Finite Element Analysis Of The Effect Of Foundation Excavation On The Adjacent Piers Of A Built Viaduct

In the late eighties of the twentieth century,China began to vigorously develop infrastructure,after more than 40 years of construction,the urban area of the city has long been towering high-rise buildings,bridges connected to the heavenly graben,tunnels are endless,and the road of infrastructure construction is still continuing,more and more deep foundation pit projects have followed,in recent years,foundation pit engineering safety accidents have emerged one after another.With the continuous compression of ground space,the foundation pit project is very likely to intersect with existing buildings(structures),roads,bridges and underground pipelines,which will inevitably cause some adverse effects on the surrounding existing buildings.Based on a proposed box culvert under the built viaduct project in Jingzhou,this paper uses numerical simulation analysis to study the influence of precipitation excavation of foundation pit on the supporting structure and the piers adjacent to the built viaduct,and preliminarily evaluates its safety.The main research work and results carried out in the paper are as follows:(1)Model establishment and validity verification.Based on the background of a proposed box culvert crossing the existing viaduct project in Jingzhou,the modeling analysis was carried out based on MIDAS-GTS NX software;The horizontal displacement analysis results of the cement-soil rotary blast pile wall with the one-time precipitation excavation model were compared with the empirical formula for the calculation of the horizontal displacement of the cement-soil wall and the calculation results of Beijing Lizheng Software,and the difference between the three calculation results was small.The correctness of the modeling method and material constitutive selection are verified,which provides a basis for subsequent simulation analysis of the reliability of the impact of precipitation excavation on the adjacent piers of the built viaduct.(2)Analysis of the influence of construction conditions on the structure of foundation pit and adjacent piers.Use MIDAS-GTS NX to establish a model and restore the construction conditions of the project;The horizontal displacement of the envelope structure,the uplift of the bottom of the foundation pit,the settlement of the surface,the horizontal displacement,vertical displacement and internal force of the bridge pile were analyzed with the excavation process of foundation pit precipitation.The analysis results show that the horizontal deformation of the foundation pit envelope is linear,and gradually increases with the increase of precipitation excavation depth.The uplift value of the pit bottom gradually changed from settlement to uplift with the precipitation excavation of the foundation pit,and the maximum uplift value was close to the slope excavation side.The surface settlement near the pier is greater than that far away from the pier,and the distant surface settlement in the middle layer of the two rows of piers on the same side is smaller than that in other places.The horizontal displacement,bending moment,shear force,axial force and side friction resistance of the bridge pile foundation gradually increase with the precipitation excavation of the foundation pit,and the vertical settlement gradually decreases with the precipitation excavation of the foundation pit.The lateral horizontal displacement of the cement-soil retaining wall and the indicators of the bridge pile did not exceed the warning value.(3)Sensitivity analysis of construction factors.Using the combination of MIDAS-GTS NX software and orthogonal test,the sensitivity analysis of the original support method in three factors: retaining wall thickness,retaining wall strength and retaining wall embedding depth was carried out.The analysis results show that for the horizontal displacement index of retaining wall,the strength of the retaining wall > the thickness of the retaining wall > the embedded depth of the retaining wall.For the horizontal displacement index of pile foundation,the embedded depth of the retaining wall> the strength of the retaining wall > the thickness of the retaining wall;According to the analysis results,an optimization scheme is proposed,and compared with the original scheme,the optimization effect is verified,which provides certain reference value for the subsequent design of similar envelope structures.