Experimental Research on the Dilatancy of Rock Joints With Different Opening Values Under Freezing Conditions

Direct shear tests were conducted on frozen rock joints. The variations in the dilatancy features of these joints were investigated under the correlativity of different opening values and the maximum fluctuation degrees of the joints. Furthermore, a contrastive analysis of the dilatancy features of rock joints at freezing and normal temperatures was conducted. Results showed the total regularity of the "initial dilatancy and subsequent compression." However, different dilatancy features were revealed under different normal stresses when the opening value of a joint was smaller than its maximum fluctuation degree. The dilatancy amount of the joint reach edits maximum value under a medium stress level, and the final normal displacement increased as the normal stress increased. By contrast, only a minimal dilatancy effect was induced in the growth stage of the shear stress because of the ice microcrystalline particle dislocation, which occurred when the opening value was greater than the maximum fluctuation degree of the joint. Under the same normal stress, when the joint opening value was large, the amount of dilatancy was relatively small compared with that when the joint opening value was small, and the final normal displacement of the joint surface was relatively great compared with that when the opening value was small. The contrastive analysis results on the dilatancy features of joints under normal temperature showed the following: at a normal temperature, the dilatancy amount of the joint monotonously increased with an increase in the shear displacement, and the final dilatancy amount was larger than that under freezing conditions.