A.E. Álvarez-Vigil

Influence of depth and geological structure on the transmission of blast vibrations

Vibrations generated by blasting carried out during the quarrying of material induce dynamic stresses that can give rise to damage of diverse considerations in surrounding buildings and structures. The adverse effects of vibrations caused by explosives used in mining and civil works can be controlled by suitably planning blasting operations, appropriately managing and optimising the equipment used, and monitoring the processes that cause these vibrations. The aims of the present study were to discuss and test the existence of a damping of underground vibrations, besides defining a transmission law for such vibrations which will depend on the directionality between the blast and the measurement point. Besides, the damages that vibrations can produce on the rock mass are evaluated. Their effects are very similar to those produced by an earthquake that disconnects the rock mass integral blocks.

Hexahedral mesh smoothing using a direct method

This paper develops a generalisation of the mesh smoothing direct method proposed by Balendran, to three dimensions by applying its methodology to smoothed hexahedral meshes. A geometric criteria is used where irregular quadrilaterals are converted to regular quadrilaterals on each face of the hexahedron using a local stiffness matrix. This matrix is then converted to a spatial stiffness matrix with reference to absolute coordinates in order to assemble the geometrical stiffness matrix as a global stiffness matrix. The fixing of boundary conditions is analysed and results obtained in a series of hexahedral meshes, used in finite difference method analysis, are illustrated. To evaluate the quality of the obtained results, a degree of uniformity is calculated and a comparative study of the improvement obtained in each zone of the hexahedral mesh is conducted. The proposed method permits the marking out of the portions of mesh in which a Laplacian smoothening fails to improve the mesh quality, therefore, requiring the use of other methods in which inserted mesh points are taken into account.