Large Lateral Deformation Characteristics of Simulated Columnar Jointed Rock Mass under Uniaxial Compression Tests

The columnar jointed rock mass is a common structure in extrusive igneous rocks. Due to the columnar joints network, large lateral deformation may result from slipping along these columnar joints and the corresponding lateral strain ratio may greatly exceed the upper limit of Poisson's ratio. Correct understanding of the large lateral deformation characteristics of columnar jointed rock mass is essential to the design of tunnels and underground caverns where the uniaxial compression condition usually occurs. Therefore, in order to perform uniaxial compression tests, simulated columnar jointed rock mass specimens with different dip angles were prepared using plaster mixtures, and the curve of variation of lateral strain ratio to dip angle was obtained. The shape of the curve resembles as inverted U-typed and the maximum of lateral strain ratio occurs at β = 30°. The mechanism of large lateral deformation is explained in light of the dip angle and failure modes, and an experimental equation is presented to predict the variation of lateral strain ratio to dip angle.