Research On Initiation And Motion Characteristic Of Debris Flow

In recent years，the outbreak of debris flows appear more and frequently in thewest of Sichuan region affected by earthquakes，has become a heated topic. However，some low-frequency debris flows that covers flourish vegetation always causedfearful casualties and property losses due to lack of attentions. Flow velocity，as acore parameter of debris flow，is hard to monitor and calculate because of the debrisflows’ emergentness and complicated character. Now the experience velocity formulathat widely used have strong subjectivity，affecting the prevention and controlmeasures.Majingzi gully located in Shimian，Sichuan Province，which covers flourishvegetation and lack of massive sources. Debris flow hasn’t occurred for nearlydecades of years. There are many constructions on both sides of the channel and thedeposition fan. On July4,2013, Majingzi gully debris flow triggered by heavy rainand caused fearful casualties and property losses. In order to propose appropriatecontrol measures, it is necessary to understand the formation conditions, mechanismand achieve accurate parameter of such debris flow.In this paper, through field investigation and indoor simulation test, the mainconclusions are as followed：（1）Though Majingzi gully has flourish vegetation，the a mass of solid sourcehas gradually accumulated in the valley year after year. So the debris flow will beeasily triggered by heavy rain. When such debris flow just took shape，it had formedsome barrier dams. Due to the collapse of such barrier dams，the scale of debris flowhad enlarged.（2）Based on the data from field investigation，a indoor test was designed whichcould simulate the freeboard phenomenon of debris flow. According to the mud markdata from different velocity and bend condition，the formula has been verificated andcorrected by statistic analysis. The new correction formula is h2.8VlgRR.（3）Applied the correction formula into the parameters calculation of Majingzigully debris flow，the unit weight，flow velocity，flow and impact force were acquired. In contrast with the fan volume，housing damage and the witness description，the datais reasonable and prove the correction formula is reliable.