富水砂层土压平衡盾构小半径曲线始发掘进参数控制研究

盾构始发是盾构施工的关键环节，也是盾构施工时的高风险环节。为给南昌地区富水砂层条件下盾构曲线始发施工提供掘进参数设置样本，以南昌市轨道交通3号线绳金塔站—六眼井站盾构始发工程为背景，对富水砂层盾构小半径曲线始发段主要掘进参数进行统计分析，确定相关参数的优势区间，并基于盾体姿态控制参数和地表沉降进行掘进参数控制效果评价。结果表明： 1）盾构水平方向2组油缸推力在曲线段和直线段变化差异明显，线路平曲线半径越小，差值越大，在左右线曲线段和直线段水平方向2组油缸推力分别相差872%和758%； 2）线路平曲线半径越小，所需的总推力和刀盘转矩越大，而掘进速度略有降低，左右线总推力均值为1 3976 t和1 6717 t，刀盘转矩均值为3 1011 kN·m和3 7239 kN·m，掘进速度均值为388 mm/min和351 mm/min； 3）由于始发段掘进断面地层相对均一，土舱压力基本随隧道埋深呈线性增加，而由于右线曲线半径更小，因此右线土舱压力离散程度相对较高； 4）左右线盾尾注浆量差异不大，优势区间均为3~6 m3，均值约为4 m3； 5）左右线曲线始发段水平方向盾体姿态超限率分别为2%和4%，地表累积沉降最大值仅为625 mm，表明本工程小半径曲线始发段掘进参数控制效果较好，掘进参数对地层条件和线路线型具有良好的适应性。

Study on Tunneling Parameters Control for EPB Shield Launching along a Small radius Curve in Water rich Sandy Stratum

Shield launching is a key link in shield tunneling, and also a high risk link. Based on the shield launching project of Shengjinta Station Liuyanjing Station of Nanchang Rail Transit Line 3, a statistical analysis on the main tunneling parameters of the shield launching along a small radius curve in the water rich sandy stratum is conducted, and the advantage interval of related parameters are determined. Finally, based on the shield attitude control parameters and surface subsidence, the driving parameters control effect is evaluated. The results show the following. (1) In the horizontal direction, there is a significant difference between the two groups of cylinder thrust changes in the curved section and the straight section. The smaller the radius of the line horizontal curve, the greater the difference. The thrust differences of the two groups of cylinders in the horizontal direction of the left and right line in curved and straight section are 87.2% and 75.8% respectively. (2) The smaller the horizontal curve radius, the greater the total thrust and cutterhead torque, while the tunneling speed is slightly reduced. The average total thrusts of the left line and the right line are 1 397.6 t and 1 671.7 t, the average cutterhead torques are 3 101.1 kN·m and 3 723.9 kN·m, and the average tunneling speed is 38.8 mm/min and 35.1 mm/min, respectively. (3) As the stratum of the excavation section of the initial section is relatively uniform, the pressure of the soil chamber increases linearly with the buried depth of the tunnel, and due to the smaller radius of the curve on the right line, the dispersion degree of the soil chamber pressure is relatively high. (4) The grouting amounts of shield tail on the left and right lines vary little, and the dominant interval is 3~6 m3, with an average of about 4 m3. (5) The horizontal shield posture overrun rates of the initial section in the left and right line are only 2% and 4% respectively, and the maximum accumulated surface settlement is only 6.25 mm, which indicates that the control effect of driving parameters in the launching section in small radius curve in this project is good, and the driving parameters have good adaptability to stratum conditions and line type.