ABSTRACT
For the study of grotto 3 in Longyou grottos, many scholars have done some significant work. For example, in order to understand the integrality of the pillars, Xia et al. carried out sonic wave detection to research the stability of rock pillars, drawing the conclusion that the sonic wave velocity in the parts without distinct fractures on the three pillars (3-1, 3-2, 3-3) is similar to that of intact rock, and two fractures appeared on the pillars at the opening of grotto No. 3 (Xia et al. 2006). Fu et al. have studied the cracking mechanism by monitoring the deformation process of pillar 3-2 in grotto 3 (Fu et al. 2009). The water penetration, the alternation between drying and wetting, and change of temperature enhanced the weathering, and resulting in the strength reduction of the pillars. Wang et al. studied the effects of deformation of pillar 3-2 on the stress change of grotto No. 3. Results showed that strength decreasing of pillar 3-2 exacerbated the appearance of cracks on the grotto roof (Wang et al. 2010). Deterioration of meso-structure in rock material results in the continuous deformation and failure to pillar, and this would further affect the stability of the overall grotto. Therefore, the research on the failure cracking process of rock pillars is helpful to grasp the failure mechanism, and provide theoretical basis for pillar refinement.
