盾构隧道穿越含微浅层气地层变形影响因素研究
杨昕1,2洪义1王立忠1
Deformation Influencing Factor Analysis for Shield Tunnelling under Micro-shallow Gas Strata
YANG Xin1,2HONG Yi1WANG Lizhong1
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作者信息:1.浙江大学建筑工程学院， 310058， 杭州
2.重庆大学溧阳智慧城市研究院， 213332， 溧阳
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Affiliation:1.College of Civil Engineering and Architecture, Zhejiang University, 310058, Hangzhou, China
2.Liyang Institute for Smart City of Chongqing University, 213332, Liyang, China
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关键词:
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Key words:
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DOI:10.16037/j.1007-869x.20230582
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中图分类号/CLCN:U455.43
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栏目/Col:土建工程
摘要:
［目的］我国滨海地区广泛分布浅层气地层，影响地铁隧道工程施工安全。因此，有必要对盾构穿越浅层气地层变形影响因素进行深入研究。［方法］依托杭州地铁1号线盾构隧道下穿萧山机场工程，通过萧山机场附近超前放气工程结果分析了盾构区间浅层气地层埋深及峰值气压分布。根据饱和土和含气土三轴不排水卸荷试验及数值模拟结果，分析了微浅层气地层盾构开挖施工风险，提出了风险控制因素。选取典型监测断面，分析了地面沉降与盾构施工过程的关系，得到了盾构隧道在含气软土地层施工时地层损失沉降和固结沉降界限值。基于随机森林模型分析了盾构在含气土层施工中盾构掘进参数对地面沉降重要性影响。［结果及结论］该盾构区间浅层气富集层埋深在20~30 m范围内，且峰值气压在0.01 MPa左右，属于微浅层气层；盾构穿越含气地层施工过程中应特别注重土仓压力控制，降低开挖面含气土层液化失稳、地层坍塌等风险；盾构在含气地层开挖时，取盾尾离开2~3 d划分地层损失沉降和固结沉降；盾构掘进参数对地面沉降影响重要性排序依次为土仓压力、扭矩、注浆量、推力、出土量、推进速度。
Abstracts:
［Objective］ Shallow gas stratum is widely distributed in coastal areas of China, affecting the safety of subway tunnel construction. Therefore, it is necessary to deeply study the factors influencing deformation of shield tunneling through shallow gas stratum. ［Method］ Relying on the shield tunnel project of Hangzhou Metro Line 1 crossing under Xiao-shan Airport, the buried depth and peak gas pressure distribution of shallow gas strata in the shield section are analyzed through the results of the advanced gas releasing project near Xiaoshan Airport. Based on triaxial undrained unloading test of saturated soil and gas-bearing soil, as well as the numerical simulation results, the excavation risks of shield construction in micro-shallow gas strata are analyzed, and risk control factors are proposed. A typical monitoring section is selected to analyze the relationship between land subsidence and shield construction process, determining the boundary values of stratum loss settlement and consolidation settlement during shield tunnel construction in gas-bearing soft soil strata. The importance of shield tunneling parameters on land subsidence during shield construction in gas-bearing soil layers is analyzed based on a random forest model. ［Result & Conclusion］ The buried depth of the shallow gas-rich layer in the shield section ranges is from 20 m to 30 m, with a peak gas pressure of approximately 0.01 MPa, indicating a micro-shallow gas layer. During shield construction crossing gas-bearing strata, special attentions should be paid to the pressure control in the earth chamber to reduce the risks of liquefaction instability and stratum collapse in the gas-bearing soil at the excavation face. When excavating in gas-bearing strata, the stratum loss settlement and consolidation settlement should be distinguished 2 to 3 days later after the shield tail has left. The importance ranking of shield tunneling parameters affecting land subsidence is as follows: earth chamber pressure, torque, grouting volume, thrust, soil discharge volume, and advancing speed.
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