繁华城区浅埋隧道应用单臂掘进机开挖适用性研究——以新红岩隧道下穿地下商场工程为例

Adaptability Analysis of Single-Cantilever Tunneling Machine in Shallow-Covered Tunnel Excavation in Busy Urban Areas:a Case Study on New Hongyan Tunnel Crossing underneath Underground Shopping Mall

为进一步探索单臂掘进机在浅埋、近接既有建(构)筑物和铁路大断面隧道开挖中的适用性,以成渝客专新红岩隧道下穿地下商场为工程背景,从隧道非爆法开挖方法的比选、外围环境及围岩岩性的分析、数值模拟计算和现场试验等方面进行了分析研究。主要结论如下:1)在浅埋、近接既有建(构)筑物环境中应用单臂掘进机切削法进行隧道开挖,在减小对周边围岩及建(构)筑物的扰动、控制沉降方面效果明显,安全性高;2)在围岩强度为30 MPa左右时,单臂掘进机的开挖掘进效率较高;3)从经济效益上分析,单臂掘进机开挖的成本由于设备投入、功效等因素,较普通机械开挖成本有比较大的增加,在开挖Ⅳ、Ⅴ级围岩时单臂掘进机的施工成本基本一致;4)单臂掘进机开挖受大断面隧道尺寸、隧道安全步距控制等方面的制约,影响其功效正常发挥,导致开挖过程工序相对繁多,降低了隧道掘进速度。对于单臂掘进机切削法,建议在特殊环境、敏感工点、短距离隧道掘进中应用,对于长距离隧道掘进还需进一步优化单臂掘进机开挖的工法体系,以及在砂岩、泥岩夹砂岩围岩环境中的降尘措施。

The aim of this study is to analyze the applicability of single-cantilever tunneling machines in shallow-covered tunnels adjacent to existing buildings and large-section railway tunnels.Studies regarding comparison and selection of non-blasting excavation methods are conducted along with investigation of the surrounding environment and lithology of the surrounding rocks,numerical simulation,and field test of New Hongyan tunnel on Chengdu-Chongqing high-speed railway crossing underneath underground shopping mall.Following conclusions are drawn:(1)The single-cantilever tunneling machine can decrease the construction disturbance on surrounding rocks and buildings,considerably affecting the deformation control and construction safety.(2)The excavation efficiency of single-cantilever tunneling machine is high in surrounding rocks with a strength of approximately 30 MPa.(3)The single-cantilever tunneling machine costs much more than the conventional tunneling machine,and it costs almost the same in GradeⅣandⅤsurrounding rocks.(4)The excavation of a single-cantilever tunneling machine is subject to restrictions of tunnel cross-section size and safe step pitch control,leading to complex excavation procedures and low tunneling efficiency.The machine is recommended for short-distance excavation in delicate construction sites of special environments.Long-distance tunneling requires further optimization of the excavation method system of single-cantilever tunneling machine,as well as dust control measures in the environments mixed with sandstone and mudstones.