## 3 Plate Load Test Data Interpretation  
In the interpretation of test results, several parameters can affect the test results and lead to incorrect determination of the deformation modulus. These parameters are classified into two groups [10]; operational factors which are directly related to the quality of the test components such as the resolution of the measuring instruments, and the quality of site preparation and installation of the test apparatus. Blast damage and rock disturbance around the test gallery are important examples of this category. In this case, the effect of blast damage will vary with several features, such as rock properties, amount of explosive used, number of holes detonated at the same time, and the quality of site preparation [4]. The incompatibility between assumptions made within the ISRM suggested method and the actual mechanisms involved in the practice, leads to some errors in the interpretation of test data. In the ISRM method, it is assumed that the rock masse is homogenous, isotropic, and continuum with linear elastic behavior which is not in harmony with actual rock mass conditions. Moreover, the effects of test gallery boundary conditions and induced stress state around the test location are not considered in calculations. Besides, these equations require prior knowledge of Poisson's ratio of the rock as input, which is difficult to determine at the rock mass scale. The other important issue in this test is the scale effect on the test results. [PERSON] and [PERSON] [15] presented a study looking into the scale effects in plate load tests in unsaturated soils. A good description of scale effects on plate load testing results in rock is given by [PERSON] and [PERSON] [4]. [PERSON] et al. [16] further discussed the significance of scale in in-situ measurement. In the study by [PERSON] et al. [13], it was shown that the uncertainties associated with plate load tests are caused by the confining effects of the adjoining rock, blast-induced damages induced to test gallery walls, distressing of gallery walls, and the insufficient volume of rock tested. The dependency of calculated modulus magnitude to the displacement measurement depth in the borehole is another shortcoming of the ISRM suggested method. Furthermore, in the PLT procedure, the load is measured at the plate surface while displacements are measured by extensometers installed at varying depths within the borehole. Accordingly, the calculated moduli at higher depths may be significantly higher and sometimes unrealistic for a given test. In another attempt, [PERSON] et al. [17] employed continuum modeling to overcome the limitations proposed by the ISRM-suggested approach in the interpretation of plate load test data. They postulated that because of the inconsistency of the test gallery geometry with the half-space medium assumption embedded in the analytical relations, a systematic error occurs in the calculation of the deformation modulus. Furthermore, when the tests are conducted on jointed rock masses, the test results show a considerable scatter, mainly due to the anisotropy of the deformability of the jointed rock masses. Accordingly, numerical modeling was used to interpret the results of a series of PLTs conducted at the Bakhtiary dam site in southwest Iran. An equivalent continuum model was used to back-calculate the stiffness of bedding planes from the test results. The equivalent continuum deformation moduli of the rock mass were determined numerically for various directions of loading relative to the orientation of major joint sets. Their numerical study showed that the deformation of the rock mass is highly anisotropic and highly dependent on the geometry and mechanical properties of the discontinuities. The developed continuum model overestimates the stiffness of the jointed rock mass. The proposed model's application is limited to the rock media where the rock mass deformation does not involve large dislocation and detachments of blocks. [PERSON] et al.