The Weathering Factor Study On The Formation Of Gully-type Debris Flow

The earthquake disaster area appears a large number of landslides and othergeological disasters, the ultimate manifestation of the various geological disasters aredebris flow’s formation, and the more serious the dangers of the earthquake zone ofsecondary debris flows relative to the average of geological disasters.which ischaracterized by an outbreak of a sudden, compared to before the earthquake, in thesmaller rainfall may trigger debris flows, and the main hazard is flooding theupstream and downstream infrastructure such as roads, villages, towns, bridges andfarmland. For example, in the earthquake zone in Longchi town, Yingxiu town,Qingping Township surrounding areas are outbreaks of large-scale mass of debris flow,resulting in huge casualties and property losses in August13,2010.The main features of the secondary debris flow caused by the earthquake disasterrelatively larger scale, and the disasters caused losses more serious than the averagerainfall debris flow. After the earthquake, many debris flow disaster conditions change.Outbreak of large-scale mass debris flow, even in very low frequency of debris flowareas, the formation process of such disasters and mitigation measures are alsodifferent from the heavy rain of debris flow. Therefore, the correct prediction andreduction of earthquake debris flow disaster has come to the urgent time. This articlefrom the debris flow material source conditions related to lithologic factors proven themechanism and characteristics of its provenance, which projected the frequency ofdebris flow and debris flow on the three major factors of geology, topography andrainfall formation and analysis of outbreak conditions, to study earthquake typicaldebris flow prediction methods and indicators, to lay the foundation for the correctprediction of the earthquake a typical debris flow and provide the basis for disastermitigation.From the survey of the existing debris flow gully to all kinds of rock Plattssturdy coefficient based on the lithology of consolidated previous debris flow, seismicand tectonic fault zone factors considered in detail, and on this basisphysical andchemical weathering on the formation of debris flow; detailed analysis and correction of various types of environmental conditions, factors involved in each type ofweathering, and then the outbreak of Qingping and Beichuan two typical mass regionof the debris flow as a research object,whether it is reasonable to verify the variousamendments to the relationship between the physical and chemical weathering.Combination of geological factors F and terrain factors of G and other parameters onthe conditions of the outbreak of the debris flow analysis applied to the mass of debrisflow area of the Wenchuan earthquake zone, and eventually get the debris flow of Fand of G, and thus provide the basis for the earthquake the typical mass of debris flowforecast.The paper obtained the following conclusions:（1）Sources of three conditions to forming and breakout debris flow mainly areprovided by crash of parent rock, The crash of parent rock mostly caused bymechanical （physics） effloresce, and weatherproof capability are relate to rock’ssolidity itself.（2）In a comprehensive analyze measures of earthquakes, conformation andphysics effloresce, use modified solidity factor to estimate frequency of debris flowhave accuracy reached84.6%. It is advisable to research the form of debris flow bymodified solidity factor.（3）The carbonate rock have different chemical weathering degree by differentcontent of carbonate, it indirectly effect the forming of debris flow. According tocontent of carbonate correspond to chemical weathering, obtained comprehensivegeology T=F₀C₁C₂C₃C₄。（4）Use debris flow comprehensive T factor of breakout or not, link tocomprehensive topography G factor to obtain the relation of geology and topographyin same rainfall condition: G/F=C （C is constant）.（5）Apply the relation of G/F=C to other earthquake zone: Longchi, Qingping,Beichuan and Nanba of group debris flow, analyzed the breakout condition, obtainedthe better result and coherence.