Research On The Mechanical Performance Of Segmented Underground Comprehensive Pipe Gallery Across Ground Fissures

As a major infrastructure project that guarantees the lifeline of the city,the underground pipe gallery is characterized by a large span,low longitudinal rigidity,and a thin-walled structure,.At the same time,as a city with typical ground fissure activity,Xi’an,the development of ground fissure activity seriously restricts the use of underground urban space.Ground fissure activity will bring serious safety hazards to the underground integrated pipeline gallery.Under the action of faults and earthquakes,the stress and deformation of the pipeline gallery will suddenly increase,resulting in damage to the pipeline gallery structure and huge losses.Existing research mainly focuses on the stress analysis and deformation law study of the pipe gallery under ground fissure fault activity.Most of the cast-in-place monolithic pipe gallery is used for numerical simulation without considering the influence of deformation joint.At present,national and local codes rarely consider the impact of ground fissures in the design of underground pipeline gallery;at the same time,the impact of ground fissures is not considered in the seismic design of underground pipeline gallery,and no relevant design is given for the bearing capacity and deformation calculation under rare earthquakes.Based on the Xi’an Xingfu Forest Belt Project,this paper is of great significance to study the deformation law and seismic performance of the segmented integrated pipe gallery across the ground fissure area.The thesis establishes the finite element analysis model of the segmented underground comprehensive pipe gallery in the Xingfu forest belt.The main conclusions are as follows:(1)A non-linear spring is used to simulate the waterstop of the deformation joint,and the viscoelastic boundary is used to deal with the boundary conditions of the site in the seismic design.The error of the finite element model analysis result is less than 10%,and the degree of agreement is good.(2)Quantitative analysis of the displacement change,the range of the void area,the force and deformation characteristics,and the stress law of the segmented pipe gallery under different dislocations under the orthogonal and oblique crossing modes are quantitatively analyzed.Determine the impact area of the ground fissure dislocation on the upper and lower walls of the pipe gallery and give the range of the void area in two ways.(3)Quantitatively analyze the changes in the pipe gallery and soil acceleration of the segmented pipe gallery under different seismic accelerations in the orthogonal and oblique crossing modes,and qualitatively analyze the mechanical characteristics of the pipe gallery stress,crack development,and displacement.As a result,small earthquakes and moderate earthquakes have little effect on the pipe gallery cracks and displacement changes,and the oblique crossing method has a significant influence on the pipe gallery and soil acceleration,and lateral horizontal displacement under the action of large earthquakes.(4)Through seismic and dislocation analysis: define the horizontal displacement of10 mm as the upper limit of the pipe gallery bending failure warning,and it is recommended that the thickness of the waterstop should be at least 150 mm.It is advisable to take 1/1000 as the limit of displacement angle between layers of pipe gallery under frequent earthquakes;1/500 as the limit of displacement angle between layers of pipe gallery under rare earthquakes.