Study On Dynamic Response And Reliability Of Buried Pipelines Under Blast Loading

As an economical,efficient and widely used way of energy transportation,pipeline plays an important role in the current social life in the world.With the continuous expansion of the scale of infrastructure construction in China,especially with the advent of the era of underground space,the contradiction between the construction of a large number of blasting construction projects and buried pipelines in active service continues to emerge.the influence of explosion seismic effect on the safe operation of adjacent buried pipelines has become a research hotspot in the fields of pipeline engineering,tunnel engineering and blasting engineering.The analysis of the dynamic response characteristics and laws of pipelines under explosion load and the study of the reliability and vibration velocity prediction of adjacent buried pipelines under explosion waves are of great practical significance to the safety control of adjacent buried pipelines in blasting engineering.The thesis addresses the problems that the dynamic response mechanism of buried pipelines under the action of blast waves is unknown,the reliability analysis of pipelines is rarely covered and the prediction of vibration velocity is mostly based on empirical formulas,etc.A series of pipeline model tests were designed and implemented.A combination of theoretical analysis,model tests,numerical simulations and machine learning is used to investigate the dynamic response mechanism of buried pipelines under blast waves,strain vibration velocity law,pipeline reliability analysis and peak vibration velocity prediction.(1)According to the characteristics of buried pipeline affected by blast seismic wave,the tensile and compressive strain model under load is established through the coupled strength model of pipe and soil and elastic model,and the formula of tensile and compressive strain generated by blast seismic wave on the pipe wall of the pipeline is proposed.According to the stress characteristics of the thin-walled cylinder combined with the theory of blast seismic wave P-wave action,the buried pipeline dynamic stress calculation model under the action of blast seismic wave is established,and the peak vibration speed and incidence angle of the incident wave are introduced to propose the buried pipeline dynamic response calculation method based on the incident blast P-wave.(2)A series of model experiments of buried pressurized pipelines under explosive waves are designed and carried out,and the dynamic testing system of strain and vibration velocity is established.By changing the charge quantity,blasting center distance,pipeline internal pressure and other factors,combined with the analysis of test data and numerical simulation results,the dynamic response law of buried pipeline under the action of explosion wave is studied systematically.the relationship between peak strain,proportional distance and surface vibration velocity of pipeline under test conditions is obtained.the relevant conclusions can provide reference for the prediction of buried pipeline response in practical blasting engineering.(3)Based on the traditional blasting vibration prediction formula,the traditional formula is modified by dimensional analysis of pipeline internal pressure and pipeline wall thickness,and the modified formula for blasting vibration prediction of buried pipeline is obtained.A LS-SVM model for predicting blasting vibration velocity of buried pipelines is established.The parameters of LS-SVM model are optimized by PSO algorithm,and the optimal parameter combination of LS-SVM model is determined.The prediction results show that this method is an ideal artificial intelligence prediction method.(4)The results of model tests and numerical simulations were used to establish a database for reliability analysis of buried pipelines under blast waves,so as to construct a BP network analysis model and a prediction model for buried pipelines.The results showed that the error of comparison between predicted stress values and actual values was within 5%,which indicated that the prediction effect of BP network could meet the needs of actual engineering.The results show that the prediction of BP network can meet the practical engineering needs.The reliability index and failure probability of buried pipeline are obtained by sampling probability analysis using the Monte-Carlo method.The results of the study can provide technical support for quantitative risk evaluation and safe operation analysis of buried pipelines adjacent to blasting construction.