# A Case Study of a Large Unstable Mass Stabilization:
## 3 Results
### Limit Equilibrium Analysis  
Several slope profiles were analysed using limit equilibrium methods by means of the method of slices. The geotechnical parameters obtained in the field investigations and listed in Table 1 were used to conduct such analyses. The [PERSON]'s method [44] was applied to compute the safety factor without considering the seismic action. The Morgenstern-Price method [45] was applied to compute the safety factor considering the seismic action, which was taken into account by a pseudo-static approach considering two orthogonal forces, their value based on the Spanish code [28].  
Figure 8: Main landslides detected in the area under study.  
Under natural conditions, once the parking area was excavated and prior to implementing any corrective measure, profile I-I\({}^{\prime}\), according to Figures 2 and 5, was found to be the most unfavourable profile. Without taking into account the seismic component, the safety factor at that profile resulted in 0.86. That confirms the existence of the landslide produced by the parking excavation and the subsequent movement of the slope. It should be mentioned that this landslide was a first-time failure, not a reactivation of a previous one. When the seismic action was taken into account, a safety factor of 0.59 was obtained for the same profile (i.e., about 30% lower).  
The analyses were run again introducing the projected measures and considering the final stage of the projected slope. The water table was located following the data obtained from the inventory of water points carried out in the new investigations and considering that the capacity of California drains is greater than the recharge of the aquifer (an average level was considered since the water table depends on rainfalls, see the next section). Profile I-I\({}^{\prime}\) was still found to be the most unfavourable. In this case, the safety factor without taking into account the seismic component increased to 1.3; taking into account the seismic acceleration, the safety factor was 1.1 (about 15% lower). That result indicates that the slope is stable and the landslide is expected to be under control with the projected measures. Figure 9 shows the results computed by the [PERSON]'s method for profile I-I\({}^{\prime}\) before and after implementing the stabilization measures using the software Slide v5.028 [48].  
It is interesting to mention that the stability analysis calculations conducted considered the whole slope and the corrective measures were designed accordingly. Considering only a part of the slope was not correct, this may have given rise to erroneous results. For  
Figure 9: Safety factor analyses of profile I-I\({}^{\prime}\) (see Figure 2): (**a**) slope in its natural state after the parking excavation; (**b**) slope state after implementing the stabilization measures.  
instance, Figure 10 shows a stability analysis carried out by both the Bishop [44] and the Morgenstern-Price [45] methods taking into account only the area around the toe wall. The safety factor obtained was nearly 1.6 in both cases, about 23% and 45%, respectively, greater than that computed in the scenario considered in Figure 9b. This may have led to an assumption that the installation of that wall was the unique corrective measure needed, which resulted in it not being enough for controlling the hillside movement.