石灰桩热融加固高温冻土机理研究

According to the design principles of pre-thawing of permafrost foundation, using the water absorption and heat release of lime to pre-thawing and reinforce permafrost foundation is a new method for keeping engineering stability. This method has been used in airport construction in warm permafrost regions. With consideration of moisture and thermal characteristics of warm permafrost, this project will study the thermal-reinforce mechanics of lime pile on warm permafrost foundation. Methods including laboratory mode test, numerical simulations, and field monitoring will be used to quantify the heat release processes of lime pile, moisture and thermal responses of surrounding soils, and reinforcement effect of thawed soils. The quantified relationship between the total heat release of lime pile and the pile mixture ratio, and type, temperature and ice content of foundation soils will be gained, and a heat release model of lime pile will be constructed. Then, the thawing process and extent of surrounding soils will be studied, and a calculation method of thawing extent considering multi-factors will be proposed. With the results above, optimization method of pile spacing will be presented for pre-thawing of warm permafrost foundation. The research achievement will provide some scientific basis for application and optimization of lime pile in warm permafrost regions.

根据多年冻土地基预先融化原则，利用石灰桩吸水放热特性对高温冻土地基进行预先融化加固，是一种处理高温冻土地基的新思路，目前已在高温冻土区机场建设中试验性应用。本项目针对石灰桩热融加固高温冻土地基机理，充分考虑高温冻土的水、热特征，利用室内模型试验、有限元数值仿真试验、现场监测相结合的方法对石灰桩放热演化规律、放热过程中桩周土体水热响应规律以及融化范围内土体的加固效果开展研究。明确石灰桩放热量与桩体材料配合比、地基土质、温度、含冰量等因素间的定量关系，建立石灰桩放热演化模型。确定放热过程中桩周冻土融化过程及范围，建立考虑多因素的桩周冻土融化半径数学计算方法，并结合实际加固效果对桩距进行优化。项目的顺利实施，将为石灰桩在高温冻土地基加固中的应用和优化设计提供科学依据。

基于多年冻土地基预先融化的原则，利用生石灰的吸水、放热、膨胀特性对高温冻土地基预先融化并加固，是一种处理高温冻土地基的新思路。但目前石灰桩多用于湿陷性黄土、软土地区，对石灰桩热融加固高温冻土地基方面的研究较少。. 为此，首先根据漠河机场下多年冻土2007~2016年的地温数据，研究了该处多年冻土的退化过程与活动层冻融特点，明确了石灰桩的工程应用背景。其次，开展了石灰桩放热室内模型试验，掌握了生石灰掺量、桩周冻土土质、温度及含冰量对石灰桩放热量的影响，揭示了石灰桩在高温冻土地基中的放热演化规律。试验结果表明：桩周土土质、温度、含冰量以及生石灰掺量对石灰桩放热均有影响，其中生石灰掺量的影响最大。对试验结果拟合，得到了石灰桩放热演化模型即石灰桩放热量与时间的关系函数。再次，利用模型试验获得的放热模型及计算参数，建立了石灰桩放热数值模型，进行桩周冻土融化过程的数值仿真正交试验，提出了石灰桩融化半径计算公式，并对石灰桩桩距设计进行了优化。