Research On Crack Network Of Soil By Fractal Dimension Theory

The distributing regularities of cracks are fundamentary for the cracked soil mechanics and permeability. It is hard to describe the distributing regularities of cracks which have reticular shape by using the traditional statistical method. It is reasonable to use the theory of fractal dimensions to describe the development of reticular cracks which have fractal characteristics. A method for defining fractal dimensions by photograph is presented in the thesis, which makes the definition of fractal dimensions easy and credible. And the following conclusions are also obtained: the fractal dimension can be used to indicate the development degree of cracks, and the fractal dimensions are increased with the increasing of cracks' density, cracks' width and the development degree of secondary cracks.The continuous medium method which widely used in soil is no longer applicable for discontinuous medium such as cacked soil. The equivalent continuous medium model is a widly used model for cracked soil. However, how to determine the size of representative elementary volume is a key problom in the application of the model. By applying the model, it can be found that: the size of representative elementary volume of cracked soil is larger than the size of traditionary test instruments, so it is necessary to use bigger instruments to test the permeability coefficient of cracked soil. The uniformity of crack width and crack density has close relationship with the representative elementary volume.The network analogy of cracked soil is the precondition of numerical simulation and the rationality of the network analogy has direct affection on the credence of numerical simulation. The detailed characters of soil cracks are simulated by the fractal interpolation method and the network of soil cracks are also developed by synthetic use of stochastic network method.