Analysis Of The Influence Of Different Pile Foundations On The Stability Of Adjacent Foundation Pits

Considering the current status of foundation pits,many new foundation pits are faced with the phenomenon of being surrounded by existing buildings.However,there is an interaction between the existing building and the adjacent foundation pit,not just one side affecting the other side.Under such circumstances,it is of great practical significance to safely,economically and reasonably deal with the interaction between existing buildings and adjacent foundation pits.Based on this background,this paper analyzes and summarizes the corresponding changes from the perspective of the influence of existing pile foundations on adjacent foundation pits.Firstly,based on the foundation pit of underground garage in Tiandiyuan Qujiang Xiangdu Area A,this paper constructs two models of "pile foundation" and "no pile foundation" according to the actual situation.From the angle of horizontal stress and displacement on retaining pile of adjacent foundation pit,analyze and summarize the influence of the foundation of the building pile on the adjacent foundation pit.It is worth mentioning that two new models of "pile foundation" and " no pile foundation " are also set up here.Compared with the previous two models,this only removes the influence of the upper high-rise building(building load).This is to analyze the influence of pile foundation on adjacent foundation pits when there is no building load and only the variable of pile foundation is retained.Then this paper analyses the mutual influence factors between building pile foundation and adjacent foundation pit.Combining with the gist of this paper,the horizontal distance D between pile foundation and adjacent foundation pit and the length L of pile foundation are selected for detailed analysis,exploring the effects of these two factors on adjacent pits.Finally,the following conclusions were made:1?When the upper high-rise building(building load)exists,the horizontal displacement and horizontal stress on the adjacent foundation pit slope protection pile in the “pile foundation” model are significantly smaller than the “no pile foundation” model.Therefore,it can be seen that the existence of the pile foundation can significantly reduce the horizontal displacement and horizontal stress on the adjacent slope protection pile.In the final analysis,the effect of the pile foundation reduces the effect on the soil around the foundation pit,so that the stress around the foundation pit is reduced on the slope protection pile.2 ? After removing the upper high-rise building(ie the building load).In the “pile foundation” model,the horizontal displacement and horizontal stress on the adjacent foundation pit slope retaining pile are still smaller than the “no pile foundation” model,just because there is no impact of the upper building load,the horizontal displacement and horizontal stress on the slope protection pile are smaller than the construction load.On the one hand,it shows that the existence of the pile foundation is like setting up a new supporting structure near the new foundation pit,which reduces the stress on the slope protection pile around the foundation pit.On the other hand,this also explains the influence of building load on the adjacent foundation pit.When the building load exists,it will increase the stress of the soil around the foundation pit on the slope protection pile.At the same time,it also shows that the pile foundation plays a certain role as a “bridge”.The “reinforcement zone” formed by the interaction between the pile foundation and its surrounding soil transfers most of the stress to the soil at the bottom of the pile foundation,reducing the impact of the load on the adjacent foundation pit.Therefore,the existence of the pile foundation plays a "favorable influence" on the adjacent foundation pit.3?When the horizontal distance D between the pile foundation and the adjacent foundation pit is different(the maximum D is 50 m in this paper),it can be seen from the overall horizontal displacement cloud map of the model that the pile foundation and the slope protection pile always limit the diffusion of the maximum horizontal displacement zone.When the horizontal distance D increases,the horizontal displacement and horizontal stress on the slope protection pile are not what we think is “the farther apart,the smaller the displacement and stress”.In general,the horizontal displacement on the slope protection pile undergoes four changes:(1)When D is within 1 times of the depth of the foundation pit,with the increase of D,the horizontal displacement of the slope protection pile is larger and larger at the upper part,and the lower part is getting smaller and smaller;(2)When D is within 1~2 times of the depth of the foundation pit,the horizontal displacement of the slope protection pile increases gradually with the increase of D;(3)When D is within 2~4 times of the depth of the foundation pit,the horizontal displacement of the slope protection pile decreases with the increase of D;(4)When D is greater than 4 times the depth of the foundation pit,the change of the horizontal distance D between the pile foundation and the adjacent foundation pit has little effect on the adjacent foundation pit.The change of the horizontal stress of the slope protection pile is basically consistent with the displacement change.4?As the length L of the pile foundation increases(the longest length of this paper is 40m),the horizontal displacement and horizontal stress on the slope protection pile gradually decrease.It shows that the increase of the length L of the pile foundation will reduce the force of the soil around the foundation pit to the slope protection pile,and it is more advantageous for the foundation pit.This paper also introduces the concepts of “main influence zone”,“secondary impact zone”,“no impact zone” and “short pile foundation”,“medium long pile foundation” and “long pile foundation”.In this paper,the pile foundation can be divided into short pile foundation(L is 2~10m),medium and long pile foundation(L is 10~15m),and long pile foundation(L is greater than 15m).When the length L of the pile foundation is different,the influences on the different affected zones are different.