Abstract: This study aims to research mechanical properties of deep mixed ground under condition of different confining pressures and different thickness ratios between hard rock and soft rock. The cement and kaolinite have been used as simulation materials to make the artificial mixed ground; and then the mechanical tests and numerical simulation FLAC3D are used to study the influence of various surrounding pressures and different thickness ratios on the mechanical properties. The results show that the artificial mixed ground can satisfy the need of strength difference. And the mixed ground has the strain hardening phenomenon when the confining pressure ascends, then this phenomenon disappears due to the discordant deformation between the soft and hard rock, and the irregular fractures increase in the soft part of the mixed ground. It is also shown that the mechanical properties of deep mixed ground are controlled by the rock in majority without considering the structural plane effect. The numerical simulation and the mechanical tests show similar stress-strain curves and both indicate that deformation of mixed ground mainly occurs in the soft part.

Key words: mixed ground, mechanical properties, physical simulation sample, FLAC3D