Experimental and numerical simulation studies on blast-induced craters in calcareous sand
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摘要: 为了建立钙质砂场地爆炸成坑效应的计算方法,首先在开挖出的钙质砂模型场地开展了不同当量、不同埋深的野外爆炸实验,然后基于有限元与光滑粒子流耦合算法建立了适用于钙质砂爆炸成坑计算的数值模型,并分析了炸药形状和土体参数对爆坑形态的影响,最后建立了适用于钙质砂场地中的爆坑计算公式。结果表明:埋置爆下,钙质砂场地爆坑尺寸大于硅质砂土中的爆坑尺寸;光滑粒子流算法能较好地揭示钙质砂场地中爆坑轮廓的形成机理;炸药形状和土体密实度等参数对于钙质砂爆坑形态具有不同程度的影响,拟合得到的钙质砂场地接触爆和埋置爆抛掷型爆坑尺寸计算公式,可较好地预测不同爆炸当量作用下的爆炸成坑尺寸。Abstract: With the further development of ocean engineering, the dynamic response of calcareous sand sites under strong dynamic loading has received broad attention. In order to investigate the crater characteristics of calcareous sand sites under explosion impact, filed experiments and numerical simulations were conducted. Firstly, a series of field explosion experiments were conducted on calcareous sand sites, with different equivalent sizes and burial depths. The longitudinal and transverse diameter, as well as the depth of craters were measured for each case. Secondly, a new numerical algorithm (FEM-SPH) was used to simulate the formation process of explosion craters, combining the finite element model (FEM) and the smoothed particle hydrodynamics (SPH). Furthermore, the simulated crater dimensions were compared with the experimental results to validate the accuracy of the FEM-SPH model. Thanks to the advantage of the FEM-SPH in simulating large deformations, the crater formation process of ground contact explosions and buried explosions agreed well with the experimental results. The experiment research showed the crater size resulting from buried explosions is larger in calcareous sand compared to siliceous sand. The phenomenon was mainly attributed to the higher porosity and lower interparticle bonding strength of calcareous sand. With the validated FEM-SPH model, parametric analyses, including soil parameters and shapes of charges, were detailed discussed. Under the same equivalent, the influence of soil parameters on the size of the crater was about 6%, while the change in the shape of the charge caused a significant influence on the shape and size of the craters. Finally, empirical formulas were derived to determine the carter diameter and depth under cubic charge explosion according to the FEM-SPH numerical results in calcareous sand sites. The formulas can predict the dimensions of ground contact explosions and buried explosions within different equivalent charge weight ranges (0–500 kg). The above research results provided a useful reference for the blast-resistant protection design and emergency reinforcement of calcareous sand foundations.
