输水隧洞软岩段TBM掘进挤压大变形与支护受力分析

隧洞软岩大变形严重威胁到 TBM 安全运行,软弱围岩的变形具有明显的蠕变特性。针对某深埋输水隧洞软岩TBM掘进洞段的围岩变形和支护结构安全展开分析和评价,研究高应力条件下软岩的蠕变特性,比较不同支护方式管片结构的受力状态。研究表明:软岩洞段TBM掘进采取大断面扩挖和管片+豆砾石层+聚乙烯泡沫板缓冲层支护,缓冲层的施加明显改善管片的受力状态,有效地提高了管片结构的安全裕度。建议在类似的深埋软岩隧洞工程中,开展有针对性的岩体流变试验和变形监测,选取合适扩挖断面尺寸和支护方式,给围岩变形预留足够空间,为TBM的顺利掘进提供可靠的作业条件。研究成果为保障隧洞顺利掘进提供了技术支持,也可为其他同类超长深埋隧洞的修建提供参考。

Analysis of Large Deformation and Supporting Force of TBM Tunneling in Soft Rock Section of Water Conveyance Tunnel

The large deformation of soft rock, which is of obvious creep characteristics, seriously threatens the safe operation of TBM (tunnel boring machine). In this paper we analyze and evaluate the deformation of surrounding rock and the safety of supporting structure in the soft rock TBM tunneling segment of a deep-buried water conveyance tunnel. We also investigate into the creep characteristics of soft rock under high stress conditions and compares the stress states of segment structures supported with different methods. Results demonstrate that the stress state of segment and the safety margin of segment structure can be effectively improved by adopting large cross-sectional expansion excavation in association with a buffer layer consisting pea gravel layer and polyethylene foam plate. We suggest to provide reliable working condition for TBM by selecting suitable expansion excavation section and support method as well as reserving enough space for surrounding rock deformation via targeted rock rheological tests and deformation monitoring for similar deep buried tunnel projects. The research findings offer technical support for smooth tunneling, and also provide reference for the construction of similar ultra-long deep-buried tunnels.