岩石节理面粗糙度的分形效应与试件尺寸影响分析

 岩石节理面的粗糙度是影响岩体形变、位移和强度的主要因素,准确量测岩石节理表面的粗糙度对评价岩石力学特性非常重要.根据分形理论,岩石节理表面具有分形特征,可用分形维数描述节理表面的起伏度,但是岩石节理表面粗糙度一般不具有严格的自相似分形性质,因此,表面分形参数(分形维数D和截距A)的量测结果受到尺度的影响.本文运用三维表面激光形貌仪扫描10个不同尺度的试件(尺寸为100mm×100mm—1000mm×1000mm),结果表明,D和A随试件尺寸增大而减小,两参数都有尺度效应,但存在一个极限尺寸.综合考虑岩石表面尺寸、试件长度以及测量尺度对岩石节理表面粗糙度的影响,提出可靠的分形测量途径.

Analysis of the Fractal and Sample Size Effects of the Rock Joint Surface Roughness

The surface roughness of rock joints is a major factor that influences the rock mass deformation, displacement and strength. So its determination is very important for the evaluation of rock mechanical properties. The rock joint surface may be assumed to have fractal characteristics, and its fractal dimension can be used to describe the roughness of the surface joints, but the surface roughness of rock joints generally does not strictly have the nature of fractal self-similarity, so, the measurement results of surface fractal parameters (fractal dimension D and the intercept A) would be affected by the scale. In this study, the 3-D superficial laser topography instrument was used to scan samples of 10 different sizes (ranging from 100mm×100mm to 1000mm×1000mm ). It is shown that both the fractal dimension D and the intercept A are indeed scale-dependent, but the scale effect and their values decrease with the increase of the size of the sampling windows, and a limit size exists. Considering the rock surface size, the sample length and the measurement scale on the rock joint surface roughness, an acceptable solution for fractal measurements is proposed to assess the properties of rocks.