VIBRATIONAL ENERGY ANALYSIS OF GROUND/STRUCTURE INTERACTION IN TERMS OF WAVE TYPE

The vibrational interaction of underground structures such as tunnels or building foundations with the ground involves different types of waves both in structures and in ground. In this paper, a wave approach is used to study these waves in the simple case of an infinite slab laying on a half-space homogeneous soil. The results are expressed in terms of energy quantities such as input line mobility and radiated power in the case of line force excitation of the slab and power injected to the slab in the case of forced vibration by an incoming ground borne wave. It is shown that in the case of line force excitation of the slab, the radiation loss factors obtained are 10 times higher than common values of structural loss factors, showing that the energy losses of an underground structure are mainly radiated into the ground. In the case of forced vibration by an incoming ground-borne wave, the slab wave type depends on the type of incident ground-borne waves: P waves mainly generate quasi-longitudinal waves in the slab at low frequencies and bending waves at higher frequencies; SV waves generate both bending and quasi-longitudinal waves with a percentage depending on the type of ground.