Experimental study on deformation field evolution during failure procedure of a rock borehole structure

The failure procedure of a rock borehole structure is experimentally studied using a specially designed deformation field inspection system (Geo-DSCM system). The borehole specimen, which is manufactured by drilling a hole at the center of a marble plate, is uniaxially compressed to failure with the speed of 0.02 mm/min. Deformation fields through all the loading procedure are inspected and analyzed. It is shown that the deformation field localizes on the sections in tension at the early stage of loading.. While when specimen is loaded almost to the peak of loading curve, two new X-shaped localization bands, which are at angle from the loading direction, occurred. Finally only one localization band maintained and formed the macro fracture that failed the structure.