硫酸盐侵蚀水泥改良路基段上拱研究

首先对某高速铁路无砟轨道路基上拱问题进行了资料调研,通过现场变形监测、填料取样试验、矿物成分分析等手段,明确了硫酸盐侵蚀水泥改良填料膨胀是引起路基上拱主要原因,然后结合化学反应机理和室内模拟试验,对发生此类膨胀变形的反应条件、膨胀变形特征进行了分析。研究结果表明,膨胀变形主要发生在路基水泥改良填料层位,该土层具有大量硫酸盐侵蚀水泥产物钙矾石和硅灰石膏发育的特征,路基上拱与硫酸盐侵蚀水泥改良土形成钙矾石和硅灰石膏晶体相关;水泥改良填料中相对潮湿的高PH值碱性环境和石膏等硫酸盐矿物的存在是发生此类膨胀变形的必要条件;硫酸盐侵蚀水泥改良填料将发生持续性膨胀变形,上拱持续时间可达数年,破坏性强。本文研究成果可供类似环境下路基工程的建设及相关研究借鉴。

Subgrade heave of sulfate attacking on cement-stabilized filler

A high-speed railway subgrade which experiences a continuous and severe heave after construction is investigated through the delamination deformation monitoring, expansive tests and XRD tests. Sulfate attacking on cement-stabilized filler is the main reason of subgrade heave, and the reaction conditions and the development process of sulfate attacking expansion are analyzed based on the mechanism of crystal growth and chemical reaction. The results show that the cement-stabilized filler where the ettringite and thaumasite are identified has obvious swelling deformation, and the subgrade heave relates to the crystal formation of ettringite and thaumasite caused by sulfate attacking on cement-stabilized filler. The relatively humid alkaline environment and existence of sulfate minerals in cement stabilized filler are the necessary condition for such sulfate attacking expansion. The sulfate attacking on cement-stabilized filler exhibits a long-term persistent heave characteristic, and typical expansion of this type may develop for several years to create a critical and dangerous situation.