Study On Influence Of Large Area Pile Squeezing Effect On Adjacent Foundation Pit Excavation

With the continuous development of China’s urbanization process,the application of pile foundation is more and more extensive.During the construction of prefabricated piles,large displacement fields and stress fields are generated in the surrounding soil,which produces a large squeezing effect,and it will have a greater impact on the surrounding environment,.this paper focuses on the analysis of the effect of precast pile group squeezing effect on subsequent foundation pit excavation.This paper improves the simulation method of pile sinking process of soil compacted piles,and it uses the method of simultaneously applying volumetric strain and vertical compression load,it not only ensures the three-dimensional finite element simulation of the pile-sinking process,that is,the expansion method simulation,but also makes the simulated soil displacement field distribution more consistent with the actual situation.On this basis,the effect of large-area pile squeezing effect on the excavation of adjacent foundation pits is studied.It is found that the larger the initial displacement of the cantilever supporting structure of the foundation pit without considering the squeezing effect,the smaller the effect of the pile squeezing effect on the deformation and force of the foundation pit support.The surface settlement of the foundation pit is affected by the soil compaction effect as a result of the combined effects of its support lateral movement and the pit bottom uplift;the impact of the squeezing effect on the bottom pit uplift decreases with the size of the foundation pit.When the side length is increased from 20 m to 40 m,the influence of the pit bottom uplift by the squeezing effect is reduced from 90.3% to41.5%.When the depth of the foundation pit is increased from 4m to 6m,the influence of the pit bottom uplift by the squeezing effect is reduced from 100.5% to 75.6%.For the case where there is a certain angle between the boundary of the foundation pit and the group pile,the larger the angle between the boundary of the foundation pit and the group pile,the less the degree of the foundation pit affected by the squeezing effect.After the offset of the central axis of the foundation pit and the group pile exceeds a certain range,that is,after the central axis of the foundation pit exceeds the boundary of the group pile,the larger the offset,the smaller the impact of the foundation pit on the soil squeezing effect;the distance between the foundation pit and the group pile beyond a certain range,the impact of the soil pit on the foundation pit is negatively related to the distance between them.In order to quantify the impact of large-area group pile squeezing effect on the subsequent excavation of foundation pits,this paper proposes a relationship between the excess pore water pressure generated by the soil squeezing effect and the subsequent excavation of the foundation pit supporting soil pressure,the calculation method of the earth pressure increment of the foundation pit supporting structure is obtained,which has certain reference value to the actual project.Finally,this paper analyzes the weakening effect of the stress relief hole on the squeezing effect of the pile,and finds that it has a significant effect on reducing the effect of single pile squeezing and obtains the most suitable hole depth.In addition,the squeezing effect does not only have an adverse effect on the soil.After the pore pressure is sufficiently dissipated,it can improve the bearing capacity of the surrounding soil to a certain extent.