基于水气二相流的边坡降雨入渗有限元分析
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摘要
为揭示边坡降雨入渗基本规律,基于水气二相流理论,以三峡库区大坪滑坡为例,采用有限单元法分析边坡降雨入渗水气运动规律。结果表明:根据水气流入、流出的方向不同,坡表可分为吸入区和溢出区,通常坡体上部为水、气吸入区,下部为水、气溢出区;水、气进出坡表的总速率受降雨特性、坡面产流情况、气温变化等外在因素的影响较小,具有相对稳定性;在坡表吸入区,当降雨强度大于水气入渗总速率时,入渗强度等于水气入渗总速率,吸入区产流;反之,入渗强度等于降雨强度,吸入区不产流。此外,坡表饱和区水压力可通过孔隙气传递到地下水面,增大地下水的压力水头,不利于坡体稳定。
On the basis of the theory of two-phase(water and air) flow,the law of water-air movement caused by rainfall infiltration in slope was revealed by means of finite element method. Daping landslide in Three Gorges Reservoir was taken as a case study. The simulation results show that the slope surface can be divided into the inflow area and the outflow area according to the inflow and outflow of water and air. Usually the upper part of slope is inflow area,and the lower part is outflow area. The total infiltration rate of water and air in slope is relatively stable,slightly affected by rainfall characteristics,slope surface runoff and temperature changes. In the inflow area,when rainfall intensity is greater than infiltration rate,water in slope will run off,otherwise water or air will completely infiltrate. The saturation pressure of slope surface could transmit to groundwater surface through pore air,which increases the groundwater pressure head,unfavorable for slope stability.
On the basis of the theory of two-phase(water and air) flow,the law of water-air movement caused by rainfall infiltration in slope was revealed by means of finite element method. Daping landslide in Three Gorges Reservoir was taken as a case study. The simulation results show that the slope surface can be divided into the inflow area and the outflow area according to the inflow and outflow of water and air. Usually the upper part of slope is inflow area,and the lower part is outflow area. The total infiltration rate of water and air in slope is relatively stable,slightly affected by rainfall characteristics,slope surface runoff and temperature changes. In the inflow area,when rainfall intensity is greater than infiltration rate,water in slope will run off,otherwise water or air will completely infiltrate. The saturation pressure of slope surface could transmit to groundwater surface through pore air,which increases the groundwater pressure head,unfavorable for slope stability.
引文
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[2]周家文,徐卫亚,邓俊晔,等.降雨入渗条件下边坡的稳定性分析[J].水利学报,2008,39(9):1066-1073.
[3]荣冠,张伟,周创兵,等.降雨入渗条件下边坡岩体饱和非饱和渗流计算[J].岩土力学,2005,26(l0):1544-1550.
[4]朱伟,陈学东,钟小春.降雨入渗规律的实测与分析[J].岩土力学,2006,27(11):1873-1879.
[5]LALOUI L,KLUBERTANZ G,GULLIET L.Solid-liquid-air Coupling in Multiphase Porous Media[J].International Journal for Numerical and Analytical Methods in Geomechanics,2003,27:183-206.
[6]王叶娇,曹玲,徐永福.降雨入渗下非饱和土边坡临界稳定性分析[J].长江科学院院报,2013,30(9):75-79.
[7]唐海行,苏逸深.考虑气压势影响的降雨入渗数值模拟研究[J].水科学进展,1996,(7):8-13.
[8]彭胜,陈家军,王金生,等.包气带水气二相流国外研究综述[J].水科学进展,2000,(3):333-338.
[9]孙冬梅,朱岳明,张明进.降雨入渗过程的水-气二相流模型研究[J].水利学报,2007,(2):150-156.
[10]TONG F G,JING L,ZIMMERMAN R W.A Fully-coupled Finite Element Code for Modeling Thermo-hydro-mechanical Processes in Porous Geological Media[C]∥Proceedings of the 43rd US Rock Mechanics Symposium,Asheville,NC,USA,June 28-30,2009:28-30.
[11]VAN GENUCHTEN M TH.A Closed Form Equation for Predicting the Hydraulic conductivity of Unsaturated Soil[J].Soil Science Society of America Journal,1980,44(5):892-898.
[12]MUALEM Y.A New Model for Predicting the Hydraulic Conductivity of Unsaturated Porous Media[J].Water Resources Research,1976,12(3):513-522.
[13]COREY A T.The Interrelation Between Gas and Oil Relative Permeabilities[J].Producers Monthly,1954,19:38-41.