Research On Dynamic Response And Damage Of CFRP Buried Oil And Gas Pipeline Under Shallow Blast Loading

The safe operation and maintenance of oil and gas pipelines are crucial to ensuring national energy security and social stability.With the widespread use of manual blasting construction techniques,coupled with the impact of military operations and terrorist attacks against oil and gas pipelines,blast loading as a potential factor for possible third-party damage to oil and gas pipelines can no longer be ignored.Therefore,it is extremely important to study the damage pattern and dynamic response of reinforced buried oil and gas pipelines under explosive loading,especially for the explosion protection of buried oil and gas pipelines.In this paper,a combination of experimental analysis,theoretical research,and simulation is used to investigate the dynamic response of soil under blast loading and numerical simulation methods,the dynamic response and damage evaluation of oil and gas pipelines,and the dynamic response and damage evaluation of CFRP-reinforced oil and gas pipelines.The main research contents and conclusions are as follows:(1)Experimental study on the dynamic response of buried oil and gas pipelines under the action of blast loads.To verify the validity of the numerical model and the numerical method,a shallow burial explosion test scheme was designed for a common buried oil and gas pipeline and a CFRP-reinforced buried oil and gas pipeline under the action of 9.35 kg of explosives.The damage characteristics of the burst crater and the damage characteristics of the test pieces were measured by the shallow burial explosion test,and it was found that CFRP cloth properly wrapped and reinforced can optimize the blast resistance of the current oil and gas pipeline,and can reduce the damage of the oil and gas pipeline under the blast load to a certain extent while alleviating the plastic depression deformation of the oil and gas pipeline.external damage.(2)numerical simulation method based on the explosion in soil research.The accuracy of the SPH-FEM coupled algorithm and the ALE algorithm in simulating the process of soil explosion cratering was verified by comparison with experiments.The peak overpressure of the blast wave simulated by the two algorithms decreases rapidly with increasing depth and distance,which is consistent with the theoretical analysis results.Compared with the ALE algorithm,the SPH-FEM algorithm is faster and more efficient,and the SPH participation is performed to avoid problems such as mesh tangling and distortion in the large deformation region of the soil.(3)Dynamic response study of explosion in soil.Based on the ALE method and SPH-FEM method,the attenuation of the blast wave overpressure in soil under different folding distance conditions of 9.35 kg TNT was obtained,the relationship between the explosive quantity and the volume of the blast crater was analyzed,and the empirical curve equation of the explosive quantity and the blast crater was obtained by mathematical fitting.The possible damage to the surrounding objects from the blast load under shallow buried near-field blast conditions was obtained.Due to the difference in the material properties of soil and air,the difference in the velocity propagation of the blast shock wave in the two media leads to inconsistent characteristics of the shock wave pressure distribution in soil and air,with waveform ejection phenomena on the surface of the soil media and air media.From the numerical simulation study of the blast shock wave propagation process,it can be found that the shallow buried near-field blast can cause damage to objects both near and on the surface of the ground.(4)The dynamic response characteristics of CFRP-buried oil and gas pipelines under the action of blast loading are studied.Through numerical simulation methods,the blast shock wave overpressure distribution,the maximum equivalent force,and the maximum effective strain on the blast face and back face of the pipeline were analyzed,and the effects of the number of CFRP layers,explosive quantity,and blast center distance on the pipeline were studied.It was found that CFRP cloth could improve the blast resistance of buried oil and gas pipelines.In terms of blast load strength parameters,CFRP cloth could significantly mitigate the peak pressure of blast shock waves,thus reducing the damage to buried oil and gas pipelines caused by blast load.After CFRP reinforcement of the pipeline should still pay attention to the fold distance change and near-field blast shock wave attenuation characteristics,to avoid excessive positive pressure holding time for buried pipeline damage.(5)Damage assessment study of CFRP oil and gas pipelines under shallowly buried blast loading.By defining the critical depression depth-length ratio of CFRP buried oil and gas pipelines,the damage under the influence of blast loads can be effectively evaluated.To better evaluate such damage,a complete set of overpressure-impulse damage criteria is proposed based on the critical depression depth-length ratios of the two types of oil and gas pipelines to better evaluate the safety of CFRP buried oil and gas pipelines.After numerical simulations,damage class limits,i.e.P-I curves,were established for the two types of oil and gas pipelines under explosive loading.To better evaluate the damage level of these two types of pipelines,a derivation was made and a relationship was derived and applied to the evaluation of damage to pipelines under shallowly buried blast loads.Based on this criterion,the safety evaluation of the two types of buried oil and gas pipelines after being subjected to buried near-field blast loads can be effectively evaluated.