Flow distribution and transport of matter in fractured rock media is largely controlled by their intrinsic heterogeneities that are present both at the network and individual fracture levels. In both cases the structures are generally characterized by multiple characteristic length scales which strongly influence the transport properties. A study of the influence of the wall rugosity on the flow field in single fractures will be presented as an example: the rugosity of many fracture surfaces can often be characterized as a self-affine geometry of characteristics depending on the consolidation of the material and on the inter- or intra- granular nature of the fracture mechanism. The basic phenomenon of grout propagation is tried to be described as a continuous fluiddisplacement in deformable saturated porous media. The solution of mathematical formulation results in a highly coupled and non-linear system requires specific numerical techniques. The pressure – displacement formulation is discretized in porous media by application of the weighted residual method. The whole system is then integrated in time by means of a simple three level scheme for non-linear variation of parameters. This paper describes a new approach to modeling injecting domain (fractured rock) based on a nonlinear Darcian flow and theory of consolidation. The proposed model utilizes the variation of the coefficient of permeability with respect to the pore fluid pressure based on a nonlinear Darcian flow characteristic below certain hydraulic gradients. The potential of the proposed model is evaluated in predicting the propagation of grouting due to a single injection bore hole. The general comparison indicates that this approach is capable of solving injection boundary value problem.
Chemical grouting has been used extensively as a way to improve rock characteristics. Mechanism of grout propagation in porous media as a coupled problem is deplored by the lack of design technology. Among the various basis hypotheses necessary to derive a macroscopic model of flow in porous media, the most relevant one may be adopted as a diffusion of grout in the fluid phase. Generally, grouting is terminated either when a defined grouting pressure is obtained, or when the capacity of the available pump does not allow an additional increase. However, it is quite logic to assume the pressure increase due to either to plugging or to narrowing of such a flow path through porous media. Although, it can be assumed that the thin sections in porous media display homogeneous cement stone with dewatering canals, which are filled with the solid particles floated in grouting materials. Grouting tests using performed cracks showed that a complete filling cannot be achieved if excessive bleed water is present. Since this water must escape, a system of draining canals with nonhomogeneous cross sections along the water paths must develop. Furthermore, it seems also to be certain that grout hardening takes place in a motionless state because no indications for a parallel orientation of longish grains, similar to a flow texture, have been found experimentally [3], in the thin sections.
