地下工程中金属门非核电磁脉冲屏蔽效能研究

Shielding effectiveness of metal door of underground engineering to non-nuclear EMP

以圆形截面坑道为简化模型,运用旋转对称体时域有限差分法将三维问题转化为二维问题处理,计算了地下防护工程口部金属门对高功率微波、超宽带电磁脉冲的屏蔽效能,分析了门缝大小、门框嵌入岩土介质深度对屏蔽效能的影响,确定了场泄漏的主要途径。计算结果表明,门对坑道中不同的传输波模具有不同的屏蔽效能;泄漏场主要是通过门框的绕射进入工程内部,门缝的泄漏较小,门缝大小以及门框嵌入岩土介质的深度对屏蔽效能的影响是次要的;另外,通过门的泄漏场在工程内部迅速衰减;HPM的载频越高,UWB的脉宽越窄,门的屏蔽效能越好。最后对数值计算结果和实验测得数据进行了比较,二者吻合较好,证实了数值计算的有效性。

The shielding effectiveness of the metal door to non-nuclear EMP （HPM and UWB） at the entrance of the underground protection engineering was analyzed in this paper. In order to save CPU running time and reduce memory requirement, the protection engineering was considered as circular tunnel and the body of revolution finite-difference time-domain method was used which allowed one to reduce a intractable three-dimensional problem to a solvable two-dimensional one. The numerical results indicate that the shielding effectiveness of the door varies with the wave mode propagating in the protection engineering. The main coupling path of electromagnetic energy into the protection engineering through the metal door is the rock and soil layer around the doorframe. The width of slot on the door and the depth of the doorframe embedded in the rock and soil layer are secondary factors that have an effect on the shielding effectiveness. The electromagnetic leakage attenuates quickly in the protection engineering. The higher the carrier frequency of HPM, or the narrower the pulse width of LTWB, the better the shielding effectiveness. The numerical results are good agreement with those obtained from experiment.