Corrugated cardboard is widely used in underground logistic transportation and warehousing and it has become an important fire hazard source. According to previous warehouse fire studies, upward flame spread on corrugated cardboard plays an important role during the initial stage of warehouse fires and can decide the occurrence of subsequent increasing fire hazards. However, the wavy structural effect of corrugated cardboard on fire spread still lacks enough attention. This work studies the fire spread behavior of vertically-set corrugated cardboard with thicknesses of 1.5 mm, 3.0 mm and 4.0 mm. The cardboard inner hollow gaps are set either parallel (defined as along grain direction) or perpendicular (defined as across grain direction) to buoyancy direction. Experimental results show that: (1) along grain sample has better flammability than across grain sample; (2) the relationship between flame height (or pyrolysis height) and time has a best fit with power law, and the difference of the exponents between two grain orientations decreases with the increasing of the sample thickness; (3) for cardboard of different grain orientations and thickness, the ratio of average flame height to average pyrolysis height is a constant. The hollow gaps inside along grain sample, working as passage, are beneficial for the transportation of heated pyrolysis gases and preheating of upper virgin area, hence increasing burning rate and flame upward spread. However, it is observed that the phenomenon (flame luminance, delamination of front layer, extinguishment of flame base, etc.) difference between different grain orientations decreases as sample thickness increases. This study reveals the effects of grain orientation and sample thickness on the corrugated cardboard fire spread behavior which is common in commodity fire in underground logistic transportation and warehousing. The conclusions are beneficial for fire risk assessment as well as the improvement of related codes and regulations.

瓦楞纸板广泛应用于地下物流运输和仓储，已成为重要的火灾隐患源。根据以往的仓库火灾研究，瓦楞纸板向上蔓延的火焰在仓库火灾的初始阶段起着重要作用，可以决定后续火灾隐患的发生。然而，瓦楞纸板的波浪状结构对火势蔓延的影响仍缺乏足够的重视。这项工作研究了厚度为 1.5 毫米、3.0 毫米和 4.0 毫米的垂直设置瓦楞纸板的火势蔓延行为。纸板内部中空间隙设置为与浮力方向平行（定义为沿纹理方向）或垂直（定义为跨纹理方向）。实验结果表明：(1)顺纹试样比横纹试样具有更好的可燃性；(2)火焰高度(或热解高度)与时间的关系最符合幂律，两种晶粒取向的指数差异随着试样厚度的增加而减小；(3)对于不同晶粒取向和厚度的纸板，平均火焰高度与平均热解高度的比值是一个常数。沿谷物样品内部的空心间隙作为通道，有利于热解气的输送和上部原始区域的预热，从而提高燃烧速度和火焰向上蔓延。然而，观察到这种现象（火焰亮度，前层分层，火焰底部熄灭等）。) 不同晶粒取向之间的差异随着样品厚度的增加而减小。本研究揭示了纹理方向和样品厚度对瓦楞纸板火灾蔓延行为的影响，该行为在地下物流运输和仓储中的商品火灾中很常见。研究结论有利于火灾风险评估以及相关法规的完善。