When the sand dries out or gets wet, the shape of a structure may change, and "landslides" are common. Furthermore, the mixture of fine (mostly sharper) and coarse sand granules is very important to achieve good "sand construction" results. Fine granules that have been rounded by the natural influences of seas, rivers or fluvials, in turn negatively influence the bonding between the individual granules as they more easily slide past each other. Research is thus necessary to find the most suitable sand to achieve an optimal, landslide-free construction.