川中红层水理特性及对无砟轨道变形影响机制分析

WATER-PHYSICAL PROPERTY OF SICHUAN CENTRAL REDBEDS AND IT’S INFLUENCE ON THE DEFORMATION MECHANISM ANALYSIS BALLASTLESS TRACK

针对川中红层易引起无砟轨道上拱变形的问题,开展了川中红层泥岩膨胀特性、水理特性试验研究,在掌握川中红层泥岩膨胀、渗透特性的基础上,结合实际工程进行上拱变形病害区水文环境调查、原位抽水试验以及现场监测,揭示了川中红层的赋存水环境及其运移特征,即川中红层为相对隔水层,所夹节理裂隙及与砂岩界面是其与外界水力联系的主要形式,水力联系通道都是局部、随机分布的,且与自然降雨联系不紧密,赋存水多以透镜体形式存在。在上述特征地层中深挖无砟轨道路基,形成卸荷红层风化裂隙带的同时,改变了原有随机分布的水力联系通道,使得天然状态下相对隔水基底弱风化泥岩与外界建立新的水力联系,膨胀性红层泥岩遇水后膨胀是导致无砟轨道路基持续上拱的内在机制。

For the problem of the upper arch deformation on ballastless track caused by Sichuan Central Redbeds,Experimental study on swelling characteristics and hydraulic properties of mudstone has been carried out. Based on the characteristics of swelling and permeability of the red mudstone in the middle of Sichuan Central Redbeds, combined with actual engineering, hydrological environment investigation, in-situ pumping test and on-site monitoring of the upper arch deformation zone, the water environment and its migration characteristics of Sichuan Central Redbeds are revealed. Sichuan Central Redbeds are relatively aquifer, and the jointed fissures and the interface with the sandstone are the main forms of hydraulic connection with the outside environment. The hydraulic connection channels are localized and randomly distributed, not closely related to natural rainfall and it's occurrence of water is in the form of lens body. Deeply excavating the ballastless track subgrade in the above characteristic stratum cause the unloading Redbeds weathering fissure zone. This changes the original randomly distributed hydraulic connection channel, and makes a new hydraulic connection with the outside environment in the natural state with weakly weathered mudstone. The swelling of expansive Redbeds mudstone after water absorption is the internal mechanism of the continuous upper arch deformation of the ballastless track subgrade.