为解决围岩劣化所导致的深埋老黄土隧道初期支护破裂问题，以蒙华铁路阳山隧道深埋老黄土围岩劣化初期支护破裂段为工程依托，通过补勘、数值分析、应力监测等手段对深埋老黄土及围岩劣化工况的支护受力特征作对比分析，得到如下结论： 1）在原围岩参数工况下，喷射混凝土全环受压，上台阶喷射混凝土受力较大，最大压应力位于拱顶，同时上台阶拱脚有较大剪切应力； 2）在围岩劣化但未形成连续滑移面的工况下，上台阶的弯曲压应力显著增大，最大压应力仍位于拱顶，且上台阶拱脚处易发生压剪破坏； 3）在围岩劣化且形成连续滑移面的工况下，最大剪切应力与最大压应力位于同一位置——滑移体与衬砌接触的上部边界，此处易发生压剪破坏且位置随着破裂滑移面的变化而变化，分布范围在上台阶拱腰至拱脚处。

The solution to the broken of deep old loess tunnel primary support caused by surrounding rock degradation is necessary. Hence, by taking the primary support broken section caused by surrounding rock degradation of deep old loess of Yangshan Tunnel on Menghua Railway for example, the stress characteristics of deep loess and surrounding rock under the condition of deterioration are compared and analyzed by means of supplementary survey, numerical analysis and stress monitoring. The conclusions are drawn as follows: (1) Under the condition of the original surrounding rock parameters, the shotcrete is under full ring compression, the shotcrete on the top heading is under greater stress, the maximum compressive stress is at the crown, and the arch foot on the top heading has greater shear stress. (2) Under the condition that the surrounding rock is deteriorated but no continuous slip surface is formed, the bending compressive stress of top heading increases significantly, the maximum compressive stress is still located in the crwon, and the arch foot of the top heading is prone to compression shear failure. (3) Under the condition of surrounding rock deterioration and continuous slip surface formation, the maximum shear stress and the maximum compressive stress are located in the same position, the upper boundary of the contact between the slip body and the lining, where compressive shear failure is easy to occur and the position varies with the variation of the rupture slip surface, and the distribution range is from the arch waist of the top heading to the arch foot.