In this study, in order to observe how nano-materials have an effect on the engineering properties of a high plasticity building soil with 91.56% clay and silt; Atterberg limits test, standard proctor compaction tests and unconfined compressive strength tests were performed on samples containing 0.25%, 0.5%, 0.75%, 1% percentages of nano-clay. In addition, a 3D crack roughness and fractal analysis associated with micro-structural investigation were carried out on the damaged samples to clarify the failure process of the samples. The results proved that nano-clay reduces pores by filling the gap between the particles, binds the particles together and consequently reduces the optimum water content of the soil as confirmed by a quantitative micro-structural analysis. Finally, the micro-structural analysis also shows lack of nano-clay close to the confined area and more nano-clay were found concentrate at the middle section indicating superior compressive and shear strength. However, when the three-dimensional surface curves and fractal analysis results are examined, the depths of the points of the sample with 0.25% nano-clay are much greater in each location compare to those of the other samples.