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Key words:
- calcareous sand /
- blast crater /
- explosion experiment /
- smoothed particle hydrodynamics
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区别于一般的爆炸力学和冲击动力学计算,毁伤仿真计算往往需要对完整目标场景甚至阵地场景进行武器打击全过程计算,同时又需要近实时给出计算结果。这种大场景和快速计算在武器研发和运用的工程实际中有着强烈的应用需求。现有爆炸和冲击动力学计算方法(如FEM)由于计算规模和计算效率的限制,在进行毁伤场景计算时往往只能对目标构件或者局部区域进行计算,很难满足毁伤仿真的应用需求。近年来出现了一些快速算法,如镜像爆源法、侵彻微分面元法和破片射线追踪法等,这些快速算法充分利用解析公式、经验数据或代理模型,结合计算机仿真与可视化技术,形成实用工具,有力支撑了国防工业和军事领域的应用。
毁伤快速算法的求解时间必须满足强制时间约束条件,在优先满足时间效率要求的前提下,综合采用解析公式、经验数据、数值计算、人工智能、计算机仿真等方法,进行算法创新和集成应用。毁伤快速算法是一种既区别于解析公式法,又区别于传统有限元的求解方法,既有解析公式稳健可靠的特性,又有有限元方法良好的复杂几何形状适用性,填补了解析公式和有限元方法之间巨大的方法空白。这类方法能够抓住毁伤的主要特征进行快速求解,其特点主要包括:复杂三维场景适用,时间差分推进,数据驱动为主、模型驱动为辅,“绝对的时效性、相对的准确性”,物理毁伤、功能毁伤和任务毁伤的一体化计算等。毁伤仿真是一个典型的多学科交叉、多技术融合的领域,尤其对于计算机图形学等计算机仿真学科和相关技术有很强的依赖性,典型例子就是射线追踪法(ray tracing)在破片场求解中的应用。此外,在实际应用中,对于软件友好操作、三维可视化等功能也有很强的技术需求,可以说毁伤快速算法和计算机仿真技术构成了深度耦合的关系。
根据工作需要,我国不少科研单位开展了一些相关基础研究,并形成了相应的研究成果,但是针对这一领域进行系统学术交流的平台一直缺乏。为了推动毁伤快速算法和仿真技术领域的科学发展,促进此类方法在国防安全领域的运用,2023年7月,在中国力学学会爆炸力学分会计算爆炸力学专业组的指导下,国防科技大学理学院和湖南大学土木工程学院联合承办了2023年毁伤快速算法与仿真技术研讨会,旨在探讨毁伤快速算法和仿真技术的关键技术和发展方向。我国本领域专家学者积极参会和投稿,贡献出了精彩的学术报告和高质量的学术论文,会议规模远超组委会的预期。经过《爆炸与冲击》期刊的严格审稿流程,多篇文章有幸获得发表,形成本期专题。会议组委会由衷感谢全部参会人员、论文作者和审稿专家,特别感谢《爆炸与冲击》编辑部为本专题出版做出的贡献!
国防科技大学 卢芳云 教授
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表 1 实验工况
Table 1. Experimental cases
工况 W/kg d/m λ/(m∙kg−1/3) 工况 W/kg d/m λ/(m∙kg−1/3) C1 0.2 0 −0.021 C6 0.4 0.5 0.712 C2 0.8 0 −0.026 C7 0.8 0.5 0.565 C3 1.6 0 −0.042 C8 0.2 1.0 1.731 C4 3.2 0 −0.033 C9 0.4 1.0 1.391 C5 0.2 0.5 0.876 表 2 地面接触爆的爆坑尺寸
Table 2. Sizes of craters induced by ground contact explosion
工况 W/kg D1/m D2/m H/m C1 0.2 0.64 0.65 0.23 C2 0.8 1.05 1.05 0.33 C3 1.6 1.10 1.08 0.28 C4 3.2 1.05 1.30 0.36 表 3 埋置爆的爆坑尺寸
Table 3. Sizes of craters induced by buried explosion
工况 W/kg d/m λ/(m∙kg–1/3) D1/m D2/m Dav/m H/m 爆坑类型 C5 0.2 0.5 0.87 1.05 1.44 1.25 0.51 抛掷型 C6 0.4 0.5 0.71 1.32 1.50 1.41 0.70 抛掷型 C7 0.8 0.5 0.56 1.63 1.63 0.83 抛掷型 C8 0.2 1.0 1.73 1.00 0.95 0.98 塌陷型 C9 0.4 1.0 1.39 1.56 1.50 1.53 塌陷型 表 4 密实度为90%的钙质砂的材料参数
Table 4. Parameters of calcareous sand with the compactness of 90%
