Study The Relationship Between Frequency Of Debris Flows And The Particles Size In Channels Of Debris Flows

Debris flow is a natural disaster in the mountains, it is composed with the mud, rocks, water and other loose debris material, often with the characteristics of complex formation, outbreaks of a sudden, ferocious, short-lived, large destructive and so on, it caused great damage to the mountain economic development. China is one of the countries with widespread and serious debris flow disaster in the world , it is widely distributed in china's 31 provinces, municipalities and autonomous regions. According to statistics, we have about 80,000 debris flow in china. and about 8,500 of them are serious. in recent years, as the western development and the economic development of mountain areas, debris flows have increased, frequent casualties, destruction of infrastructure and other accidents, it is a serious threat to lives and property of inhabitants of mountain. Since the 90s of the 20th century, debris flow caused economic losses of about 3.0 billion per year. the number of deaths caused by debris flow annually 250-500 people, such a huge loss has attracted the world attention on the debris flow disaster in general.Debris can be separated into high-frequency and low frequency debris flow, by statistical data of debris flow disaster, in these cases, causing heavy casualties and property loss is low frequency debris flow .for example, July 9, 1981 liziyida ditch of Sichuan ganluo county outbreak low-frequency debris flow, destroyed Chengdu-Kunming railway bridge, interrupt the train 372 hours, Direct economic losses more than 2,000 million. december 1999 occurred low-frequency debris flow in Venezuela's Caribbean coast, almost destroyed all the towns along the coast within 40 km. caused 3-5 million deaths, direct economic loss more than 10 billion U.S. dollars, it makes the level of socio-economic development back 20 years. For a typical high-frequency debris flow, people attaches great importance to it, and maintain a high level of vigilance, local government and the people can project management and prediction, arrangements for a person to prevent in the flood season, to minimize the losses caused by debris flow, however, the low-frequency debris flow outbreak is very low, it may break a major debris flow after decades or even centuries, low-frequency debris flow is hidden and destructive, moment caused great damage and severe impact to mountain people's lives, property and mountain eco-environment in heavy rain conditions, as the low-frequency debris flow occurred suddenly, it is very difficult to predict and studies it, low-frequency debris flow is a immediately solved difficult problem of debris flow prevention at home and abroad, more and more experts have noted that low-frequency debris flow and the resulting disaster, and began to study it.Low frequency debris flow widely distributed in the mountainous southwest China , its forming conditions are very special, such as heavy rain, torrential rain, landslides, earthquakes, glacial lake or reservoir outburst, and other special factors . these unusual and special excitation conditions cause debris flow frequency is very low, generally more than 20 years, some even have to only occur once a century, therefore, residents living near hazardous gradually relaxed its vigilance, and the awareness of prevention is weak, preventive measures are unfavorable. especially the residents living in the mountains, due to the mountainous conditions restrictions, want to find a flat place for housing or farming is very difficult, therefore, many mountain residents were forced to build settlements, arable land, roads, railways and other infrastructure on debris fans or relatively flat next to debris flow gullies. These sites are often destroyed directly by debris flow, there is great risk of hidden dangers, once outbreak a low-frequency debris flow with tremendous destructive power , may result in serious casualties and property losses and devastating destruction to towns, roads, railways, etc, therefore, study the process of low-frequency debris flow disaster on the mountain in southwest China has a very important practical significance.The thesis by actual field investigation seventeen debris flow, study focused on fifteen low-frequency debris flow, and also select two high-frequency debris flow gullies to inspect and analyze, collect the background information on geological environment of these areas, measure and record the stone size distribution at different positions of debris flow channel, further study the relationship between debris flow frequency and large stone size of debris flow formation zone and debris accumulation zone , draw final conclusions through statistical reasoning, in the hard rock areas, the debris flow frequency is lower and the stone size is larger, through the rock lithology, particle size to determine the frequency of debris flow method, provide basic data for depth study the formation mechanism of low-frequency debris flows and provide help for predict or help combat low-frequency debris flows.