The Effects Of Free Surface On Blast Vibration

Geological and topographical conditions have direct influence on the method of blasting, extent of damage scope, direction and distance of throwing,shape of the muck pile,cleaning after blasting,and the arrangement of the construction site.So, the microtopography, especially the existence of free surface,have to be introduced to the blasting theories and blasting methods as one of the main conditions or parameters.If not, modern blasting technology is difficult to adapt to the large mountainous area construction in our country, especially be employed in the mountains, undulating roads, railways, water conservancy, and mining or other projects.So, it is valuable to research the influence of Free Surface in the process of blasting.This paper have made three sets of blasting vibration experiment and discussed vibration velocity as well as the vibration frequency of the blasting for the existence of one,two,or three free surface.we get regularities through the analysis from large amounts of measured data we obtained:Under the condition of the existence of free surface, the number of free surface has a great influence to blasting vibration velocity, with the increasing of the number of free surface, vibration velocity decreases as a result of the reflected wave. Moreover, applying the Sadov’s formula to analyse the experimental data comes from each group produced one formula demonstrated the rate of decline in Vibration velocity is faster with the increasing of distance.Because the measured data is subject to many cases, experimental results from the data is not necessarily accurate. In order to overcome this difficulty,we simulated the blasting condition in the way of numerical simulation,and reach a same conclusion with above experiments after reprocessing analysis. At the same time,I was analyzed the influence of different types of freedom surface to blasting by numerical model,and come up with a rough estimate that the free surface which is denser have stronger reflection ability and smaller vibration velocity.