Study On The Effect Of Water Stop And Excavation Deformation Of Deep Foundation Pit With Hard Occluded Bored Pile

With the development of the city,the groundwater resources in Beijing are becoming increasingly insufficient.At present,the groundwater in the urban plain area has been in a state of serious loss.The shortage of water resources has become a bottleneck restricting the economic development and urban construction of Beijing.Under the current environment,it is not only the general trend,but also the promotion of the subway project to control the groundwater in the subway construction Historical opportunity for upgrading and transformation of groundwater control construction.Therefore,in the case of the shortage of groundwater resources in Beijing,taking the shield shaft between xuemiqiao station and Xitucheng station as the test shaft,the study on the water stop effect and excavation deformation of the deep foundation pit hard occluded bored pile is of great significance for the water stop project of the occluded pile in the subway construction in the same area.In this paper,based on the water stop construction project of Shield Shaft interlocking pile between xueyuanqiao station and Xitucheng station in bid 06 of Beijing Metro Line 27 phase II(South extension of Changping line),field detection,indoor test and numerical simulation are used to study.The main research contents are as follows:(1)Inspection and analysis of hole forming quality of pile body.The qualified inclination of hole forming can directly guarantee the quality of pile bottom engagement,and make the engagement pile have a good function of retaining soil and water.Through testing the hole diameter,inclination and hole forming quality of 16 plain concrete piles and 48 reinforced concrete piles in the foundation pit construction site,the law that the hole diameter and inclination decrease with the depth is obtained,and the method to improve the hole forming quality of the occluding pile body is obtained.(2)Study on material properties of plain pile.In the process of construction,the strength of plain concrete pile is an important factor affecting the inclination of reinforced concrete pile,and the good impermeability of plain concrete pile is also the guarantee of the sealing effect of the occluded pile.Through 10 groups of concrete compressive strength test and 7 groups of concrete impermeability test,test the development and growth rule of the strength and impermeability of the curing specimens with the curing time,analyze the influence of the water cement ratio,sand ratio and the amount of water reducing agent on the strength and impermeability of the concrete,and finally give the recommended mix ratio that meets the engineering needs,the water cement ratio is 1.80,and the sand ratio is 0.55 without water reducing agent.(3)Numerical simulation analysis of foundation pit construction.In this paper,Midas GTS NX finite element software is used to simulate the excavation and support process of deep foundation pit,and the influence of the occluding pile as the retaining structure in the excavation process on the basement and surrounding ground deformation is analyzed.The results show that the horizontal displacement of the interlocking pile increases first and then decreases with the increase of the depth in the excavation process,which is parabola distribution;the basement uplift is "convex" distribution,and the surrounding surface settlement increases first and then decreases with the increase of the distance from the pit edge,the main range of influence is about 30 m from the pit edge.(4)Study on sealing effect of occluded pile.In this paper,Midas GTS NX software is used to simulate the sealing effect of the occluded pile,and the influence of two geometric defects of the diameter and inclination of the occluded pile on the impermeability of the occluded pile is mainly considered.The research shows that the geometric defects increase the risk of leakage of the occluded pile structure in the deep foundation pit,the impact of the reduction of the pile diameter is more obvious than that of the inclination of the pile,which makes the impermeability of the occluded pile worse,and the superposition of the two defects greatly reduces the impermeability of the occluded pile.