From previous research, it has been proven that rock roughness and closure are two important factors for stability of backfilled stope and exposed backfill. In order to estimate the important parameters of roughness, several investigations have been conducted in other scientific fields to study roughness. The results showed that the important roughness parameters are application-dependent. In geology and rock mechanics the Joint Roughness Coefficient (JRC) is a critical factor that incorporates the roughness in stability problems. Although JRC is widely used, it is very subjective and highly depends on the experience of the individual conducting the analysis. During the last several decades there were attempts to use different methods such as fractal geometry, Fourier analysis, analytical methods, etc. to convert a random surface profile into a JRC. The goal of the current research is to estimate with greater accuracy the contribution of roughness to the shear strength of the interface at the paste-rock contact when backfilling. Four hundred and fifty backfill samples were constructed and tested in a shear box. The variables of the tests are three: binder percentage, roughness and cure time. From the test results the importance of each of those parameters to the final shear strength of the paste-rock interface was estimated. The normal stress that acts on the samples is also a critical factor. From the tests that were tried, it was concluded that there are limits in normal stress for which roughness is important. / Thesis (Master, Mining Engineering) -- Queen's University, 2009-08-27 16:07:21.916