## 1 Introduction  
The great success of fully mechanized mining with a large mining height of 8 m and above in Mongolia and Shaanxi proves the feasibility of this technology for thick coal seams. This technology is conducive to centralized production, with advantages such as high yield, high efficiency, fewer roadways, and a simple system. The thickness of Huoxi Coalfield is 7.5-9.3 m with an average of 8 m. In actual engineering, equipment reliability, coal seam depth, mining conditions, etc., are important bases for determining whether fully mechanized mining with a large mining height can be adopted, where coal wall stability is one of the main factors for the efficient advancement of coal mining [1, 2, 3, 4]. As Huoxi Coalfield is characterized by a thick coal seam and roofs, the adoption of fully mechanized mining with a large mining height will bring about slight roof caving and serious spalling [5; 6; 7]. Spalling of coal walls is a traditional problem in mining engineering, greatly restricting the development of coal mining. Upon analysis of the mechanism of spalling, [PERSON] [8; 9], [PERSON] [10], and [PERSON] et al. [11] adopted the theory of idealized rods to locate the spalling of coal walls; [PERSON] et al. [12] analyzed the mechanism of coal wall failure on the working face with large mining height under three soft conditions, and proposed to extend the study of coal wall stability from a simplified plane problem to a treatment of a three-dimensional space, thereby establishing a mechanical model of wedge-shaped sliding bodies; [PERSON] et al. [13; 14; 15] revealed the mechanical causes of spalling in different forms from the angle of coal wall failure. The coal wall instability in fully mechanized mining with a large mining height is the result of a series of behaviors such as transfer of dynamic load and deformation. In order to control the risk of instability of the coal mining face, the [PERSON] [16], an Academician of Chinese Academy of Engineering, established a theoretical system involving face support and hydraulic support based on the coupling between the working face support and the brackets. [PERSON] and [PERSON] et al. [17] proposed flexible reinforcement engineering for preventing and controlling hard coal wall failure, which provided a lot of experience in controlling coal wall stability. In the early days of the development of deep coal mining technology, roof-cutting technology was mainly used to control intense mine pressure [18; 19]. The former Soviet Union first proposed roof-cutting technology and achieved successful applications. In the 1950s, China began to pay attention to roof-cutting technology and successively carried out experimental research. Due to its advantages, such as high safety and easy operation, it has been vigorously promoted and has now become an important research direction for mining in China. Among them, Academician [PERSON] and others [20; 21], based on different mine conditions, through a large number of verifications, proposed the theory of roof cutting short cantilever beams, artificially changing the structure of the overburden bearing beam. [PERSON] and others [22], through the derivation of theoretical formulas, obtained the method for determining the key parameters of roof cutting. With the joint efforts of many scholars, China has made great progress in the theory of roof cutting, and gradually discovering other functions of roof cutting, providing a scientific theoretical basis and data support for the further promotion and deepening of the application of roof-cutting technology. At present, academic research on spalling and its control in Huoxi Coalfield often focuses on top coal caving. Although scholars have studied the law of mineral pressure, the characteristics of migration of overburden, and the support technology of mining with a large mining height [23; 24; 25; 26; 27], the simple \"application\" of existing experience cannot completely solve the problem of mining face spalling in Huoxi Coalfield.