The Debris Flow Gully Loose Material Starting Model Test

During the whole process of debris flow occurrence,the starting process is the key link.The law of starting is the theoretical basis of the prediction and control of debris flow.Therefore,this paper aims to study the sensitivity in the starting process by a fixed gradation,clay model of the quasi-debris flow accumulation body under different saturation and shear strength in the case of dry density,as well as different channel slope,rainfall conditions and groove roughness of the indoor model experiment.At the same time,with the help of digital imaging technology and the pore water pressure measurement technology,The damage process and pore water pressure of the incompact substan in the process are revealed.The main conclusions are as follows:?1?There is a non-linear positive correlation between shearing strength and dry density of channel loose material,which is a non-linear negatively correlated with saturation.Moreover,under the condition of fixed dry density,the shear stress increases greatly in the early stage and then tends to be stable.and it converges.?2?Four levels of three factors are considered in this study by 2 groups of L₉?3⁴?orthogonal indoor model test,according to the data obtained from the pore water pressure meter in 5#,it was found that that major factor influencing the startup of the incompact substa of debris is the channel grade,second is rainfall intensity,lastone is channel roughness.?3?Under the same working condition:a.The pore water pressure in the leading edge of the accumulation body is relatively large compared with other positions;b.The pore water pressure in the leading edge position was obvious during the early stage of the experiment,and the latter appeared up and down.Which is indicated that the rainfall and the rear water flow are more than the leading edge of the debris flow,and the pressure of pore water in the front edge of the debris flow is more obvious.Under the same slope condition,the measured data of the pore water pressure gauge in the leading edge increased with the increase of rainfall.?4?According to the digital imaging technology and pore water pressure,the data analysis shows that:a.the incompact substan accumulation body starts to show the characteristics of the source erosion under the effect of the downstream water.b.The loose material starting mode of debris flow channel is the slope surface confluence,infiltration,erosion?erosion and lateral erosion?,gully,both sides collapse and collapse,and than debris flow.?5?Through the measurement of the width of the leading edge,the middle part and the trailing edge of the channel formed after the completion of the start,and the data analysis and fitting,the functional relation of the width of the leading edge,the middle part and the trailing edge of the groove is obtained.By further simplification,the amount of solid matter can be calculated in the starting process of the loose material in an indoor model ditch.The extent of injury and degree of damage can be predicted.Therefore,we can carry out evacuation in advance of the disposal of residents in the surrounding area.It is also possible to guide the subsequent related projects according to the prediction of the starting process.