## 7 Conclusions and Future Work  
Since the pipe was locally impacted by the blast wave, the stress distribution was not uniform in the near and middle field of the blast wave. Both the peak strain and average frequency are closely related to the scaled distance. Using the scaled distance as the main variable to describe the problem, which includes two factors, the charge mass and the blast center distance, simplifying the influence of other complex factors into a proportional coefficient and attenuation index proved to be an effective method of solving this practical engineering problem, which is consistent with general engineering practices. Here, it was shown that the pipe vibration is a low-frequency vibration. Therefore, the dynamic effect of pipe vibration can be ignored, and the process can be considered to be quasi-static when blasting criteria are analyzed. 1. When the scaled distance is in the range of 4-11, the PCS is generally larger than the PAS at the same test point. The hoop stress level is related to the pipe-soil relative stiffness and the mechanical properties of the material. The shape of the circular section of pipe changes and the local deformation characteristics are obvious. As the scaled distance increases, the blast wave transforms from a compression wave to a seismic wave. The difference between the PHS and PAS value decreases progressively, the local deformation effect steadily weakens, and the overall deformation effect is relatively enhanced and gradually begins to dominate [35]. Therefore, the hoop stress should be fully considered in the safety check in the near and middle field of the blast wave. 2. The peak strain and scaled distance have a good power attenuation relationship as demonstrated by dimensional analysis and experimental data analysis. 3. According to the strain and velocity spectrum analysis, all of the average frequency is between 10-50 Hz and the vibration frequency is low. The average frequency of strain has a power attenuation relationship with the increase in the charge mass. Additionally, the average frequency of velocity is attenuated with the increase in the scaled distance, and inversely proportional with the blasting cavity factor. 4. There was a strong linear correlation between the peak strain, PPVV, and GPPV in this experiment. Thus, we determined that GPPV can directly and effectively reflect the stress level. Moreover GPPV monitoring has the advantages of simple operation, reliable testing, and so on. Therefore, GPPV monitoring should be adopted and promoted as a technical means of on-site monitoring of buried pipelines. 5. A single velocity criterion does not reflect the complex influence of various factors, such as pipe type, pipe material, soil properties, blasting source, and so on. Therefore, it is more reasonable to adopt 10% MRS of PE pipe as the blasting criterion. This criterion is accurate and easy to calculate. In this research, we studied a PE pipeline's dynamic response after being subjected to non-destructive blast tests. In future work, we will study the structural health monitoring (SHM) of buried PE pipelines subjected to increased blast levels that will actually cause damage to the pipeline. We will use piezoceramic patch transducers due to their advantages of high bandwidth [36; 37; 38], dual sensing and actuation capacity [39; 40; 41], and ease of bonding to the surface of a pipeline [42]. We plan to use the active sensing method [43; 44] to perform the SHM of the pipeline by using distributed surface-bond piezoceramic patches [45]. With piezoelectric transducers, we can monitor the dynamic response of the pipeline in its passive mode [46; 47; 48] and perform damage detection using the active sensing method [49; 50; 51]. **Author Contributions:** Data curation, X.G., F.H. and L.L. ; Formal analysis, X.G. ; Funding acquisition, D.Z. ; Project administration, D.Z. ; Resources, L.L. ; Supervision, D.Z. ; Validation, X.G. ; Original draft preparation, X.G. and F.H. ; and Review and editing, D.Z. and X.G.