Real Contact Area for Mated Rock Joint Using Pressure-Sensitive Film Comparing With the Result of Boundary Element Method Including Plastic Deformation

Abstract The real area of contact between rock surfaces plays a key role in determining the deformation properties of rock joints. There has been a growing trend toward measuring the real area of contact of rock joints using pressure-sensitive films, which are commonly used in the mechanical engineering industry as pressure sensors. A rock joint closure test was conducted, in which the real area of contact was measured using the pressure-sensitive film. The boundary element method (BEM), considering plastic deformation, which takes into account the measured topographies of the rock surfaces, was used to predict the real area of contact. The current investigation provides valuable insights into the proper usage of pressure-sensitive films in rock joint tests. The results show that, without considering destructive deformation, the elastic–plastic model effectively simulates the contact distribution. Under the studied loading conditions, the proportion of plastic deformation decreases as the load increases for the contact area. The negative exponential relationship between the load and the average aperture based on the Hurst index (H) is proposed. The contact stress can be calculated by the BEM according to the contact area comparison. This provides a valuable reference for rock fracture contact deformation theory.