Differences in the failure process of grottoes sandstone in southern and northern China determined by microstructure

Grottoes rock in northern and southern China exhibit distinct failure modes, which is perhaps attributed to different rock microstructures. To elucidate the controlling mechanisms of microstructure on the grottoes’ failure mode, comparative studies were conducted on sandstones from seven grottoes. By uniaxial compression and ultrasonic wave tests, correlations between microstructure and crack critical stress were established. Critical crack stress has a strong negative correlation with grain size and a positive correlation with cementation, whereas its correlation with mineral content is weaker relatively. Grain size and cementation almost determine crack initiation and propagation. Due to the large grain size and low cementation of the grottoes sandstone in northern region, the macro failure exhibits an instantaneous failure pattern. In contrast, for grottoes sandstone in southern region, smaller grains and higher cementation results in a progressive failure pattern. Accordingly, conservation programs for different grottoes in northern and southern China have been proposed.