Damage characteristics of anchored fractured rock masses under freeze–thaw cycling by computed tomography

Abstract

The freeze–thaw (F-T) damage characteristics of anchored fractured rock masses are different from those of fractured rock masses without bolts. To explore the F-T damage location and characterize zonal damage of anchored rock masses, two stages of F-T cycle tests were conducted for the samples with no bolt, 45° bolt and 90° bolt respectively. CT scan tests were performed before and after F-T cycling. Visual damage was qualitatively evaluated through 3D image reconstruction of CT data. The zonal damage characteristics of the samples were quantitatively analyzed using 2-d CT slices, areal porosities, and damage variables of each slice. The results show that the F-T cycles can cause damage in the rock zone, propagation zone, and anchor zone. The damage to samples with a bolt was relatively small, and the damage to the 90° anchor samples was less severe than that to 45° anchor samples. Compared with the samples with no bolts, some of the damage in the propagation zone of the samples with a bolt was transferred to the anchor zone through the bolt, which led to the deterioration of anchoring performance of the bolt. It is necessary to pay attention to the effective reinforcement range within a rock mass reinforced by bolting, and the rock mass outside the reinforcement range is more prone to crack propagation due to the increased frost heaving caused by prestress. The results provide a reference value for the reasonable design of anchorage engineering works in cold area.