-family:Verdana;">requirements,</span><span style="font-family:Verdana;"> and follows to discuss the complex </span><span style="font-family:Verdana;">soil structure</span><span style="font-family:Verdana;"> interaction involved among the fundamental components</span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">: </span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">the retaining wall, mat, piles, cushion, and the soil. After bringing consensus points to practicing engineers and </span><span style="font-family:Verdana;">decision makers</span><span style="font-family:Verdana;">, it then suggests possible future research directions.</span></span></span></span>
基金the financial support provided by the Natural Science Foundation of China(Grant No.41972273).
文摘There is growing engineering concern about the base heave and post uplift phenomena in deep excavation in soft clay,which may pose a risk of instability of retaining systems.The purpose here is to conduct a detailed case study on the post uplift observed in a 17.6-meterdeep braced excavation of a subway station in thick soft clay(total thickness up to 42 m)in Shanghai.In this case,a large uplift up to 87 mm unexpectedly developed for the post founded on a 30-meter-long pile foundation.Efforts were first made to examine the complex relationships between the post uplift with the excavation depth(H),Terzaghi’s safety factor against base heave(Fs)and maximum deflection of retaining wall.A simplified approach for soil-post-strut interaction analysis was then proposed and used for quantitative research.The working characteristics of the long pile foundation under low safety factor against base heave(Fs<1.5)are summarized as following:(a)the back-analyzed neutral plane,where soil uplift equals the post uplift,lies at approximately 0.68 times the pile length from the pile top;(b)deep soil movement below the neutral plane results in the observed post uplift;(c)strut reaction plays a minor role in the restriction of post uplift.The influence of base treatment and excavation/construction procedures on post uplift and the principles of pile foundation design are also discussed in this paper.
