重载铁路膨胀土路堑基床结构长期动力稳定性研究

Compared with the high-speed railway, the subgrade dynamic characteristics of heavy-haul railway is significantly different, and it directly affects the long-term dynamic stability of subgrade. Establishing and improving the long-term dynamic stability evaluation system of subgrade is a vital theoretical and engineering problem extremely anxiously to solve at this stage China’s heavy-haul railway. With the cutting subgrade structure of expansive soil of heavy-haul railway project, as the research objective, study on the long-term dynamic stability of cutting subgrade structure by combing theoretical analysis, real vehicle experiment and numerical simulation method to study. Based on dynamic triaxial of fatigue test, resonant column test and cross hole wave velocity method for achieve the dynamic stability evaluation indicators of expansive soil. Establishing the humidity field calculation model of expansive soil foundation for consider humidity changes cause the expansive force, and proposing the evaluation methods and evaluation indicators of long-term dynamic stability of expansive soil cutting subgrade of heavy-haul railway. Building the dynamic computational model of track – ballastbed – subgrade - expansive soil foundation system for developing the dynamic analysis program of cutting subgrade structure of heavy-haul railway. Revealing dynamic response characteristics and load transfer rule of expansive soil cutting subgrade structure under heavy-haul loads coupling with climate factors. On the base of this method, make sure of the reasonable replacement thickness of cutting subgrade of expansive soil and reinforcement depth of foundation. Improving and perfecting the long-term dynamic stability evaluation system, the innovation results of theoretical depth and application prospect is obtained, and its will be incorporated in the "code for design of heavy-haul railway subgrade". The results can provide theoretical base and evaluation systems for similar projects.

与高速铁路相比，重载铁路路基动力特征发生了显著变化，直接影响路基的长期动力稳定性，尽快建立路基长期动力稳定性评价体系,是我国重载铁路面临的重大问题。项目以重载铁路膨胀土路堑基床结构长期动力稳定性为研究对象，运用理论分析、模型试验和数值模拟相结合的方法，开展疲劳动三轴等试验，获得膨胀土动力稳定性评价指标；建立膨胀土地基湿度场模型，考虑湿度变化导致膨胀力变化特点，提出重载铁路膨胀土路堑基床长期动力稳定性评价方法和评价指标；构建道床－基床－膨胀土地基动力计算模型，编制重载铁路路堑基床结构动力分析软件；揭示重载和气候因素耦合作用下膨胀土路堑基床结构动力响应特征、荷载传递规律及动力稳定性；确定膨胀土路堑基床合理换填厚度和地基加固深度；改进和完善长期动力稳定性评价体系，获得具有一定理论深度和应用前景的创新成果，并纳入《重载铁路路基设计规范》，为类似工程提供理论依据和评价体系。

重载铁路与高速铁路的路基动力特性存在明显差异，传统的路基长期动力稳定性评价方法并不能适用于重载铁路路基。此外，膨胀土显著的胀缩变形特性使得铁路膨胀土路基面临更为不利的动力与变形响应状态，降低了铁路路基的长期动力稳定性。本课题依托云桂铁路、京沈铁路及浩吉铁路膨胀土路基、路堑工程，通过室内模型试验、现场实车试验、理论分析及数值模拟方法研究了重载铁路膨胀土路基/路堑基床结构长期动力稳定性。开展了动三轴、共振柱和和跨孔波速法等试验，获得了膨胀土的基本性能参数与动力参数；基于膨胀土地基湿度监测结果，建立了膨胀土地基湿度场模型，揭示了不同服役环境下膨胀土地基中应力场、位移场与湿度场的关系；构建了重载铁路轨道-道床-基床-膨胀土地基动力计算模型，并编制了对应的铁路路基动力分析软件；结合动力模型试验、现场实车试验和数值分析，揭示了列车荷载与气候环境耦合作用下膨胀土路基/路堑基床结构的动力响应、衰减及其分布特征；考虑湿度变化导致膨胀力变化特点，提出了重载铁路膨胀土路基/路堑基床长期动力稳定性评价指标(即累积塑性变形)，建立了改进的长期动力稳定性评价体系；利用新的评价体系确定了依托工程中的膨胀土路基/路堑基床结构合理换填厚度与地基处治深度。本课题研究成果对膨胀土地区铁路路基结构设计、施工及其维护具有重要的理论意义和工程价值，力争在《重载铁路设计规范》下一轮修订中将研究成果纳入其中，便于在类似工程中推广应用。