根据成昆铁路小平地隧道洞口岩体结构发育分布情况，结合三维激光扫描技术解释，确定落石的最大直径及方量；通过落石模拟计算，分析危岩体的运动特征，包括落石落下的最大可能位置、弹跳高度和能量等；分析采用被动防护网和钢棚洞相应的安全性，在保证铁路运营安全的前提下合理确定整治措施的规模，进而提出了洞口防治的综合处理措施。该设计思路、落石防护结构型式具有代表性，对今后类似工程的处理具有很好的参考价值。

The development of the rock mass around the entrance portal of Xiaopingdi tunnel on the ChengduKunming railway is presented in this paper. The maximum diameter and volume of the falling rocks are determined by means of 3D laser scanning technology. The movement characteristics of the falling rocks, including the most likely place the rocks are going to fall, the bounce height of the falling rocks and their energy, are analyzed by means of rock fall simulation. The advantages of using the passive protective net and the steel shed tunnel as the safety measures are analyzed, and comprehensive countermeasures are proposed to cope with rock falls, so as to ensure the operation safety of the railway. The design concept and the rock fall protection structure presented in the paper can provide reference for similar projects in the future.