## 1 Introduction  
When studying the movement rules of coal mining overburden, researchers usually divide the overburden into three horizontal zones and three vertical zones according to the shape of rock mass in front and back of the working face. To be specific, along the horizontal advancing direction of the working face, the overburden is divided into the recompacted zone, separation zone, and coal wall supporting zone; along the vertical direction, the overburden is divided into the caving zone, crack zone, and bending subsidence zone from the bottom up [1]. The strata that play the control effect in the activity of rock masses were designated as the key strata, and the rules of deformation, separation, and fracture of the strata affected by the key stratum behavior were studied in detail [2]. The position, size, and development characteristics and their influence factors of bed separations have been analyzed deeply by experimental and theoretical methods. The results show that bed separations mainly occur below the key strata [3]. [PERSON] and [PERSON] investigated the effect of key stratum on the mining abutment pressure with different key stratum thicknesses and heights by numerical simulations [4]. An in situ investigation was carried out to determine the law of fracture and movement of a key stratum [5]. A distributed optical fiber sensor (DOFS) and multipoint borehole extensometers (MPBXs) were collaboratively employed to monitor the deformation of high-level key strata [6]. The corresponding relationship between the change of goat pressure and the key stratum break by physical simulation and field measurements [7]. [PERSON] et al. used the key stratum theory to study the fracture mechanism of overlying strata during longwall mining [8]. According to the present research results, key strata controlled the development height of water-conducting fractures [9]. A water-flowing fractured zone height prediction method based on an improved key stratum theory was established and applied [10]. The influence of periodic movement of key strata on the downward leakage law of harmful gases was analyzed [11]. Fracture types of key strata were identified through the moment tensor inversion [12]. A fracture aperture mechanical model based on key stratum fracture was used to analyze the main influencing factors of high key stratum fracture and rotation [13]. The fracture characteristics of overlying strata during underground coal mining were analyzed via similar simulation [14]. The dynamic disturbance effect on front coal-rock masses as the key layer fractures which shows that dynamic disturbance effect caused by high intensity mining is relatively conspicuous on the fractured stratum [15]. Changes in overburden movement, groundwater level, and groundwater intrusion were monitored by means of borehole and working face observations, water leakage, and real-time video imaging [16]. The distribution characteristic of mining-induced horizontal fracture in longwall panel has been studied by field investigation and a prediction model [17]. The range of abundant restriction of strata separation fracture is elaborated, and the interstice permeability and the characteristic of gas delivery in the restriction of strata separation fracture are analyzed [18]. The effect of seam separation distances and key stratum configurations on characteristics of strata movement and surface subsidence was evaluated using the discrete-element method [19]. A study on the movement laws of the overlying strata at the working face ends assessed their effects on the surface deformation using field monitoring as well as physical and numerical modeling [20]. Characteristics of multi-seam subsidence are investigated by means of several sand-plaster physical models [21]. In the past, few studies have taken the full-columnar overburden as the research object. Full-columnar overburden refers to the whole overlying rock from coal seam to the ground surface.