| Popis: |
Understanding the frictional behaviour of rock joints and its associated fluid flow is critical in numerous subsurface engineering applications. Development of underground projects and mitigating their associated hazards, in fact, require a full understanding and accurate modelling of joint shearing processes. Characterising the joint frictional behaviour during shearing, however, offers significant experimental and theoretical challenges. This dissertation, therefore, aims to understand the shearing and fluid flow behaviour of rock joint systems with complex void geometries through assessing the joint contact area evolution both experimentally and numerically. To achieve this aim, first, a large number of direct shear tests at varying normal stresses on dry, and saturated natural and synthetic rock joints are performed. The effect of joint contact area and its influence on actual stresses acting on joint asperities in these tests are then investigated. Furthermore, a novel experimental system coupled with time-lapse X-ray micro-computed tomography (XRCT) is used to measure the contact area and joint aperture evolution during shearing process of several natural joints. The time-lapse XRCT measurements are then extended to synthetic rock joints with varying roughness while joint conductivity is measured under both normal deformability and direct shear testing. Finally, the Discrete Element Modelling (DEM) tool, PFC, is used to model the contact area evolution during shearing of synthetic joints and understand whether the physical processes have been suitably captured. The most important contributions of this dissertation are: i) understanding the effect of joint contact area evolution on joint frictional behaviour and its associated fluid flow, ii) implementing the effect of contact area in hydraulic aperture prediction for more accurate modelling of fluid flow behaviour in joints, and iii) showing that the identified micro-to-macro scale processes involved in contact area evolution can be adequately captured numerically using DEM modelling. These findings provide great insight into the significance of contact area evolution in determining the joint frictional characteristics that influence the hydraulic behaviour of rock joints during complex shearing processes. |
