水致黄土深层滑坡灾变机理
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摘要
在黄土地区,雨后观测和人工降雨试验均表明地表水在黄土中的入渗深度有限,并不影响黄土深部的含水率。因此水分入渗是否直接造成斜坡深层滑移颇受争议。本文通过黄土地区自然降雨条件下的现场观测,发现地表水在黄土中的入渗沿垂直剖面可以划分为3个带:即活动带,稳定带和饱和带。活动带受大气降雨和蒸发的影响,为瞬态流,向下则转化为稳定流;稳定带含水率不变,但仍有稳定的水分运移至地下水位。地下水以下降泉的形式排泄。在入渗和排泄条件长期不变的情况下,地下水位可维持动态平衡。若地表入渗量加大,如灌溉或管道漏水等,稳定带含水率升高,并伴随地下水位抬升,以达到新的平衡,此水文动态转化过程会诱发滑坡。以延炼滑坡为例,分析了长期地表水间歇性滴渗条件下,边坡的水力动态变化过程,及其对边坡稳定性的影响。观测及分析结果表明,黄土深层滑坡主要与地表水入渗导致的地下水位抬升有关,由于其过程缓慢,容易被忽视而致灾。
In loess area,both artificial rainfall field test and in-situ observation under natural rainfall conditions suggest that the influence of surface water is limited to the top several meters,below which the variation of soil water content is little.Therefore,it is a controversy to fact that the surface water infiltration can induce loess landslides with deep seated failure surfaces.In this study,an in-situ observation test is undertaken in a thick loess layer for a period of one year from June 1 st,2015 to May 31 st,2016.Results show that water infiltration in the loess can be divided into three zones,namely,active,stable,and saturated zones.The active zone is influenced significantly by precipitation and evaporation events,where water flow is a transient behavior.The stable zone is characterized with a stable water content and steady seepage flow.The saturated zone is where groundwater exits,which can be drained in the forms of spring.In the long run,the hydraulic condition reaches an equilibrium state with a stable water content in the stable zone and stable ground water table level.However,this equilibrium statecan be disturbed with a higher surface water infiltration,for example irrigation water and leakage from pipelines,which contributes to a new equilibrium state with higher stable water content in stable zone and higher GWT level.Loess landslides with deep seated failure surfaces may occur during the transitional process from the initial equilibrium state to the new equilibrium state.Yanlian deep loess landslide is taken as an example to illustrate the mechanism of surface water infiltration induced deep landslides.The hydraulic response to long-term surface drop water and its influence to slope stability are analyzed.Results highlight the close relationship between deep loess landslides and long-term surface water infiltration,which is easy to be neglected due to its slow flow rate.
In loess area,both artificial rainfall field test and in-situ observation under natural rainfall conditions suggest that the influence of surface water is limited to the top several meters,below which the variation of soil water content is little.Therefore,it is a controversy to fact that the surface water infiltration can induce loess landslides with deep seated failure surfaces.In this study,an in-situ observation test is undertaken in a thick loess layer for a period of one year from June 1 st,2015 to May 31 st,2016.Results show that water infiltration in the loess can be divided into three zones,namely,active,stable,and saturated zones.The active zone is influenced significantly by precipitation and evaporation events,where water flow is a transient behavior.The stable zone is characterized with a stable water content and steady seepage flow.The saturated zone is where groundwater exits,which can be drained in the forms of spring.In the long run,the hydraulic condition reaches an equilibrium state with a stable water content in the stable zone and stable ground water table level.However,this equilibrium statecan be disturbed with a higher surface water infiltration,for example irrigation water and leakage from pipelines,which contributes to a new equilibrium state with higher stable water content in stable zone and higher GWT level.Loess landslides with deep seated failure surfaces may occur during the transitional process from the initial equilibrium state to the new equilibrium state.Yanlian deep loess landslide is taken as an example to illustrate the mechanism of surface water infiltration induced deep landslides.The hydraulic response to long-term surface drop water and its influence to slope stability are analyzed.Results highlight the close relationship between deep loess landslides and long-term surface water infiltration,which is easy to be neglected due to its slow flow rate.
