###### Abstract  
The stability of the filling roof--as an important bearing unit in the stope of the access stope in the filling mining method--is of great significance to guarantee the safe and efficient production of the mine. Arrangement of the mining approach in downward cemented filling stope is the key factor affecting the stability of the filling body roof. Based on a combination of laboratory tests, theoretical analysis, and numerical simulation, the influence of different mining approach arrangements on the stability of the filling body roof is analyzed. The weak filling surface is formed between adjacent mining paths. The mechanical strength of the weak filling surface is significantly reduced by laboratory experiments. The relationship between the distribution of the weak filling surface, azimuth angle, and the stability of the filling roof is further studied by numerical simulation. The results show that, when the upper and lower layered mining approaches are arranged vertically or nearly vertically, the areas of stress concentration and the plastic zone in the numerical simulation results are the smallest, and the stability of the filler roof is the best.  
d 2023 13  
the upper- and lower-stratified mining approaches are arranged parallel, the angle between the filling weak surface and the direction of the mining approach is a 180\({}^{\circ}\) location relationship. The research shows [4; 5; 6; 7; 8] that in the field of geotechnical engineering, the occurrence of weak surfaces in the engineering structure body is different, and the deterioration degree of the stability of the engineering structure body is also different. Even though existing research [9; 10; 11; 12; 13; 14] has used numerical simulation to simulate and optimize the layout of upper and lower layers for mining access, the distributions of the stress and plastic zones in the two different mining and filling sequences were obtained through numerical simulations by [PERSON] et al. [9]; the reasonable mining face width was determined combined with numerical simulation [10]; and field investigation and numerical simulation were combined to study the mechanisms of roof collapse by [PERSON] et al. [11]. Research on the intrinsic mechanisms of the layouts of upper and lower layers is still lacking, which puts engineering scheme practice far ahead of scientific theory. [PERSON] et al. [15] studied the relationship between the rectangular section size and stop stability using FLAC\({}^{\text{3D}}\) based on practical engineering and analyzed the distribution of stresses, displacement, and the plastic zone.  
For the direct shear tests on cemented paste backfill, [PERSON] et al. [16] prepared a two-layered cemented paste backfill (CPB) with layering angles of 5\({}^{\circ}\), 10\({}^{\circ}\), 15\({}^{\circ}\), 20\({}^{\circ}\), 25\({}^{\circ}\), and complete CPB to conduct direct shear experiments. [PERSON] et al. [17] performed direct shear tests on CPB-CPB interfaces in order to assess the frictional shear strength parameters. The action of compression-shear, measured using 30\({}^{\circ}\), 45\({}^{\circ}\), and 60\({}^{\circ}\) variable angle shear tests (VAST) was conducted by [PERSON] et al. [18] to investigate the mechanical properties. Researchers have studied the strength, deformation, and failure of the direct shear tests on CPB [19; 20; 21; 22; 23; 24].  
Under this engineering background, combined with the direct shear test of the weak surface of the filling body in the chamber, the stability of the filling roof under different layered mining approaches is numerically simulated and analyzed using a medium interface unit in FLAC\({}^{\text{3D}}\), the finite difference numerical simulation software. Finally, the optimal layered layout scheme of upper and lower layers is determined, which provides a theoretical basis for mines adopting the downward horizontal layered cemented filling method.