Laboratory impacts into dry and wet sandstone with and without an overlying water layer: Implications for scaling laws and projectile survivability
Laboratory impacts into dry and wet sandstone with and without an overlying water layer: Implications for scaling laws and projectile survivability
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DOI：
10.1111/j.1945-5100.2007.tb00549.x
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发表时间：
2007-11-01
影响因子：
2.2
通讯作者：
Crawford, I. A.
中科院分区：
文献类型：
--
作者：
Baldwin, E. C.;Milner, D. J.;Crawford, I. A.
描述弹坑尺寸的标度律是根据弹丸速度和质量、所涉及材料的密度、目标的强度和局部重力来定义的。在这里，通过15个实验室的影响，1毫米直径的不锈钢弹丸在5公里秒（-1）到a）一个最初未表征的砂岩（孔隙度类似于17%）和B）可可尼诺砂岩（孔隙度类似于23%）的目标孔隙度和饱和度，以及上覆水层的额外的重要性被认为是。孔隙度较高的干砂岩允许形成直径较大但深度较小的火山口，而不是孔隙度较低的干砂岩。此外，对于这两种孔隙度，从湿目标中挖掘的材料体积大于从干目标中挖掘的材料体积（27-30%）。我们的结果与Pi标度（在一系列尺度上表征陨石坑数据的关键参数的无量纲比率）的比较表明，孔隙度对标度律很重要，因为新数据在pi（v）与pi（3）图上明显低于当前对冰和岩石目标的拟合（pi（v）给出陨石坑效率，pi（3）目标强度的影响）。上覆的水层导致弹坑尺寸减小，与不饱和目标相比，在饱和目标中产生更大的弹坑。在目标上不再观察到弹坑之前，需要大约12倍于射弹直径的水深。以前的实验研究表明，这个比例在10和20之间变化（Gault和Sonett 1982）。在我们的实验中，近似25%的原始射弹质量在撞击中幸存下来。
Scaling laws describing crater dimensions are defined in terms of projectile velocity and mass, densities of the materials involved, strength of the target, and the local gravity. Here, the additional importance of target porosity and saturation, and an overlying water layer, are considered through 15 laboratory impacts of 1 mm diameter stainless steel projectiles at 5 km s(-1) into a) an initially uncharacterized sandstone (porosity similar to 17%) and b) Coconino Sandstone (porosity similar to 23%). The higher-porosity dry sandstone allows a crater to form with a larger diameter but smaller depth than in the lower-porosity dry sandstone. Furthermore, for both porosities, a greater volume of material is excavated from a wet target than a dry target (by 27-30%). Comparison of our results with Pi-scaling (dimensionless ratios of key parameters characterizing cratering data over a range of scales) suggests that porosity is important for scaling laws given that the new data lie significantly beneath the current fit for ice and rock targets on a pi(v) versus pi(3) Plot (pi(v) gives cratering efficiency and pi(3) the influence of target strength). An overlying water layer results in a reduction of crater dimensions, with larger craters produced in the saturated targets compared to unsaturated targets. A water depth of approximately 12 times the projectile diameter is required before craters are no longer observed in the targets. Previous experimental studies have shown that this ratio varies between 10 and 20 (Gault and Sonett 1982). In our experiments similar to 25% of the original projectile mass survives the impact.