Abstract: Uniaxial compression test, splitting test and SEM scanning test were performed to investigate the splitting mechanical properties and microstructure of rock containing natural microfractures. The failure modes and tensile strength of rock containing natural microfractures undergone uniaxial compression test and splitting test were analysed; the microstructure of the broken part of rock specimens of splitting failure mode was examined as well. In uniaxial compression test, the failure modes of rock specimens containing natural microfractures were mainly tension failure, shear failure along natural fracture surface, and tension-shear composite failure; the dip angle of natural microfracture had a remarkable influence on the tensile strength of rock which increased with the increase of dip angle. On the other hand, after splitting failure, the splitting mechanical properties were largely determined by the microstructure of natural microfractures which can be classified as three types, namely, root structure, fog area structure, and step structure, among which root structure had the most inferior mechanical properties whereas step structure was of good mechanical properties.

Key words: natural microfractures, dolomite, splitting test, SEM scanning test, failure mode