Study On The Behavior And Laws Of Rainfall Erosion For Rallway Embankment Slope

In the past30years, the average annual railway interruption in China caused byflood was159times. The average annual traffic interruption was over2000hours,which had great impact on the national economy, as well on the lives and property ofpassengers and daily life. Statistics shows that80percent of the water hazard is watererosion of the roadbed, which suggests that the key issue be the research of watererosion of the embankment.Hydraulic erosion of embankment is affected by manyfactors, such as slope complex boundary conditions, variation in rainfall and thecharacteristics of slope flow hydraulics.the process of erosion is complex. Most of thecurrent study are starting from the soil and water conservation, such as the soil erosionmodel, rainfall characteristics, slope shape, soil properties etc.The systematictheoretical of railway embankment siope erosion is still a lack. This thesis, taking therailway embankment as the research object, gives a systematic analysis of the basiclaw of the railway embankment slope hydraulic erosion, considering thecharacteristics of the embankment structure, packing, slope morphology, rainfallfactor, combined with hydraulics, soil mechanics and principles of sedimentmovement mechanics. The main contents are as follows:1. It summarizes the different levels of the railway embankment slope height,slope ratio, roadbed width of the top surface and other technical indicators, proposesthe index value of the analysis of embankment slope erosion; sums up the type ofhydraulic erosion damage of railway embankment slope. It puts forward, on the basisof the present railway engineering classification of filling and the hydraulic stabilityof the packing, that the filler be divided into four types as non cohesive homogeneoussoil, non cohesive and non homogeneous soil, clay and dispersive clay. It indicatesthat the rainfall characteristics are the major dynamic factors of the slope surfaceerosion, and that the minute’s rainfall be used as reasonable indicators in the analysisof embankment slope erosion.2. A comprehensive analysis is made of the stress state of the non cohesive homogeneous soil particles on the slope under the effect of scouring flow. Based onthe limit state of power balance, taking the starting drag force as an indicator, analysisis also made of the effect on the starting drag force of the embankment slope soilparticles under such factors as the particle size of soil particles, the depth of overlandflow, the flow resistance of the slope surface and the slope grade. The relationshipbetween the slope surface water flow rate of non cohesive uniform filler and thestarting particle size is established. It puts forward, by using the skeleton principle offiller penetration stability and particle interference theory, that the d23be used as theindex of judgment for non homogeneous and non cohesive filler erosion stability. Itanalyses the characteristics of cohesive soil erosion damage and establishes therelationship between the cohesive soil starting particle size and the erosion velocity.3. Hydraulics principle is used to deduce the relationship between the smoothslope flow rate of the roadbed and rainfall intensity. Comparative analysis is given tothe variation law of slope flow rate and starting particle size for non cohesivehomogeneous filler and cohesive filler in three erosion status: the roadbed top withoutcatchment, singlet roadbed and two-lane roadbed. It also analyzes the effect law ofslope height and gradient to the slope velocity.4. Calculation model of bending slope embankment erosion is established.Analysis is made on the variation law of slope flow rate and starting particle size fornon cohesive homogeneous filler and cohesive filler in three erosion status (theroadbed top without catchment, singlet roadbed and two-lane roadbed) whendepression of the bending slope is different.5. Calculation model of the flow erosion of the roadbed slope groove. Analysis ismade on the variation law of slope flow rate and starting particle size for non cohesivehomogeneous filler and cohesive filler in three erosion status (the roadbed topwithout catchment, singlet roadbed and two-lane roadbed) when erosion groovesdistribution density is different.6. Calculation model of analysis of the shoulder grooves erosion is established.Analysis is made on the shoulder gully damage time for the different filer particlesizes, when shoulder erosion grooves density is different for the single-line roadbed and two-lane roadbed erosion status.