研究目的: 崩塌落石是高陡的岩质边坡中，一种常见地质灾害，如不加以治理，可能造成交通中断以及巨大的人员伤亡和经济损失。在山区修建铁路工程时，尤其是隧道进出口段，为了防止崩塌落石对轨道结构的影响，常采用明洞、棚洞等处理措施，落石冲击力是进行明洞、棚洞及拦石墙等被动防治结构设计的主要荷载之一。目前，落石冲击力主要是通过一些半经验半理论的公式计算得到，这些方法的适用性、合理性有待通过充分研究讨论。
研究结论: 本文对几种已有的落石冲击力计算方法进行了探讨分析，结合襄渝铁路隧道口增设棚洞工程，采用路基工程手册法、隧道手册法、Labiouse 法、Kawahara 法、杨其新法等方法进行了落石冲击力计算，结果表明这 5 种计算方法的计算结果在量值上相差不大，路基工程手册法、隧道手册法计算结果稍大。考虑到两手册中的经验方法经过了大量的工程验证，因此推荐以两手册方法的计算结果作为增设棚洞工程设计时的设计荷载，并据此开展工程设计。
Research purposes: Collapse and rockfall are the most common geological disasters for the steep rock slope．If the they are not treated in time，they may cause the traffic interruption，huge economic loss and life casualty． When railway is built in mountain area，the open tunnel and hangar tunnel are adopted to prevent the impact of the collapse and falling stone on the track structure，especially to prevent the collapse and falling stone in exit and entrance of the tunnel． The impulsive force of falling stone is one of main load indexes to be considered in design of the preventive structure，such as open tunnel，hangar tunnel and stone retaining wall． Now the impulsive force of falling stone is often computed with the semi － experience and semi － theory formula，but the applicability and the rationality of them should be verified before application．
Research conclusions: In this paper，the analysis and discussion were made on the commonly － used calculation methods for the impulsive force of falling stone． The calculation of the impulsive force of falling stone was made for the additional hangar tunnel at the tunnel portal of Xiangfan － Chongqing Railway with the subgrade technical manuals method，tunnel technical manuals method，Labiouse method，Kawahara method and Yangqixin method． It was shown that the calculation results obtained by these five methods were almost the same in magnitude． The results obtained by the subgrade technical manuals method and tunnel technical manuals method were a little bigger than the others．However，on consideration of that these two methods had been applied and verified in a large number projects，it was proposed to use the calculation results obtained by these two methods as the design load of the additional hangar tunnel and based on them to make the design．
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