贵州关岭大寨崩滑碎屑流灾害初步研究
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摘要
2010年6月28日,贵州省关岭县岗乌镇大寨村发生特大型崩滑碎屑(石)流灾害,造成99人死亡或失踪。通过现场考察崩滑区的地质环境与斜坡岩体结构,认为斜坡体由似"干砌块石结构"的裂隙化岩体组成是发生崩溃式破坏的主要内在原因。超常暴雨(过程雨量237mm)条件下斜坡岩体后缘裂缝充水形成持续的"水楔作用"是斜坡岩体松动、倾倒垮塌的主要外部引发因素。碎屑(石)流块度的空间分布具有从源头向沟口逐次减小,碎屑(石)流运动冲击高度逐步降低,冲击速度逐步减小,并显示4个能级4个冲程的特点。根据动势能守恒定律,计算了每个冲程的最大速度,得出第1冲程为高速崩滑,其它冲程属于碎屑(石)流动冲击。未发现区域天然地震、光照水库诱发地震与外围历史采矿活动与本次事件相关的直接证据。由于滑坡后缘仍存在不稳定岩体,碎屑(石)流堆积体上多处分布直径3～5m的堰塞塘,说明碎屑(石)空隙的排泄能力不足,在未来暴雨条件下引发新的崩滑或形成沟谷型泥石流的可能性是存在的。
The Dazhai event happened on June 28,2010 in Guling county of Guizhou province of China.It was a sliding in rockfall and debris flow events.Its volume was about 78.8×104m3.It was oversized geological disaster with 99 missed and killed people.Field inspection of the collapse phenomena indicated that the rockmass broken down was mainly due to the"dry building block structure"in fissured rockmass in internality of Dazhai slope.The sustaining "water wedge"pressure acts on the crown cracks by pouring rainwater from extreme rainstorm was the main external triggering factor.The rainfall was about 237mm.These factors resulted in the loosening,toppling,rotating and falling finally of the slope rock mass.The grain size distribution of debris(crushed stone)flow changed from larger to smaller sizes gradually from the rock fall headstream to the deposition outlet of the ditch.Still,its impact height was to knock down and its strike velocity was to decrease gradually.The total process of the debris flow displayed that a four-level of potential energies transformed into a four-level of kinetic energies accordingly.They occurred in four-strike paths.Based on the law of conservation of energy,the maximum velocity in each strike path is calculated and obtained the following results.The first stage belongs to rockfall and slip in high velocity(V1=24.25m·s-1).The others are debris(crushed stone)flows.Direct evidences were not found that the event was related to natural earthquakes,Guangzhao reservoir induced seismic activity and/or historic coal mining in the region.Moreover,it may be predicted that possibility of debris flow happening again is high because there are unstable rockmasses in the collapsed slope and dammed ponds in the debris deposits of 3m to 5m in diameter.They showed that the capacity of drainage in open space of crushed stones was not enough.
The Dazhai event happened on June 28,2010 in Guling county of Guizhou province of China.It was a sliding in rockfall and debris flow events.Its volume was about 78.8×104m3.It was oversized geological disaster with 99 missed and killed people.Field inspection of the collapse phenomena indicated that the rockmass broken down was mainly due to the"dry building block structure"in fissured rockmass in internality of Dazhai slope.The sustaining "water wedge"pressure acts on the crown cracks by pouring rainwater from extreme rainstorm was the main external triggering factor.The rainfall was about 237mm.These factors resulted in the loosening,toppling,rotating and falling finally of the slope rock mass.The grain size distribution of debris(crushed stone)flow changed from larger to smaller sizes gradually from the rock fall headstream to the deposition outlet of the ditch.Still,its impact height was to knock down and its strike velocity was to decrease gradually.The total process of the debris flow displayed that a four-level of potential energies transformed into a four-level of kinetic energies accordingly.They occurred in four-strike paths.Based on the law of conservation of energy,the maximum velocity in each strike path is calculated and obtained the following results.The first stage belongs to rockfall and slip in high velocity(V1=24.25m·s-1).The others are debris(crushed stone)flows.Direct evidences were not found that the event was related to natural earthquakes,Guangzhao reservoir induced seismic activity and/or historic coal mining in the region.Moreover,it may be predicted that possibility of debris flow happening again is high because there are unstable rockmasses in the collapsed slope and dammed ponds in the debris deposits of 3m to 5m in diameter.They showed that the capacity of drainage in open space of crushed stones was not enough.
引文
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[2]潘家铮.建筑物的抗滑稳定与滑坡分析[M].北京:水利出版社,1980.Pan Jiazheng.Analysis on the Anti-sliding Stability of Buildingsand Landslides.Beijing:Hydropower Publishing House,1980.
[3]胡广韬.滑坡动力学[M].北京:地质出版社,1995.Hu Guangtao.Landslide Dynamics.Beijing:Geological PublishingHouse,1995.
[4]王恭先,徐峻龄,刘光代.滑坡学与滑坡防治技术[M].北京:中国铁道出版社,2006.Wang Gongxian,Xu Junling,Liu Guangdai.Landslidology andLandslide Prevention Technology.Beijing:Railway PublishingHouse of China,2006.
[5]Varnes,D.T.Slope movements,type and processes,in R.L.Schus-ter and R.J.Krizek(Eds.),Landslide Analysis and Control[M].Transportation Research Board,National Academy of Sciences,Washington,DC,Special report 176,1978,11～33.
[6]刘传正.重大地质灾害防治理论与实践[M].北京:科学出版社,2009.Liu Chuanzheng.The Theory and Its Application on Megageo-hazards Mitigation.Beijing:Science Press,2009.
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