沟道松散物质起动形成泥石流实验研究
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摘要
为研究震后环境突变条件下的泥石流形成模式和机理,开展震后泥石流防治和预测,根据震后泥石流形成环境特点,设计泥石流起动装置,开展震后泥石流形成模式和机理试验。本研究共进行了25组试验,主要研究了泥石流在不同坡度情况下的泥石流形成模式和机理,结果表明:1)在坡度8°～12.5°情况下,泥石流的形成模式是冲蚀→冲沟→崩塌→堵塞→溃决→泥石流的模式;2)在坡度12.5°～17.5°情况下,泥石流的形成模式是逐渐侵蚀加剧(朔源侵蚀、下切侵蚀和侧蚀),容重逐渐增加形成泥石流的模式;3)在坡度17.5°～25°情况下,泥石流的形成模式是坡面流水→入渗→失稳→下滑→流态化的模式;4)根据孔隙水压力变化特征,不同的起动模式下的土体内部孔隙水压力变化特征不同,孔隙水压力的变化可以解释不同泥石流起动模式的机理特征。根据研究结果,可以对不同起动下的泥石流模式进行不同的防治规划,同时结合泥石流起动过程中孔隙水压力的变化,可以解释泥石流起动的模式,对开展震后泥石流预报提供了参考。
In order to understand the initiation model and mechanism of debris flow,and forecast and prevent it after earthquake,the facilities of debris flow initiation were designed according to the post-earthquake environment to study the debris flow initiation mechanism.The tests of 25 groups were carried out at different slopes using the same soil material to study the debris flow initiation at varies slopes.The results showed that the initiation mode of debris flow was erosion → gully → collapse → block → failure and transformed into debris flow between 8° ~ 12.5° as initiation due to dam-failure.The initiation mode of debris flow was increased erosion gradually(down cut erosion,back word cut and lateral erosion) with the bulk density increasing and transformed into debris flow between 12.5° ~ 17.5° as initiation due to erosion.The initiation mode of debris flow was surface flow → infiltration → failure → fluidization and transformed into debris flow between 17.5° ~ 25° as initiation due to slope failure.The change character of water pore-pressure was different at different slope experiments,and the water pore-pressure inner soil revealed the initiation mechanism of debris flow at different slope.
In order to understand the initiation model and mechanism of debris flow,and forecast and prevent it after earthquake,the facilities of debris flow initiation were designed according to the post-earthquake environment to study the debris flow initiation mechanism.The tests of 25 groups were carried out at different slopes using the same soil material to study the debris flow initiation at varies slopes.The results showed that the initiation mode of debris flow was erosion → gully → collapse → block → failure and transformed into debris flow between 8° ~ 12.5° as initiation due to dam-failure.The initiation mode of debris flow was increased erosion gradually(down cut erosion,back word cut and lateral erosion) with the bulk density increasing and transformed into debris flow between 12.5° ~ 17.5° as initiation due to erosion.The initiation mode of debris flow was surface flow → infiltration → failure → fluidization and transformed into debris flow between 17.5° ~ 25° as initiation due to slope failure.The change character of water pore-pressure was different at different slope experiments,and the water pore-pressure inner soil revealed the initiation mechanism of debris flow at different slope.
引文
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[22]Wang G H,Sassa K.Pore-pressure generation and movement of rainfall-induced landslides:effects of grain size and fine-particle content[J].Engineering Geology,2003,69:109-125.
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[24]康志成,李卓芬,马蔼乃,等.中国泥石流研究[M].北京:科学出版社,2004:58-59.
[2]May C L,Gresswell R E.Processes and rates of sediment and wood accumulation in headwater streams of the Oregon Coast Range,USA[J].Earth Surface Process and Land-forms,2003,28:409-424.
[3]Crosta G B,Dal N P,Frattini P.Soil slips and debris flows on terraced slopes[J].Natural Hazards and Earth System Sciences,2003(3):31-42.
[4]Guadagno F M,Forte R,Revellino P,et al.Some aspects of the initiation of debris avalanches in the Campania Region:the role of morphological slope discontinuities and the development of failure[J].Geomorphology,2005,66:237-254.
[5]Gabet E J,Mudd S M.The mobilization of debris flows from shallow landslides[J].Geomorphology,2006,74:207-218.
