The Preliminary Experiment Research Of The Mechanism And Main Affect Factors On The Finger Flow

This paper was supported by Project about Colleges and Universities Key Laboratory Visited Scholar Plan in shannxi province,Which focus on the infiltration law with homogeneous soil and layered structure soil of the three typical soils (Xifeng soil of Gansu province,Yulin soil of Shannxi province and Xinjiang sand soil )in the area of Northwestern China. The goal of this study was to disclose the basic law of the finger flow, and enrich the theory of finger flow research and provide practical guidance. This study was based on extensive review of finger flow research achievements from domestic and abroad. Through systematic experiment indoors, model study and analysis on mechanisms, there are some major achievements and findings as follows:1 For the requirement of experiment, s series of equipment was developed, including of soil box and uniform speed move device and so on,which is possible to supply high degree of accuracy for infiltration experiment with condition of sufficient and insufficient water supply. It is a characteristic production.2 Three kind homogeneous soils can not crate finger flow in sufficient water supply,insufficient water supply,redistribution water supply and original state soil insufficient water supply, but when three soils as upper soils and bulky grain as lower soils, the finger flow could appear in sufficient water supply.3 The difference between upper soil texture and lower soil texture the more, in other word the different between the hydraulic conductivity rate of the upper soil and lower soil more, the finger flow is more easily created. For example, when Xifeng soil as upper soils and small sand as lower sand, the finger flow isn't obvious, but when big sand as lower sand, the finger is very obvious.4 The hydraulic conductivity rate of upper soil is the key factor on finger flow movement in lower soil, the hydraulic conductivity rate of upper soil larger, the movement of finger flow in lower soil is faster, and vice versa. There was a good linear relationship between the hydraulic conductivity rate of upper soils and the average rate of finger flow.5 It is reasonable to use finger flow length(Lp),finger flow width(Bp) and the rate of finger flow as basic parameter to describe development of finger flow.Main problems and shortage: The experimental design for studying finger flow in homogeneous soil and layered soils is not comprehensive because of time,experiment equipment and so on, and it is impossible toresearch all kinds of soil in northwest area of China.The achievement still exist some limitation, further research is needed to supplement the current findings. The research on finger flow in domestic and foreign is still preliminary, only phenomenon was analysised. There is no rational models have been proposed theoretically. It's needed to be further study for the future.