Determination of Strength and Deformation Properties of Columnar Jointed Rock Mass Using Physical Model Tests

The strength behavior and deformation modulus of columnar jointed rock mass have been investigated by conducting a series of uniaxial compressive tests, along with consideration of columnar joint effect. The tests have been performed on the artificial physical model samples, incorporating different angles beta (which was the between the loading direction and axial direction of the columns) and heights of specimen. Columnar joint is a special geological structure with self-organized joint network which separates the rock into an assemblage of blocks. Due to the special joint network, the anisotropic characteristics of columnar joint rock mass is very remarkable. The physical model consisted of "intact rock" and "jointed filler", replaced by cement mortar and white cement, respectively. The angle beta were set to 0A degrees, 15A degrees, 30A degrees, 45A degrees, 60A degrees, 75A degrees and 90A degrees, respectively, and the heights of specimen were set to five different values. Through the test, failure strength and failure modes of columnar joint rock mass with different angles beta were observed. Based on the analysis of the test results, the uniaxial compression strength and average modulus of columnar joint rock mass showed strong anisotropy, showing a special "U" shape in terms of loading orientation. The size effect of columnar jointed rock mass was very typical, and the failure mode of columnar joint rock mass were analyzed. Furthermore, the relationship between failure strength and joint factor was studied.