汶川震区的坡面泥石流调查研究
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摘要
汶川地震造成的大量崩塌、滑坡和颗粒侵蚀堆积体,为泥石流提供了丰富的松散物质来源。在过去的两年内暴雨引发大量的坡面泥石流,对山区公路和河流造成危害尤为严重。坡面泥石流是一种发生在有碎屑堆积物的陡坡上,由降雨引发的高浓度碎屑与水的混合物沿坡面运动的现象。本文作者通过野外调查和测量,得到19个坡面泥石流的降雨量、形成与堆积坡度、颗粒级配等数据,并估算得到坡面泥石流的行进速度。研究发现降雨是震区坡面泥石流爆发的决定性因素,当代表日降雨量超过20mm/d就可能引发坡面泥石流;当代表日降雨量超过30mm/d,坡面泥石流就可能群发;当代表日降雨量超过90mm/d,震区就会大量爆发坡面泥石流。坡面泥石流形成坡度和堆积坡度很大,构成颗粒较粗。此外,震区频发的坡面泥石流是两相泥石流,水体成稀泥浆在运动中主要是润滑体而不是承载体。坡面泥石流运动距离只有几米到几十米。由于固体颗粒运动中剧烈碰撞消耗了大部分能量,运动速度很小。建排水系统和发育植被可以最终控制坡面泥石流。
Avalanches and landslides,induced by the Wenchuan earthquake on May 12,2008,resulted in a lot of loose materials on slopes and provided plenty of solid materials for debris flows.Rainstorms triggered numerous slope debris flows with great damage to highways and rivers in the past two years.The slope debris flow is defined as the phenomenon that a high-concentration mixture of debris and water flows down the slopes for a short distance and reaches highways and river banks.Based on field investigation and measurements of 19 slope debris flows,the main characteristics and control strategies of slope debris flows were studied.It was found that the high rainfall intensity was the main triggering factor.The critical rainfall intensities for simultaneous occurrence of single,several and numerous slope debris flow events were 20 mm /day,30mm / day,and 90 mm /day,respectively.Field investigations also revealed that the slope of forming section was steep and the deposit was deep.The slope debris flows consist of high concentration of cobbles,boulders and gravel.They are two-phase debris flows.The liquid phase plays a role of lubrication instead of carrier.Solid particles collide with each other in the motion and consume a lot of energy.The velocity of the slope debris flows was very low and traveled for a distance of only several tens of meters.The slope debris flows may be controlled by construction of drainage systems and reforestation.
Avalanches and landslides,induced by the Wenchuan earthquake on May 12,2008,resulted in a lot of loose materials on slopes and provided plenty of solid materials for debris flows.Rainstorms triggered numerous slope debris flows with great damage to highways and rivers in the past two years.The slope debris flow is defined as the phenomenon that a high-concentration mixture of debris and water flows down the slopes for a short distance and reaches highways and river banks.Based on field investigation and measurements of 19 slope debris flows,the main characteristics and control strategies of slope debris flows were studied.It was found that the high rainfall intensity was the main triggering factor.The critical rainfall intensities for simultaneous occurrence of single,several and numerous slope debris flow events were 20 mm /day,30mm / day,and 90 mm /day,respectively.Field investigations also revealed that the slope of forming section was steep and the deposit was deep.The slope debris flows consist of high concentration of cobbles,boulders and gravel.They are two-phase debris flows.The liquid phase plays a role of lubrication instead of carrier.Solid particles collide with each other in the motion and consume a lot of energy.The velocity of the slope debris flows was very low and traveled for a distance of only several tens of meters.The slope debris flows may be controlled by construction of drainage systems and reforestation.
引文
[1]王兆印,刘丹丹,施文婧.汶川地震引发的颗粒侵蚀及其治理[J].中国水土保持科学,2009,7(6):7-15.
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[3]Wang Zhaoyin,Cui Peng,Wang Ruiyu.Mass movements triggered by the Wenchuan earthquake and managementstrategies of quake lakes[J].River Basin Management,2009,7(1):1-12.
[4]王兆印,崔鹏,余斌.泥石流的运动机理和减阻[J].自然灾害学报,2001,(03):37-43.
[5]Kang Zhicheng.Dynamic analysis of stable movement in viscous debris flow[J].Mountain Research,1995,13(2):128-132.
[6]Wang Zhaoyin,Wang Guangqian,and LIU Cheng.Viscous and two-phase debris flows in southern China’s YunnanPlateau[J].Water International,2005.30(1):14-23.
[7]Yano K,Daido A.Fundamental study on mudflow[R].Bull.Disaster Prev.Res.Inst.,Kyoto Univ.Japan.14,part 21965.69-83.
[8]Wang Zhao-yin.A study on debris flow surges[J].Hydraulic Engineering,1993,2:1616-1621.
[9]Bagnold R A.The flow of cohesionless grains in fluids[J].Philosophical Transaction of the Royal Society of London,1956,249(964):235-297.
[10]Takahashi T.Mechanical characteristics of debris flow[J].Hydraulic Division,1978.104,1153-1169.
[11]Takahashi T.Debris flow in prismatic open channel[J].Hydraulic Division,1980.106,381-386.
[12]Takahashi T.Debris flows[J].Fluid Mechanics,1981,13:55-77.
[13]王兆印.泥石流龙头运动的实验研究及能量理论[J].水利学报,2001,(03):20-28.
[14]康志成,李焯芬,马蔼乃,罗锦添.中国泥石流研究[M].北京:科学出版社,2004.79-81.
[2]Wang Zhaoyin,Lee J.H.W.and Melching C.S..Integrated River Training and Management[M].Berlin and Beijing:Springer Verlag and Tsinghua Press,2010:1-200.
[3]Wang Zhaoyin,Cui Peng,Wang Ruiyu.Mass movements triggered by the Wenchuan earthquake and managementstrategies of quake lakes[J].River Basin Management,2009,7(1):1-12.
[4]王兆印,崔鹏,余斌.泥石流的运动机理和减阻[J].自然灾害学报,2001,(03):37-43.
[5]Kang Zhicheng.Dynamic analysis of stable movement in viscous debris flow[J].Mountain Research,1995,13(2):128-132.
[6]Wang Zhaoyin,Wang Guangqian,and LIU Cheng.Viscous and two-phase debris flows in southern China’s YunnanPlateau[J].Water International,2005.30(1):14-23.
[7]Yano K,Daido A.Fundamental study on mudflow[R].Bull.Disaster Prev.Res.Inst.,Kyoto Univ.Japan.14,part 21965.69-83.
[8]Wang Zhao-yin.A study on debris flow surges[J].Hydraulic Engineering,1993,2:1616-1621.
[9]Bagnold R A.The flow of cohesionless grains in fluids[J].Philosophical Transaction of the Royal Society of London,1956,249(964):235-297.
[10]Takahashi T.Mechanical characteristics of debris flow[J].Hydraulic Division,1978.104,1153-1169.
[11]Takahashi T.Debris flow in prismatic open channel[J].Hydraulic Division,1980.106,381-386.
[12]Takahashi T.Debris flows[J].Fluid Mechanics,1981,13:55-77.
[13]王兆印.泥石流龙头运动的实验研究及能量理论[J].水利学报,2001,(03):20-28.
[14]康志成,李焯芬,马蔼乃,罗锦添.中国泥石流研究[M].北京:科学出版社,2004.79-81.
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