Study On Mechanical Properties Of The Unloading Columnar Jointed Basalt Rock Mass

The under-construction largest total instal ed capacity, Baihetan Hydropower Station on Jinsha River has exposed a large number of column jointed basalt rock mass. Since the structural particularity of the of the columnar jointed basalt rock mass, it is necessary to research the mechanical behavior of the unloading column jointed basalt rock mass, means the column jointed basalt rock mass unloading layer.By material gathering,testing on the spot and acoustic wave test of rock mass etc. The deformation and strength characteristics of the unloading column jointed basalt rock mass were studied based on the unloading relaxation characteristics of the dam area of columnar basalt. The main study works of this paper focus on the following several aspects:Firstly,the longterm-acoustic wave test of column jointed basalt rock mass both adits and slopes by Huadong Engineering Corporation Limit suggestsd that the unloading relaxation of the column jointed basalt rock mass are both timeliness and dimensional effect:the relaxation depth is positively correlated with the size while size is not large enough,and no longer increases when size is large enough and usual y stability in 0.6~2.9m, and also influenced by shear zones with varying degrees.Secondly,both the rigid bearing plate test and triaxial test show that the deformation modulus of the unloaded-relaxation column jointed basalt rock mass have a obvious anisotropy affected by both Confining pressure and normal stress, the effect of normal stress level on the deformation modulus is a nonlinear relationship between stress and strain,the rebound deformation curve has significant nonlinearity.Finally,we find out the model parameters of both Mohr-Columb and Hoek-Brown strength criterion of unloaded-relaxation column jointed basalt rock mass on Baihetan by triaxial test.