【作者】 鲁四平；

【导师】 黄方林；

【作者基本信息】 中南大学 ， 土木工程， 2013， 博士

【摘要】 摘要：大型综合交通枢纽的建设,加剧了站房改造深、大基坑开挖与既有线运营的矛盾。为缓解矛盾、缩短工期、降低成本,线下深基坑与其他区域深基坑同步开挖的“一步走”模式应运而生。该模式要求为线下深基坑开挖设计特殊桥梁,深基坑开挖使得桥梁结构的边界条件不断变化,导致列车-轨道-桥梁-基坑这一庞大系统的静力、动力相互作用。为确保“一步走”模式的安全实施,对这种具有强时变特征的时变系统的力学性能进行研究显得非常迫切和重要。目前,国内外尚没有针对这种强时变系统的相关研究。鉴于此,本文以宁波南站交通枢纽改建工程为背景,对软土深基坑开挖条件下宁波南站新型铁路桥(以下简称宁波桥)的静、动力学性能及其在施工和运营过程中的安全监测技术进行了研究。主要研究内容和取得的成果如下：1.比较了“一步走”和传统“两步走”施工模式的优劣,对软土深基坑开挖条件下,列车-轨道-桥梁大系统的相互作用及安全监测、信号处理等方面的研究现状进行了系统回顾。2.采用实体单元模拟道床建立了轨道-桥梁有限元模型,探讨了土与结构相互作用的有限元模拟方法,提出了土弹簧竖向刚度的计算公式,研究了桥下深基坑开挖过程中恒载、温度等对其力学性能的影响,确定了桥两侧基坑开挖不同步的允许深度差限值,为施工和行车安全提供了依据。3.采用接触单元模拟轮轨作用,基于ANSYS建立了考虑桥下深基坑开挖的列车-轨道-桥梁大系统模型。以APDL编制了“位移耦合法”系统非线性动力响应分析程序、“位移耦合法”结合“动态特征值法”非线性动力稳定性分析程序。以宁波桥为例,对其在深基坑开挖条件下的动力特性、车桥响应和动力稳定性进行了分析,验证了程序的有效性。4.提出了强时变概念,明确了强时变铁路桥梁安全监测系统的基本特征,确立了监测系统设计的指导思想和原则,确定了分批安装、分步实施、阈值动态变化的监测系统建设方案,并对该安全监测系统组成、监测内容及仪器选取等问题进行了探讨。5.建立了具有信号采集、处理、报表生成、报警等功能的宁波桥自动化安全监测系统,自主研发了动力监测系统的控制软件和信号分析处理软件,实现了该桥监测信号的在线、高效处理。6.分析比较了宁波桥安全监测系统实测值与有限元计算结果,验证了本文建立的考虑桥下深基坑开挖的列车-轨道-桥梁大系统有限元模型的合理性。监控期间,该桥各项监测指标安全可控且运营状态良好。本文研究成果为枢纽改建工程实现“一步走”模式的成功运用提供了重要的实测数据和有力的技术支持。更多还原

【Abstract】 Abstract:The construction of large-scale comprehensive transport hub, lead the contradiction between large and deep excavation and existing railway line operation to further intensified. To ease the contradiction, shorten the construction period and reduce costs, the "one step" mode that the deep pit of all regions include both sides and down of the existing railway excavated synchronously emerge as the times require. This mode requires the design of special bridges to realize the deep excavation under the existing railway line. The boundary conditions of this special bridge are constantly changable during the process of excavation, which leads out the static and dynamic interaction problems of the Train-Track-Bridge-Pit large system. To ensure the security of the "one step" mode in implementation, it is an urgent and important subject to study the mechanical properties of this time-varying system that has strong time-varying characteristics. Currently there is still no related research response to this strong time-varying system at home and abroad. In view of this, taking the construction of Ningbo south station hub transformation as the background, the static and dynamic performance of the new bridge used in construction of Ningbo South Station Hub transformation (Ningbo Bridge) under deep excavation in soft soil and the safety monitoring techniques during the process of deep excavation are studied in this paper. The main contents and results obtained are as follows:1. The advantages and disadvantages of the "one step" and the traditional "two-step" construction mode are summarized, and the research status of interactions of Train-Track-Bridge system and safety monitoring, signal processing and other aspects are reviewed.2. A finite element model of Track-Bridge is established by using solid elements to simulate the ballast, finite element simulation method of the interaction between soil and structure and the determination of its parameters is discussed. The vertical stiffness formula of soil spring is proposed. Taking the Ningbo Bridge as the object, the static performance under dead load and seasonal temperature variation are analyzed. The allowed difference between two sides of the bridge is determined when the pit is excavated unsynchronized, which provides evidence for the construction and operation safety.3. Using contact element to simulate the wheel-rail contact relation, a finite element model of Train-Track-Bridge coupling system by considering deep excavation is established based on ANSYS. The nonlinear dynamic response analysis procedures "displacement coupling method" and nonlinear dynamic stability analysis procedures "dynamic eigenvalue method" combined with "displacement coupling method" are programmed by using APDL. Taking the Ningbo Bridge as the object, its dynamic characteristics, train-bridge responses and dynamic stabilities under deep excavation are analyzed. The effectiveness of the program is verified.4. The concept of "strong time-varying system" is proposed, the basic characteristics of safety monitoring system for strong time-varying railway bridge are made clear, and the guidelines and principles in design of the monitoring system is established. The construction scheme of the monitoring system installation in batch and implement step by step with dynamic thresholds is determined. The basic components, monitoring content and selection of sensors and instruments are investigated in detail.5. The automated safety monitoring system for the Ningbo Bridge with functions of signal acquisition, processing, report, early warning and alarm is built. The dynamic control software for monitoring system and signal analysis software are developed independently to achieve the monitoring signals processing online and efficiently.6. The measured signals by the Ningbo Bridge safety monitoring system are analyzed and compared with the finite element results. The rationality of the finite element model of Train-Rail-Bridges large system by considering deep excavation is verified. All the monitoring indicators are safe and controllable, and the operation is in good condition during whole monitoring period. The study achievements of this paper provide important measured data and strong technical support for the successful use of "one step" mode in construction project of hub transformation.更多还原