## 4 Discussion  
In this section, the results in terms of torsion-shear capacity obtained using the SiD-MACIB and 3 DEC models are presented and compared to each other, in order to propose a reliable calibration of the SiDMACIB model. These are referred to as the samples in Figure 2 of two stacked blocks with three and five locks. Figure 6 shows the torsion-shear curves obtained for the sample with three locks, using the SiDMACIB model and the four distribution scenarios for the contact points reported in Figure 3, assuming a material shear strength \(\tau\) = 8 \(\times\) 10\({}^{4}\) N/m\({}^{2}\). These curves show the maximum lateral force that can be applied to the lateral face of the upper block for different eccentricities from the centroid of the face. Knowing the maximum lateral force \(V_{y}\) and the eccentricity \(\epsilon_{x}\), the corresponding maximum torque \(M_{y}\) can be computed. It is worth highlighting that the four scenarios herein used for the contact points (two points per lock) involve linear curves in favour of safety in terms of torsion-shear capacity, while other options considering three points per lock imply bi-linear and convex curves [31]. In Figure 6, while Options 1 and 4 show the highest and lowest pure torsion, respectively, the computed pure shear force for all the options is equal to 720 N. This value is, in fact, the product of the assigned cohesion \(\tau\) and the width and the length of the interlocking interface, composed of three inner surfaces. Figure 7 instead shows the torsion-shear graphs obtained by 3 DEC for two different mesh sizes of 0.02 and 0.005 m, the latter being a particularly fine size. The first fundamental observation is that both curves are concave and composed of two discrete linear segments. Parametrizing the curve, the turning point from which the curve's slope changes is approximately at the two-third length of the curve; after that, the torsion-shear curve of the model with 0.02 m mesh size is slightly steeper than the other. Apparently, it is expected that the results of the model with a finer size are more accurate. Figure 6: Torsion-shear capacities of the sample with three locks found using four options of contact point distribution in SiDMACIB. However, the torsion-shear capacities found with SiDMACIB (for all four options) are considerably larger than 3 DEC. As mentioned above, the pure shear capacity of all four options of SiDMACIB is 720 N, while this capacity is reduced to 240.76 and 240.83 for the 3 DEC models with mesh sizes 0.02 and 0.005 m, respectively. Taking a closer look, it can be observed that the pure shear obtained by SiDMACIB is almost three times larger than the pure shear found with 3 DEC. Figure 8 illustrates the distributed shear stresses on the three-lock interfaces when the upper interlocking block is subjected to pure shear forces. It can be noted that while the side lock closer to the subjected lateral forces (directed as shown in Figure 5) experiences failure, the other two locks have not yet initiated failure. This observation aligns with findings previously reported by [PERSON] et al. [35], who analysed the pure shear strength of interlocking precast concrete blocks utilised in segmental bridges. These authors also presented the sequence of cracking formation for multi-lock joints, both experimentally and numerically. To demonstrate the variable contribution of locks to the load-bearing capacity of the interlocking interface, a parameter \(W\) can be introduced, representing the \"weight\" of each lock in the capacity of the entire interface. This is achieved by determining the ratio of the uniformly distributed shear stress at the inner interface of each loc  
Figure 8: Pure shear stress at different inner interfaces of the model with three locks found using 3 DEC.  
Figure 7: Torsion-shear capacities of the model with three locks found using 3 DEC.  
and defining the total factor. For the case of pure shear forces applied to the model with three locks in Figure 8, it is evident that these weights are  
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