Research On The Influence Of Foundation Pit Excavation On Adjacent Buildings With The Pile-anchor Support

With the strengthening of our country's economic strength,the construction of infrastructure and high-rise buildings in every city is in full swing,new high records are set up in new buildings every year,and the subway is also built in dozens of large and middle cities throughout the country;the construction of the subway and high-rise buildings can not be separated from the excavation and support of the foundation pit.With the influx of the population,the urban construction land becomes more and more tense,and the space is becoming more and more crowded.The buildings,roads and pipelines have been built near the foundation pit.It is particularly important to ensure the safety of the adjacent facilities during the excavation of the foundation pit,especially for some historical protective buildings,needs more safety and meticulous monitoring and protection.It is of great significance to study the influence of the excavation of the foundation pit to the adjacent buildings because of the complex and regional characteristics of the foundation pit.There are many supporting methods for foundation pit.Pile anchor support combines the advantages of two kinds of supporting methods:row piles and anchor bolts.It has a flexible layout and construction method.It has good effect and does not occupy the space inside the foundation pit,is one of the main supporting methods of the deep foundation pit.Based on the introduction of the foundation pit deformation theory,this paper took a foundation pit of Kaifeng City as example,compared and analyzed the calculation results of the deep foundation pit support designed with calculated values data,then used the finite element analysis software ABAQUS simulated the excavation process of the foundation pit.The results are compared with the measured data,and the results are better.It is proved that the excavation process of the foundation pit is reliable by using the finite element analysis software.On the basis of the finite element simulation analyzed of the foundation pit,the influence of the excavation process on the adjacent buildings is analyzed in the built model,and the influence of the excavation on the building is analyzed mainly in the distance between the building and the foundation pit and the load on the upper part of the building.The following conclusions are drawn:(1)Based on the current foundation pit calculation method,was used to calculate the foundation pit,and the calculation results was quite different from the actual monitoring results,which proved that the existing calculation theory is insufficient.By establishing finite element model to simulate the excavation analysis and numerical simulation,The analysis results are compared with the calculated values data,the numerical agreement is high.Demonstrated the reliability of the finite element analysis method.(2)By applying the building near the foundation pit,the effect of the foundation excavation on the settlement of the building is studied.When the distance was 1/2 excavation depth,the settlement near the foundation pit of the eight-story buildings was the largest,reached 18.5mm,and the maximum differential settlement was 10.9mm.With the increased of the distance,the influence of the excavation on the building was gradually reduced.When the distance was 2 times excavation depth,the building was almost unaffected by the excavation of the foundation pit.At the same distance from the foundation pit,with the increase of the storys of the building,the influence of the excavation was gradually increasing.(3)According to the finite element simulation results,the soil settlement curve between the building and the foundation pit was parabolic curve.Because the foundation stiffness of building is large,the settlement of buildings in the scope of buildings basically varies linearly.(4)Through the study of adjacent existing buildings caused by the excavation surface settlement curve,and the corresponding surface subsidence by using polynomial fitting curve of expression.A method for calculating the settlement curve of building near the foundation pit was proposed,which was one of guiding significance for excavation of similar foundation pit.