Research On Engineering Characteristics Of Preferential Flow And Its Application

Preferential flow is a common natural phenomenon in base material.Preferential flow refers to the rapid and uneven movement of water and solutes through multicellular media,especially soil,characterized by regions of stepped-up flow such that a small fraction of media(such as cracks,root holes,and wormholes)participates in most of the flow,allowing much faster transport of a range of contaminants.In the Subgrade Engineering,the existence of preferential flow can have an adverse effect on the anti-pressure ability and shear-bearing capacity of subgrade.The characteristics of low responses to the changes of load and the superpower to collect the rain of preferential flow make it possible to be used in the construction of LID(Low Impact Development).This project aims to explore the features of preferential flow,study how preferential flow paths affect the stability of subgrade and make a hypothesis of using preferential flow in the construction of LID.In this article,the concept of Essential Direction Path,Unessential Direction Path and the Sensitivity Coefficient are defined.The idea of Funneling Preferential Flow Path is presented in LID.This project is designed by creating several numerical models supplemented by the irrigation apparatus experiments.In the process,the features of preferential flow,the effective strength and shear strength of preferential flow path are all recorded and analyzed.The main conclusions are as follows:1.Preferential flow characters.In any module,the flow path can be divided into essential direction path and unessential direction path.On unessential direction path,the task of water flow is always completed as much as possible along the large porosity module.This is also an important property of preferential flow.In this process,it leads to the concepts of essential direction path and unessential direction path.2.Water transport capacity of preferential flow path.Even the width of the preferential flow path becomes very narrow,preferential flow path still has a strong capacity of water transport.3.The influence of preferential flow on roadbed stability.If any position in soil matrix is replaced by the preferential flow path,the effective stress and shear stress of the original position will increase.But the variation trend for every part will remain unchanged.The concept of Sensitivity Coefficient is presented.Sensitivity Coefficient of flux to width in preferential flow is inversely proportional to the width of the flow path.Sensitivity Coefficient of shear Stress to width is directly proportional to the width of preferential flow path.The larger of the loan on preferential flow path appears,the more obviously the stress on preferential flow path changes.On the other hand,the smaller load the preferential flow suffered,the smaller stress the preferential flow caused.In the transport of water flow,most water flow through the preferential flow path.4.Application of preferential flow on low impact development.The depth of preferential flow is inversely proportional to the flow ratio that flow through preferential flow path,and the depth is proportional to the flow rate in the preferential flow path.The incline angle of preferential flow path is proportional to the flow ratio that flow through preferential flow path,and the incline angle is proportional to the flow rate in the preferential flow path.