Dynamic Response Of Underground Structures Research Articles

Dynamic response of underground structures to pressure waves: The strip approximation

A simplified method is proposed to treat the dynamic response of rigid embedded structures in either a full or a half-space subjected to plane P-waves. The soil-structure interface is discretized into a finite number of strips, resulting in an analysis which involves only plane surfaces and plane waves. Interaction forces on any strip are determined easily, and the contributions from all the strips are superposed to obtain the resultant forces and torque on the structure. Equations of motion then yield the steady state response of the structure. The Green function for the structure is obtained by Fourier synthesis, and the transient response to any other excitation is then obtained by using the Green function and the Duhamel integral. The entire analysis can be conveniently programmed.

Dynamic response of underground structures by time domain SBEM and SFEM

The dynamic interaction problems of three-dimensional linear elastic structures with arbitrary shaped section embedded in a homogeneous, isotropic and linear elastic half space under dynamic disturbances are numerically solved. The numerical method employed is a combination of the time domain semi-analytical boundary element method (SBEM) used for the semi-infinite soil medium and the semi-analytical finite element method (SFEM) used for the three-dimensional structure. The two methods are combined through equilibrium and compatibility conditions at the soil-structure interface. Displacements, velocities, accelerations and interaction forces at the interface between underground structure and soil medium produced by the diffraction of wave by an underground structure for every time step are obtained. In dynamic soil-structure interaction problems, it is advantageous to combine the SBEM and the SFEM in an effort to produce an optimum numerical hybrid scheme which is characterized by the main advantages of the two methods. The effects of the thickness, the ratio of length and diameter of underground structure and the soil medium on dynamic responses are discussed.

Dynamic Similitude of Underground Structures

Similitude requirements for predicting the response of dynamically loaded buried structures by means of scale models were developed by dimensional analysis and were checked experimentally. Hollow circular and square aluminum tubes were buried in dry compacted Ottawa sand and loaded dynamically by dropping a cylindrical weight on the soil surface. The strains induced on the inner surfaces of the tubes were measured using SR-4 strain gages. Complete strain-time curves and data indicating the variation of peak strain and rise time with depth of burial are presented. Reasonable correlation is obtained between both the peak strain data and the complete strain-time curves for the several structures tested. In general, the study demonstrates the feasibility and value of the use of scale models for the prediction of the dynamic response of underground structures.