NUMERICAL SIMULATION OF SUBSEA SHIELD TUNNELING PROCESS
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摘要: 为精确模拟海底盾构隧道掘进过程的施工力学效应,以厦门地铁2号线海底盾构段工程为依托,建立盾构机-注浆体-围岩-海水相互作用的三维数值模型,全面考虑施工影响因素,如开挖面泥水压力、千斤顶推力、盾构机超挖、机身与土体相互作用、注浆压力、海水压力、壁后注浆的时空变化性质等,通过计算结果与实测的验证后,对开挖面支护压力、地层损失率、注浆压力和千斤顶力等4种因素进行参数变化分析。结果表明:初期管片水土压力受到的施工扰动较为强烈,之后先大幅快速下降,降幅在100kPa左右,再缓慢降低,降幅在20kPa左右,最后趋于稳定;开挖面支护压力设为320kPa左右最为合理,增大支护压力,仅对开挖面前方一定范围内土体变形有影响,由于埋深较大,对地表竖向位移基本没有影响;地层损失率对地层沉降、管片上浮及管片内力的影响较大,随着地层损失率增大1%,地表沉降增大241.3%,管片上浮量降低38.2%,弯矩减少23.9%;注浆压力对管片上浮和管片内力有较大影响,注浆压力增大10%,管片上浮量增大32.1%,弯矩增大24.3%;千斤顶力主要对沿隧道轴向的管片轴力有一定影响,对管片上浮和管片弯矩影响很小。研究成果可为管片结构设计及海底盾构施工参数控制提供更加合理的参考建议。Abstract: To accurately simulate the construction mechanical effects of the subsea shield tunneling process, this study develops a three-dimensional numerical model of shield machine-grouting body-surrounding rock-seawater interaction based on the subsea shield section of Xiamen Metro Line 2. By validating the analysis results with measured data of the project, the effects of four main factors(excavation face support pressure, formation loss rate, grouting pressure, and jacking force) are further investigated. The results show that the water and soil pressure of the segment is strongly disturbed by the construction at the initial stage, and then decreases sharply and rapidly at a decrease of about 100kPa, and then decreases slowly at a decrease of about 20kPa, and finally tends to be stable. It is most reasonable to set the support pressure of the excavation face at about 320kPa. The increase of the support pressure only affects the soil deformation within a certain range in front of the excavation. Due to the large buried depth, the vertical displacement of the surface is basically not affected. The ground layer loss rate has a great influence on ground settlement, segment buoyancy, and segment internal force. As the stratum loss rate increases by 1%, the surface subsidence increases by 241.3%, the segment buoyancy decreases by 38.2% and the bending moment decreases by 23.9%. The grouting pressure has a great influence on segment buoyancy and internal force. The grouting pressure increases by 10%, segment buoyancy increases by 32.1%, and bending moment increases by 24.3%. The study also demonstrates that the jacking force has a certain influence on the axial force of the segment along the tunnel axis but has little influence on the segment floating and bending moment. This research provides a reliable analysis of the construction mechanical effects of the subsea shield tunneling process, which has an in-depth influence on the segment structure design and subsea shield construction parameter control.
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表 1 围岩材料参数
Table 1. Material parameters of surrounding rock
参数 中砂 重度γ/kN·m-3 20 三轴固结排水剪切实验的参考割线模量E50ref/kN·m-2 7000 固结实验的参考切线模量Eoedref/kN·m-2 7000 三轴固结排水卸载-再加载试验的参考卸载再加载模量Eurref/kN·m-2 35 000 与模量应力水平相关的幂指数m 0.5 有效黏聚力c′/kN·m-2 1 有效内摩擦角Ф′/(°) 32 割线剪切模量衰减为0.7倍的初始剪切模量G0时对应的剪应变γ0.7 0.000 25 小应变刚度试验的参考初始剪切模量G0ref 70 000 x、y、z向渗透系数/m·d-1 5 表 2 管片和注浆材料参数
Table 2. Parameters of segment and grouting material
参数 管片 注浆体(1~4d) 注浆体(>5d) 材料模型 线弹性 莫尔-库仑 莫尔-库仑 单元类型 实体单元 实体单元 实体单元 γ/kN·m-3 25 14 14 E/kN·m-2 26.62×106 12×103 20×103 v 0.15 — 0.2 c′/kN·m-2 — 525 1030 Ф/(°) — 40 45 表 3 板单元材料参数
Table 3. Material parameters of plate element
参数 γ/kN·m-3 d/m E/kN·m-2 v G/kN·m-2 盾构机 25 0.17 200e6 0 100e6 内力积分板 0 0.35 35.5e3 0.15 15.43e3 表 4 盾构从第5环推进到第6环的模型设置
Table 4. Model setting of shield from ring 5 to ring 6
步骤 说明 1 冻结第5环管片端面的千斤顶反力 2 冻结第6环范围内的盾壳板单元、接触面单元及板单元收缩 3 激活第6环范围内的管片和注浆体单元,并替换相应的材料 4 激活第6环范围内的注浆体单元的体积应变,并设置双向膨胀系数,模拟注浆压力 5 激活第6环管片端面的千斤顶反力,法向压力-1500kN·m-2 6 冻结原开挖面上的支护压力 7 冻结原开挖面前方一环范围内的土体 8 激活原开挖面前方一环盾壳及接触面 9 激活新的开挖面支护压力 10 激活盾壳收缩,对整个盾壳设定收缩率 表 5 地层损失率影响
Table 5. Influence of formation loss rate
地层损失率/% 地表沉降/mm 管片上浮/mm 管片弯矩/kN·m 0.5 10.9 34.3 176.4 1.0 22.7 25.6 148.9 1.5 37.2 21.2 134.3 表 6 注浆压力影响
Table 6. Influence of grouting pressure
膨胀系数/% 管片上浮/mm 管片弯矩/kN·m 40 34.3 176.4 50 45.3 219.2 60 54.9 249.3 表 7 千斤顶力影响
Table 7. Jack force effect
千斤
顶力
/kN·m-2管片
上浮
/mm管片轴力
N1
/kN·m-1管片轴力
N2
/kN·m-1管片弯矩
M11
/(kN·m)·m-1管片弯矩
M22
/(kN·m)·m-11500 34.3 1288/-4353 1408/-5609 77.2 176.4 2000 34.4 1066/-4581 1388/-5586 76.9 176.4 -
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