盾构隧道穿越松散填土江堤的沉降放大效应及加固效果研究

Study on Settlement Amplification Effect and Reinforcement Effect of Shield Tunnel Crossing Loose Fill River Embankment

为探究盾构隧道施工对长江大堤的影响,依托南京新济洲输水工程利用非线性高级本构模型建立了31组不同工况下的三维有限元模型,综合现场实测数据和Peck公式理论计算结果,研究江堤及地表最大沉降量之间的关系,揭示沉降分布规律和加固效果。研究结果表明:盾构隧道下穿松散填土江堤时,堤顶最大沉降显著大于地表最大沉降,松散填土江堤存在沉降放大效应;土层力学性质对沉降放大效应影响显著,江堤几何外形对其影响较小;类似工况下放大系数为0.976~1.295;堤身及隧道上方土体采用高压旋喷桩加固后,由于“架梁效应”堤顶沉降显著减小;加固体刚度和深度对加固效果影响较大,而加固宽度为隧道直径的4~7倍即可。综合以上研究结果提出相关施工建议。

In order to investigate the impact of shield tunnel on Yangtze River embankment,31 sets of 3D finite element models under different working conditions were established based on Nanjing Xinjizhou water transmission project using nonlinear advanced constitutive model.The results of field measurements and theoretical analysis were integrated to study the relationship between the maximum settlement of the river embankment and the ground surface,revealing the settlement distribution law and reinforcement effect.The results show that when the shield tunnel penetrates the loose fill river embankment,the settlement at the top of the embankment is significantly larger than that at the surface,which weans the presence of the embankment amplifies the surface settlement.The mechanical properties of the soil layer have a significant effect on the settlement amplification effect,while the geometric shape of the embankment has less influence on it.The amplification effect under similar conditions is about 0.976~1.295.After the embankment body and the soil above the tunnel were reinforced by jet grouting piles,the top settlement of the embankment is significantly reduced due to the beam-shape reinforcement.The stiffness and depth of the reinforcement have a greater impact on the reinforcement effect,and the reinforcement width can be 4-7 times of the tunnel diameter.Therefore,the above research results could provide relevant construction suggestions.