Effects Of Different Soil-rock Mixed Interlayer On Soil Water Infiltration

In this experiment,adopted one-dimensional vertical infiltration method.The gravel with 2 different particle sizes(0.5?1.5cm and 1.5?2.5cm)were mixed with fine soil as the separation layer according to 5 different volume contents(0%,10%,20%,30% and 40%).The thickness of the separation layer was 10 cm and the filling height of soil column was 30 cm.The influence of gravel particle size,volume content and the location of the separation layer on soil moisture infiltration was studied by changing the position of the separation layer(the upper layer is 0?10 cm,the middle layer is 10?20 cm and the lower layer is 20?30cm).The results are as follows:(1)Gravel particle size,volume content and the location of the separation layer have obvious influence on the characteristic parameters of infiltration.When the gravel volume content and the location of the separation layer are fixed,the stable infiltration rate decreases and the time of stable infiltration will extend with the particle size increases.When the gravel particle size and the position of the separation layer are constant,the stable infiltration rate decreases and the time of stable infiltration extend with the gravel content increase.When the gravel particle size and volume content are constant,the stable infiltration rate increases and the time to reach the stable cutdown with the increase of the distance between the soil and stone layer and the soil surface.(2)When the gravel particle size and the location of the separation layer are fixed,the cumulative infiltration decreases with the increase of the gravel content.Compared with CK,the cumulative infiltration does not monotonic increase and monotonic decrease with the increase of the gravel content.There is a threshold,which is related to the location of the soil and stone separation layer.The threshold value is about 10% when the separation layer is in the upper layer.The threshold value should be between 20% and 30% when the separation layer is in the middle layer.The threshold is about 30% when the separation layer is in lower layer.(3)Under the condition of certain gravel particle size and content,the same infiltration duration,the cumulative infiltration amount at different positions of the separation layer presents the trend is lower layer > middle layer > upper layer.Compared with CK,the influence of the position of the separation layer on soil water infiltration is related to the gravel content.When gravel content is 10% it can promote the infiltration,the content of 40% hinders infiltration.When the content is between 20% and 30%,soil water infiltration changes from promotion to hindrance with the location of separation layer move up.(4)The influence of gravel particle size on water infiltration is closely related to the location of the separation layer.When the separation layer located in the upper layer of soil column,the cumulative infiltration amount is large particle size > small particle size;when the separation layer located in the middle layer and the lower layer of soil column,the cumulative infiltration amount is small particle size > large particle size.(5)When the gravel particle size and the location of the separation layer are fixed.With the increase of gravel content,the migration distance of wetting front decreases at the same time.Under the condition of the same gravel particle size and content,the change of wetting front migration distance compare location separation layer is the lower layer > the middle layer > the upper layer.(6)The gravel content has a significant influence on the saturated water conductivity.With the increase of the gravel content,the saturated water conductivity first increases and then decreases.The gravel particle size and the position of the separation layer have no significant influence on the saturated water conductivity.(7)The Philip model kostiakov model and the general empirical model can well fit the infiltration process of this experiment.In comparison,the Philip model has the best fitting effect,and the average value of R~2 is 0.9974.