[6]Imaizumi F,Sidler C,Kamei R.Effects of forest harvesting on the occurrence of landslides and debris flows in steep terrain of central Japan[J].Earth Surface Processes and Landforms,2007,33:827-840.
[7]Iverson R M,Reid M E,Iverson N R,et al.Acute sensitivity of landslide rates to initial soil porosity[J].Science,2000,290:513-516.
[8]Cannon S H,Gartner J E,Parrett C,et al.Wildfire-related debris flow generation through episodic progressive sediment bulking processes,western USA[C]//Rickenmann D,Chen C.Debris Flow Hazards Mitigation:Mechanics,Prediction,and Assessment.Millpress,Rotterdam,The Nether-lands,2003:71-82.
[9]Berti M,Simoni A.Experimental evidences and numerical modeling of debris flow initiated by channel runoff[J].Landslides,2005(2):171-182.
[10]Godt J W,Coe J A.Alpine debris flows triggered by a 28 July 1999 thunderstorm in the central Front Range,Colorado[J].Geomorphology,2007,84:80-97.
[11]Martin D A,Moody J A.Comparison of soil infiltration rates in burned and unburned mountainous watersheds[J].Hydrologic Process,2001,15:2893-2903.
[12]Tognacca C,Bezzola G R.Debris flow initiation by channel-bed failure[C]//Chen C.Proceedings First International Conference on Debris Flow Hazards Mitigation:Mechanics,Prediction and Assessment.1997:44-53.
[13]Cui P,Zhu Y Y,Han Y S,et al.The 12 May Wenchuan earthquake-induced landslide lakes:distribution and preliminary risk evaluation[J].Landslides,2009(6):209-223.
[14]Zhuang Jianqi,Cui Peng,Ge Yonggang,et al.Hazard assessment of debris flow valleys along Dujiangyan-Wenchuan highway after“5.12”Wenchuan devastating earth-quake[J].Journal of Sichuan University:Engineering Science Edition,2009,41(3):131-139.[庄建琦,崔鹏,葛永刚,等.“5.12”地震后都汶公路沿线泥石流沟危险性评价[J].四川大学学报:工程科学版,2009,41(3):131-139.]
[15]Meyer G A,Wells S G.Fire-related sedimentation events on alluvial fans,Yellowstone National Park USA[J].Journal of Sedimentary Research,1997,67(5):776-791.
[16]Coe J A,Glancy P A,Whitney J W.Volumetric analysis andhydrologic characterization of a modern debris flow near Yucca Mountain Nevada[J].Geomorphology,1997(20):11-28.
[17]Zhuang J Q,Cui P,Ge Y G,et alProbability assessment of river blocking by debris flow associated with the Wenchuan Earthquake[J].International Journal of Remote Sensing,2010,31(3):1-14.
[18]Tang C,Zhu J,Li W L.Rainfall triggered debris flows after Wenchuan earthquake[J].Bulletin Engineer Geology Environment,2009,68:187-194.
[19]Chen Xiaoqing,Cui Peng,Feng Zili,et al.Artificial rainfall experimental study on landslide translation to debris flow[J].Chinese Journal of Rock Mechanics and Engineering,2006,25(1):106-116.[陈晓清,崔鹏,冯自立,等.滑坡转化泥石流起动的人工降雨试验研究[J].岩石力学与工程学报,2006,25(1):106-116.]
[20]Iverson R M,Lahuse R G.Dynamic pore-pressure fluctuations in rapidly shearing granular materials[J].Science,1989,246:796-799.
[21]Cui P.Studies on condition and mechanism of debris flow initiation by means of experiment[J].Chinese Science Bulletin,1992,37(9):759-763.
[22]Wang G H,Sassa K.Pore-pressure generation and movement of rainfall-induced landslides:effects of grain size and fine-particle content[J].Engineering Geology,2003,69:109-125.
[23]Gao Y L,Zhou S Q.Influence of ultra-fine fly ash on hydration shrinkage of cementpaste[J].Journal of Central South University of Technology,2005,12(5):596-600.
[24]康志成,李卓芬,马蔼乃,等.中国泥石流研究[M].北京:科学出版社,2004:58-59.
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