Study On Deformation Characteristics Of Steel Sheet Pile Supporting Structure In Utility Tunnel Foundation Pit

Compared with the traditional support form,the steel sheet pile has stood out in various foundation pit supporting schemes because of its quick and convenient construction and good water stopping performance.In the current study of foundation pit support,there are few researches on the deformation characteristics of the pipe slab foundation pit supported by steel sheet piles.The field data is very rare,and most of them are limited to the simple construction description and summary,and the deformation stress characteristics are not In-depth research,and in the numerical simulation analysis of the steel sheet pile support,most of them are analyzed on the 2D plane,and the research on the characteristics of the force and deformation is limited.The work is mainly concerned with a numerical simulation of the foundation earth excavation method and steel support form in the "steel sheet pile+internal support" underground pipe gallery retaining structure system.The paper's main content and research conclusions are as follows:(1)A literature review is made on national and international mechanisms of deformation of foundation pits and current steel sheet pile retaining studies.(2)Monitoring data are sorted out with a summary and analysis on the law of deformation.In the area of the study,the deformation at both northern and southern sides of the foundation pit presents a characteristic that front and rear retaining walls in the foundation pit have a lower horizontal displacement than middle ones,wherein the horizontal displacement values of the front and rear ones are 63.2% and 77.4% of that of the middle ones respectively.Besides,the northern and southern sides of the foundation pit show different laws of deformation regarding the horizontal displacement,wherein the former has a greater deformation than the latter;to be specific,different positions at the southern side of the foundation pit have a similar deformation curve but there is a great difference among different positions at the northern side of the foundation pit.The maximum horizontal displacement at the northern side of the foundation pit is about 6.6mm,approximating to 79.5% of that at the southern side of the foundation pit 8.3mm.(3)A simulation is made by the software FLAC3 D,including a correction done to the model in view of the uniform load and correction coefficient a and verification of accuracy of the model.In this simulation,whereas the uniform load arises out of muck trucks and material stacking area,when a is 0.23,the model's horizontal displacement is the closest approximation to monitoring data.(4)When the excavation cycle is 5 m and space between steel supports is 5 m,the maximum horizontal displacement is 9.96 mm and maximum horizontal displacement at the same height is 4.1mm,which meet deformation control requirements and have the minimum impact on the progress of construction.Thus,this scenario is considered the most cost-effective and safest excavation system in this project.In the municipal pipe gallery foundation pit excavation project(full length: 2.5km),it can reduce duration of construction to a great extent.