高压富水碎裂状岩层小半径曲线盾构隧道施工技术

Construction Techniques for the Small-radius Curved Shield Tunnels in Water-rich Fractured Stratum with High Pressure

在不良岩土工程条件下,盾构施工将会遇到刀具切削效果差、掘进参数设置不合理以及喷涌等技术难题。文章针对福州地铁高压富水、碎裂状岩层和长距离小半径曲线等施工难点,通过对滚刀切削力的理论计算,分析了刀具的力学性能,提出了合理的刀具配置、掘进参数和刀具更换时机;通过实践探索,采用了螺旋输送机改造、出碴控制和地面降水相结合的防喷涌措施;通过数值模拟方法分析了小半径曲线段盾构掘进开挖面稳定情况,并总结出了长距离小半径曲线段盾构掘进以及姿态控制措施。结果表明:(1)盾构机在碎裂状岩层中掘进时,岩块对于刀具的侧向冲击力很大,需对滚刀采取加固措施;(2)在总推力上升4 000～7 000 kN、扭矩上升1 000～1 500 kN·m、掘进速度小于10 mm/min时,应结合碴样情况,考虑在合适的时机进行换刀;(3)采用所研发的螺旋输送机防喷涌装置,结合地面降水和出碴控制措施,可有效减少喷涌的发生;(4)本工程盾构机在小半径曲线上长距离掘进过程中,轴线最大偏移量、管片安装高程偏差均满足盾构施工规范要求。

A variety of construction problems, such as bad cutting effects of cutters, unreasonable boring parame-ters and blowout, are often encountered during shield tunnelling under unfavorable geological conditions. Aimed atthese construction difficulties of high pressure, abundant underground water, fractured rock stratum, long distanceand small-radius curves of Fuzhou metro, the mechanical behaviors of cutting tools were analyzed through theoretical calculations of cutter cutting force, then the reasonable cutter configuration, tunneling parameters and the propertime for cutter replacement were presented. Some measures, such as screw conveyor renovation, mucking controland lowering of groundwater, were adopted for controlling blowout based on practice. The stability of excavation facewas analyzed by numerical simulation, and the measures for shield boring and posture control in the long distanceand small radius curved tunnels were summarized. The conclusions are as follows: 1) when shield machine is drivenin fractured stratum, the effect of lateral impact force produced by spalling rock on cutter will be very large and rein-forcement is needed for cutter; 2) cutter replacement should be taken at proper time based on muck samples in conditions of increasing of total shield thrust by 4 000-7 000 kN, cutter torque by 1 000-1 500 kN·m and drivingspeed smaller than 10 mm/min; 3) adopting screw conveyor device with innovative anti-blowout devices and controlmeasures for ground precipitation and mucking, it controls blowout effectively; 4) the maximum axis offset and theheight offset of segment meet the requirements of shield construction specifications during shield construction oflong distance small-radius curved tunnel.