Chen Hao, Zheng Haozan, Liu Bolong, Huang Man, Liu Jiawei
School of Civil Engineering, Shaoxing University, Shaoxing, China.
Key Laboratory of Rock Mechanics and Geohazards of Zhejiang Province, Shaoxing University, Shaoxing, China.
PLoS One. 2025 Jan 3;20(1):e0316736. doi: 10.1371/journal.pone.0316736. eCollection 2025.
The excavation of the super-large cross-section tunnel portal section is prone to causing serious engineering distresses. The key factors to ensure the safe construction of portal section are to clarify the construction mechanic characteristics and select a reasonable construction scheme. In this paper, a bidirectional six-lane expressway tunnel in Southwest China was selected as an engineering case. Three excavation schemes, namely, the three-bench seven-step excavation method (TEM), the central diaphragm method (CDM), and the double side drift method (DSDM), were compared and analyzed. Findings revealed that due to the effect of the asymmetrically loaded and super-large cross-section, the surrounding rock deformation and supporting structure stress at the deep buried side were greater than those at the shallow buried side. The CDM and DSDM could reduce the tunnel span and provide temporary support in time, which could effectively control the surrounding rock deformation and improve the structural stress and the slope stability. According to the topographic condition, the excavation sequence of the DSDM was optimized. Excavating the shallow buried side drift first could alleviate the surrounding rock deformation and improve the slope stability in the early stage of construction. Finally, the optimal excavation scheme was successfully implemented.
超大断面隧道洞口段开挖易引发严重的工程病害。确保洞口段安全施工的关键因素是明确施工力学特性并选择合理的施工方案。本文选取中国西南地区某双向六车道高速公路隧道作为工程实例，对三台阶七步开挖法（TEM）、中隔壁法（CDM）和双侧壁导坑法（DSDM）三种开挖方案进行了对比分析。研究结果表明，由于不对称加载和超大断面的影响，深埋侧围岩变形和支护结构应力大于浅埋侧。CDM和DSDM能够减小隧道跨度并及时提供临时支护，可有效控制围岩变形，改善结构受力及边坡稳定性。根据地形条件，对DSDM的开挖顺序进行了优化，先开挖浅埋侧导坑可在施工前期缓解围岩变形，提高边坡稳定性。最终，成功实施了最优开挖方案。
