摘要:
轻非水相液体(LNAPL)在变隙宽裂隙中的迁移和残留机理复杂,在"裂隙-水-LNAPL"三相系统中,LNAPL和水流运动之间相互作用和影响,同时两者又共同受到裂隙表面和隙宽的影响和控制。采用27.4 cm×20.0 cm(长×宽)的透明仿真裂隙开展甲苯(地下水中常见的LNAPL污染物之一)迁移试验,监测并获取变隙宽裂隙中LNAPL的迁移过程与残留分布的图像,通过数学统计和数值模拟的方法,分别揭示LNAPL 残留分布规律以及"裂隙-水-LNAPL"系统内的相互影响机制。研究结果表明:自由相的LNAPL主要沿着裂隙中的狭长通道迁移到内部,在隙宽较小的区域有少量孤立的LNAPL液滴残留。LNAPL在变隙宽裂隙中的迁移、残留与裂隙隙宽的分布密切相关,LNAPL残留的隙宽符合正态分布规律。甲苯残留的隙宽分布范围为0.01~1.40 mm,残留最多的隙宽分布在0.20~0.30 mm。LNAPL的残留增大了裂隙内水流运动的阻力,使得裂隙两端的压力差增加。LNAPL残留使裂隙内水流流速重新分布,同时也改变了裂隙原有的沟槽流分布和数量。
Abstract:
The mechanism becomes very difficult to realize when light non-aqueous phase liquid (LNAPL) migrates with residue in the variable-aperture fracture. The immiscible liquids in the 'fracture-water-LNAPL' system can affect and interact with one another. Meanwhile, these liquids are confined and controlled by the fracture surfaces and the aperture. We performed a toulene migration experiment with the use of a transparency replica fracture with a length of 27.4 cm and a width of 20.0 cm. Some LNAPL migration images and entrapment configuration were first acquired. We then analyzed the geometric characteristics of the LNAPL entrapment configuration and clogged aperture. We also compared the water flow in the fracture before and after LNAPL entrapment through numerical modeling. Results show that free phase LNAPL invaded the fracture through a gallery with large aperture, and some isolated LNAPL blobs were entrapped at a tight aperture area. The location of the LNAPL migration and residue is closely related to the aperture, and the frequency of the clogged aperture followed a normal distribution. The range of the clogged aperture is from 0.01 mm to 1.40 mm, whereas the distribution centered at 0.20 mm to 0.30 mm. As the water flow resistance was increased in the entrapment configuration, the pressure difference between the inlet and outlet increased after the entrapment. Residual LNAPL caused water flow velocity redistribution, and changed the distribution and amount of channel flow.
百度学术
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