## 4 Discussion
\begin{array}{c}W_{1}=0.99;\qquad\quad W_{2}=0.77;\qquad\quad W_{3}=0\\ W_{sum}=W_{1}+W_{2}+W_{3}=1.76\end{array}  \tag{3}\]  
These observations mean that, unlike the initial assumption of the SiDMACIB model, the three locks of an interlocking interface are not all involved in the overall planar capacity equally. Based on these outcomes, several scenarios can be considered for adjusting the SiDMACIB formulation. The simplest one involves reducing the number of active locks so that it corresponds to the value of \(W_{sum}\) rounded down to an integer value, in favour of safety. This straightforward modification minimally alters the original SiDMACIB model, with the absolute value acting as a safety factor to prevent overestimation of the load-bearing capacity. Different weights of locks in load-bearing capacity can also be noted for interlocking blocks subjected to torsion-shear loads, as illustrated in Figure 9. Based on the previous observation, the SiDMACIB numerical model is revised so that an interlocking interface with three locks only includes the side lock in the analysis. Implementing this modification, Figure 10 shows the torsion-shear results considering Options 1 to 4 of the revised SiDMACIB model in terms of continuous curves. It is evident that Option 4 is in good agreement with the torsion-shear results obtained by 3 DEC.  
Figure 10: Torsion-shear capacities of the model with three locks found with the revised SiDMACIB model and 3 DEC.  
Figure 9: Torsion-shear behaviour at the interlocking interface with three locks. More complex scenarios may entail assigning different weights to the control points and/or determining the optimal layout of control points on an interlocking interface when subjected to torsion-shear combinations. However, these intricate modifications can only be pursued after conducting a comprehensive study involving different block sizes and lock numbers, both experimentally and numerically. Such investigations are beyond the scope of this paper. As mentioned above, to have a more comprehensive observation, a similar analysis is carried out on the sample composed of two stacked blocks with five locks at the interlocking interface. Figure 11 shows the torsion-shear results computed by SiDMACIB (4 options) and 3 DEC (two different mesh sizes) using continuous and dashed lines, respectively. Similar to the model with three locks, the results obtained by SiDMACIB are larger than the results found with 3 DEC. Comparing the pure shear capacities obtained by the two methods, those computed by 3 DEC with 0.02 and 0.005 m mesh sizes are equal to 408.26 and 410.52 N, respectively, which are slightly less than the pure shear of two locks (480 N). In this case, the calculation of the weight of each lock is determined as follows (Figure 12):  
\[W_{1}=0.99;\qquad W_{2}=0.57;\qquad W_{3}=0.68;\qquad W_{4}=0.68;\qquad W_{5}=0 \tag{4}\]  
Figure 11: Torsion-shear capacities of the model with five locks found considering four options of contact point distribution in SiDMACIB and 3 DEC.  
As for the case of pure shear, for the torsion-shear combination (Figure 13), the most important role in the overall performance of the interlocking interface is played by the lock closer to the face at which the distributed force is implemented. Three other central locks have relatively fewer roles in the interlocking capacity, and the last side lock does not participate in this task at all. Figure 14 shows the results of the modified SiDMACIB model, in which the number of active locks of the interlocking interface is reduced from five to two. These results are illustrated by continuous lines, while the dashed lines represent the torsion-shear results obtained by 3 DEC. It can be observed that, same as the model with three locks, Option 4 of the revised SiDMACIB model has the best agreement with the results found with 3 DEC.