含黄铁矿填料的高速铁路路基上拱特性与机理

Characteristics and Mechanisms of Heave of High-Speed Railway Subgrade Containing Pyrite Filler

黄铁矿氧化膨胀对建筑物、铁路、公路等结构的影响较大,易引发结构物上拱。通过现场勘察、矿物成分分析和变形监测,系统研究含黄铁矿填料路基上拱病害特征,探究摩擦板及端刺结构型式、路基填料高度对路基上拱变形的影响,分析黄铁矿氧化膨胀反应机理和膨胀特性,以明确路基上拱原因。结果表明:所有上拱区段路基填料均检测出含有少量黄铁矿和石膏;上拱变形主要产生在路基高度范围内,线路开通后路基以0.13~0.46 mm·m^(-1)的速率持续上拱;半填半挖区段轨道结构的上拱量沿路基横向随填方高度的降低呈递减关系;路桥过渡段范围轨道垂向变形特征与摩擦板及端刺结构型式密切相关,摩擦板及端刺结构对路基上拱变形存在抑制作用;黄铁矿氧化是一个长久且持续过程,其生成硫酸盐引发的一系列化学反应所伴随的体积膨胀是造成路基上拱的主要原因;为彻底消除该隐患,应对含黄铁矿填料采取暗挖置换措施。

Pyrite oxidation expansion has significant engineering implications,easily inducing heave deformation in structures such as buildings,railways and highways.Through the field investigation,deformation monitoring and mineral composition analysis,this paper systematically analyzes characteristics of heave diseases in subgrade containing pyrite fillers,explores the correlation between heave deformation and the friction plate and end spine,as well as the height of subgrade filler,and analyzes the expansion reaction mechanism and characteristics of pyrite oxidation,so as to clarify the cause of subgrade heave.The results show that small amounts of pyrite and gypsum are detected in all subgrade fillers of the heave section.The heave deformation mainly occurs within the height range of subgrade,with a continuous heave rate of 0.13-0.46 mm·m^(-1) since the opening of the railway.The heave deformation of track structure in the half-filled and half-excavated section decreases along the transverse direction of subgrade with the decrease in the filler height.The vertical deformation characteristics of the track in the transition zone between the road and bridge are closely related to the structure of friction plate and end spine,which exhibit inhibitory effects on the subgrade heave deformation.Pyrite oxidation reaction is a long-term and continuous process,and the volume expansion accompanying the chemical reactions resulting from sulfate production is the main cause of subgrade heave deformation.To thoroughly eliminate this hazard,underground excavation and replacement measures should be taken for the filler-containing pyrite.