## 1 Introduction  
For an extended period, the persistent and high-intensity exploitation of coal resources has led to surface fissures, land subsidence, solid waste accumulation, and water resource contamination, significantly impacting ecological and environmental security. The need for environmentally conscious mining practices with minimal resource damage is increasingly evident [1; 2; 3]. Strip filling mining employs supporting filling materials to stabilize the overlying strata, preventing the extensive subsidence and deformation of the overlying rock layers, thus accomplishing the objectives of controlling land subsidence and safeguarding the environment. This approach holds considerable practical value in terms of reducing fill costs, enhancing coal utilization efficiency, preserving the ecological environment, and prolonging the mine's operational lifespan. It has emerged as the future direction of eco-friendly mining and represents an optimal solution to address the pressing concerns associated with coal pressure and ecological issues in Central and Eastern Chinese mining regions [4; 5; 6]. And it can effectively reduce the displacement of the overlying strata after coal seam mining. Nonetheless, due to the complexities inherent in rock layer and coal seam occurrences, numerous factors influence surface subsidence and coal mining roof stability in strip filling mining. Determining the relative importance of each factor is crucial for optimizing filling strategies, managing surface subsidence, and regulating rock movement. Owing to the intricate nature of coal seam occurrences, numerous factors influence the stability of overlying strata during the coupled processes of mining and filling. Estimating the relative significance and hierarchy of these factors solely through theoretical analysis or on-site monitoring is challenging. The orthogonal design of experiments enables the attainment of results comparable to comprehensive tests while minimizing the number of tests conducted. This approach is widely employed for scheme optimization and parameter influence analysis in mining engineering [7]. In recent years, numerous scholars have utilized orthogonal experimental methods to investigate the influence of the optimal mix ratio of filling materials on the strength performance of filling bodies [8; 9; 10; 11; 12], emphasizing the enhancement of their mechanical properties. However, due to the limited control range of strip filling on the immediate roof, an ill-conceived design of the filling body width and spacing may result in the excessive bending deformation or even breakage of the immediate roof [13]. Consequently, the structural parameters of the mining site also play a crucial role in influencing surface subsidence and coal mining roof stability. [PERSON] [14] determined the optimal structural parameters of strip filling stops through orthogonal test simulations; [PERSON] [15] conducted numerical simulation orthogonal calculations on roof stability under multiple factors' influence, obtaining the influence laws of various factors on roof tensile stress; [PERSON] [16] achieved optimization decisions on the structural parameters of strip filling stopes by establishing an orthogonal numerical model; [PERSON] [17] examined the sensitivity of coal seam dip angle, extraction width, extraction thickness, and filling rate to surface subsidence in strip filling mining; [PERSON] [18] studied the stability of the roof and floor during longwall mining through numerical simulation and experimental testing, and the author identified various factors that affect the state of the roadway. Numerical simulation research on filling stopes based on orthogonal experimental design not only overcomes the shortcomings of overly idealized theoretical analyses but also conserves experimental costs. However, the number of factors and levels selected in existing studies is relatively limited, hindering a comprehensive reflection of the impact of filling body strength and stope structural parameters.