The Longitudinal Behavior Of Buried Large-diameter Reinforced Concrete Pipeline Subjected To Traffic Loading

China is a country with severe water shortage.However,the leakage of water supply and drainage pipelines has caused serious waste and pollution of precious water resources in China,r esulting in huge social and economic losses.In view of the serious damage of joints in pipeline engineering and the deficiency designing of longitudinal reinforcement in concrete pipeline in design specifications,this paper aims to study the longitudinal behavior of large-diameter concrete pipes which are buried underground and subjected to the surface load,by means of centrifuge test,numerical simulation and theoretical derivation.The following work has been completed:(1)Based on the centrifuge test,three-dimensional numerical simulations were conducted to analyze the deformation characteristics of the bell-and-spigot joint,the influence of the number of pipe segments,the stiffness of joints,the stiffness of the foundation soil,and the relative positional relationship between the load and the joint on the overall and local deformation of the pipeline.The deformation mechanism of the bell-and-spigot joints in reinforced concrete pipelines has been analyzed systematically.(2)A centrifuge test with uniform silt under the pipeline was designed.The numerical model was calibrated by the centrifuge test.The deformation of the jointed pipeline along the longitudinal direction under uniform ground conditions was discussed through parameter analysis.T he study found that the condition of non-uniform stiff native soil under the jointed pipeline is even less favourable than that of a soft but uniform native soil.Possible non-uniform soil support should be considered when designing new pipe products or in stalling pipelines.(3)Centrifuge test was first used to study the vertical deformation of jointed pipeline along the longitudinal direction and the variation of the circumferential and longitudinal internal forces of the pipe body when there is a void near the joint.The ‘Salt-Bag-Dissolution’ method is creatively proposed by the author to simulate the void in the centrifuge test,and solved three difficult problems.That is,before and after the test,salt bag can closely adhere to the outer wall of the pipeline.Before the formation of the void,it can simulate the uniform ground conditions.And after the formation of the void,the mechanical boundary conditions of the void area are very clear for the next numerical analysis.(4)the analytical solution of the longitudinal bending moment of the pipeline under traffic loading is derived,based on the elastic cylindrical shell theory.Then the reliability of the analytical solution is proved by the centrifuge test.On the basis of the analytical solution,the influence of pipe radius and burial depth on the longitudinal internal forces is analyzed.Also the required minimum longitudinal reinforcement to satisfy the longitudinal bearing capacity at different burial depth is analyzed,which provides a referen ce for engineering design.