Experimental study of the mechanical, energy conversion and frictional heating characteristics of locking sections

Experiments on sandstone specimens are conducted to investigate the mechanical, energy conversion and frictional heating characteristics of locking sections in two types of large-scale rockslides. The flaw geometry of the conceptual model is a combination of two preexisting flaws and a locking section. A deep insight into the failure mechanism of locking sections is gained by using digital image correlation (DIC) technology, thermal imaging technology, and thermodynamics theory. Two different types of failure patterns are reproduced in our experiments: the retaining wall type and step-path type, which are shear and tensile in nature, respectively. The results obtained by DIC measurements demonstrate that the failure process of a locking section is a progressive development of strain localization zones, which actually reflects the displacement discontinuity when a crack propagates. The variance and differentiation rate are defined to provide differentiation and precursory information on the deformation and fracturing process of a locking section. From the energy point of view, the strain energy conversion (accumulation, dissipation and release) during loading significantly influences the failure pattern of the locking section. The faster the post-peak conversion rate of strain energy, the more violent is the post-peak fracturing behavior of the locking section. A strong positive correlation is found between the post-peak conversion rate of strain energy and the brittleness index. Furthermore, thermal imaging technology is applied to describe the frictional heating behavior. The correlation among the failure pattern, energy conversion, and thermomechanical response is analyzed. The frictional heating phenomenon is related to the shear failure, and a fast post-peak conversion rate of strain energy occurred along the locking section.