DYNAMIC ANALYSIS OF LARGE 3-D UNDERGROUND STRUCTURES BY THE BEM

An up to date literature survey on the dynamics of underground structu res is presented briefly. The dynamic response of large three-dimensio nal underground structures to external or internal dynamic forces or t o seismic waves is numerically determined by the frequency domain boun dary element method. This method is used to model both the structure a nd the soil medium, which are assumed to behave as linear elastic or v iscoelastic bodies. The full-space dynamic fundamental solution is emp loyed in the formulation and this requires a free soil surface discret ization, confined to a finite portion around the area of interest, in addition to soil-structure interface and free structural surface discr etizations. The dynamic disturbances can have a harmonic or a transien t time variation. The transient case is treated with the aid of numeri cal Laplace transforms with respect to time, Various numerical example s involving lined cavities and long lined tunnels buried in the full- or the half-space subjected to harmonic or transient external forces o r seismic waves are presented to illustrate the method and demonstrate its advantages.