Research on the morphological characteristics and the sequence determination method of the collapse of combined rock strata structures

The collapse of rock strata results from the widespread movement of overlying rock strata induced by damage in stope structures. To analyze the caving process of the overburden in coal mines, this research divides the overburden in the working face into multiple combined strata structures, transforming the complex problem of strata caving into the problem of determining the caving sequence of multiple combined strata structures. This paper believes the rigidity of rock layers is a key indicator for classifying bearing layers and deformation-controlled layers within the combined strata structures. Based on the characteristics of the controlled deformation and collapse in the overburden, the paper also defines key strata and ordinary bearing layers. The former controls both the deformation and the collapse of the combined rock strata while the latter only has control over their deformation. This paper has studied the mechanism of stepped subsidence of combined strata and put forward the method of determining the caving sequence of combined rock strata. Taking near-horizontal mining as an example, this paper has simulated the caving process of combined rock strata by using the RFPA2D numerical simulation software and summarized that the caving process of the overburden is relevant to the transition failure law of combined strata structure. The research result can quickly determine the caving layer of the overburden in mining fields and provide theoretical basis for selecting supporting equipment and warning of mine pressure disasters.