Study On Influence Of Reinforcement Form On Deformation Of Soft Soil Foundation Pit

In order to broaden the construction space,there are more and more super high-rise buildings and underground space projects in recent years,resulting in a large number of deep,large and long foundation pit projects.It is helpful to restrain the deformation of the foundation pit by reinforcing the soil within the excavation scope,and it is also helpful to the supporting structure of the foundation pit.With the research of foundation pit reinforcement,there have been some achievements,but it is difficult to make a quantitative analysis of the effect of foundation pit reinforcement.In practical engineering,designers and constructors often rely on engineering experience to choose the reinforcement form;Considering the spatial effect in the excavation process,systematic research on the influence of different reinforcement forms on the deformation of foundation pit is still lacking.Based on the foundation pit engineering of a subway station in Foshan,this paper systematically studies the influence of plane layout and vertical layout of foundation pit reinforcement on the deformation of foundation pit by Midas GTS finite element simulation;Through orthogonal test and single factor analysis,the sensitivity of soil mechanical parameters is analyzed.1.With the increase of reinforcement area,the horizontal displacement and surface settlement of diaphragm wall are gradually reduced.However,there is a limit value for the reinforcement area.When the reinforcement area reaches the limit value,the effect of restraining the deformation of foundation pit has not been significantly improved.2.Under the condition of the same reinforcement ratio and reinforcement depth,among the four plane layout reinforcement forms of grid reinforcement,strip reinforcement,strip reinforcement with skirt reinforcement and full hall reinforcement,strip reinforcement has the best effect to limit the deformation of foundation pit,and strip reinforcement is better than 25%-50%.3.In the deep foundation pit engineering of the sea land interaction muddy soil layer,the three vertical reinforcement arrangements of excavation area reinforcement,excavation area and base reinforcement at the same time,and foundation pit bottom reinforcement all limit the deformation of the foundation pit,but the limiting ability is obviously different.The results show that the effect of soil reinforcement at the bottom of foundation pit is the best,and the effect of soil reinforcement at the excavation area and the bottom of foundation pit is the second,and the effect of soil reinforcement at the excavation area is the worst.4.The sensitivity law of each parameter to the horizontal displacement of diaphragm wall is:reinforcement depth h>internal friction angle of undisturbed soilφ₁>The elastic modulus of reinforced soil E₂>internal friction angle of reinforced soilφ₂>The elastic modulus of undisturbed soil E₁>cohesion of undisturbed soil C₁>cohesion of reinforced soil C₂.5.With the increase of the reinforcement depth below the pit bottom,the deformation of the foundation pit decreases,but the relationship curve between the reinforcement depth and the deformation of the foundation pit gradually slows down.For this project,when the reinforcement depth is more than 10 m,increasing the reinforcement depth has no obvious effect on limiting the deformation of foundation pit.