EXPERIMENTAL STUDY ON MECHANICAL PROPERTIES AND DAMAGE EVOLUTION OF FRACTURED ROCK UNDER FREEZING-THAWING ACTION

Damage of the fractured rock mass tends to be more serious under the freezing-thawing action. It is of great practical significance to study the related mechanical properties and damage evolution law. In this paper,the rock-like material is used to simulate the influence of different length fissures and freezing-thawing action on the mechanical properties of rock. The compressive strength,elastic modulus and stress-strain curves of the rock after multi freeze-thaw action are obtained. The results show that the compressive strength and elastic modulus of the rock decrease with the crack length,but the peak strain increases. The whole deformation process of the specimens can be divided into four stages:(1) Prefabricated fissure closed stage,(2) Prefabricated fissure opening stage,(3) Trunk fissure extension stage and (4) Fracture failure stage. The effect of freezing and thawing on the formation of (1) and (3) is the most obvious. The stage (1) increases. For the stage (3),the secondary fissures of the rock accompanied by the expansion of the main fissures are obviously reduced. The testing samples undergoing freeze-thaw action is much looser than the reference samples after experiment is finished,accompanied by a large number of rock powder and mineral particles. For the different lengths of the fracture specimens,increase of the crack length makes the sample more fragmented,and the destruction mode is more and more complex. The results of this study can be expected to provide a reference for the study on the damage and fracture characteristics of fractured rock mass undergoing freeze-thaw action.