Study On The Influence Of CFG Pile Construction On The Foundation Pit Engineering And Its Surrounding Environment

With the acceleration of urbanization in China,high-rise buildings came into being.High foundation bearing capacity of tall buildings,simple treatment technology of CFG pile composite foundation and good economic benefit are often used.During the construction of CFG pile,the early concrete strength is lower and the whole construction area is fluid,which has a great influence on the disturbance and damage of foundation soil,and then on the displacement field of supporting structure and the stability of foundation pit supporting structure.In practical engineering,there are a certain number of projects CFG pile construction has caused varying degrees of damage to the supporting structure and the surrounding environment,resulting in adverse social impact.This paper takes the CFG pile foundation treatment project in a small district of Zhengzhou as an example to consult the relevant literature and establish a numerical calculation model by using MIDAS GTS to study the influence of different construction schemes of CFG piles,the change of concrete strength with age on the foundation pit support structure,the surface subsidence around the foundation pit and the base uplift.The main contents and conclusions are as follows:(1)Research and analysis of the research literature of scholars at home and abroad on the three aspects of CFG pile construction on soil settlement around foundation pit,deformation of supporting structure and numerical simulation are carried out,and the calculation models and calculation methods of horizontal displacement,surface settlement and deformation of foundation uplift of foundation pit are summarized.(2)Using MIDAS software to carry out numerical model of foundation pit section affected by CFG pile construction,under the supporting scheme of foundation pit with pile-anchor structure,the CFG pile construction is divided into four schemes considering the increase of pile strength with concrete age and different construction sequence,and the influence of four different construction schemes on foundation pit engineering and surrounding environment is simulated.(3)The results of simulation and calculation show that the surrounding environment of foundation pit and the horizontal direction of supporting structure show integral lateral movement,the maximum horizontal displacement is long side sequence construction,the maximum value is 61.24 mm,in the middle and lower position of supporting structure,The short-side jump construction is 11.64 mm,which appears in the lower part of the supporting structure.The field surface settlement of foundation pit is parabolic,the maximum surface settlement is long side jump construction,the surface settlement value is 33.26 mm,and the minimum settlement amount is 9 mm.in short side jump construction The maximum settlement is about 23 m in the field of foundation pit.The maximum uplift value of the foundation is 76.33 when the foundation is constructed along the short side of the foundation pit mm,and the minimum uplift amount of the foundation is 21.46 mm.when the foundation is jumped along the long side of the foundation pit(4)The maximum influence of the four construction schemes on the horizontal displacement,surface subsidence and base uplift of foundation pit is compared with the monitoring value.The horizontal displacement and surface subsidence of the support structure are closest to the monitoring value,and the deformation of the base uplift is closest to the monitoring value.Four kinds of construction schemes are analyzed synthetically,and the influence of short-side jump construction is chosen as the actual construction scheme.(5)Based on the pile-anchor support structure,the CFG pile construction of foundation pit affects the safety area of the foundation,and puts forward the corresponding construction countermeasures,that is,to slow down the construction speed in the area near the supporting structure of foundation pit,At the same time,the jumping construction is used to reduce the impact on the passive area range.The research in this paper is the design of similar projects,the construction has some guiding significance.