Given that rock bulking is of great significance to water storage capacity and ground surface subsidence of coal mine underground reservoir

the 22615 working face in one mine of Shendong coalfield was selected as the engineering background. The stress and the bulking coefficient distribution laws of caving rock in goaf were analyzed by using the similar material model test

and then the stress-bulking coefficient relation of caving rock was established

which was verified by rock compaction experiment. Moreover

the compaction characteristic of saturated rock was revealed. The results show that: along goaf advancing direction

overlying strata subsidence is limited by the structures of cantilever beam near the boundary where the stress of caving rock is relatively low (0.32 MPa)

and the corresponded maximum bulking coefficient reaches 1.48. Due to the instability of main roof structure

caving rock is compacted by overlying strata in the middle area

rock stress trends toward 1.5 MPa

while bulking coefficient reduces to 1.09. It is clear that the height exhibits a negative correlation with caving rock stress but a positive correlation with bulking coefficient in goaf vertical direction. There is a negative logarithmic relationship between stress and bulking coefficient of caving rock along either advancing direction or vertical direction. By comparing with natural rock

the bulking coefficient damping of saturated rock shows obviously under loading

which has a difference of 8.514%. This study provides a theoretical basis for water storage capacity and ground surface subsidence predictions of coal mine underground reservoir.