The Research On Dynamic Response And Vibration Energy Attenuation Of Buried Pipeline Under Blasting Dynamic Load

With the construction of underground projects such as urban subway tracks and integrated pipe galleries,blasting operations are often used to excavate underground spaces,and blasting operations near buried pipelines will cause risks and even damage the pipelines.Therefore,the research on the energy attenuation law and dynamic response of the blasting dynamic load on the adjacent pipelines has important engineering reference significance for the safety control in blasting operations.In this research,the finite element dynamic software ANSYS / LS-DYNA was used to establish a pipe-soil coupling model containing explosives,rock and soil,and buried pipelines.Through numerical simulation of blasting dynamic load,combined with the propagation law of blasting load and the load-strain relationship of the pipe-soil coupling model,the dynamic response of the pipe-soil coupling model subjected to blasting load is analyzed.The superposition effect of two groups of unequal shock waves propagating in the opposite direction is analyzed,and the increase of wave amplitude does not follow the linear superposition law.Due to the different failure modes of the rock-soil and the pipeline,the failure criterion of the pipe-soil coupling model was established based on the strength criterion and the tension-compression strain formulas.The blasting numerical simulation was carried out by establishing different pipe wall thickness models.The front and back explosion surfaces of the pipeline were taken as the analysis objects,and the dynamic response analysis of the effective stress,vibration velocity,strain displacement along the axial and circumferential directions of the pipeline were performed.It is found that there is a stress concentration effect at 3/4 of the two ends of the pipeline’s axial frontal explosion surface,and due to the superposition of reflected waves from the free surface of the ground and the forward wave of the explosion source,the stress time history curve has a certain amplification effect.With the increase of the thickness of the pipe wall,the axial and circumferential elements’ stress and peak vibration velocity of thepipe gradually decay.Combining the calculation formula of blasting vibration wave energy flux,the propagation attenuation of the pipeline’s loaded vibration energy in the axial and the circumferential directions is solved.Through the regression analysis of the peak velocity and vibration wave energy of the pipeline elements,the two are approximately quadratic positive correlation.Simultaneously,based on the energy attenuation coefficient of the pipe-soil coupling,a modified proportional coefficient ? was introduced to modify the Sadowsky formula,and the modified vibration velocity formula of the pipe-soil coupling model was obtained.The vibration velocity data in related experiments were used as model verification.The BP artificial neural network,which has multi-factor inputs is used to predict the vibration velocity.A model with predictive performance that meets the accuracy is obtained through the neural network sample learning and training.Comparing the prediction results of the neural network with the simulation results in the model,the error is about 1%,which has a good prediction effect.The research model and results obtained can be used as a reference for engineering practice.