## 7 Comparison and Discussion of Results  
To verify the conducted numerical study, the obtained results were compared against the actual in-situ tests conducted at the Bazoft concrete dam site and also the ISRM suggested method which is based on elasticity theory. Two objectives were the focus of this comparison. The first goal was to validate the numerical results and demonstrate the accuracy of 3D modeling for PLT simulation. The second objective was to compare the modulus calculation results obtained based on elasticity theory (the ISRM method) and the application of the Mohr-Coulomb model within the 3D numerical methods. The modulus values calculated at varying depths below the plate by the ISRM method, 3D simulation  
Figure 16: Variations of plastic strain as a function of change in loading plate diameter measured at a depth of; (**a**) 20 cm beneath the plate, (**b**) 40 cm beneath the plate, and (**c**) 60 cm beneath the plate.  
of an actual horizontal plate load test in a test gallery at the Bazoft dam right abutment, and the actual in-situ PLT test conducted at the same location, were compared against one another and presented in Figure 17.  
Referring to Figure 17, the ISRM suggested method determines larger modulus values in comparison to the other two methods. Concerning the fundamental limitation associated with this method, the values predicted at higher measurement depths are unrealistic and should be avoided. For example, the calculated modulus for the massive limestone of Bazoft dam right abutment, at a depth of about 170 cm below the loading plate, is measured to be slightly over 200 GPa which is higher than the stiffness of steel. These values are incorrect and must be excluded when reporting the test results. Also, it can be seen that for measurement depths of up to the loading plate radius, the in-situ data and numerical modeling data are in good harmony and match each other. At measurement depths beyond plate radius, the pattern of modulus variation as a function of depth changes significantly. The modulus obtained from the test data is solely based on the deformation measured at a single point below the plate. Depending on the load level, plate diameter, and the quality of rock, at depths beyond one plate diameter, the recorded displacements can be very small and sometimes negligible. Regardless of the method of modulus calculations (e.g., [5,7], etc.), the data reported for higher depths are unrealistic and must not be reported as the rock mass modulus. This problem becomes more pronounced if smaller size plates are used in the plate load tests. The numerically produced data show a different trend for modulus variation as a function of depth. In the constructed Flac-3D model, the test key boundary conditions were considered properly. These conditions are dam right abutment geometry and height, test gallery shape and dimension and associate gallery induced stress change at the test location, and the PLT geometry and direction. Moreover, a Mohr-Coulomb constitutive model was used for the rock mass to allow for plastic deformations as a function of loading. Accordingly, it is believed that the in-situ confining effects of the rock mass, significantly enhances the rock load-bearing capacity and its in-situ stiffness. The modeling results show that the depth has a much more pronounced effect on rock mass in-situ stiffness as can be seen from Figure 17.