# Safety Analysis of Buried Corrosion-Defect Gas Pipeline in Ceramic Soil Layer Under Blasting Action
## 4 Numerical Simulation of Corroded Defective Gas Pipelines
### Numerical Simulation and Field Test and Theoretical Comparison  
In the study of pipeline dynamic response under blasting action, three methods--a numerical simulation, model test, and theoretical analysis--are comprehensively adopted to verify the accuracy and reliability of the research results. For this purpose, according to the data obtained from the field model test and the theoretical model, the monitoring points at the same position as in the model test are selected in the numerical model for data comparison. In particular, the key monitoring index of the peak stress of the pipeline is set. During the comparison, the data obtained by numerical simulation showed high agreement with the field model test and theoretical analysis. The detailed comparison results are shown in Table 4 and Figure 7. Taking the peak stress as an example, the difference between the numerical simulation results and the model test results is small, with a maximum relative error of 11.36%. This shows that the numerical simulations have high accuracy in predicting the dynamic response of the pipeline under blasting. This is because the numerical simulation method can fully consider many factors, including the nonlinear characteristics of the pipeline material, the dynamic change of the blasting load, and the interaction between the pipeline and the surrounding media. Thus, the dynamic response process of the pipeline under the action of blasting can be simulated more truly. At the same time, the model test also provides an important verification basis for the numerical simulation. By comparing the two results, the correctness of the numerical simulation model and the rationality of the parameters can be further verified. In the study of pipeline dynamic response under blasting action, the results of numerical simulation have high consistency with the results of model test and theoretical analysis data, and the error is within the acceptable range, which proves the accuracy and reliability of the numerical simulation method and the parameters used. The strain curve of the data of channel 1 under experimental conditions (\(S_{1}\) measuring the axial point) is shown in Figure 8. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Materials**} & \multirow{2}{*}{**Density/(g\(\cdot\)m\({}^{-3}\))**} & \multicolumn{2}{c}{**Modulus**} & \multirow{2}{*}{**Shear**} & \multirow{2}{*}{**Poisson’s Ratio**} & \multirow{2}{*}{**Cohesion/MPa**} & \multirow{2}{*}{**Internal Friction Angle\({}^{/o}\)**} & \multirow{2}{*}{**Tensile Strength Sigma/MPa**} \\  & & & & & & & \\ \hline Pipes & 7.85 & 205 & 6 & 0.3 & — & — & 235 \\ Silty clay & 1.98 & 0.039 & 4.3 & 0.35 & 0.035 & 15 & 0.028 \\ Sandstone & 2.68 & 52 & 11.2 & 0.25 & 5.5 & 43 & 2.58 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Numerical simulation parameters table. According to the numerical calculation model, the overall effective stress distribution and change of the pipeline were studied. The effective stress distribution of the pipeline under the most dangerous working condition (3) is shown in Figure 9 below. As can be seen from the analysis of Figure 9, the blasting seismic wave begins to propagate in the pipeline at around 0.04 s, which causes the change of the effective stress of the pipeline unit, enhances the vibration of the pipeline, and gradually increases the effective stress of the pipeline. The blasting seismic wave energy reaching the pipeline peaks at around 0.1 s, and the effective stress of the pipeline also peaks. Then, the stress waves oscillate continuously in the pipe structure, causing the effective stress oscillation of the pipe. After 0.2 s, the blasting seismic wave energy in the pipeline medium gradually disappears, and the effective stress of the pipeline is reduced. The effect of the pipeline on the pipeline is reduced.