Experimental Study Of Debris Flow Starting Based On The Concentration Of Water

Debris flow is in the mountains or other deep valleys, steep terrain regions, because of heavy rain, blizzard, human engineering activities, or other natural disasters caused by landslides and special with a large number of sediment and rocks in the torrent. 5.12 wenchuan after the earthquake, affected by the earthquake, a strong earthquake happened within the scope of large amount of secondary disasters such as collapse, landslide and debris flow. On the one hand, collapse, landslide into debris flow directly provides a rich source for, on the other hand, the seismic load of reciprocating effect caused a large number of slope instability, rock mass damage, makes the trend of the debris flow gully activities remain strong. Therefore, to carry out the meizoseismal area starting mechanism of typical mountain valleys type debris flow research is very necessary, can provide such type mountain gully debris flow forecast provides the basis of the theory and method.This article mainly through to the aba Tibetan and qiang autonomous prefecture, sichuan province maoxian county dongxing township of bamboo package gully on the basis of data collection and field investigation, the research which the starting mechanism of debris flow gully bed. To obtain material starting conditions of the study area is a typical debris flow influence factors, through indoor physical simulation experiment, the conditions of water(water or mud flow rate and concentration), gully bed slope, starting water depth, flow rate per unit width and surface flow velocity, the relation between the related analysis to gain the typical debris flow ditch the critical starting condition of the study area. Through the above method to draw the following conclusion:(1) through the survey found in the study area, zhubao package ditch basin has favorable conditions of debris flow development. Look from the topography and geomorphology, bamboo package ditch basin relative elevation difference is big, steep terrain, valleys and longitudinal slope is relatively slow, upstream is steep, narrow channel, is advantageous to the landslide material collection and hazard; Look from the content source condition, the debris flow in the solid content rich source, source total volume of 733.93 x 104 m3, which an animal source volume 168.95 x 104 m3, look from the water conditions, groove width domain in upstream and downstream small and middle groove domain width larger nearly date type of form, gully point not have domain springs, ditch water mainly accept rainfall water supplies, large flow, valleys hydrodynamic condition is strong, easy to form debris flow.(2) Physical simulation of debris flow channel starter set of experiments were conducted 12, critical starting the depth of the channel slope, debris flow, surface flow velocity and flow rate per unit width were analyzed, and the debris flow is obtained starting critical water depth, flow rate per unit width and channel slope and flow concentration into linear negative correlation, and surface flow velocity and the channel slope into linear positive correlation.(3) through the debris flow starting process analysis concluded that DEBRIS FLOW way as the water concentration change varies. When the water concentration of 0 and 1%, when the flow reaches the desired value mudslides start, starting mainly in the ditch bed material flow on the lower portion of the trench soil particles were deposited Ripping up the Bottom, which led to the upper portion of the layer of coarse particles roll starter mode ditch erosion start; when the water concentration of 5%, when the flow reaches the desired value starting mudslides, due to the increased concentration of water, reduce water flow and shear enhancement of penetration, so that the upper layer is roughened direct contact surface along the roughened layer and the lower soil particles rolling phenomenon occurs when the upper portion of the roughened layer Jiedi, the water began to lower portion of the soil particles eroded erosion, starting mode roughened layer Jiedi mode.(4) Data obtained through field investigation, bamboo bag tributary ditch # 1, for example, take the form of rain Hongfa survey and calculated the field starting a single-wide traffic flow will start experiments calculated calculation and bamboo package debris flow site starting flow rate was subjected to comparative analysis showed that bamboo starter package debris flow concentration between 1% and 3%, then the use of experimental data difference obtained starting flow rate 17 ° slope, the critical water depth and concentration correlations will flow into the starting spot calculate correlations, whereby bamboo bag ditch # 1 tributary start time concentration of 1.64%, starting depth of 0.33 m.