引文
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Ding Y.2011.Study on the stability of high loess slope under artificial rainfall simulation[D].Xi'an:Northwest University.
Dong Y,Sun P P,Zhang M S,et al.2013.The response of regional groundwater system to irrigation at Heifangtai terrace,Gansu Province[J].Geological Bulletin of China,32(6):868-874.
Feda J.1988.Collapse of loess upon wetting[J].Engineering Geology,25(2-4):263-269.
Fredlund D G,Rahardjo H.1993.Soil mechanics for unsaturated soils[M].New York,USA:Wiley.
Garakani A A,Haeri S M,Khosravi A,et al.2015.Hydro-mechanical behavior of undisturbed collapsible loessial soils under different stress state conditions[J].Engineering Geology,195(9):28-41.
Hou X K,Vanapalli S K,Li T L.2018.Water infiltration characteristics in loess associated with irrigation activities and its influence on the slope stability in heifangtai,loess highland,China[J].Engineering Geology,234:27-37.
Jin Y L,Dai F C.2007.Analysis of loess slope stability due to ground water rise[J].Journal of Engineering Geology,15(5):599-606.
Lei X Y.1994.The hazards of loess landslides in the southern tableland of Jingyang county,Shaanxi and their relationship with the channel water into fields[J].Journal of Engineering Geology,3(1):56-64.
Li A G,Yue Z Q,Tham L G,et al.2005.Field-monitored variations of soil moisture and matric suction in a saprolite slope[J].Canadian Geotechnical Journal,42(1):13-26.
Li J,Gao G Y,Huang X F.2011.Experimental research on immersion for unsaturated intact loess slope[J].Chinese Journal of Rock Mechanics and Engineering,30(5):1043-1048.
Li P,Li T L,Vanapalli S K.2016.Influence of environmental factors on the wetting front depth:a case study in the Loess Plateau[J].Engineering Geology,214:1-10.
Lin R F,Wei K Q.2006.Tritium profiles of pore water in the Chinese loess unsaturated zone:implications for estimation of groundwater recharge[J].Journal of Hydrology,328(1-2):192-199.
Lin X Y,Li T L,Zhang Z R,et al.2013.Causes of Gaoloucun loess flowslide in Huaxian county,Shaanxi province[J].Journal of Engineering Geology,21(2):282-288.
Qi X,Xu Q,Li B,et al.2016.Preliminary study on mechanism of surface water infiltration at Heifangtai loess landslides in Gansu[J].Journal of Engineering Geology,24(3):418-424.
Richards L A.1931.Capillary conduction of liquids through porous mediums[J].Physics,1(5):318-333.
Shen W,Zhai Z H,Li T L,et al.2016.Simulation of propagation process for the Dabaozi rapid long run out loess landslide in the south bank of the Jinghe River,Shaanxi province[J].Journal of Engineering Geology,24(6):1309-1317.
Tu X B,Kwong A K L,Dai F C,et al.2009.Field monitoring of rainfall infiltration in a loess slope and analysis of failure mechanism of rainfall-induced landslides[J].Engineering Geology,105(1-2):134-150.
Van Genuchten M T.1980.A closed-form equation for predicting the hydraulic conductivity of unsaturated soils[J].Soil Science Society of American Journal,44(5):892-898.
Wang H,Li T L,Fu Y K.2014.Determining permeability function of unsaturated loess by using instantaneous profile method[J].Journal of Hydraulic Engineering,45(8):997-1003.
Wen B P,Yan Y J.2014.Influence of structure on shear characteristics of the unsaturated loess in Lanzhou,China[J].Engineering Geology,168:46-58.
Xi Y,Li T L,Li P,et al.2017.Mechanism of an unsaturated loess landslide induced by dropping of condensed water vapor[J].Hydrogeology&Engineering Geology,44(4):145-152.
Xing X L.2013.The mechanism of irrigation-induced flow-slide and its motion simulation-taking Gaolou village landslide as the research object[D].Xi'an:Chang'an University.
Zhang C L,Li P,Li T L.2014.In-situ observation on rainfall infiltration in loess[J].Journal of Hydraulic Engineering,45(6):728-734.
Zhang M S,Li T L.2011.Triggering factors and forming mechanism of loess landslides[J].Journal of Engineering Geology,19(4):530-540.