ε1 ε2 ε3 ε4 ε5 ε6 ε7 ε8 ε9 ε10 0 0.02 0.10 0.15 0.20 0.25 0.30 0.40 0.50 0.60 p1/MPa p2/MPa p3/MPa p4/MPa p5/MPa p6/MPa p7/MPa p8/MPa p9/MPa p10/MPa 0 3.66 8.43 10.87 14.51 19.56 26.48 46.89 82.18 141.09 ε1 ε2 ε3 ε4 ε5 ε6 ε7 ε8 ε9 ε10 0 0.02 0.10 0.15 0.20 0.25 0.30 0.40 0.50 0.60 p1/MPa p2/MPa p3/MPa p4/MPa p5/MPa p6/MPa p7/MPa p8/MPa p9/MPa p10/MPa 0 2.30 5.80 8.50 11.70 15.83 21.03 36.43 62.23 105.59 ρs/(g·cm−3) G/MPa Ku/MPa a0 /kPa2 a1/kPa a2 1.780 107.7 647.3 84.77 16.23 0.777 表 6 爆坑尺寸的数值模拟结果与实测结果对比
Table 6. Comparison of simulated and measured results of sizes of explosion-induced craters
工况 W/kg d/m 实测值/m 计算值/m 计算值与实测值的偏差/% D1 D2 H D1 D2 H D1 D2 H C1 0.2 0 0.64 0.65 0.23 0.49 0.69 0.25 –23.4 6.20 8.70 C2 0.8 0 1.05 1.05 0.33 0.86 0.89 0.42 –18.9 –15.20 27.20 C3 1.6 0 1.10 1.08 0.28 1.09 1.13 0.38 –0.9 4.60 35.70 C5 0.2 0.5 1.05 1.44 0.51 1.04 1.10 0.73 –0.9 –23.60 43.10 C6 0.4 0.5 1.32 1.50 0.70 1.19 1.31 0.76 –9.8 –12.67 8.60 C7 0.8 0.5 1.63 0.83 1.63 1.63 0.80 0.6 –3.61 表 7 不同装药形状下爆坑尺寸对比
Table 7. Comparison of sizes of craters induced by explosions with different charge shapes
W/kg d/m 长方体装药 立方体装药 D1 D2 H/m D/m H/m 0.4 0 0.68 1.18 0.16 0.83 0.28 0.4 0.5 1.19 1.31 0.76 1.39 0.78 表 8 不同密实度钙质砂的爆坑尺寸对比
Table 8. Comparison of sizes of craters induced by explosions in calcareous sand with different compactness
密实度/% W/kg d/m D/m H/m 直径变化/% 深度变化/% 30 0.2 0 0.77 0.25 5.2 4.0 90 0.73 0.24 30 0.8 0 0.99 0.32 1.0 6.3 90 0.98 0.30 30 0.4 0.5 1.34 0.79 −3.6 2.6 90 1.39 0.78 30 0.8 0.5 1.70 0.83 −3.4 1.2 90 1.76 0.82 表 9 立方体装药地面接触爆形成的爆坑的尺寸的计算结果
Table 9. Numerical results of sizes of craters induced by ground contact explosions using cubic TNT charges
工况 W/kg d/m D/m H/m 工况 W/kg d/m D/m H/m E1 0.20 0 0.73 0.24 E7 9.50 0 1.69 0.55 E2 0.40 0 0.83 0.28 E8 20.00 0 2.11 0.71 E3 0.80 0 0.98 0.30 E9 35.00 0 2.21 0.92 E4 1.63 0 1.19 0.35 E10 53.00 0 2.62 1.06 E5 2.80 0 1.21 0.39 E11 89.00 0 2.73 1.08 E6 6.67 0 1.52 0.49 E12 100.00 0 3.06 1.09 表 10 立方体装药埋置爆形成的爆坑的尺寸的计算结果
Table 10. Numerical results of sizes of craters induced by buried explosions using cubic TNT charges
工况 W/kg d/m D/m 工况 W/kg d/m D/m D1 0.80 0.5 1.76 D8 200.00 1.5 8.30 D2 0.40 0.5 1.39 D9 200.00 2.0 7.49 D3 1.20 0.5 2.02 D10 286.00 1.5 8.89 D4 0.83 0.8 1.72 D11 350.00 2.0 8.90 D5 0.40 0.8 1.51 D12 420.00 2.0 9.80 D6 100.00 1.2 7.04 D13 512.00 1.5 10.81 D7 150.00 1.5 7.14 D14 512.00 2.5 10.60 -
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