舟曲“8.8”特大泥石流对建筑物的破坏方式

Building Destruction Patterns by August 8,2010 Debris Flow in Zhouqu,Western China

2010-08-07—08发生的甘肃舟曲特大泥石流造成了1 765人死亡和失踪,33幢面积共11.472 km2的建筑物被直接冲毁,有20幢面积约69 km2建筑被部分损坏。现场的调查表明,泥石流破坏建筑物主要有冲击、淤埋和摩擦三种方式。通过对8座破坏建筑物的具体分析,发现泥石流破坏建筑物有正向以撞击为主、侧向以淤埋和摩擦为主,沿流向呈现波浪式变化以及遮蔽效应等特点。根据泥石流的破坏方式、特点和建筑物类型,初步提出了我国山区居民住宅两种常见结构的泥石流破坏分级标准。最后提出了几条能有效减轻泥石流对建筑物破坏的具体措施,可供坐落于泥石流危险区的山区城镇借鉴。

A destructive debris-flow calamity hit the city of Zhouqu, Gansu Province, western China at midnight on August 7th, 2010, following a local intensive rainfall of 77.3 mm/（40 min） in Sanyanyu and Luojiayu ravines which are located in the north of the urban area. As of September 1 st, the disaster claimed 1471 fatalities, and 294 htissing persons. Nearly one-third of the town was inundated by the debris-flow dammed lake. 33 buildings with 11 472 m2 area were completely destroyed by the debris flow, and 20 were partially damaged. Eight damaged buildings were investigated in details to study the ways or patterns of building destruction by debris flows. The damage pat- terns of debris flow can be classified into impact, deposition and abrasion. The destructive power decreased initially after impacting an array of buildings, but can increase again by gaining power from gravitational energy and central flow kinetic energy when the flow kept mo^ing a distance. It is termed as the longitudinal fluctuation of debris-flow destruction. The orthogonal impact was the most destructive pattern whereas the transverse impact caused sediment accumulation. The damage depended on not only flow＇ s property such as density, velocity and depth, but also building＇ s orientation, structural strength and regularity. Comparing with nonresistant and collapsed buildings with brick-concrete structure, the reinforced concrete structure can resist effectively debris-flow impact. A classification scheme to assess building damage by debris flows was proposed with reference to the Classification System of earth- quake damage to buildings. According tO the on-spot investigation, five effective countermeasures for mitigating the building＇ s damage are proposed： 1. to reduce the surface normal to the flow direction, 2. to use reinforced con- crete structure, 3. to design no protruding part as far as possible, 4. to keep enough room between buildings, and 5. to prevent the first floor of high buildings from living or business.