丁勇.2011.人工降雨模拟作用下的黄土高边坡稳定性研究[D].西安:西北大学.
董英,孙萍萍,张茂省,等.2013.诱发滑坡的地下水流系统响应历史与趋势---以甘肃黑方台灌区为例[J].地质通报,32(6):868-874.
金艳丽,戴福初.2007.地下水位上升下黄土斜坡稳定性分析[J].工程地质学报,15(5):599-606.
雷祥义.1994.陕西泾阳南塬黄土滑坡灾害与引水灌溉的关系[J].工程地质学报,3(1):56-64.
李佳,高广运,黄雪峰.2011.非饱和原状黄土边坡浸水试验研究[J].岩石力学与工程学报,30(5):1043-1048.
蔺晓燕,李同录,张子然,等.2013.陕西华县高楼村黄土滑坡-泥流的成因分析[J].工程地质学报,21(2):282-288.
亓星,许强,李斌,等.2016.甘肃黑方台黄土滑坡地表水入渗机制初步研究[J].工程地质学报,24(3):418-424.
沈伟,翟张辉,李同录,等.2016.陕西泾河南岸大堡子高速远程黄土滑坡运动过程模拟[J].工程地质学报,24(6):1309-1317.
王红,李同录,付昱凯.2014.利用瞬态剖面法测定非饱和黄土的渗透性曲线[J].水利学报,45(8):997-1003.
习羽,李同录,李萍,等.2017.蒸汽凝水滴渗诱发的一个非饱和黄土滑坡机理研究[J].水文地质工程地质,44(4):145-152.
邢鲜丽.2013.灌溉诱发的黄土滑坡-泥流形成机理及运动学模拟---以陕西华县高楼村滑坡为例[D].西安:长安大学.
张常亮,李萍,李同录,等.2014.黄土中降雨入渗规律的现场监测研究[J].水利学报,45(6):728-734.
张茂省,李同录.2011.黄土滑坡诱发因素及其形成机理研究[J].工程地质学,19(4):530-540.
Ding Y.2011.Study on the stability of high loess slope under artificial rainfall simulation[D].Xi'an:Northwest University.
Dong Y,Sun P P,Zhang M S,et al.2013.The response of regional groundwater system to irrigation at Heifangtai terrace,Gansu Province[J].Geological Bulletin of China,32(6):868-874.
Feda J.1988.Collapse of loess upon wetting[J].Engineering Geology,25(2-4):263-269.
Fredlund D G,Rahardjo H.1993.Soil mechanics for unsaturated soils[M].New York,USA:Wiley.
Garakani A A,Haeri S M,Khosravi A,et al.2015.Hydro-mechanical behavior of undisturbed collapsible loessial soils under different stress state conditions[J].Engineering Geology,195(9):28-41.
Hou X K,Vanapalli S K,Li T L.2018.Water infiltration characteristics in loess associated with irrigation activities and its influence on the slope stability in heifangtai,loess highland,China[J].Engineering Geology,234:27-37.
Jin Y L,Dai F C.2007.Analysis of loess slope stability due to ground water rise[J].Journal of Engineering Geology,15(5):599-606.
Lei X Y.1994.The hazards of loess landslides in the southern tableland of Jingyang county,Shaanxi and their relationship with the channel water into fields[J].Journal of Engineering Geology,3(1):56-64.
Li A G,Yue Z Q,Tham L G,et al.2005.Field-monitored variations of soil moisture and matric suction in a saprolite slope[J].Canadian Geotechnical Journal,42(1):13-26.
Li J,Gao G Y,Huang X F.2011.Experimental research on immersion for unsaturated intact loess slope[J].Chinese Journal of Rock Mechanics and Engineering,30(5):1043-1048.
Li P,Li T L,Vanapalli S K.2016.Influence of environmental factors on the wetting front depth:a case study in the Loess Plateau[J].Engineering Geology,214:1-10.
Lin R F,Wei K Q.2006.Tritium profiles of pore water in the Chinese loess unsaturated zone:implications for estimation of groundwater recharge[J].Journal of Hydrology,328(1-2):192-199.
