为解决高原铁路某隧道进口细砂状强风化黑云角闪斜长片麻岩富水土石混合地层坍塌的问题，对坍塌发生过程、原因与机制进行深入分析。经分析可知： 富水土石混合地层在水力渗透破坏的情况下，自稳性差，预留核心土易被剪切破坏甚至被推出，拱顶易掉块，进而引发掌子面局部失稳或拱顶坍塌。通过方案比选，最终采取掌子面回填反压、局部回填与注浆、分部开挖与支护等方式，创新性地提出 “333”复合式加固支护技术，快速有效地处置了坍塌段，并在后续类似围岩中采用此工法有效预防了坍塌。

To prevent the waterrich soilstone composed strata at entrance of a plateau railway tunnel from collapse, the process, causes, and mechanism of the collapse are examined in detail. The investigation results show that under the condition of hydraulic power permeation, the waterrich soilstone composed strata have a poor selfstability, and the reserved core soil and the crown is prone to shear damage and block falling, respectively, which will further lead to local instability or crown collapse. After scheme comparison, the technologies, such as tunnel face backfilling, local backfilling and grouting, and sectioned excavation and support, are adopted, and a composed consolidation support technology is innovatively proposed, which effectively consolidates the collapse section and prevents the followed surrounding rocks from collapse.