水泥改良集料侵蚀膨胀性能研究

Erosion and Heave Property of Cement Stabilized Aggregate

在高速铁路路基工程中,盐分引起水泥改良集料侵蚀膨胀进而导致线路上拱破坏的问题日益显现。以我国西部某客运专线铁路车站无砟轨道结构上拱为工程背景,在分析无砟轨道上拱变形原因的基础上,结合室内侵蚀膨胀试验,进行水泥改良集料侵蚀膨胀性能研究。结果表明:无砟轨道上拱变形主要由水泥改良集料的侵蚀膨胀导致,基床表层及地基垫层细颗粒含量及水泥含量高,盐分易聚集且受外部环境影响剧烈,因此更易发生侵蚀膨胀;在较低的碱性(pH<10)环境下侵蚀膨胀也可能发生;盐分侵蚀条件下,水泥改良集料膨胀应变曲线可分为快速增加、缓慢增加和相对平稳3个阶段,持续的上拱变形主要由阶段2导致;侵蚀膨胀量随硫酸钠含量增加而增加,随水泥含量增加先增而后基本稳定;在满足集料强度及变形要求的前提下,可采取降低水泥含量、合理设置隔离层防止盐分迁移的措施,避免发生持续性侵蚀膨胀。

The problem of upper arch damage on lines has been revealed increasingly,as a result of sulfate attack-induced erosion and heave of cement stabilized aggregate,in subgrade projects for high speed railway.Taking the upper arch of the ballastless track structure of the railway station of a passenger dedicated line in western China as the project background,based on analyzing the causes of upper arch deformation of the ballastless track,the research on the erosion and heave property of cement stabilized aggregate was conducted combined with the indoor erosion and heave experiments.The results show that the upper arch deformation on ballastless track is mainly caused by the erosion and heave of cement stabilized aggregate.Due to the high content of fine particles and cement in the surface layer of subgrade bed and the subgrade cushion layer,salt is easily accumulated and severely affected by the external environment,so the cement stabilized aggregate is prone to erosion and heave;the erosion and heave may happen in a relatively low-alkaline environment with pH<10.Under sulfate attacked conditions,the heave strain curve of cement stabilized aggregate can be divided into 3 stages:the rapid increase stage,the slow increase stage and the relatively stable stage,and the continuous deformation of upper arch is mainly caused by the second stage;the erosion and heave increase with the increase of NaSO~2 content,and increase initially and then become leveled off with the increase of cement content.On the premise of meeting the requirements for aggregate strength and deformation,measures including decreasing cement content and adding reasonable separation layers to prevent salt migration can be taken to avoid continuous erosion and heave.