【作者】 左珅；

【导师】 徐林荣；

【作者基本信息】 中南大学 ， 土木工程， 2014， 博士

【摘要】 伴随高速铁路快速发展,出现越来越多的新老线并行情况,新建铁路施工往往导致紧邻运营路基变形过大而直接影响到紧邻运营铁路行车安全,故仅仅考虑路基稳定性分析不足以确保安全运营,为此,开展新建高铁对紧邻运营铁路路基服役状态研究。本文依托沪宁城际铁路科研项目,研究通过静动力现场测试、理论分析、有限元计算与轨检车资料分析等手段,在新老线紧邻位置设置试验段,开展施工扰动下紧邻运营路基变形应力与动力响应测试,从力学角度计算施工不同阶段运营路基内部变形与应力,数值分析施工扰动下运营路基服役状态与极限状态,依据测试与计算提出并实施工程应对措施,建立运营路基状态评估体系,研究主要取得了以下成果：(1)针对新建高铁施工对紧邻运营铁路路基扰动影响这一新的问题,提出一套静、动力相结合的运营路基安全监控方法。静力测试得到运营铁路路基最敏感指标——路基坡脚水平位移；动力测试获取路基振动加速度、振动位移等变化分布规律,分析列车类型、车速对路基的影响,实现了施工扰动下运营路基服役状态监测。(2)针对施工扰动下运营铁路路基不同区域应力变形等参量变化无法监测的问题,基于圆柱形孔扩张理论,考虑路基基坑开挖与地基沉桩,建立了计算邻近运营路基径向应力与位移的解析公式,并给出了群桩挤土效应叠加计算方法。计算结果与试验数据相互验证,实现对运营铁路路基内部变形预测,可为类似邻近工程建设提供理论支撑。(3)采用有限元模型计算分析施工三阶段(路基基坑开挖、成桩、路基填筑),得出开挖阶段运营路基最危险,并分析列车通过速度的影响；在此基础上,获取新建路基基坑长期浸水条件下运营路基稳定性变化规律,振动打桩对紧邻运营路基动力扰动影响；此外,数值分析获取了运营路基振动位移、振动加速度、侧向位移阈值,为测试与计算数据提供安全控制标准。完善了施工期间对运营铁路路基服役状态的监控与预警。(4)针对测试与计算发现的施工扰动导致运营路基存在变形超限与失稳的隐患,提出并在工程现场成功实施了地基处理设计变更和边坡防护措施。建议将原CFG桩改成浆固碎石桩与管桩,总结提出紧邻既有线静压预应力管桩施工工艺,该技术已申报成为部级工法。工程措施有效的确保了运营铁路行车安全。(5)针对运营铁路路基状态评估影响因素复杂、尚未有权威机构和研究报道建立路基状态评估体系的现状,基于灰色理论与神经网络原理,建立运营路基状态评估模型,模型以路基变形应力数据(测试试验)、TQI(轨检车分析)、稳定性(理论计算)为评价指标,采用灰色聚类法进行指标归一化处理,BP神经网络减小分配权重过程误差,实现多指标影响下运营路基状态评价。更多还原

【Abstract】 With the rapid development of high speed railway, the parallel phenomenon of new built and existing railway becomes more and more problematic. The construction of new built railway often affects the safety of adjacent existing railway subgrade, which often leads to overly large deformation. Thus, analysis only considering the stability of subgrade is not enough to ensure the safe operation of the existing railway. Therefore, the research on new built high-speed railway’s effect on the subgrade service status of adjacent operating railway is carried out in this dissertation. Relying on the Shanghai-Nanjing intercity railway projects, through the static and dynamic field test, theoretical analysis, finite element calculation and data analysis methods (such as track inspection car), located in a test section adjacent to the new and old line position, test items such as deformation stress and dynamic response of operating subgrade are tested. During different construction stages, subgrade deformation and its internal stress are calculated by various mechanics formula. Numerical analysis is adopted to obtain subgrade service and limit state under the construction disturbance. Thus, some engineering measures are suggested and implemented, on the basis of the test and calculation results, and an assessment system of operating subgrade condition is established. Some major achievements of this research are as follows:(1) In view of the new built high-speed railway construction effecting adjacent existing railway subgrade, a set of methods of static and dynamic test are set up to monitor the embankment safety. Subgrade slope toe of existing railway subgrade is tested in static testing, whose results show that the most sensitive index is horizontal displacement; Dynamic test is carried out to obtain subgrade vibration acceleration, vibration displacement change distribution, as well as impact of vehicle types and speed, which realize the dynamic monitoring for existing railway subgrade under construction disturbance.(2) Due to the deformation and stress of existing railway subgrade in different areas cannot be monitored under construction disturbance, based on the cylindrical cavity expansion theory, considering the subgrade and foundation pit excavation and foundation, established analytic formula is given to calculate radial stress and displacement of adjacent existing subgrade. Hence, calculation method considering effect of clump of piles is proposed, whose results are verified by test data. Thus, inside deformation of existing railway subgrade can be predicted, which could provide theoretical support for similar adjacent construction.(3) Finite element analysis is used to analyze the three phases of construction (including pit excavation, piling, subgrade filling), which concluded that the most dangerous stage is during excavation, and the influence of train speed is analyzed; On this basis, long-term stability of operating railway is obtained under foundation pit flooding. Dynamic disturbance influence of pile driving vibration on adjacent existing subgrade is also obtained; In addition, through the numerical analysis, the existing subgrade vibration displacement, vibration acceleration, and lateral displacement threshold are acquired, which provides safety control standard for test and calculated data. Thus, monitoring and early alarm for existing railway subgrade are optimized.(4) Considering the instability and overrun deformation of existing subgrade, foundation treatment design optimization and slope protection measures are put forward and implemented successfully in engineering field. Original design of CFG pile is recommended to convert into solid gravel pile and pipe pile. The construction technology of static pre-stressed pipe pile adjacent to existing railway is proposed, which has been verified as ministerial declaration method. The above engineering measures effectively ensure the safety for operating the existing railway.(5) Aiming at problems such as assessment factors of operating railway subgrade condition are complex, no authority or studies established any subgrade condition assessment system, based on grey theory and neural network principle, existing subgrade condition assessment model is established, whose evaluation index features as subgrade deformation stress (by field test), TQI (by track inspection car analysis), stability (by theoretical calculation). The grey clustering method is adopted for index normalized processing, and BP neural network is used for reducing error of the weight distribution process, which can realize the operating state of subgrade assessment under the influence of multi factors eventually.更多还原