A review of test methods for uniaxial compressive strength of rocks: Theory, apparatus and data processing

The uniaxial compressive strength (UCS) of rocks is a vital geomechanical parameter widely used for rock mass classification, stability analysis, and engineering design in rock engineering. Various UCS testing methods and apparatuses have been proposed over the past few decades. The objective of the present study is to summarize the status and development in theories, test apparatuses, data processing of the existing testing methods for UCS evaluation. It starts with elaborating the theories of these test methods. Then the test apparatus and development trends for UCS evaluation are summarized, followed by a discussion on rock specimens for test apparatus, and data processing methods. Next, the method selection for UCS measurement is recommended. It reveals that the rock failure mechanism in the UCS testing methods can be divided into compression-shear, compression-tension, composite failure mode, and no obvious failure mode. The trends of these apparatuses are towards automation, digitization, precision, and multi-modal test. Two size correction methods are commonly used. One is to develop empirical correlation between the measured indices and the specimen size. The other is to use a standard specimen to calculate the size correction factor. Three to five input parameters are commonly utilized in soft computation models to predict the UCS of rocks. The selection of the test methods for the UCS measurement can be carried out according to the testing scenario and the specimen size. The engineers can gain a comprehensive understanding of the UCS testing methods and its potential developments in various rock engineering endeavors.