During the development of hydropower stations in Southwest China

more and more attentions have been paid to the engineering mechanical properties of columnar joints rock mass. As dam foundation of Baihetan Hydropower Station is composed of columnar joints basalt

of which the magnitude of RQD is widely lower and integrity is poor; and the mechanical indices such as deformation modulus

is relatively lower. Meanwhile

the rock mass significantly shows anisotropy. Therefore

it has imposed a certain impacts on the deformation of arch dam

and the stability of abutment

high slope

and underground rock caverns; it has become one of the key technical issues of Baihetan Hydropower Station. As we know

the researches on columnar joints rock mass and related engineering experiences at home and abroad are few. Therefore

in order to obtain the first-hand observation data reflecting mechanical properties of columnar joints rock mass

we plan to develop the large-scale columnar joints experimental cavity. The geologic origin and characteristics of columnar basalt and the design proposal of experimental cavity are introduced here; the combination of in situ experiment and numerical experiment is discussed. Then anisotropic constitutive is use to simulate the excavation and in-situ experiment and the representation sites are appraised.