新建高速铁路施工开挖使紧临既有线路基边坡一侧临空,列车动载作用下动态变形或累积变形过量将影响路基的正常服役,甚至导致路基失稳.本文依托紧临京沪既有线的沪宁城际高铁建设工程,开展确保既有线安全运营的路基动力响应测试,试验获取既有路基施工三阶段(路基开挖、成桩、路基填筑)振动位移、频率、加速度等参量.测试表明:路基开挖阶段振动响应峰值最大,为既有线路基最危险阶段；各动力响应参量中振动加速度、振动位移在反映路基动力性能、指标控制标准建立具有优势,可作为路基动力稳定性监控的控制指标；路基状态动力测试为开挖边坡防护与施工天窗合理开设时机提供数据支持.%Excavation of newly built high-speed railways adjacent to existing railway lines cause the subgrade slopes of the adjoining sides of the existing lines to midair,excessive dynamic deformations and accumulated deformations under dynamic train loading will affect the normal service of the subgrades of the existing lines and even lead to subgrade instability.Making use of the Shanghai-Nanjing Intercity High-speed Railway Construction Project which was executed along the existing Beijing-Shanghai Railway Line,dynamic subgrade response tests of the existing Beijing-Shanghai Railway Line were carried out in order to ensure the safe operation of the existing Line.From the tests were obtained the parameters of vibration displacements,frequencies and accelerations of the subgrade of the existing Line corresponding to three stages of construction,i.e.,subgrade excavation,pile formation and roadbed filling.The test results show as follows:The largest vibration response peak occurs in the excavation stage,namely the most dangerous stage for the existing subgrade; out of the dynamic response parameters vibration accelerations and vibration displacements are superior in reflecting the dynamic subgrade performance and in establishing the index control standards,so they can be used as the control indexes for dynamic subgrade stability monitoring;dynamic subgrade tests provide data support for slope protection and time of skylight opening in construction.
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