Study On The Influence Of Open-cut Construction Of Utility Tunnel On Adjacent Buildings And Supporting Parameters

With the continuous advancement of China’s urbanization process,major cities are becoming highly intensive,and the contradiction between the construction of municipal infrastructure and the shortage of urban land resources is becoming increasingly prominent.The underground comprehensive pipeline corridor concentrates a variety of municipal pipelines in artificial underground spaces to form a modern and intensive urban infrastructure that fully utilizes the underground space and improves the city’s carrying capacity.The construction of integrated pipe corridors is generally located in the center of the city,often crossing existing structures on the ground or underground.The construction process involves the excavation of the foundation pit,the disturbance of the surrounding strata and the support of the foundation pit.How to ensure the safe construction of the integrated pipe corridor without affecting the stability of the existing buildings around,has become an important issue that must be solved in the construction of the urban underground comprehensive pipe corridor.Based on this,relying on the Han zhong underground comprehensive pipe corridor project,the stability of the foundation pit and adjacent buildings during the open-cut construction of the comprehensive pipe corridor is studied by numerical simulation.The field monitoring data and simulation results are compared,and finally the influence of various parameters of the supporting system on the envelope structure and buildings is analyzed.The main research contents are as follows:(1)By on-site monitoring and data analyzing,the number of differential settlements at weak locations such as deformation joints,structural cross-sections,and changes in stratumconditions during the construction of pipe corridors in the Western Bid Section are all less than the warning data,and the construction of pipe corridor structures is safe.Due to differential settlement of buildings near the middle section,the building is inclined to the foundation pit,and the settlement data and inclination are far less than the warning data,so the design and construction are safe.(2)Midas GTS/NX is used to simulate the dynamic process of pipe gallery construction,and analyze the deformation characteristics of the envelope,surrounding soil and adjacentbuildings.The envelope structure has a "bow" horizontal displacement and the surface outside the pit has a groove settlement.The influence area of horizontal displacement of the surrounding soil layer is triangular,and the surface influence area is 1.5H,which tends to zero at the bottom of the foundation pit.Plastic uplift occurs at the bottom of the foundation pit,and the uplift shape is "M" shape inclined to the building side.The adjacent buildings have uneven settlement and horizontal displacement,and the horizontal displacement has the phenomenon of stratification.Settlement of buildings develops rapidly during excavation.(3)The influence of various parameters of pipe gallery foundation pit supporting system was studied.The influence of the diameter,spacing,length of piles,internal stiffness and horizontal spacing on the horizontal displacement of the envelope structure and building settlement are discussed,and reasonable supporting parameters are given.(4)By the orthogonal test analysis,the factors of affecting the settlement of buildings are:pile diameter,support stiffness,pile length,and horizontal spacing of supports.In the design and construction of building settlement control,priority can be given to pile diameter and support stiffness,and then other factors are considered in order to seek the solution with the least investment of economic cost and the greatest support benefit.