砂卵石地层双线盾构隧道下穿框架桥变形规律及控制技术研究

Research on Deformation Laws and Control Technology of Double Line Shield Tunnel under Frame Bridge in Sand and Gravel Strata

为探究砂卵石地层双线盾构隧道下穿框架桥变形控制技术与结构变形规律及内力特征,采用经验分析、数值模拟与现场监测的方法,对济南轨道交通4号线一期工程盾构隧道下穿高铁框架桥进行分析。研究表明,360°径向深孔注浆与架设便梁作为盾构下穿铁路施工行车安全关键防护措施,辅以防水加强、行车限速等细部措施,可以保障盾构与铁路安全;轨道竖向位移数值模拟曲线呈漏斗状,受双线盾构叠加影响略微偏移,拉应力最大值在左边跨底板支座处,最大为0.81 MPa,压应力最大值在连续跨右侧顶板跨中处,最大为1.36 MPa,径向注浆深度1.5 m时混凝土结构应力与轨道变形均处于控制范围内;路基与轨道竖向沉降现场实测值波动式增加,时程曲线呈“二谷一峰”,轨道沉降最大值为0.64 mm,框架桥竖向沉降主要由下穿期间施工造成,径向注浆加固与便梁起到较好的隔离加固作用,下穿施工顺利通过铁路影响区,框架桥竖向沉降最大值为0.84 mm。

In order to explore the deformation control technology and structural deformation laws and internal force characteristics of the double line shield tunnel under the frame bridge in the sand and gravel layer,empirical analysis,numerical simulation,and on-site monitoring methods were used to analyze the shield tunnel under the high-speed rail frame bridge of Jinan Metro Line 4 Phase I project.The research results are as follows:360°radial deep hole grouting and installation of temporary beams are selected as key safety protection measures for shield tunneling under railway construction,supplemented by detailed measures such as waterproof reinforcement and speed limit to ensure the safety of shield tunneling and railway.The numerical simulation curve of vertical displacement of the track shows a funnel-shaped shape,slightly offset due to the influence of double line shield tunneling.The maximum tensile stress is located at the left span bottom plate support,with a maximum of 0.81 MPa.The maximum compressive stress is located at the mid span of the right continuous span top plate,with a maximum of 1.36 MPa.When the radial grouting depth is 1.5 m,both the stress of the concrete structure and the deformation of the track are within the control range.The measured vertical settlement values of the roadbed and track on site fluctuate,and the time history curve shows a“two valleys and one peak”pattern.The maximum settlement value of the track is 0.64 mm.The vertical settlement of the frame bridge is mainly caused by the construction during the underpass period,and the radial grouting reinforcement and the convenience beam play a good isolation and reinforcement role.The underpass construction smoothly passes through the railway influence area,and the maximum vertical settlement value of the frame bridge is 0.84 mm.