为优化高地应力软岩隧道支护结构受力以及控制围岩变形，开展隧道洞型与双层初期支护支护时机研究。首先，通过现场监测数据分析高地应力软岩隧道单、双层初期支护的支护效果及围岩变形规律；然后，采用FLAC3D软件对比分析马蹄形（高跨比0.80）、类圆形（高跨比0.90）、圆形（高跨比1.00）3种洞型下以及第1层初期支护变形达300、350、400 mm时施作第2层初期支护时隧道的受力与变形情况。研究结果表明： 1）对于高地应力Ⅲ级大变形围岩2车道隧道，采用双层初期支护较单层初期支护虽有效控制了围岩变形，但在施工过程中仍出现了拱肩破坏、仰拱开裂等现象； 2）适当增大隧道高跨比可有效降低围岩变形与支护结构受力，高跨比为1.00时效果最好； 3）适当增大第1层初期支护的预留变形量，推迟第2层初期支护的支护时间，支护应力大幅降低，因此，建议第1层初期支护变形达400 mm时施作第2层初期支护。
To optimize the stress of support structure and
control surrounding rock deformation of soft rock tunnel with high insitu
stress, the hole type and supporting time of doublelayer
primary support are examined. First, the supporting effect of single and doublelayer primary support and
surrounding rock deformation law of soft rock tunnels with high insitu stress
are analyzed based on onsite monitoring data. Then,
FLAC3D software is used to compare and analyze the force and deformation of the
tunnel under three kinds of hole types, such as horseshoe (heightspan ratio of 0.80), quasicircular (heightspan ratio of 0.90), and circular (heightspan
ratio of 1.00), and the tunnel force and deformation conditions after applying
second primary support when the deformations of the first primary support reach
300, 350, and 400 mm. The results are as follows: (1) As for the twolane tunnel in grade Ⅲ surrounding rock with
high insitu stress, the doublelayer primary support
can effectively control the surrounding rock deformation better than the singlelayer one, but the phenomena of arch shoulder failure and inverted
arch cracking still occur. (2) Appropriate increase in tunnel depthspan ratio can effectively reduce the deformation of surrounding
rock and supporting structure. The effect reaches the highest when the heightspan ratio is 1.00. (3) Appropriate increase in reserved deformation
space in the first layer of primary support and delay of the second primary
support will cause a great reduction of supporting stress, so it is recommended
to apply the second primary support when the deformation of the first primary
support reaches 400 mm.
