Continuous Porous Medium (CPM) models

Continuous Porous Medium (CPM) models are considered the appropriate models for certain types of rock and porous materials, in which flow is predominantly through an interconnected network of pores between the solid grains making up the rock or material, such as for many sandstones, soils, clays, unconsolidated deposits, and backfill material. The model assumes continuity in three dimensions and hence a high degree of connectivity between points in the modelling domain. Connectivity is only reduced when very low conductivity layers or flow barriers are incorporated in to the model. The flow through such domains is modelled by Darcy's law, which relates specific discharge (Darcy flux) to the driving force, i.e. the pressure gradient and/or buoyancy force.

It is generally not appropriate to represent fractured rocks as a CPM as it does not represent the discontinuous, heterogeneous and anisotropic characteristics of flow in such rocks. However, it can be used to represent parts of the system such as the backfilled tunnels that behave like porous media, or far from the region of interest where it is only necessary to provide an approximate representation of bulk properties over large volumes. The concept can be elaborated to represent some of the characteristics of fractured rock by use of an Equivalent Continuous Porous Medium (ECPM) representation where hydraulic properties within each finite-element are anistropic and differ between each finite-element to represent the underlying structure and properties of a fracture network.

In ConnectFlow, CPM models can be used to represent the following:

ConnectFlow CPM models have been used in the following applications: