Design Of Debris Flow Prevention In Huanglianggenqiao Gully, Fengjiayu Town

The mountainous area of Beijing belongs to Yanshan Mountain and Taihang Mountains, it has steep terrain and big elevation difference; ancient strata and poorly cemented rock distributes widely, it also has a large precipitation and ever lead to debris flow. So it is very necessary and realistic to predict and control the debris flow in Beijing. The main purpose of this paper is to analyze the Utopian root bridge gully debris flow characteristics of Beijing, combined with the local social and economic conditions, associated debris flow prevention and control measures to layout of debris flow prevention and control measures of Huanglianggenqiao gully in Fengjiayu Town. The study mainly includes the following four aspects:1) We did field investigation of basic geology, topography and geomorphology characteristics, combined with Arcgis software to extract the digital elevation information, and analysising of the occurrence of debris flow. The results show that Huanglianggenqiao gully has a total area of 1.41 km2, average slope is 182.9‰, more than 55% of the basin area has a slope that is greater than 25 c. providing a favorable terrain conditions in the process of the debris flow development; Geological structure developed and the rock broked extremely, rock stability was not well, residual volatile diluvial layer along the slope sliding collapsed, provided more loose solid for landslides, once the rain excitation conditions is mature, it was so easy to outbreak of debris flow.2) we collected soil sample within gully, combined with the indoor experiment analysis of characteristics of granularity. It showed that the more was debris flow source, The larger was particle size. The debris flow is dilute debris flow that has a density of 1.55 g/cm2. In the condition of 20 years rain return period, the debris flow peak flow is 184.29 m3/s, one time solid debris flow is 44700 m3, one total time debris flow is 134000 m3, and it belonged to medium of debris flow.3) The prevention of Huanglianggenqiao gully mainly includes civil engineering measures and biological engineering measures. This paper will be divided into three functional prevention areas that is debris flow forming area, circulation area and accumulation area. Forming region is mainly the area that the channel slope is greater than 25°, it will carry on nurture and protective measures, including the Seal sign; The circulation area is located in the main channel and the middle branch lander, slope become relatively slow, gully bed is wide, the prevention measures mainly include refurbished terrace on both sides and dam built; Accumulation zone is located beside the edge of channel which will design a main dam. According to the debris flow prevention design rules in Beijing. Debris flow engineering measures are built with 20 years in a heavy rain return period design standard. Including a total of 7 LanDang dam, a one-time LanDang debris flow solids 49800 m3; Refurbishment terrace 772 m, cultivating the sign 15 pieces.4) Estimating debris flow project investment of Huanglianggenqiao gully, The result shows that project construction cost has a total investment of 1.0048 million yuan, including civil engineering measures of the total cost of 788000 yuan, biological engineering measures of 216800 yuan. Project scheduling ranges from March 2017 to October 2018, the time limit for the project is 14 months.