*3.3. Loading Scheme*

Assuming that the roof pressure acting on the crushed rocks in the gob area remains unchanged during the two caving activities of roof strata, it was considered necessary that the axial pressure acting on the crushed rocks in the gob area to be increased in a stepped manner [22]. Thus, the tests were conducted under incremental loading as shown in Figure 6. In GERRF method, the support structures of gangue rib deformed in response to lateral stress generated by crushed rocks in gob side. In engineering practice, the support structures of gangue rib are not allowed to produce large deformations. So, in the tests, the maximum axial pressure was set at a value corresponding to when the support structure will begin to deform, which was set as 1.5 MPa according to preliminary experiments results. In order to observe the periodic deformation behavior of crushed rocks in greater detail, the loading increment Δ*P* was designed as 0.15 MPa.

**Figure 6.** Loading path in the tests.
