软岩大变形是滇中引水工程建设中较为突出的工程地质问题之一,以大楚段芹河隧洞4#支洞为研究对象开展软岩大变形特征及承载结构受力研究。4#支洞在施工过程中发生影响洞室稳定的问题,洞周围岩大变形不同程度侵限,导致钢拱架扭曲断裂、喷混凝土掉落现象时有发生。为了充分认识隧洞变形特征、破坏模式及成因机制,结合工程地质勘察、现场监控量测、数值反演及施工模拟分析等手段和方法对其进行综合研究。研究成果表明:破碎软岩洞段施工期围岩监测变形量大、变形速率较快,变形具有明显的时效性;围岩完整性差,洞周变形差异大;围岩以剪切破坏为主;围岩时效变形对支护结构受力影响大,部分承载结构受力超限,导致局部结构破坏。可见,针对破碎的软岩隧洞施工,需要采取超前注浆、减少减小施工扰动、及时跟进初期支护、尽快封闭成环,加强施工期围岩变形监测,选取合理的衬砌支护时机,实时指导和优化隧洞支护结构施工设计。
Abstract
Large deformation of soft rock is a prominent engineering geological problem in the construction of Central Yunnan Water Diversion Project. Taking the 4th branch of the Qinhe Tunnel in Dachu segment of the diversion project as research object, we examined the characteristics of large deformation in soft rock and the stress on the bearing structure. The construction of the 4th branch has encountered recurring stability issues within the tunnel chamber. The surrounding rock has experienced varying degrees of deformation, resulting in the distortion and fracture of the steel arch frame and the detachment of sprayed concrete. To comprehensively analyze the deformation characteristics, failure modes, and their underlying mechanisms, we employed a comprehensive research approach combining engineering geological surveys, on-site monitoring measurements, numerical inversion, and construction simulation analyses. The findings indicate that, during construction at the fractured soft rock tunnel section, the surrounding rock exhibits substantial, rapid, and time-dependent deformation. The integrity of the surrounding rock is compromised, with significant variations in deformation. Shear failure predominantly affects the surrounding rock. The time-dependent deformation of surrounding rock significantly impacts the stress on the support structure, leading to local structural failures as some load-bearing structures surpass their limits. Thus, we suggest taking some effective measures when constructing tunnels in fractured soft rock. Such measures include: advance grouting, minimizing construction disturbances, promptly providing initial support, expediting ring closure, strengthening deformation monitoring during construction, selecting appropriate lining support timing, and continuously guiding and optimizing the construction design of the tunnel support structure in real time.
关键词
破碎软岩 /
大变形 /
支护结构 /
蠕变 /
拱架断裂
Key words
fragmented soft rock /
large deformation /
support structure /
creep /
broken arch frame
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基金
云南省重大科技专项计划项目(202102AF080001)
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