| The Xiongmao gully debris flow is a typical gully debris flow.There was a large-scale debris flow in 1964,and before 2008,this gully was in the recession,and there were scattered small debris flows.After the two earthquakes of"5.12"and"4.20",the debris flow broke out on July 26,2016,and the debris material formed about 30 meters wide and 120 meters long weir plug to block the barang river,causing the river to divert to the left bank and destroy about 300 percent of the provincial line303.It caused great damage to S303 roads,Bridges,agricultural houses,cultivated land,crops,cultivated land,livestock,power lines,water conservancy and drinking water facilities for people and animals.Xiongmao gully is characterized by the development of debris flow in a typical earthquake area.Although the carrying capacity of the barang river is not strong,due to the short distance between the Xiongmao gully mouth and the barang river,the occurrence of debris flow is likely to block the river and lead to secondary disasters.Restricted by topographic conditions,some material sources should be discharged into the barang river during the drainage.Therefore,it is of practical significance to study the development characteristics of debris flow in Xiongmao gully and to study the prevention and control measures based on laboratory tests.Based on the field survey,this paper studies the development characteristics of Xiongmao gully and simulates the movement process of Xiongmao gully with three rainfall frequencies,P=1%,P=2%and P=5%,using flo-2d.Based on the influence of flow ratio of indoor flume test to debris flow plugging river,Suggestions for debris flow control are put forward.Get the following recognition:(1)The area of the Xiongmao gully region is 23.6km~2,and the branch gully is developed.After the two earthquakes of"5.12"and"4.20",the total amount of material source is about 203.1x104m~3,which may be involved in the mudstone flow reserves of about 52.38x104m~3.The material source in the gully is rich,and it is prone to debris flow in the gully under the condition of continuous rain and heavy rain.(2)The debris flow in Xiongmao gully is the old debris flow gully.The debris flow once broke out in large scale in 1964.After this large-scale debris flow,the activity intensity of debris flow weakened,which was reflected in the regressive activity of debris flow deposits covering the accumulation fan in the earlier stage.In the late debris flow activity,its gully pass by the left side of the old accumulation fan.(3)In order to study the motion characteristics of the debris flow in the Xiongmao gully more intuitively,this paper adopted flo-2d software to simulate the movement speed,accumulation depth and accumulation range under three rainfall frequencies:P=1%,P=2%and P=5%.Then the debris flow which has occurred for 50years is compared and the simulation results are good.(4)According to the indoor water tank test,other factors were controlled to remain unchanged,and the study concluded that the dilute debris flow blocked the river in the form of submerged dam yong plug in the process of accumulation.When the flow ratio was less than 0.5,the increase speed of the blockage coefficient increased with the increase of the flow ratio.When the flow ratio is greater than 0.5,the increasing speed of the clogging coefficient decreases.When the plug coefficient is less than 0.4,the phenomenon of high water level accumulation does not appear in the upstream.When the plug coefficient is greater than 0.4,the high water level with the increase of the plug coefficient increases,but there is no obvious correlation.(5)According to the development characteristics of debris flow and gully topography conditions,combined with indoor water tank test,the project management measures of"comb bar+drainage trough"are proposed. |
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