Analysis Of The Influence Of Open Excavation For Tunneling On Adjacent Buildings In Loess Areas

In the new construction and reconstruction of urban transportation and other infrastructures,the open cut method is widely used in the construction of down tunnel and its lead line project and subway station.In urban commercial district,the deformation of retaining wall and its influence on the surrounding buildings caused by excavation are the focus of the design and construction of open cut tunnel.Based on the analysis of the surface subsidence characteristics of the retaining soil caused by the excavation of the excavation in the loess area,and its correlation with the excavation depth of the foundation pit and the type of the supporting structure system of the foundation pit,discuss the influence of the construction of open pit with loess as the main foundation for adjacent buildings in Xi’an area.Based on the engineering example of a certain geological condition in Xi’an loess area,using Midas/GTS finite element analysis software,research the influence of the distance from the building to the foundation pit,the form of support in the foundation pit and the depth of the foundation pit on the supporting structure,the surrounding surface and the deformation of the building during deep foundation pit excavation under loess stratum condition.The main conclusions are as follows:(1)The pile body horizontal displacement curve deformation of arcuate middle two small,the maximum horizontal displacement at 12m(0.75 times the excavation depth)from the pile top;The surface subsidence curve is concave,the maximum surface settlement is located at the edge of the pit 12 m,and in the distance from the foundation pit 32m(2 times the excavation depth),the settlement of the soil tends to be stable.(2)The load of the building will increase the horizontal displacement of the pile and the surface settlement of the pit,but the effect is not significant,and the effect will decrease with the distance of the building from the foundation pit.(3)The first layer of concrete support can play a certain role in controlling the deformation of foundation pit excavation.It has obvious control effect on the deformation of the pile body of erection position and the deformation of the pile body of the maximum horizontal displacement of the pile;It has obvious control effect on soil deformation of closing to the edge of the pit and the soil deformation of the maximum surface settlement;when the terminal of the building close to the foundation pit happens at the lowest point of the settlement(0.75 times the excavation depth),concrete support to control the building of differential settlement is the most obvious.(4)With the change of the distance of the building,the curve form of the absolute settlement of the building is changing,and the absolute settlement curve of the building is similar to the corresponding surface settlement,and slightly smaller than the surface settlement;differential settlement of a building is smaller when a building stride a settlement trough,and reaches the maximum value when the terminal of the building close to the foundation pit happens at the lowest point of the settlement,and then as the distance from foundation pit increases,differential settlement decreases gradually,and eventually become uniform settlement.