## 2 Creep Tests of AS  
### AS Samples  
The AS samples were collected in Quandian Coal Mine, which is located in Henan Province, China. The average burial depth of the belt conveying roadway in its 22 mining areas is \(-700\) m. After the excavation of the roadway, it is observed by the \"cross point method\" that the deformation continues to increase with time after systematic support using \"anchor-net-shotcrete\". Thirty days after the excavation of the roadway, the deformation continues and the surrounding rock creep effect is significant; when the roadway was excavated for 70 days, the surrounding rock continued to deform at a high deformation rate. The average deformation rates of the roof subsidence, the convergence of the two sides, and the floor heave were 14.4 mm/d, 12.9 mm/d, and 7.3 mm/d, respectively. As introduced above, the AS samples were taken from the roof of the belt conveying roadway in Quandian Coal Mine 22. In the AS samples, clay materials account for 35.8%, while sand materials account for 64.2%. After the rock samples were collected in accordance with the International Society for Rock Mechanics (ISRM) recommendations for rock mechanics tests, the samples were processedinto cylindrical specimens with a diameter of 50 mm and a height of 100 mm. The parallelism and flatness of the two ends of the processed specimens were controlled to be less than 0.02 mm and 0.5 mm, respectively. Figure 1 shows some AS samples used in this study. The basic physical and mechanical properties of the AS samples are listed in Table 1. The equipment used in the test was an MTS815.02 electro-hydraulic servo rock mechanics test system from the United States. Each index of the system was ensured to meet the requirements of uniaxial, triaxial, and creep tests. The test equipment and loading method of AS samples are shown in Figure 2. The circumferential deformation of the sample was measured by a circumferential extensometer. First, the compressive deviatoric strength of the specimens under different confining pressures was tested. Second, according to the compressive deviatoric strength, the specimens were subjected to multi-stage loading. Five-stage loading was employed for each confining pressure, and the loading interval for each stage was 48 h. Finally, the multi-stage loading curve was processed to obtain the stress-strain and mechanical parameters of specimens. The selection of confining pressures was based on the engineering conditions. The depths of the underground roadway were 644.5-814.7 m. The average minimum in situ stress in the stability zone of the roadway was determined to be 18.23 MPa. Therefore, in order to analyse the creep behaviours in different positions along the roadway, the confining pressure C was set to 3 MPa, 6 MPa, 9 MPa, 12 MPa, 15 MPa, and 18 MPa. The setup for the multi-stage loading was also determined carefully. The results of triaxial tests showed that the maximum deviatoric stress corresponding to the elastic deformation of specimens under different confining pressures was approximately 60% of the deviatoric strength \(\sigma_{c}\). Under different confining pressures, the first-stage loading \(\sigma_{1}\) was determined to be 55-59% of the deviatoric strength. The second- to fifth-stage loadings were increased progressively considering the first-stage loading, and each time, the loading was increased by 4 MPa. If the specimens under the fifth-stage load were not damaged, further loading was carried out with the same increment. If the tertiary creep stage occurred before the fifth-stage load was applied and the AS specimens were destroyed, no further loading was applied afterwards. In the current study, the loading time per stage was determined to be 48 h. Several previous tests determined that the deformation rate of specimens after 24 h was less than 0.002 m/h at each stage when the tertiary creep stage was not reached. Thus, 48 h was considered long enough to reach a stable creep stage.