摘要
2017年8月28日,贵州省纳雍县张家湾镇普洒村发生山体崩塌,崩塌方量约6×10~5m~3,造成35人遇难。本文通过应急调查、过程还原及工程地质分析,对崩塌破坏过程及机理初步研究,以期有益于后续防治及类似灾害防范。研究发现,崩塌主要发生在三叠系下统夜郎组灰岩和粉砂岩地层中,岩层面近水平,受构造和卸荷作用,发育有平行于坡面的陡倾节理,受长期重力作用和风化作用影响,溶蚀漏斗和塌陷发育,节理在长期的风化过程中形成裂隙带和沉陷带;崩塌过程还原显示,崩塌可分为"沉陷带变形崩塌-坡面局部崩塌-整体溃屈崩塌-撞击地面-碎屑流"五个阶段;根据崩塌变形和运动特征,崩塌可分为崩塌源区、崩积区、碎屑流区和变形区四个区;崩塌体在降雨和采矿作用影响下,拉裂沉陷带和水体的楔形侧向挤压和劈裂作用加剧了坡顶临空岩土体的变形,崩塌发生前的降雨过程对崩塌的发生有重要的促进作用。
A rock collapse with volume of about 6 × 10~5 m~3 occurred in Pusa village,Zhangjiawan Town,Nayong County,Guizhou Province on August 28,2017,causing 35 deaths. A preliminary study on the failure process and mechanism of this disaster is conducted in this paper by a series of emergency investigation,failure evolution reproducing and engineering geological analysis,aiming at a better management of the problems induced by this collapse and prevention of similar disasters in the future. This study suggests that the collapse mainly occurred in the limestone and siltstones layers which belong to the Yelang Formation of lower Trias. Due to the structural activities and unloading effects,the sub-horizontal strata have many steep joints which are parallel to the slope surface. Because of the long-term gravity and weathering effects,the corrosion funnels and subsidence are developed,and the fissure zone and subsidence area are formed. By reproducing the failure process,it is shown that the collapse can be divided into five stages as follows:( 1) deformation and collapse of the subsidence area;( 2) local collapse of the slope surface;( 3) complete collapse;( 4)impacting the ground; and( 5) formation of debris flow. According to the deformation and movement characteristics,the collapse area can be divided into four zones:( 1) the source zone,( 2) the collapsedeposits zone;( 3) the debris flow zone; and( 4) the deformation zone. Influenced by rainfall and mining activities,the deformation of the upper rock mass and soil are enhanced owing to the extension induced subsidence area as well as the lateral wedge splitting effects of the water,therefore the rainfall played an important role in the occurrence of this collapse. In addition,the risk of high-speed debris flow should be studied based on the investigation,evaluation,monitoring,warning and prevention of high collapse.
引文
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