Size Effect on Surface Height and Aperture Distributions of a Fracture

Surface heights of a fracture about 1 m in length were measured by using a large measuring system with a laser type displacement transducer to clarify the size effect on surface height and aperture distributions of a fracture. Based on the measured data, the size effect on the standard deviation and mean aperture of the fracture was studied. The results are summarized as follows: 1. Standard deviations of both surface height and initial aperture increased with an increase in the fracture size. However, standard deviation of the initial aperture did not increase as that of the surface height did. 2. When the wavelength exceeded 100 mm, the power spectral density function of the initial aperture became constant. Moreover, the standard deviation of the aperture was estimated to become almost constant when the fracture size is greater than 1000 mm. On the other hand, the mean aperture is still increases at fracture size of 1000 mm. This is because a few sharp asperities are greatly influenced by a certain projected contacting point.