土压平衡盾构施工穿越钱塘江大堤沉降控制分析
Settlement control of Qiantang River embankments during undercrossing of EPB shield tunnels
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摘要: 针对杭州地铁1号线区间隧道土压平衡盾构穿越钱塘江大堤的施工过程,建立隧道-土体-大堤三者相互作用的三维非线性有限元模型,分析了大堤沉降和变形的特点,得出盾构穿越施工对防洪堤的影响主要是由于土体的变形和位移而造成。考虑到防汛大堤的重要性,结合工程实践,提出了土压平衡盾构穿越大堤时有效控制地面沉降的措施。现场测试结果表明数值分析反映了穿越施工的基本性状,但施工前进行沼气释放的江南大堤沉降明显大于数值分析结果,表明沼气释放引起的底层损失对于地面沉降和结构安全有巨大影响,今后同类施工中应加以注意。Abstract: The earth pressure balance (EPB) shield has been widely used in construction of cross-river tunnels, and it is difficult to protect the embankments during crossing. Based on the construction of Hangzhou No. 1 subway tunnel under crossing Qiantang River, a tunnel-soil-levee interaction nonlinear finite element model is established. Through analyzing the characteristics of displacement and deformation, it is found that the settlement of embankment is mainly caused by deformation and displacement of soils when the shield traverses the embankment. Considering the significance of the embankment, some practical and effective measures are suggested for the earth pressure balance shield. The field test results show that the numerical analysis reflects the basic characters of construction. The settlement caused by releasing methane before construction is significantly greater than that of numerical analysis, and the releasing methane has a huge impact on the ground settlement and structural safety. Attention should be paid to similar projects.