考虑地下水位变化特征的高速铁路桥梁桩基沉降精细化计算方法

Currently, settlement control of bridge pile foundation for most of the high-speed railway lines in operation is very effective, but there are the total settlement and differential settlement seriously exceed the norm provision of 20 mm and 5 mm, respectively, some lines even operate within the speed limit to 60 km/h, and the results showed that settlement of pile foundation and groundwater level lowering has a strong correlation. However, there are little literatures can be available on the influence mechanism of pile foundation stability based on groundwater lowering, and the effect of groundwater on the settlement of pile foundation is not considered in design specifications, which will have a significant impact on the high-speed train comfort and security operations. So this project mainly focuses on the refined calculation method of high-speed railway bridge pile foundation based on the variation of groundwater level. Firstly, the typical characteristics of the variation of groundwater level are obtained through the investigation and research, then the systematic study on the influences of variation of groundwater level on the bridge pile foundation under the full considering foundation stress was carried out, soil mechanical parameter, pile-soil interaction and so on, the refined three-dimension finite element model for pile foundation based on the seepage field and stress field are established, to analyze the impaction evolution of bridge pile foundation under groundwater lowering. Based on the characteristics of variation in groundwater level, the improved analytical algorithm of bridge pile foundation settlement are proposed, and the modification proposals for settlement control standard of bridge pile foundation are suggested, and it has great significance for improving the design method and maintenance in bridge pile foundation of high-speed railway technology.

开通运营的大部分高速铁路桥梁桩基沉降控制十分有效，但局部地段存在整体沉降和差异沉降超出现行标准20mm和5mm现象，有的线路甚至限速至60km/h运营，现场长期监测表明桩基沉降与地下水位下降有很强相关性。目前关于地下水变化对桩基影响机理的研究相对较少，设计规范尚未考虑地下水变化对桩基沉降影响，这对高速列车舒适安全运营造成重大影响。本项目以高速铁路桥梁桩基础为研究对象，研究基于地下水变化的桩基沉降精细化算法。通过研究获取典型地区地下水长期变化特征；充分考虑水位下降过程引起的地基应力、土性参数、桩土接触等因素变化，揭示地下水变化过程对桥梁桩基应力变形的影响规律；建立基于渗流场和应力场三维耦合模型、建立考虑地下水变化影响特征的桩基沉降改进解析算法，提出典型地区高速铁路桥梁桩基沉降控制标准的修改建议。研究成果将发展和完善高速铁路桥梁桩基设计方法，为高铁桥梁桩基工程实践和养护维修提供理论和技术支撑。

本课题结合当前地下水位变化对高速铁路桥梁桩基沉降影响的应用需求，开展了地下水变化对高铁桥梁桩基沉降影响规律、基于地下水变化影响特征的桥梁桩基沉降改进解析算法和基于地下水位变化特征的高速铁路桥梁桩基沉降控制标准制定等方面研究，建立了基于密度变化的降水引起桥梁桩基沉降的仿真分析模型、基于渗流分析的降水引起桥梁桩基沉降的桩基渗流-应力耦合分析的三维有限元模型、考虑水位下降的基于佐藤•悟双折线模型的桩侧摩阻力荷载传递模型，构建了基于改进荷载传递法的降水引起基桩沉降的解析计算方法。提出了地下水变化影响高铁桥梁桩基沉降的评估标准和方法。.通过系统研究，提出了地下水变化影响高铁桥梁基础变位的评估方法和控制对策，区域性水位下降引起桥梁桩基沉降主要的分析方法，可采用基于密度变化的降水引起桥梁桩基沉降仿真分析方法、基于渗流分析的降水引起桥梁桩基沉降的仿真分析方法、基于改进荷载传递法的降水引起基桩沉降的解析计算方法等；对于单井抽水水位下降引起桥梁桩基影响的分析方法，可采用完全潜水井单井抽水的渗流分析方法。.当前全球地下水位下降严重，对基础设施长期服役性能影响极大，研究成果对深入认识地下水下降对桥梁桩基沉降的影响问题具有重要意义，成果首次应用于贵广铁路尖山营特大桥地下水引起墩台沉浮的评估，并推广应用于京津城际杨村特大桥、渝利铁路上水涟河双线大桥等多个工点的基础变位评估，为高铁桥梁基础精准维护提供了技术支撑。