The Stability Analysis Based On Fluid-structure Interaction For A Riverside Deep Foundation Pit's Excavation

This paper is researched on the background of riverside deep foundation pit which has high groundwater level,Fluid-Solid Interaction analysis has been used for excavation stability analysis of deep foundation pit in Wuhan 27 Road Business district,measuring method of soil parameters has been simplified by using the principle of porous media,four factors has been considered during the excavation process of riverside deep excavation pit,including the distance between the foundation pit and the riverbank,the height of the river,the nature of the soil and the shape of foundation pit,So as to provide the reference for excavation of deep foundation pit in 27 business district.The main job content and result are as follows:(1)The soil is simplified as a porous medium,and the simplified theory of soil medium is described in detail.Digital imaging technology has been used to simplify the measurement method of soil porosity parameter.A program with image processing and user interface is programmed,which can measure the porosity of coarse-soil easily.The program measuring the picture is effective.Those pictures of soil have visible pores and high pixel density,clear and distinct.(2)Based on the character of riverside deep foundation pit in the 27 Road Business District,four factors have been summarized,they are the distance between the foundation pit and the riverbank,the height of the river,the nature of the soil and the shape of the deep foundation pit respectively.Comparing the difference between normal method and fluid-structure interaction method,illustrate the necessity of the fluid-structure interaction method.(3)Building a 2D model,and the influence of the distance between the foundation pit and the embankment,the height of the river and the nature of the soil on the deformation of the riverside deep foundation pit are analyzed.The results show that the height of the river has the greatest influence on the excavation of the deep foundation pit,followed by the influence of the distance between the deep foundation pit and the embankment on the foundation pit's excavation.When the influence of soil properties on the excavation deformation of the deep foundation pit is analyzed,it is found that the flow direction of the groundwater determines the direction of the foundation pit's deformation.In the soil with large permeability coefficient,the deformation of the foundation pit's excavation becomes bigger.(4)Build a 3D model,to analyze the influence of the deep foundation pit's shape.Changing the deep foundation pit's shape seems like the changing of the total excavation quantity.When it is near the embankment,changing the deep foundation pit's shape will reduce the deformation of the deep foundation pit's excavation.When it is far away from the embankment,although changing the shape of deep foundation pit will reduce the excavation's deformation,the amount of deformation is small.(5)According to the preliminary design of the riverside deep foundation pit in 27 Road Business District,a 2D fluid-structure interaction is established to simulate the influence of well point dewatering on the 27 Road deep foundation pit and its settlement,and choose a good time for excavation.The results show that the well point dewatering has large influence area on the side of the embankment,but the settlement is small.The total influence range is about 100 m in the surrounding area of the deep foundation pit.This range reaches 70 m on the side of embankment.According the level of the groundwater,time for excavation has been determined,they are 70 days,110days and 150 days from the excavation.(6)According the excavation's time,simulate the process of deep foundation pit's excavation in 27 Road Business District.It is found that the deformation of the deep foundation and embankment all meet the requirement of current specification.The deformation of the underground continuous wall is mainly concentrated on the top of third of the wall's height,which is deformed to the inside of the foundation pit.The embankment reduces the horizontal deformation and increases the vertical one.With the excavation,the embankment's vertical displacement is increasing obviously,the vertical one is not obvious.