Numerical Analysis Of Adjacent Foundation Pits In Soft Clay

As the exploitation of underground space and the high-rise construction in a city,a large number of deep foundation excavations have appeared lately.Its scale and depth increase constantly.Urban deep foundation excavations are generally surrounded with dense buildings,therefore,building site is very narrow. Applying the traditional design theory (deformation control design) and routine construction technology,it is very difficulty to prevent surrounding buildings or structures from destabilization.Although many scholars,engineers and technicians have been researching into the deformation control design of deep foundation excavations for recent years,it's not to be solved to problems of retaining structures-soil interaction and adjacent structures-soils interaction.This article rely on the foundation pit of Lishi Finance Building and Zhenbang Building which are designed by Zhejiang Huazhan design institute,use Plaxis analytical system of finite fractile,and built deep foundation pit model which can represent it reasonably. Analysed and compared the soilmass displacement under several situations (lishi financial foundation pit excavation alone, ZhenBang building foundation pit excavation alone, two foundation pit excavation synchronization, lishi financial foundation pit when advance one condition excavation, lishi financial foundation pit when advance two condition excavation, ZhenBang building foundation pit excavation advance one condition, ZhenBang building foundation pit excavation advance two condition),the change of stess and shaftforce of sustain. First,built a simple and regular and single foundation pit model,analysing it's displacement and subsidence;then make two simple foundation pit together,analyzing it's displacement and subsidence under five conditions;last,use monitoring date of practical project to verify the reliability of the model. From which we draw:1.Along with the increase of foundation pit excavation depth, the pile soil displacement and bending moment increases. But at the bottom for ties and floor change hold stage did not happen exacerbate trend.2.The adjacent foundation pit is interior support system, the shallow foundation pit will tilt towards to the he deep foundation pit.3.Active earth pressure with the maximum horizontal displacement position, but moving downward excavation depth change with floor slab change hold ties and moving upwards4.From the axial force to support beam, either individually excavation or jointly excavation, the first line of support after the second way erection increasing support, while the second way support as conditions (in dwindling support stage) decreases.5.From the financial foundation pit and ZhenBang mansion when separate excavation pit excavation and asynchronous and synchronous excavation's maximal components analysis, the conclusion of the pit excavation adjacent deformation of retaining piles of greater influence than retaining piles bending moment influences.6.Tilt of the foundation pit, happened in its tilt side active earth pressure area no obvious horizontal displacement, passive earth pressure area also no obvious soil uplift phenomenon.7.Among the adjacent soil foundation soil pressure is obvious fold decreases.With number imitation of this article,combining the project example, and approaching the influence element of contiguous foundation pit,provid the theory evidence for the future project examples.