Reconstruction And Numerical Modeling Of Three-dimensional Random Crack Network In Soil

Cracks are common in surface soils. The presence of cracks in surface soils canreduce the shear strength and increase the hydraulic conductivity of soils. Manyexperiments have been conducted to investigate the influence of cracks on soil mass.However, experimental researches have many disadvantages such astime-consuming, difficult to control the external conditions (temperature, humidityetc.) accurately, and soil sample size restricted etc. With the development ofcomputer technology and the microscopic observation technology, crack networksimulation which is based on statistics and probability theory is brought into theresearch of cracked soil. Only has the accurate network model for soil mass beenestablished, the analysis results of seepage and mechanics would be reliable.In this paper, a three-dimensional crack network in soils is reconstructed, thestatistical parameters of the cracked network are obtained and the three-dimensionalrandom crack network can be simulated based on these parameters. Firstly, usingthe CT scanning technology, the cross section photos at different locations of thesoil samples are obtained. Then the positions of every trace line are extracted andthe crack planes in three-dimension space are reconstructed. The characteristicparameters of cracked planes are calculated. Secondly, in order to establish thestatistical model of cracked planes, the statistical parameters of planes includinginclination, dip angle, center coordinates and shape parameters are calculated andanalyzed. Finally, according to the Monte-Carlo method, random variables of thegeometric parameters are used to generate and the3-D network model for crackedsoil is formed. The analysis domain is a part of the whole3-D model which is usedto study the seepage through the cracked soil. The intersection between the crackedplanes and the boundary will be calculated. The intersecting lines among crackedplanes will also be calculated. All of the calculation programs are written inMatlab.More accurate result about the distribution of the cracked plane can be got byusing the CT technology. The results of the study show that the reconstructingtracing lines of the3d cracked plane are similar to the original tracing lines inlength, location and angle etc, although there is some difference. These indicate that the method of reconstructing the cracked plane is correct. The results of probabilityanalysis about the cracked plane show that the parameters of the crack are followingto certain distribution rules, such as obliquity and length following lognormaldistribution; tendency and angle following normal distribution; center coordinatesfollowing uniform distribution; depth and radius following index distribution. Theresult of checking computations to3-D random crack network model shows that themaximum error between the theoretical value and calculated value is only0.3%.Therefore, the calculation program can accurately realize to generate3d randomfracture network and to analysis the analysis domain with the intersection betweenthe cracked planes.