*4.1.3 Step 3: Application of strength reduction factor to strength parameter of slope*

In step 3, the time-dependent deterioration of slope was quantified by applying the SRF to the strength parameter of the soil. The strength parameters of the slope shown in **Table 1** were reduced according to the SRF as shown in **Figure 3**. The slope stability analysis is performed with the reduced strength parameters, and iterative analysis is performed until it is not converged. If it does not converge, the slope has collapsed in the finite element analysis. Until now, the modeling is identical to that of the usual strength reduction factor (SRF) method of slope stability analysis. [8, 39, 40].