Lin X Y,Li T L,Zhang Z R,et al.2013.Causes of Gaoloucun loess flowslide in Huaxian county,Shaanxi province[J].Journal of Engineering Geology,21(2):282-288.
Qi X,Xu Q,Li B,et al.2016.Preliminary study on mechanism of surface water infiltration at Heifangtai loess landslides in Gansu[J].Journal of Engineering Geology,24(3):418-424.
Richards L A.1931.Capillary conduction of liquids through porous mediums[J].Physics,1(5):318-333.
Shen W,Zhai Z H,Li T L,et al.2016.Simulation of propagation process for the Dabaozi rapid long run out loess landslide in the south bank of the Jinghe River,Shaanxi province[J].Journal of Engineering Geology,24(6):1309-1317.
Tu X B,Kwong A K L,Dai F C,et al.2009.Field monitoring of rainfall infiltration in a loess slope and analysis of failure mechanism of rainfall-induced landslides[J].Engineering Geology,105(1-2):134-150.
Van Genuchten M T.1980.A closed-form equation for predicting the hydraulic conductivity of unsaturated soils[J].Soil Science Society of American Journal,44(5):892-898.
Wang H,Li T L,Fu Y K.2014.Determining permeability function of unsaturated loess by using instantaneous profile method[J].Journal of Hydraulic Engineering,45(8):997-1003.
Wen B P,Yan Y J.2014.Influence of structure on shear characteristics of the unsaturated loess in Lanzhou,China[J].Engineering Geology,168:46-58.
Xi Y,Li T L,Li P,et al.2017.Mechanism of an unsaturated loess landslide induced by dropping of condensed water vapor[J].Hydrogeology&Engineering Geology,44(4):145-152.
Xing X L.2013.The mechanism of irrigation-induced flow-slide and its motion simulation-taking Gaolou village landslide as the research object[D].Xi'an:Chang'an University.
Zhang C L,Li P,Li T L.2014.In-situ observation on rainfall infiltration in loess[J].Journal of Hydraulic Engineering,45(6):728-734.
Zhang M S,Li T L.2011.Triggering factors and forming mechanism of loess landslides[J].Journal of Engineering Geology,19(4):530-540.
丁勇.2011.人工降雨模拟作用下的黄土高边坡稳定性研究[D].西安:西北大学.
董英,孙萍萍,张茂省,等.2013.诱发滑坡的地下水流系统响应历史与趋势---以甘肃黑方台灌区为例[J].地质通报,32(6):868-874.
金艳丽,戴福初.2007.地下水位上升下黄土斜坡稳定性分析[J].工程地质学报,15(5):599-606.
雷祥义.1994.陕西泾阳南塬黄土滑坡灾害与引水灌溉的关系[J].工程地质学报,3(1):56-64.
李佳,高广运,黄雪峰.2011.非饱和原状黄土边坡浸水试验研究[J].岩石力学与工程学报,30(5):1043-1048.
蔺晓燕,李同录,张子然,等.2013.陕西华县高楼村黄土滑坡-泥流的成因分析[J].工程地质学报,21(2):282-288.
亓星,许强,李斌,等.2016.甘肃黑方台黄土滑坡地表水入渗机制初步研究[J].工程地质学报,24(3):418-424.
沈伟,翟张辉,李同录,等.2016.陕西泾河南岸大堡子高速远程黄土滑坡运动过程模拟[J].工程地质学报,24(6):1309-1317.
王红,李同录,付昱凯.2014.利用瞬态剖面法测定非饱和黄土的渗透性曲线[J].水利学报,45(8):997-1003.
习羽,李同录,李萍,等.2017.蒸汽凝水滴渗诱发的一个非饱和黄土滑坡机理研究[J].水文地质工程地质,44(4):145-152.
邢鲜丽.2013.灌溉诱发的黄土滑坡-泥流形成机理及运动学模拟---以陕西华县高楼村滑坡为例[D].西安:长安大学.
张常亮,李萍,李同录,等.2014.黄土中降雨入渗规律的现场监测研究[J].水利学报,45(6):728-734.
张茂省,李同录.2011.黄土滑坡诱发因素及其形成机理研究[J].工程地质学,19(4):530-540.