为解决不良地质软弱围岩造成隧道失稳、软弱围岩注浆参数不确定，以及米林隧道冰水堆积体围岩注浆厚度对支护力安全性造成影响等问题，基于三维有限元FLAC3D模拟软件，建立不同注浆厚度的隧道围岩模型，得到注浆后的围岩特征曲线，通过允许变形量确定了不同注浆厚度对应的允许支护力。基于此，进一步探讨围岩不同注浆厚度下，采用上下台阶法并打设锁脚锚杆对初期支护结构的影响，并计算得到断面每个位置初期支护的安全系数。结果表明： 1）注浆圈厚度越大，基于允许变形的允许支护力越小； 且围岩条件越差，相同注浆厚度对应的允许支护力越大； 故米林隧道冰水堆积体段Ⅳ1、Ⅴ1和Ⅵ级围岩的合理注浆圈厚度建议分别取3.5、3.5、5.0 m。2）随着注浆圈厚度的增大，各级围岩各个位置对应的初期支护安全系数增大。3）初期支护安全系数一般在拱肩、拱顶和拱底较大，在拱腰和拱脚位置最小。

In order to solve the problems of tunnel instability caused by poor geological weak surrounding rock, the uncertainty of grouting parameters of weak surrounding rock, and the influence of grouting thickness of surrounding rock of ice water accumulation body of Milin tunnel on the safety of support force, the tunnel surrounding rock model with different grouting thickness is established  based on the threedimensional finite element FLAC3D simulation software. The surrounding rock characteristic curve after grouting is obtained, and the allowable support force corresponding to different grouting thickness is determined through the allowable deformation. On this basis, the influence of different grouting thickness of surrounding rock on the primary support structure is further discussed, and the safety factor of primary support at each position of the section is calculated. The results show that: （1） The greater the thickness of the grouting circle, the smaller the allowable support force based on the allowable deformation; and the worse the surrounding rock conditions, the greater the allowable support force corresponding to the same grouting thickness. It is suggested that the reasonable thickness of the grouting circle for the Ⅳ1, Ⅴ1 and Ⅵ surrounding rocks of the ice water accumulation section of the Milin tunnel should be 3.5 m, 3.5 m, and 5.0 m, respectively; （2） With the increase of the thickness of grouting circle, the safety factor of primary support corresponding to each position of surrounding rock at all levels increases. （3）The safety factor of primary support is generally large at the arch spandrel, crown, and bottom, and minimum at the arch waist and foot.