Study On The Effect Of Porosity On The Initiation Of Mud Flow In Channel Loess

Many scholars have carried out a lot of research on Loess mud flow,and have achieved a certain amount of research results,but there are still some important issues to be further studied and discussed,such as the relationship between loess porosity and start-up time,start-up water requirement,mud flow discharge,mud flow bulk density,erosion and so onThis paper systematically explores the Yellow River under different porosity conditions by means of literature review,field investigation(2 times of Qiugou small watershed and silt dam investigation),physical and mechanical properties determination test(more than 100 groups),channel loess mud flow flume test(7 groups),confirmatory test(2 groups),calculation and theoretical analysis,etc.in Yangou watershed,the third branch of Yanhe River,Baota District,Yan'an City.Under the condition of continuous catchment in the rear,the instability of soil and the phenomenon of loess mud flow are destroyed,and the following conclusions are obtained(1)When the porosity of loess varies in the range of 0.51-0.57,the form of mud flow generated during the initiation of mud flow in gully loess is surface erosion gully mud flow.When the porosity of loess varies in the range of 0.58-0.63,the form of mud flow during the initiation of mud flow in gully loess is piping burst mud flow When the porosity of loess varies in the range of 0.64-0.69,the mud flow in gully loess is piping burst mud flow.The form of mud flow during the start-up process is piping-out mud flow.The mud flow is mainly dilute mud flow(2)The start-up time of mud flow in gully loess is negatively correlated with the change of porosity,and the expression of quantitative change between start-up time and porosity is t=16.77n-5.1.(3)There is a negative correlation between the initial water requirement of mud flow in gully with the change of porosity,and the quantitative relationship between the initial water requirement and porosity is w=402.01-551.73n.(4)The initial water requirement per unit volume of loess mud flow varies negatively with the change of porosity,and the quantitative relationship between the initial water requirement per unit volume of loess mud flow and porosity is V=-9.65n+7.03(5)There is a negative correlation between the peak time of mud flow and the change of porosity during the start-up of mud flow in gully loess.The quantitative expression of the relationship between the peak time of mud flow and porosity is t1=22.33n-4.86.(6)When the porosity of loess varies in the range of 0.51-0.57,the erosion amount is positively correlated with the mud flow rate and inversely correlated with the volume density of mud flow.When the porosity of loess varies in the range of 0.58-0.69,the relationship between erosion amount and mud flow discharge and mud flow bulk density is positive correlation.The larger the porosity,the faster the rate of erosion growth and the shorter the test time.It shows that the larger the porosity is,the more obvious the erosion effect of water flow on soil is.