风化花岗岩地层隧道变形与施工技术研究Research on Deformation Characteristics and Construction Technology of Weathered Granite Formation Tunnel

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Based on the measured surrounding rock stress, deformation and support structure stress in the weathered rock formation, combined with analytical formula calculation and numerical simulation, from the surrounding rock loose circle radius, support structure deformation and force, this paper evaluated surrounding rock stability and support effect. The results show that the surrounding rock conditions of the exit section of the Yuliao tunnel are better, the maximum deformation is 7.71 mm, and the thickness of the loose roof of the arch is 3.1 m. The thickness of the loose circle at the arch waist and the arch shoulder is more than 4.0 m. The analysis reflects that the bolts in the loose area of the surrounding rock are subjected to large forces. The stress characteristics of the supporting structure indicate that the additional load transmitted to the supporting structure due to the large deformation of the surrounding rock at the vault and the arch causes the force increase. The numerical calculation results show that there is a significant difference in the deformation of the bolts installed in different processes. Based on the deformation law and the force analysis results of supporting structure, the construction measures and support structure optimization suggestions are proposed.

1. 引言

2. 渔寮隧道工程概况

Table 1. The basic information about Yuliao tunnel

Figure 1. Geology of the face in ZK368 + 248

3. 风化花岗岩地层隧道变形特征

3.1. 现场监测数据分析

3.1.1. 拱顶下沉、洞周收敛

Figure 2. Vaulting down and cave convergence of exit section

3.1.2. 拱顶下沉、洞周收敛

Figure 3. Settlement value of different mileage surface in the exit section

$S\left(y\right)={S}_{\mathrm{max}}\mathrm{exp}\left[\frac{-{y}^{2}}{2{i}^{2}}\right]$ (1)

$y={y}_{0}+A\mathrm{exp}\left[-0.5\ast \frac{{\left(x-{x}_{c}\right)}^{2}}{{w}^{2}}\right]$ (2)

(a) YK328+231地表沉降值拟合 (b) YK328 + 221地表沉降值拟合

Figure 4. Surface subsidence in YK328 + 221 and YK328 + 231

YK368 + 231、YK368 + 221：的回归模型依次为：

$y=-7.17-5.59\ast \mathrm{exp}\left[-0.5\ast {\left(\frac{x-0.0367}{3.57}\right)}^{2}\right]$ (3)

$y=-7.79-6.97*\mathrm{exp}\left[-0.5*{\left(\frac{x+0.189}{3.97}\right)}^{2}\right]$ (4)

3.2. 数值模拟分析

3.2.1. 计算模型的建立

Figure 5. Tunnel size (unit: m) and tunnel model

3.2.2. 计算参数确定

Table 2. The basic information about Yuliao tunnel

$E=\left({E}_{0}{S}_{0}+E{}_{G}S{}_{G}+{E}_{C}{S}_{C}\right)/S$ (5)

3.2.3. 计算结果分析

(a) 隧道围岩竖向变形云图 (b) 隧道围岩横向变形云图

Figure 6. Tunnel surrounding rock deformation contour (unit: m)

Figure 7. Tunnel surrounding rock plastic zone (unit: m)

(a) 拱顶下沉——计算步数曲线 (b) 拱腰收敛——计算步数曲线

Figure 8. Tunnel deformation—calculating step curve

4. 结论

1) 渔寮隧道出口段处于风化花岗岩地层中，围岩级别由洞口向内逐步自V级往IV级过渡，在隧道变形沿纵向的变化中能够反映出来，V级围岩区段的隧洞变形量比IV级围岩区段的隧洞要大，IV、V级围岩的分界线也在隧道变形中能反映出来。

2) 渔寮隧道出口段右洞地表形成了明显的沉降槽，根据实测地表沉降数据，基于Peck理论，拟合得到地表沉降预测模型表达式，据此可推测出不同水平位置处的地表沉降量。

3) 数值模拟结果显示：双侧壁导坑临时支护的拆除以及主洞拱部岩体开挖是引起隧道围岩变形的主要工况；开挖导致拱肩、仰拱和拱脚处出现较大的塑性区，是施工中重点控制变形的位置。

4) 在渔寮隧道出口段的风化花岗岩地层施工中，围岩条件较差的V级围岩段采用长管棚或超前小导管注浆预支护，节理裂隙发育和断层等软弱围岩地段设置超前砂浆锚杆，不同围岩条件采用合理的开挖工法，控制爆破减少围岩扰动和减少超挖，多项施工技术措施控制围岩变形，预防出现地表坍塌、拱顶掉块及变形超限等问题。

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