Estimating the strength and deformation of columnar jointed rock mass based on physical model test

Abstract

The complex structure of the columnar jointed rock mass (CJRM) brings difficulty in determining its field mechanical parameters, and a reliable estimation of the strength and deformation of CJRM is crucial for engineering safety. Uniaxial compression tests were conducted on artificial CJRM specimens with columnar structures of quadrangular, pentagonal and hexagonal prisms to model the mechanical behaviour of the CJRM. The strength and deformation anisotropy were compared and analyzed on the basis of the results by combining the structural features of the three models. The failure modes and mechanisms were summarized in accordance with the failure processes and final appearances of artificial specimens. The empirical relations of predicting the field mechanical parameters were derived on the basis of the joint factor approach, the empirical gradient method and the rock quality designation (RQD). For the CJRM of the Baihetan Project, the proposed empirical correlations were used to estimate the field unaxial compression strength and elastic modulus, and the predicted values were compared with those obtained from the field tests and other empirical methods. Results revealed that the estimated values calculated by the proposed empirical equations are in good agreement with the field test results, and the three empirical relations can predict the mechanical parameters of the Baihetan CJRM effectively. The empirical relation based on RQD is extremely valuable when RQD is the only available information about discontinuities in site investigations.