Effect Analysis Of Soil Reinforcement On Characteristics Of Retaining Structure And Adjacent Shiplock Of The Shoplock Foundation Excavation

In recent years,the scale of the foundation pit and the depth of excavation are getting bigger,the surrounding environment of the foundation pit is becoming more complex,many new support structures have emerged,braced retaining structure with double-row diaphragm wall is one of them.In order to ensure the safety and normal use of buildings,underground pipelines,navigation locks and other facilities around the foundation pit,soil reinforcement is often carried out in the active area,passive area and inter-wall area of the foundation pit.At present,there are few researches on the application of the braced retaining structure with double-row diaphragm wall,and the interaction mechanism between reinforced soil and double-row diaphragm wall is not clear.Based on the deep foundation pit of a new shiplock supported by the braced retaining structure with double-row diaphragm wall,three-dimensional continuous medium finite element models of deep excavation are established by MIDAS/GTS NX finite element software,and the influence of soil reinforcement in the inter-wall,active and passive areas on the stress and deformation of the supporting structure and the deformation of the adjacent shiplock is explored.And based on the soil pressure and the interaction between the soil and the supporting structure,three kinds of plane bar system calculation models of the braced retaining structure with double-row diaphragm wall are established,and the plane bar system finite element method is used to simulate and analyze them.The main contents and conclusions of this study are as follows:(1)Taking the foundation pit project of the new shiplock as the object,three-dimensional continuum finite element models of excavation are established.The influence of excavation on deformation and bending moment of the braced retaining structure with double-row diaphragm wall,heave of pit bottom and displacement of adjacent shiplock is analyzed,and the reliability of finite element model is verified by comparing the measured data.(2)Through the finite element simulation analysis,the influence of soil reinforcement parameters between the walls on the mechanical deformation of the braced retaining structure with double-row diaphragm wall and the deformation of adjacent shiplock is studied.Under the same replacement rate of reinforcement,the effect of strip reinforcement and grid reinforcement on the horizontal displacement of the front wall is significant,while the effect of skirt reinforcement on the horizontal displacement of the back wall and the displacement of the adjacent shiplock is better.The improvement effect of horizontal displacement of front row wall is closely related to the depth and area replacement rate of strip reinforcement,but is slightly related to the width of the strip reinforcement.The effect of grid reinforcement and strip reinforcement with the same replacement rate of transverse reinforcement is similar.With the increase of the width of the skirt reinforcement,the horizontal displacement of the back wall and the deformation of the adjacent lock first decrease and then increase.(3)Through the finite element simulation analysis,the influence of the depth and width of reinforcement in the passive area and the position,width and depth of reinforcement in the active area on the mechanical deformation of the braced retaining structure with double-row diaphragm wall and the deformation of adjacent shiplock is studied.The results show that the soil reinforcement in the passive area has a good effect on controlling the horizontal displacement of the front and back walls and the deformation of the adjacent shiplock,while the soil reinforcement in the active area has no effect on the horizontal displacement and the bending moment of the front wall,and has a good effect on controlling the horizontal displacement of the back wall and the deformation of the adjacent shiplock.(4)Through the finite element simulation,four kinds of composite soil reinforcement methods are compared and analyzed,including "grid reinforcement in inter-wall area and reinforcement in active area","shirt reinforcement in inter-wall area and reinforcement in active area ","grid reinforcement in inter-wall area and reinforcement in passive area","shirt reinforcement in inter-wall area and reinforcement in passive area".The results show that "grid or shirt reinforcement in inter-wall area and reinforcement in passive area" has a significant effect on the horizontal displacement of the front wall,"shirt reinforcement in inter-wall area and reinforcement in active or passive area " has a significant effect on the horizontal displacement of the back wall,"shirt reinforcement in inter-wall area and reinforcement in active area" has a good effect on the displacement of the adjacent shiplock.(5)Taking plane bar system finite element method,three kinds of plane bar system calculation models of the braced retaining structure with double-row diaphragm wall are compared and analyzed.And the results of continuous medium finite element method are compared.In the plane bar system model 1,the soil between the walls is equivalent to the compression spring connecting the front and rear row walls,the horizontal stiffness coefficient is determined by the ratio of the compression modulus to the width of the soil between the walls,and the calculated maximum horizontal displacement of the back row wall is larger than that calculated by the continuous medium finite element method.In the plane bar system model 2,the soil springs with continuous arrangement and mutual independence simulate the soil in the direction of the foundation pit of the front and rear row walls.The maximum horizontal displacement of the back wall is smaller than that of the continuum finite element method.In the plane bar system model 3,the soil between the walls is equivalent to the soil bar,the front and back walls and the soil bar element are connected by compression spring.The horizontal stiffness of the compression spring is the same as that of the model 1 on the excavation surface.Under the excavation surface,it is calculated by the "m" method.Model 3 calculates that the trend of bending moment and horizontal displacement of the wall is close to that of continuous medium finite element calculation and engineering measurement.