| As a shallow-buried underground frame structure,underground comprehensive pipeline gallery is vulnerable to the interference of heterogeneous foundation differences and other factors,resulting in uneven settlement,structural cracks,structural leakage,gallery structure torsion and other diseases.At present,the research on the influence of heterogeneous foundation difference on pipeline gallery structure mostly focuses on the construction technology of foundation treatment and the discussion of problems,lacking of relevant theoretical analysis as technical support.Based on the project of Hunan Provincial Engineering Construction New Technology Development and Soft Science Research Program:"Research and Application of Vertical Prefabrication and Assembly Complete Construction Technology of Single-cabin Rectangular Pipe Gallery"(Index No.430S00711/2018-42557),field prototype tests were carried out,including static load test of single-cabin rectangular prefabricated pipe gallery,its structural strain and surrounding soil pressure monitoring test during the whole construction backfilling process,the more practical test results are obtained.A three-dimensional numerical model is established and numerical analysis is carried out based on the relevant theory and ABAQUS finite element analysis software.The rationality and validity of the three-dimensional numerical model are verified by comparing the test results with the numerical simulation results.On the basis of the numerical model,several common heterogeneous foundation conditions in excavation and replacement section are further simulated.The stress and deformation characteristics of the underground pipe gallery under heterogeneous foundation are thoroughly discussed from both horizontal and vertical directions.The following research results are obtained:(1)The numerical analysis based on concrete damage plasticity model can simulate the non-linear damage process of vertical prefabricated pipe gallery concrete under monotonic static load,and the parameters of CDP calculation model are reasonable.At the same time,the deformation and failure mechanism of pipe gallery structure under monotonic static load and the influence of load,stress concentration and armpit angle reinforcement on the mechanical characteristics of the structure are explored.(2)The numerical model can well reflect the interaction between pipe gallery and soil,which is determined by the soil parameters based on the combination of M-C model and D-P model,the calculation parameters of CDP model,the improved initial equilibrium method of in-situ stress,the initial stress tension of the prestressing steel strand,and the dynamic construction backfilling process simulated by the birth and death elements and other methods in this paper.The soil stress around the pipe gallery increases linearly with the increase of filling height in the area with good geological condition and homogeneous foundation,which has the greatest impact on the roof and floor of the pipe gallery.(3)During the process of pipe gallery backfilling,the mechanical deformation of the pipe gallery structure increases linearly and elastically,and the deformation of the middle of roof and floor is the largest,and the floor is larger than the roof.At the prefabricated joints,the external compressive stress of the roof and floor mainly concentrates at the end of the spigot,while the internal tensile stress mainly concentrates at the end of the bell;and soil settlement accounts for 70%of the whole backfilling process in the early stage of backfilling,about 30%in the pavement backfilling and compaction stage,and the settlement at the bottom of the pipe gallery presents a "W" distribution.(4)Under transversely heterogeneous foundation,with the increase of filling height,the stress and deformation of pipe gallery structure increase continuously,and the roof and floor are opposite symmetrical,showing a transverse "S" distribution,and the left and right sides are opposite symmetrical,showing linear distribution.Among them,the floor is the largest,the roof is the second,and the side plate is the smallest;with the increase of the difference of transversely heterogeneous foundation,the structure of pipe gallery has torsional deformation,which has the greatest impact on the deformation of the right side plate and the smallest impact on the roof.And the overall vertical angular displacement is larger than the lateral horizontal angular displacement,showing a linear growth.(5)Under the difference of longitudinal heterogeneous foundation,the stress and deformation of the middle which are the roof of pipe gallery on the side joints with smaller foundation stiffness and the floor of pipe gallery on the side joints with larger foundation stiffness increases obviously,while the stress and deformation of the roof and floor of pipe gallery at the interface of replacement filling soil hardly changes,showing a longitudinal "S" distribution.At the same joints,the middle deformation of the inner part of the floor is larger than that of the inner part of the roof,and the middle deformation of the inner part of the end of the bell is larger than that of the inner part of the spigot.At the same filling height,the greater the difference of the longitudinal heterogeneous foundation,the more obvious the change of axial stress at the pipe gallery interface on both sides of the junction of the replacement and fill.(6)Under the longitudinal heterogeneous foundation,the difference of the vertical horizontal opening displacement at different interfaces increases obviously,and the roof of pipe gallery on the side joints with larger foundation stiffness has the greatest influence,and the pipe gallery on the side with larger foundation stiffness deforms upwards,while the pipe gallery on the side with smaller foundation stiffness deforms downwards,showing a longitudinal "S" distribution;vertical settlement differences along the longitudinal pipe gallery structures are obvious.Vertical differential settlement of the bell and spigot of the pipe gallery on the side with larger foundation stiffness is larger than that on the side with smaller foundation stiffness,and the overall vertical differential settlement presents the characteristics of"decreasing from the junction of the replacement and fill to both sides continuously". |
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