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高地应力软岩隧道双层初期支护围岩变形特征

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为控制高地应力软岩隧道围岩变形,优化双层初期支护结构,以宁缠隧道为工程背景,通过数值模拟方法分析隧道在双层初期支护不同厚度组合和第二层支护不同施作时机下的变形情况,结合现场监测数据分析单、双层初期支护围岩变形特征,验证数值模拟的准确性.结果表明:在第一层初期支护层厚不大于0.04倍隧道跨径时,增大第一层初期支护厚度对控制隧道拱顶和拱腰变形均有较好的效果,但随着厚度增大,控制效果增强幅度逐渐减弱.第一、二层初期支护厚度比为0.8～2.7时,围岩变形量与厚度比符合指数函数关系.拱腰收敛比拱顶沉降对第二层初期支护施作时机更为敏感.第一、二层支护厚度分别取35 cm和20 cm能较好控制围岩变形,并保证现场的可操作性.下台阶开挖完成前属于围岩应力释放的集中期,开挖卸荷影响占变形主导地位;施作二次衬砌后,围岩流变占变形主导地位.
On Surrounding Rock Deformation Characteristics in a High Geostress Soft Rock Tunnel with Double-layer Initial Support
In order to control the surrounding rock deformation of a tunnel in soft rock with high geostress and opti-mize the double-layer initial support structure,the Ningchan Tunnel is used as an example in this study.The numeri-cal simulation method is used to analyze the deformation characteristics under different thickness combinations of double-layer initial support and at different construction time of the second-layer support.The field monitoring data is also used to analyze the surrounding rock deformation characteristics of single-layer and double-layer initial sup-port,and to verify the accuracy of the numerical simulation.As the results indicate:If the thickness of the first-layer initial support is no more than 0.04 times the tunnel span,increasing the thickness of the first-layer the initial sup-port is highly effective in controlling the deformation of tunnel crown and hance.As the thickness increases,however,the controlling effect is gradually diminished.If the thickness ratio between the first-layer and second-layer initial support is 0.8-2.7,the ratio between the surrounding rock deformation and thickness is indicative of an exponential function relation.Hance convergence is more sensitive to the construction time of the second-layer initial support than crown settlement is.If the first-layer and second-layer support are 35 cm and 20 cm in thickness,the sur-rounding rock deformation can be effectively controlled,and the onsite operability can be guaranteed.The period be-fore excavation of the lower bench is completed is the period in which the surrounding rock intensively releases its stress,and the impact of the excavation-induced unloading is the dominant factor in deformation.After construction of the secondary lining,the surrounding rock rheology is the dominant factor in deformation.

Tunnel engineeringTunnel in soft rock with large deformationExtremely high geostressDouble-layer initial supportThickness ratio of initial support

陈志敏、王洪、龚军、李增印、彭易

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兰州交通大学土木工程学院,兰州 730070

中铁隧道局集团有限公司,广州 511458

隧道工程 软岩大变形隧道 极高地应力 双层初期支护 初期支护厚度比

国家自然科学基金国家自然科学基金中央引导地方科技发展资金项目

122620181166200722ZY1QA005

2024

10.13807/j.cnki.mtt.2024.03.010

现代隧道技术
中铁西南科学研究院有限公司 中国土木工程学会隧道及地下工程分会

现代隧道技术

CSTPCD北大核心
影响因子：1.493
ISSN：1009-6582
年,卷(期)：2024.61(3)