我国西南地区广泛分布有第四纪堆积体,针对堆积体内部碎石土层状分布的现象,设计了含碎石夹层堆积体降雨物理模型。并考虑了水气两相共同作用,通过有限元数值模拟进行了验证分析,深入探究含碎石夹层堆积体在间歇性降雨条件下的水气两相运移规律。结果表明:孔隙气压力的存在会阻缓降雨入渗,间歇降雨过程中首场降雨期间坡体内孔隙气压力最低,下渗速度最快;每场降雨结束后,土体内部经历暂态饱和区向非饱和区补给的土体饱和度再分布过程,后续降雨湿润锋的推进存在一定滞后性;孔隙气压力在降雨结束后并不会及时消散,其峰值的到来迟于降雨过程,且随着降雨场次的增加,峰值到得越晚;碎石夹层为孔隙气的排出提供了优势通道,相对于均质堆积体,含碎石夹层堆积体内部孔隙气压力消散时间早、速度快,一定程度上促进了雨水入渗。
Abstract
Quaternary deposits are widely distributed throughout southwest China. To address the distribution pattern of crushed stone layers within these deposits, a rainfall physical model test was designed specifically for deposits containing crushed stone interlayer. The test aimed to investigate the migration behavior of water and air within the deposits under intermittent rainfall through finite element numerical simulation. The results indicate that pore air pressure acts as a hindrance to rainfall infiltration in slopes. During the initial rainfall, pore air pressure is at its lowest level, resulting in the fastest infiltration speed. Following each rainfall event, the soil undergoes saturation redistribution from the transient saturated zone to the unsaturated zone, leading to the lag of the advancement of the wetting front during subsequent rainfalls. Pore pressure does not dissipate immediately after each rainfall, but reaches its peak later than the rainfall process. Moreover, as rainfall frequency increases, the peak pore pressure is further delayed. Crushed stone interlayers serve as primary pathways for air discharge. In comparison to homogeneous deposits, pore gas pressure in deposits containing crushed stone interlayer dissipates earlier and more rapidly, which, consequently, promotes water infiltration.
关键词
含碎石夹层堆积体 /
间歇性降雨 /
水气二相流 /
降雨入渗 /
模型试验
Key words
deposits containing crushed stone interlayer /
intermittent rainfall /
water-air two-phase flow /
rainfall infiltration /
model test
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