DENSIFICATION OF SAND BELOW DAM FOUNDATIONS BY UNDERGROUND BLASTING

Abstract

The design and construction of a big structure (as for example a high earth dam) on a thick .layer, of a cohesionle ss material like sand has been and still remains one of the most complicated problems for an engineer. Structures; resting on sand loose their stability . en they are subjected to .dynenic loading, especially the sand is saturated and the structure is situated in an active seismic zone.. Tinder dynamic loading the soil looses its shear strength sometimes completely, because of the rapid increase in the pore pressure,, . tt little of no time for the sand to dissipate the increased pore pressure. The .soil without shear strength behaves like a discous l i qunid . causing the failure .o f. the structure above it. This phenomenon is ho'en on 'liquefaction" and it depends on many factors like the properties of the sand and its depth, extent of superimposed load and the characteristics of vibrations imparted. A lot of researa has been carried out in this field both to study the causes of liquefaction and to evolve methods to reduce„ if not completely eliminate the chancer of liquefaction. A study of the available literature however shows that the information available is still insufficient for any conclusion to be drain on this phenomenon„...