Design block size is of vital importance for rockfall countermeasure design. According to the Austrian normative document ONR 24810, the design block is specified as fractile (V₉₅-V₉₈) of the block size distribution depending on rockfall frequency. For rock formations, which form very large rockfall blocks (> 10 m³), the use of fractiles V₉₅–V₉₈ appears too high with regard to economically justifiable protective measures. The paper deals with the determination of design blocks for the Dachstein Formation on the basis of data from three Austrian test regions. The formation’s bedded limestone represents a key rock of the eastern part of the Northern Calcareous Alps and is very common along some major transport routes. A range of design blocks is derived from a synopsis of block size distributions, magnitude-frequency relations, and considerations about the rockfall barriers’ service life. In the process, the knowledge of the return period of the determinated design block is considered more important than the overall rockfall frequency. Analyzing available rockfall event data and block size distributions, it is possible to identify a return period of 21–26 years for a rockfall event ≥ 1 m³/1000 m route section. Thus, such events are rare. Events that affect the V₉₇–V₁₀₀ fractiles of the block size distribution are even rarer; they yield very large design block volumes, which show return periods > 100 years. For the bedded Dachstein limestone of the test areas, the application of the fractiles V₉₅–V₉₆ (0.15–2.25 m³) is useful for adapting the return period of the design block to the working life of the rock fall barrier (25–50 years).

中文翻译：

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确定上三叠统石灰岩和白云岩中的崩塌设计块（Dachstein组，北钙质阿尔卑斯山）

设计块的大小对于落石对策设计至关重要。根据奥地利规范性文件ONR 24810，设计块被指定为取决于落石频率的块大小分布的分形（V ₉₅ -V ₉₈）。对于形成非常大的落石块（> 10 m ³）的岩层，使用分形V ₉₅ – V ₉₈在经济上合理的保护措施方面似乎显得过高。本文基于来自三个奥地利试验区的数据，确定了Dachstein组的设计区块。地层的层状石灰岩代表了北钙质阿尔卑斯山东部的关键岩石，并且在某些主要运输路线中非常常见。设计块的范围是从块大小分布，幅度-频率关系的提要以及对落石屏障使用寿命的考虑中得出的。在此过程中，对确定的设计区块的返回周期的了解被认为比整体落石频率更为重要。分析可用的落石事件数据和块体大小分布，对于≥1 m的落石事件，可以确定21-26年的返回期³个/ 1000米的路段。因此，这种事件很少发生。影响块尺寸分布的V ₉₇ - V ₁₀₀碎裂的事件更为罕见；它们产生非常大的设计块体积，显示出回收期> 100年。对于测试区域的层状Dachstein石灰石，应用碎屑V ₉₅ – V ₉₆（0.15–2.25 m ³）有助于使设计模块的恢复期适应落石屏障的使用寿命（25– 50年）。