Blocks of rock are large fragments of the bedrock that have not suffered a strong erosive process and have remained in the soil horizons. They can be oval shaped, or nearly spherical. The calculation for blasting is different, as the volume between these blocks varies, and so does the number of holes required. Thus, a calculation method (Ayres da Silva, A. & Gianotti de Andrade, G. Method) was developed for the oval-shaped rock blocks. Finally, in the blasting of blocks using explosives, it is necessary to find what is the block's volume to be blasted, because this value is fundamental to obtaining a safe amount of explosives needed for a given specific charge.
It is important to note that when using explosives to blast rock masses or boulders (which are rock blocks without a predefined shape but with a volume of fragments bigger than 1 m3), especially when carried out in urban areas, it is essential that all safety requirements in their execution are met.
The most evident risks resulting from this activity can be divided into three main types:
• Flyrock - launch of rock fragments beyond the areas circumscribed to the operations;
• Vibrations that can produce damage to the structures in their surroundings – buildings, and housing in general;
• Environmental Impacts - which may be a consequence of vibrations or noise resulting from the detonations of explosives used in rock blasting (rock mass and rock blocks).
Such risks are also the subject of internationally established technical standards or methodologies.
However, there is no standardization in the methodology of defining which charges to use and how many holes are defined for rock blocks and boulders blasts in order to meet the care defined in the above items.
The objective of this work is, therefore, to present a new blast design methodology to blast the boulders into fragments that could be thrown at safe distances, avoiding flyrocks.
