基于数字图像处理技术的岩石节理分形描述

Fractal description of rock joints based on digital image processing technique

岩石节理的粗糙度对结构面的剪切强度起着重要的作用。分形维数对节理的次级细微粗糙结构能够进行很好的描述,而对节理的一级起伏结构体现并不明显。考虑了节理形态的层次性,用分形维数代表节理的次级精细结构,即节理的粗糙度;用起伏度表示节理的一级波状形态,据此提出用分形维数D和起伏度Wd两个指标来描述JRC(节理粗糙度系数),并给出相应的计算公式。另外,针对工程实践中分形维数准确快速量测存在的困难,本文以摄影测量为基础,借助数字图像处理技术,在VC++平台下开发了节理轮廓线分形维数计算程序,为分维较准确方便地应用于工程实践做了有益的探索。

Joint roughness has an essential in？uence on the shear behavior of rock joints.Fractal dimensions（D） can be used to effectively reflect the roughness property contributed by the secondary asperity;however,it is not ideal to represent the asperity contributed by the first-order asperity.On the basis of the asperity of a rough joint occurring on many scales,the fractal parameter is used to show the roughness character offered by the secondary asperity,while the degree of a waviness（wd） is used to reflect the roughness property at the first order.In this respect,joint roughness coefficient is represented using the fractal dimensions（D） and degree of the waviness（wd）,and their relationship is established.On the other hand,in virtue of the difficulties in calculating the value of D in engineering practices,a procedure is provided for obtaining the fractal dimension based on the digital image of rock joints.It will be helpful for applying the fractal dimension to describing the JRC in engineering practices.