| The debris flow is a common geological disaster in mountain, it had a seriousimpact to the lives of people and economic. Gediluo Gully locates at Yanyuan Countyin Liangshan Prefecture, Sichuan Province. It is generated from secondary tributariesof Yalong River, Middle part of Woluo river. In the geological history, a debris flow inGediluo Gully had blocked the river for a long time. On August18,2009, the largestdebris flow in10years had broke out.It lasted45minutes and greatly influenced thepeople living there. The Gully within large amount of Quaternary loose debris, whichcould be triggered by the heavy rain, earthquakes and other natural factors. possessesa high potential to generate debris flow again. Therefore, Study the Gediluo debrisflow formation geological environment background, tendency, dynamic features isvery important to the protection of people and construction.By conducting investigation on the geological environment of the Gediluo debrisflow, this paper analyzes the nature and developmental characteristics, carrying outthe test of indoor and mudslides blocking river mudslides blocking the river, with thetest results, analysis and forecast the development trend of the mudslides anddangerous range. Then conclude:(1) Gediluo debris flow is a high mountain valley high-frequency thin debrisflow. Under natural conditions was the development of transition to the recessionoverall development trend for the middle.(2) Gediluo Gully has a large amount of solid resource. On-site investigationshows:unstable solid resources is about784,200m3,locates at both sides of the slopeand on the channel bed; semi-stable material source of approximately680,700m3,mainly locates on the unstable old slopes; stable material source is about1,439,700m3,mainly locates at the upper part of the gully and on the stable slopes, the wholeresources is roughly3million m3.(3)Using the empirical formula to conclude the dynamic index under thedifference conditions. In10,20-year flood condition, part of the source will formatthe debris flow, debris flow side were about204,700m3and440,800m3,sedimentabout88,700m3and199,500m3. In the50-year flood conditions, the mudslides wasabout741,200m3and the debris flow sediment about350,900m3. Under the conditions of100and500-year flood, the mudslides side were about1,028,800m3and1,591,300m3,including about499700m3and805700m3sediment.With higher possibility of eruption, the10and20years return flood conditionshas a high potential to generate debris flow. Within a lower possibility, under50yearsreturn flood condition, the debris flow has larger scale. Moreover, the100and500years return flood condition, the debris flow had a largest scale.(4) Through the experiment, this paper conclude that there are two ways for thedebris flow blocking the river, wedging and squeezing. In10and20years condition,debris flow blocking in wedging way;50years and100year return period debris flowoften goes by the squeezing way. The results shows the10and20years frequencydebris flow will wedge in the river when encounter in the main river and the50and100years frequency debris flow will block the river when flow into the main river.When different frequency debris flow encounter the common flow in main river, thepossibility of blocking goes lower with the frequency.(5) According to the analysis of the feature, danger, scale of the debris flow,combine with the experiment, this paper divide the research area into different parts ofdangerous area. Ⅰ level area includes proluvial fan and left part of the high land, thearea which would be flooded by10and20years frequency debris flow.Ⅱ level areaincludes part of the high land and the area which would be flooded by50yearsfrequency debris flow. Ⅲ level area includes part of high land and the area whichwill be flooded by100years return flow. |
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