为研究隧道初期支护的受力模式，以蒙华铁路在建隧道为工程依托，开展隧道洞周位移和初期支护受力状态的现场测试。结果表明： 1）初期支护普遍受压，结构处于小偏心受压状态； 2）隧道洞周位移收敛值较小，且隧道整体向净空侧变形，与初期支护普遍受压的受力模式一致； 3）洞周位移、锚杆轴力和初期支护的受力状态均不符合塌落拱式的受力模式，而符合围岩与支护相互作用而产生的形变压力特征； 4）格栅钢架对结构的抗压-剪承载力贡献非常小，初期支护斜截面的抗剪强度主要由混凝土控制，格栅钢架的作用仅是在混凝土开裂后提供峰后韧性。

The force mode of primary support of tunnel on Menghua Railway under construction is studied; and the field measurement is carried out on the displacement around tunnel and the force state of primary support. The results show that: 1) The primary support is generally compressed; and the structure is under slightly eccentricity pressing condition. 2) The convergence displacement around the tunnel is small; and the deformation of the tunnel towards the clearance side is consistent with the force mode of the primary support under general compression. 3) The displacement around the tunnel, the axial force of the bolt and the force state of primary support are not accordance with force mode under loose stress of slump arch, but in line with the deformation stress due to the interaction between surrounding rock and support. 4) The grid steel frame contributes little to stress and shear capacity of the structure; the shear strength of oblique section of primary support is mainly controlled by concrete; and the effect of the grid steel frame is only to provide postpeak toughness after concrete cracking.