Morphological Analysis And Numerical Simulation Of Soil Surface Shrinkage Crack

At present,the development law and formation mechanism of soil dry shrinkage fracture are not clea.To reveal the development law and the formation mechanism of the farmland soil surface shrinkage cracks,the crack of farmland soil were studied in this thesis,binarization,noise removal and edge extraction of fracture treatment were used on test image of farmland soil cracks by applying digital image processing technique,three morphological parameter Minkowski area,length and Euler number as indicators of quantitative fracture analysis could describe the spatial distribution of fracture as well as connectivity morphological.We dealt crack test image with morphological dilation and erosion operation,then variation of area,length,and Euler number density of operated crack test image were analyzed.Simultaneously,We constructed a two-dimensional soil cracking model based on Hooke's law,simulated dynamics cracking process among soil shrinkage.The model assumes that water evaporation is the main cause of crack,and the thickness of the soil layer where cracks are generated is small enough.Build a normal distribution N(?,?2)to soil critical strain field that the mean is ?,the variance is ?2,and take friction f as a soil static adhesion force,and grid structure contraction frequency nit,which can represent soil elasto plasticity,simulate water evaporation in hexagonal network structure composed of nodes which distance between nodes continued to reduce,resulting in network node fault as the change of force in the process.In this thesis average value of the test image area,length and Euler number density were compared with simulated fractured image.Results show that:(I)Fracture morphology could be described with Minkowski area,length,Euler number density function effectively;Minkowski area,length,Euler number density function of fracture has different variation as morphological analysis shows,among which area density function showed as an increasing function between 0 and 1;the length density function shows the variation law of increases first and then decreases tendency,the Euler number density function shows the variation law of increases first,and then decreases,finally increases again.(2)With two-dimensional soil cracking model based on Hooke's law,simulating cracking process among soil shrinkage cracking due to the evaporation of water,Calculating fracture area,length,Euler number density and the average ?,standard deviation 8 of each parameter obtained with Monte Carlo method,the average density value is basically distributed in the density value between ?±?,which indicated that results are good.(3)Relative error of test,simulation of the area density and the average value of Euler number density is small,relative error of the area density is less than 10%,relative error of the Euler number density about 15%;relative error of mean length density is larger,among 38-48h,its less than 10%,in the rest period its greater than 25%,the maximum relative error is 37.38%.Simulation of soil surface crack with numerical method is helpful to study the formation of farmland soil cracks as well as dynamic evolution mechanism law in the process that soil crack changes with time.