Study On Structural Analysis And Safety Evaluation Of Large Diameter Buried Pipeline

With the rapid development of China's modernization,prestressed concrete cylinder pipe(PCCP)is widely used in long distance water transfer project and urban pipe network.Large diameter,high pressure and ultra deep overburden makes PCCP manufacturing,installation and operation have many challenges,for the typical mechanical behavior of large caliber PCCP life cycle service in the study reveals that the PCCP socket inner ring crack formation mechanism and anti-crack measures and whole life under complicated load response of the structure,three different broken wires under the effect of ultimate bearing capacity and failure mode of pipeline.The main research contents include the following four aspects:(1)The PCCP three-dimensional nonlinear finite element model is established and the numerical simulation is carried out in the process of its production,such as the wires wrapping,the pipe lifting,to obtain the mechanical response and damage evolution behavior of pipeline.Reveals that the large diameter PCCP formation mechanism of ring crack in inner wall of spigot: core in the wire wrapping,because the spigot end to the outer core compression deformation additional longitudinal bending moment,when the additional bending moment value exceeds the critical value of core section,the inner wall of the core concrete is broken to produce cracks.(2)According to the circumferential cracking mechanisms of the inner wall of spigot in PCCP,the anti-crack measures are put forward for the structural design of PCCP.To investigate the effectiveness of the anti-cracking measures,the three-dimensional nonlinear finite element models are established respectively to analyze the strain/stress and deformation of the pipe.(3)Taking a water supply project as the background,based on the nonlinear finite element theory,the establishment of PCCP three-dimensional nonlinear finite element model of pipe soil for large caliber high pressure PCCP from manufacturing,installation,backfill,groundwater and the normal operation of the numerical simulation for the whole life process,a comprehensive understanding of PCCP from manufacturing to the normal conditions of use of the pipe body deformation characteristics,analyzes the damage mechanism of the pipeline under normal working load.(4)Based on the current commonly used three kinds of effects of broken wires simulation model,namely,full-circle exit model,partial exit model and partial linear exit model,studies mechanical response and failure mechanism of the double wire wrapped high pressure,large diameter PCCP in operation,environmental load.The ultimate bearing capacity and failure mode of PCCP are compared and analyzed under three different broken wire effects.