A New Direct Tension Test Method for Soils and Soft Rocks

Tensile strength plays a crucial role in many engineering activities involving soils and soft rocks. Currently, several methods for tensile strength determination exist, the most common of which include the direct tension method, Brazilian test, ring test, axial fracturing test, bending test, and hydraulic fracturing test. However, outstanding problems associated with these methods, e.g., undesirable eccentric forces and damage of specimen ends, significantly affect obtained tensile strength values. To overcome these problems, we propose an alternative direct tension test method together with the newly developed apparatus. The proposed method uses an annular specimen that is tension-loaded on the inner hole. The method was evaluated through a series of tests on undisturbed soil and remolded gypsum-sand mixture specimens. For validation, comparison of results between the proposed method and the International Society for Rock Mechanics (ISRM)-suggested method was performed. Based on the results of the experimental program, the proposed method is considered more capable of and more suitable for determining the tensile strength of soils and soft rocks than the ISRM-suggested method.