Research And Stability Analysis Of Deep Foundation Pit Support Methods In Karst Areas

Nowadays,the design of foundation pit supporting has been a key and difficult point of construction engineering.Stability of foundation pit supporting is directly linked to the progress of engineering projects.In China,the design theory and level of deep foundation pit supporting engineering have made great progress in recent years.With the construction of enormous high-rise buildings,super high-rise buildings,subways and tunnels,the foundation pits become increasingly wide and deep.Although the stability of deep foundation pit supporting in China has been broadly analyzed,the study on the influence of karst on the stability of deep foundation pit supporting is still insufficient.Therefore,the application of appropriate supporting form has a decisive impact on the successful excavation of deep foundation pit,which makes the design and construction of deep foundation pit supporting in karst area more difficult and requires higher safety.In this paper,taking the No.1 Foundation Pit,No.1 Plot,Kuiyong Market,North Kuixin Road,Dapeng New District,Shenzhen City as an example,based on the field engineering geological conditions and the surrounding environmental conditions of the foundation pit,the impact of increasing the construction of anchor cable on the stability of the foundation pit was analyzed.On the premise of following the requirements of safe design and rational cost,the combined supporting scheme of pile anchor and pile supporting was determined,the foundation pit supporting system was simulated,calculated and analyzed in virtue of Midas GTS NX,and the influence on the stability of deep foundation pit supporting in karst area were studied.This paper mainly contains the following works:(1)Due that the self-stability of the deep foundation pit excavation is seriously limited,the failure caused by the instability of the foundation pit supporting easily occurs,and it is difficult to control the safety of the foundation pit.Based on the field engineering conditions,through the simulation analysis of finite element software,the supporting scheme of deep foundation pit was preferably designed.(2)The 3D finite element analysis of deep foundation pit supporting pile in karst area was carried out.Based on MIDAS GTS,a finite element software for geotechnical analysis,the stability of supporting pile was analyzed by establishing models with indicators,such as horizontal and vertical deformation of supporting pile,Internal bracing deformation,soil deformation after pile completion,etc.Moreover,the field test analysis was performed,and by comparing to the results of numerical simulation analysis,the stability of the supporting structure was verified.(3)Taking this project as an example,in the case that the karst cave is located in the deep bedrock layer,the influence rules of the size of the karst cave,the depth of the fixed end of the pile,the distance between the karst cave and the supporting pile in vertical direction,the pile diameter and were analyzed,It also carries out acomprehensive analysis of the influence law of all single factors on the stability of retaining piles.Through the verification based on the engineering example,the influence rules of various factors on the stability of the deep foundation pit supporting pile were concluded,in order to provide basis for the selection of the supporting form and the stability study of the deep foundation pit supporting pile in karst area.