摘要
降雨入渗过程中铁路路基填料内水、气两相渗流特性对路基填料的服役性能具有显著影响。在以往的研究中,通常假定孔隙气压力恒等于大气压力,而忽略了孔隙气压力变化对水流运动的影响。本文基于水-气两相渗流理论,考虑孔隙气压力的影响,建立路基降雨入渗过程中的水-气两相渗流数学模型。参照高速铁路典型路基横断面结构,针对路基各层填料水力特性,利用多物理场仿真软件COMSOL Multiphysics~?中的PDE模块对上述数学模型进行求解计算,结果表明:降雨入渗的主要影响区域是基床表层,特大暴雨持续9 h左右,基床表层基本全部处于饱和状态;而基床底层、路基本体、地基层填料由于渗透性较小,降雨过程中水分很难直接迅速地渗入,通常在基床表层与基床底层交界面处产生水分淤积。此时,若列车荷载反复作用,基床表层与基床底层交界面处填料中细颗粒易软化形成泥浆,产生翻浆冒泥病害。降雨入渗初期,由于渗入路基内部的水对原孔隙内气体的挤压作用,使得孔隙气压力逐渐增大,随着降雨时间的增加,受挤压的气体逐渐向下消散,孔隙气压力逐渐减小至接近大气压力值。孔隙气压力的增加会对路基内水流的运动产生阻滞作用,使得路基内孔隙水压力的增长变缓甚至孔隙水压力略有减小,因此,在求解路基降雨入渗的问题时,不能忽略土体内受压空气对水流运动的阻滞作用。
In the process of rainfall infiltration, the seepage characteristics of water and air in the railway subgrade filler have a significant influence on its service performance. In previous studies, it is usually assumed that the pore air pressure is equal to the atmospheric pressure, and the influence of pore air pressure on the water flow characteristics is ignored. Based on the two-phase flow theory, the mathematical model of water-air two-phase flow in railway subgrade under rainfall infiltration was established. On this basis, the processes of water flow and air transport in a typical cross-section of high-speed railway subgrade substructure under a long heavy rainfall were simulated with the proposed water-air two-phase model by the PDE module in COMSOL Multiphysics.The hydraulic characteristics subgrade filler in each layer were considered. The results are drawn as follows.The rainfall infiltration mainly affects surface layer of subgrade bed, which is basically saturated with heavy rain lasting for about 9 h. Due to the low permeability of bottom layer of subgrade bed, subgrade body and base filler, it is difficult for water to penetrate below, and the water deposition usually occurs at the interface between the surface layer and the bottom layer of subgrade bed. At this time, if the train load is repeated, at the interface between the surface layer and bottom layer of the subgrade bed are easy to soften and form mud,resulting in mud pumping. At the initial stage of rainfall infiltration, the pore air pressure gradually increases due to the squeezing effect of water penetrating into the subgrade, and then with the dissipating of compressed air, the pore air pressure gradually decreases to the atmospheric pressure. The increase of pore air pressure will block the movement of water flow in subgrade, which slows down the increase of pore water pressure and even slightly decreases the pore water pressure. Therefore, when solving the problem of subgrade rainfall infiltration, the blocking effect of compressed air on water flow movement cannot be neglected.
作者
贾羽
王晅
丁瑜
张家生
陈晓斌
JIA Yu;WANG Xuan;DING Yu;ZHANG Jiasheng;CHEN Xiaobin(School of Civil Engineering,Central South University,Changsha 410075,China;National Engineering Research Center of High-speed Railway Construction Technology,Central South University,Changsha 410075,China)
出处
《铁道科学与工程学报》
EI
CAS
CSCD
北大核心
2022年第11期3225-3234,共10页
Journal of Railway Science and Engineering
基金
国家自然科学基金资助项目(51978674)。
关键词
铁路路基
降雨入渗
水-气两相渗流
数值计算
railway subgrade
rainfall infiltration
water-air two-phase flow
numerical calculation
