Physical Simulation of the Response of Overlying Rock to Additional Loads in an Old Goaf of a Coal Mine

The special overburden structure formed after coal mining is a key element for maintaining ground stability. To study the effect of additional ground loads on the overlying rock and ground deformation in the old goaf, a physical simulation test was adopted. Accordingly, a physical model of the overlying rock structure in an old goaf of a coal mine was loaded onto the upper part of the model and combined with digital speckle and optical-fiber sensing methods to analyze the influence of different levels of loads on the deformation of the overlying rock in the old goaf. The results show that additional loads have a greater impact on surface deformation. Specifically, the maximum deformation increased from 244 to 384 mm with increases in the load, mainly due to the compression deformation of the loose layer of the overburden. The additional load can be transferred to the bottom of the model; however, the increase in the maximum deformation becomes less obvious with increases in the load series, to a maximum of only 0.95%. The effect of the additional load on the overlying strata of the old goaf is mainly reflected in the shallow surface, while its influence on deep rock formation is limited. The results show that, as the additional load increases, the deformation of the overlying rock in the goaf is small.