Numerical Simulation and Deformation Control of Shield Tunneling Through Soft Soil Layer Pre-reinforcement
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摘要: 依托佛山地铁3号线创驹区间盾构隧道工程，采用数值模拟得到不同加固方式下的地表沉降和隧道变形，研究了盾构穿越全断面软土地层时的变形规律，提出一套盾构安全穿越加固建议，并结合现场实测，验证了模拟结果的正确性。研究表明：盾构在全断面软土地层中推进时，地表沉降、隧道拱顶沉降和水平收敛值均不断增大，且主要发生在盾构通过时及盾尾管片脱出后，同时该段也是预加固的主要作用范围；先行隧道对地表沉降影响大于后行隧道；盾构穿越未加固土层时地表沉降、隧道拱顶沉降、水平收敛最大值分别为27.7 mm、13.78 mm、10.57 mm，采用超前预注浆加固时各变形分别为未加固的57.0%、69.1%、61.0%，采用三轴搅拌桩预加固时各变形分别为未加固的32.1%、50.2%、43.0%，预加固可有效控制变形，且三轴搅拌桩变形控制优于超前预注浆加固。当盾构区间地面环境复杂，不具备地面加固条件时，建议采用超前预注浆加固控制地表沉降量及隧道变形。Abstract: Relying on the shield tunnel project in the Chuang-Ju section of Foshan Metro Line 3, the surface settlement and tunnel deformation under different reinforcement methods were obtained by numerical simulation, and the deformation law of the shield when crossing the full-section soft soil layer was studied. A set of suggestions for shield tunnel safety crossing reinforcement is proposed, and the simulation results are verified by combining with the field measurement. The research shows that when the shield is advancing in the full-section soft soil stratum, the surface settlement, tunnel vault settlement and horizontal convergence value all increase continuously, which mainly occur when the shield passes through and after the shield tail segment is protruded, and it is also the main scope of action of pre-reinforcement; the impact of the leading tunnel on the surface settlement is greater than that of the trailing tunnel; when the shield passes through the unreinforced soil layer, the maximum values of surface settlement, tunnel vault settlement, and horizontal convergence are 27.7 mm, 14.28 mm, and 10.57 mm, respectively. The deformations of the pre-grouting reinforcement are 57.0%, 66.6%, and 61.0% of the unreinforced ones, respectively. When the triaxial stirring piles are used for pre-reinforcement, the deformations are 32.1%, 48.5%, and 43.0% of the unreinforced ones. The pre-reinforcement can effectively control deformation, and the deformation control of the triaxial stirring pile is better than that of the advance pre-grouting reinforcement. When the ground environment in the shield tunnel is complex and the ground reinforcement conditions are not available, it is recommended to use advance pre-grouting reinforcement to control the surface settlement and tunnel deformation.
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表 1 土层物理力学参数
上层名称 厚度/m 重度γ/（kN·m−3） 切线模量/MPa 割线模量/MPa 卸载模量/MPa 黏聚力/kPa 内摩擦角/（°） 剪切模量/MPa 杂填土 3.0 18.20 4.04 6.06 32.32 6.00 15.00 80.80 淤泥质粉细砂 17.0 17.30 3.00 4.50 24.00 5.00 24.00 60.00 淤泥质土 27.5 17.10 2.50 3.80 20.00 12.70 8.00 50.00 淤泥质中砂 7.8 18.20 3.32 4.98 36.56 4.50 26.50 66.40 
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表 2 材料物理力学参数
名称 材料模型 厚度/m 重度γ/（kN·m−3） 弹性模量E/MPa 泊松比ν 剪切模量G/（kN·m−2） 盾构机盾壳 线弹性 0.35 120 2.3×104 0 11.5×106 水泥土加固体 莫尔库仑 20 165 0.2 60×103 混凝土管片 线弹性 0.35 27 3.1×104 0.1
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表 3 地表沉降随距离变化曲线拟合系数
地表沉降 拟合系数 R2 横断面 s0 a xc w 0.978 −0.678 −34.608 −1.247 5.000 纵断面 b c d 0.976 −9.360 −10.093 0.941
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表 4 隧道变形随掘进距离变化曲线拟合系数
加固方式 拱顶沉降 水平收敛 a1 b1 a1 b1 未加固 −20.10 0.972 −12.00 0.953 三轴搅拌桩预加固 −7.73 0.944 −5.76 0.965
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