面向多年冻土地区高速铁路建设的温控热桩技术及其环境影响

This project aims to propose a new kind of multifunctional pile called thermal pile to realize the mechanical reinforcement and thermal protection simultaneously against permafrost subgrade by using the model tests, numerical simulations and field tests, in order to provide technical reserves for the high-speed railway construction in permafrost regions in the future, its influence on the environment will also be stidied. For this purpose, the methods of theoretical analysis and engineering application of pile foundation will be developed and improved by systematic model tests, among which the evolutional regularity of pile-permafrost interface properties will be investigated, the calculation model of pile and permafrost will be established, the calculation formula of bearing capacity and the prediction method of long-term cumulative settlement of pile foundation will be proposed by taking the freezing and thawing into consideration, the design method of pile foundation in permafrost regions will be put forward based on the expected target of service performance, and the methods of bearing capacity compensation and settlement control will be compared and selected out. The internal causes of low heat-transfer efficiency and bad seasonal match of the ordinary heat pipe will be revealed. The solar refrigerating heat pipe, which can operate even during the thawing period, will be proposed by adopting the solar refrigerating technology to strengthen the heat transfer process of ordinary heat pipe, and its structure layout will also be optimized by numerical simulations. The thermal pile, which can resist loads and maintain thermal stability of permafrost simultaneously, will be assembled by traditional pile and the newly proposed refrigerating heat pipe. The mechanical and thermal mechanisms of thermal pile will be analyzed by field tests, so will be its structural style with optimal coordination effect. Thus, systematic methods of design, manufacture and application for thermal pile will be proposed.

本项目旨在通过模型试验、数值模拟及现场试验，研制一种能够对多年冻土同时实现力学加固和热学防护的多功能化桩基础—热桩，为未来多年冻土区的高速铁路建设提供技术储备，同时研究其环境效应。为此，系统地开展与完善冻土区桩基础的理论分析和工程应用方法，通过模型试验揭示桩-冻土界面性质的演化规律，建立桩-冻土计算模型，提出考虑冻融作用的桩基承载力计算公式和长期累积沉降预测方法，构建基于服役性能设计的冻土区桩基础设计方法，比选工后承载力补偿和沉降调控方法；揭示路基用热管传热效率低和季节匹配性差的内在原因，研究通过太阳能制冷技术强化热管的相变传热过程，研制出一种能够在暖季制冷的新型太阳能制冷热管，采用数值模拟优化结构布置方案；将普通桩基础和提出的制冷热管联合构成一种既具有力学承载性能、又可以维持冻土热学稳定性的复合热桩，通过现场试验研究热桩改进的热力学双重作用机理和协调效果最优的结构。

面向多年冻土区高速铁路建设，项目聚焦多年冻土区道路工程的稳定性问题，旨在为未来多年冻土区的高速铁路建设提供技术储备，结合模型试验、现场试验与数值模拟手段，取得了如下主要成果：.1）研制出了能够实现全季节制冷的太阳能吸附式制冷热管与压缩式制冷热管，突破了传统热棒暖季无法制冷的技术壁垒。针对制冷新能更优的压缩式制冷热管，基于理论分析，开发了压缩式制冷热管结构选型分析程序。.2）提出了一种既具有力学承载性能、又可以维持冻土热学稳定性的复合热桩，并在青藏高原多年冻土地区首次开展现场应用试验研究。通过现场试验研究与数值模拟，对太阳能制冷路基与热桩的结构参数进行优化分析。.3）系统地开展桩基-冻土界面性质演化规律研究，从冻土-结构接触面直剪试验和桩基静载试验两方面总结前人工作和对寒区桩基设计的启示，总结了从桩侧冻结强度和沉降速率两个指标出发的承载力设计方法。.4）基于层次分析法与熵权法原理，建立了冻土工程生态与地质条件评价体系，可以定性分析工程活动对冻土生态环境的影响，并对冻土地区的地表工程地质条件进行合理评价，相应地，开发出冻土工程生态条件与地质条件分析程序。.总体而言，研究工作极大地丰富了冻土工程领域研究，率先将太阳能制冷技术应用于多年冻土道路工程建设，促进了冻土工程与相关领域学科的交叉融合。