This research deals with the question of whether, and under what circumstances, the presence of underground structures should be taken into account for the earthquake resistant design of neighbouring surface structures. In order to investigate the effect of underground structures on surface seismic motion, a series of dynamic plane-strain numerical analyses were conducted, considering a circular tunnel embedded in a viscoelastic half-space, and a harmonic SV-wave excitation. The numerical methodology, based on the Finite Difference Method, aims at quantifying the effect of the soil medium characteristics, excitation frequency, tunnel diameter, depth of construction, and relative flexibility of the lining compared to that of the surrounding soil. Conclusions contain preliminary criteria identifying the cases when the presence of an underground structure should be considered in the design of a surface structure.

The fundamental influence of specimen size and micromechanical parameters on macroscopic structural behavior of natural building stone is investigated by particle flow numerical analysis. Laboratory tests of Dionysos marble cylindrical specimens under uniaxial compressive loading are simulated with a focus on the fracture development, failure mode and uniaxial compressive strength. Two series of simulations are performed with the PFC2D code, one to define the effects of different rates of deformation on the uniaxial compressive strength and fracturing of the specimens and the other to investigate the behavior of the specimens with the variation of five different parameters; platens velocity, specimen size, particle size distribution, standard deviation of randomized shear and normal strength as a micro-parameter and the ratio of shear to normal particle bonding strength. The specimen sizes also include rarely investigated smaller than NX dimensions. On selected specimens, the fracture development and the failure mode is depicted and discussed, and conclusions are drawn about the shear to tensile failure frequency and the crack patterns.