Research On The Influence Of Soil Initial Water Content On The Development Of Gully Loess Mud Flow

China is the country with the largest loess distribution area in the world,and the loess plateau is the main distribution area of loess in China,and it is also one of the most vulnerable areas in China's geological environment.Located in the hinterland of the loess plateau,yan 'an is a typical region with multiple loess mudflows.Based on the analysis of the data of gully debris flow in yan 'an region,this paper summarizes the conditions of gully debris flow in yan 'an region,and the development of debris flow in yan 'an region can be summarized as terrain,material source and water source.Based on the conditions of gully debris flow in yan 'an region,a flume model was designed in accordance with the similar ratio of 1:850.Meanwhile,taking loess as the research object,the effect of soil initial moisture content on mudflow development in yan 'an region was studied.By means of literature review,field investigation,experimental study and theoretical analysis,this paper obtained the law of soil moisture content and mudflow development in yan 'an area through real-time observation of the macro outburst phenomenon of channel accumulation soil under the action of water flow and the change characteristics of soil internal parameters.The specific conclusions are as follows:(1)the possibility of loess mudflow development in yan 'an area decreases first and then increases with the increase of the initial moisture content of the soil.When the soil is dry soil or the initial moisture content is ? 20%,the loess deposits in the channel are more likely to develop into loess mudflow under the action of water flow.(2)during the development of loess mudflow,the failure mechanism of soil mass also varies with the change of soil initial moisture content.When the moisture content is less than 5%,the failure mode of soil mass is downward cutting failure.When 5% < moisture content ? 20%,the failure mode of soil mass is comprehensive failure.When the moisture content is > 20%,the failure mode of soil mass is instability failure,and the failure mechanism of soil mass is similar to that of shallow landslide.(3)the relationship between the initial soil moisture content and the parameter changes during the development of loess mudflow can be obtained by analyzing the relationship between the initial soil moisture content and the parameter changes during the development of loess mudflow.The rule of parameter changes is similar to the difficulty degree of loess mudflow development.(4)during the development of debris flow in gully,the general variation rule of pore pressure in each group of tests was that pore pressure increased in the stage of infiltration or disturbance,pore pressure remained unchanged in the stable state,and pore pressure decreased in the stage of soil failure.The soil is saturated when the debris flow in the gully is damaged,and the excess pore water pressure is generated in the process of starting the debris flow in the gully.