Study On Stress Variation And Reliability Of Water Pipeline Under The Influence Of Erosion Viod

During its service,the water supply pipeline is easy to form an erosion void under the pipeline due to the factors such as pipe leakage,rain water scour,construction disturbance,and the pipeline can generate large bending deformation or pipe orifice rotation,which can lead to failure of the pipeline and bring serious economic loss and adverse effect to the society.The change of pipeline stress is the parameter index to directly reflect the safety condition of pipeline,and it is also the basis of pipeline reliability evaluation,which is of great significance to the safety of pipeline.In this paper,the stress variation law of water supply pipeline under the influence of erosion void is studied by numerical simulation,and the key influencing factors are analyzed.Furthermore,artificial intelligence algorithm is used to calculate the reliability of pipeline and evaluate its failure probability,which provides an important theoretical reference for the monitoring and safety assessment of pipeline stress state in practical engineering.The main research work and results of this paper are as follows:A three-dimensional pipe-soil nonlinear finite element model was established by using ABAQUS element software.In order to verify the reliability of the finite element model,the numerical results obtained from reference model were compared with the hoop stresses of the pipeline solved by material mechanics and the longitudinal bending stress of the pipeline based on Winker theory.It is found that the numerical simulation results agree well with the theoretical solutions,which verified the reliability of the finite element model.The pipe-soil finite element model of PVC pipe and DI pipe was established and the influence of the erosion void size and relative position on the pipeline stress was analyzed.The numerical results show that,as the axial length of the erosion void increases,the bending stress of the pipeline changes greatly.When the lateral depth of the erosive void increases uniformly,the longitudinal stress of the pipeline increases uniformly.A stress critical position is the circumferential angle of 90°.The influence pipe bottom located erosion void on the pipe stress is greater than the erosion void on pipe side or the pipe waist position.Furthermore,the control variable method is used to analyze the correlation between other influencing factors and pipeline stress under the action of erosion void,it found that the influence of factors on the pipe stress in order of temperature difference,the pipe diameter,pipe internal pressure,pipe buried depth and soil characteristics.The finite element simulation results are used as neural network training samples to establish a stress prediction model which can correctly map the nonlinear relationship between basic parameters and responses.The Monte Carlo method is used to randomly sample 2×10⁵ times of basic parameters as the input of prediction samples,and substitute 2×10⁵ responses in the network prediction model.Combined with the limit state equation of pipeline failure,the pipeline failure probability calculated by Bernoulli's law of large number is 0.37×10^-3,which is lower than the target failure probability.Furthermore,a parameter sensitivity index was defined from the perspective of pipeline failure probability,the influence of the basic parameters on the failure probability of the pipeline was analyzed.The results show that the axial length of the erosion void of the pipeline has the greatest influence on the failure probability,followed by the pipe diameter and wall thickness,buried depth,internal pressure of the pipeline,and elastic modulus of the soil.