汶川震区龙门山镇高架子沟“8·18”泥石流灾害机理与特征

2012年8月18日四川省彭州市龙门山镇地区遭受50年一遇的暴雨,引发大规模群发性泥石流灾害,其中以高架子沟最为突出,导致银厂沟内居民生活和交通严重受损。本文据现场调查和航空影像解译,分析高架子沟流域、物源特征的基础上讨论该次泥石流的演化过程、启动方式及灾害机理。结果表明：高架子沟在震前是一条非泥石流沟,震后流域内物源丰富,泥石流形成及演化过程为：地震-滑坡、崩塌-降雨-泥石流,其成灾启动过程包括启动阶段、加速阶段、下切拉槽阶段、堆积四个阶段,启动模式为沟床启动型。该泥石流形成过程中,＂消防水管效应＂使沟道水流快速集中,并强烈冲刷沟床中的松散堆积体,导致沟床固体物质移动形成大规模的泥石流灾害。

Mechanism and characteristics of Gaojiazi gully debris flow on august 18,2012 in Longmenshan town,epicenter of Wenchuan earthquake

On August 18,2012,most of the areas of Longmen town in Pengzhou city,Sichuan province had the biggest rain fall in a half century and led to breaking out a large scale group debris flow. The flow disaster characteristics of Gaojiazi gully is particularly outstanding. The disaster cased serious harm to local residents and traffic. This paper studies characteristics of gully conditions and source of debris flow based on field reconnaissance and interpretations of aerial photographs for discussing the evolution and initiation process and disaster mechanisms of Gaojiazi debris flow.The acknowledges obtained after investigation and analysis are as follow. Gaojiazi gully is a non debris flow gully before the Wenchuan earthquake,there are several process about its evolution： Earthquake-Landslide、Collapse-Rainfall. It can be divided into four stages about the Gaojiazi debris flow on August 18,2012： The initiated phase,Accelerated phase,Erosion phase,Diposition phase. Gaojiazi gully debris flow belong the type of the gully-bed initiation which the overland flow of water resulting from intense rainfall was concentrated in steep channels and scouring debris from gully-bed loose deposits.