ABSTRACT
In addition, many water-absorbing minerals such as montmorillonite, kaolinite and illite exist in some strata. When water or drippy air accessed the fractures of surrounding rocks, the surrounding rocks would expand asymmetrically and asymmetrical stress would distribute in the inner of the rocks. At last, it would lead to the surrounding rock fracture and collapse (Zhang et al. 2011). When the original rocks lost their water and became shrinkage, new fractures would be induced and subsequent extension would be expected. At this time, if the original rocks were exposed to water or drippy air again, the expanse would be more serious and results in a persistent deformation of the roadways. The most obvious deformation for this kind of roadways is floor heave. Especially under the repeated influence of mining stress, fatigue failure of the surrounding rocks occurred easily.
