Tortuosity factor exerts a major influence on fluid flow in porous medium. However, this factor is very difficult to quantify from experimental measurements, particularly in deformable medium. It is commonly treated as an empirical or curve-fitting parameter in determination of permeability. This study attempts to use the electrical resistivity measurement method as an ana- lytical tool to study how changes in grain fabric affect changes in tortuosity. The first phase of the study concentrates on development of a framework on the flow tortuosity behaviour observed in idealized granular assemblies of regular packings with uniform spheres subjected to various types of grain fabric alteration, such as matrix dilation and grain rearrangement (rolling and overriding). Then, the framework is extended to interpret data measured in real random systems of intact and sheared oil sand specimens. It was found that the locked structure in intact oil sand specimens produce relatively high tortuosity factors as compared to those in the idealized packings. Shear deformation disrupts this intrinsic structure reducing the tortuosity factor to about one-fifth of the initial value. This peculiar behaviour implies that the permeability of oil sand is very sensitive to shear deformation or grain fabric alteration.