软弱地层大断面隧道三台阶七步法与临时仰拱法适应性分析的对比研究

COMPARATIVE STUDY ON ADAPTABILITY ANALYSIS OF THREE BENCHING SEVEN STEPS AND TEMPORARY INVERT METHOD FOR LARGE-SECTION TUNNEL IN SOFT STRATUM

软弱围岩力学性质较差、强度低、自稳能力差。目前在软弱围岩隧道施工中常采用的三台阶七步法经大量工程实践表明存在初期支护变形大、地表沉降大、难以及时封闭、对突发事件的应变能力较差等特点。针对广东赤竹、高栋两座高速铁路隧道洞口段软弱围岩具体条件,进行三台阶七步法和三台阶临时仰拱法两种施工工法的对比试验,在隧道拱顶沉降、周边收敛和地表沉降测试基础上,从工程应用效果以及数值仿真模拟等方面进行了系统的工法适应性研究。结果表明:在该类软弱围岩地层大断面隧道施工中,三台阶临时仰拱法在控制拱顶沉降、地表沉降、围岩应力、塑性区扩展面积及深度方面要优于三台阶七步法,所得结论对其他类似工程具有借鉴意义。

Soft rock has poor mechanical properties,low strength and stability.At present,three benching seven steps commonly used in the construction of a soft rock tunnel have the characteristics of large initial support deformation,large surface subsidence,difficulty in timely closure,and low strain capacity to emergencies,etc.In view of the specific conditions of weak surrounding rock at the entrance of two high-speed railway tunnels in Chizhu and Gaodong of Guangdong province,the comparative tests of three-step seven-step method and threestep temporary inverted arch method are carried out.Based on the tests of tunnel vault settlement,peripheral convergence and surface settlement,a systematic study on the adaptability of construction method is carried out from the aspects of engineering application effect and numerical simulation.The results show that:the three-step temporary invert method is superior to three-benching seven-steps in controlling arch settlement,surface settlement,surrounding rock stress,plastic zone expansion area and depth in large-section tunnel construction of this kind of soft rock stratum.The conclusions can be used for reference to other similar projects.