RingBlast: a Excel worksheets for ring blast design

P. Berry, S. Bonduà*

The computer program RingBlast is a Excel© Worksheets, designed to calculate the pattern of the ring drill holes and charging scheme. The algorithms are coded in Visual Basic that is included in the Microsoft Office suite. The RingBlast worksheet allow the calculation for a rectangular profile of the room. Generic geometric scheme is shown in figure.

The pattern of the geometric drilling scheme is driven by the burden parameter. The worksheet allows to calculate the burden choosing between most commonly empirical approach of the literature. Optionally the burden can be manually entered. The type of explosive and rock to be blasted are selected from two worksheets tables present in the workbook, or new items can be added.

The automatic calculation of the ring blast design follows these geometrical considerations:

  1. the calculated spacing at the end of the toe cannot be greater than the spacing imposed by the user;
  2. the four corner blast holes are a fixed constraint;
  3. the charged portion of a generic hole will stop when the distance between adjacent blast hole is lower than half spacing.


The algorithm is composed of two phase of computation. In the first phase are calculated the displacement of the drill holes, respecting the constraint that the distance at the toe must be lower or equal to half spacing. To achieve this constraint, iteratively the effective spacing is reduced to obtain equal distance between holes.

In the second phase, the charging scheme is calculated. The iterative algorithms start considering the all the length of the hole is charged. Iteratively the length of the charge is decreased from the center of the ring to the toe, until the distance between the charge and the adjacent hole is lower or equal to half spacing. This process is repeated for all holes until the geometrical constraint is satisfied.

Moreover a function of sensitivity analysis is implemented.  Within a burden range, entered by the user, the drill pattern is iteratively changed, to evaluate number of drill holes, mean charge of explosive, charge consumption for cubic meter of rock. Results of iteration are presented in a table format, with 6 columns: burden (m), total charge (kg), total drill holes (number), total length of drill hole (m), mean charge for cubic meter (kg/m3).


Stefano Bonduà
e-mail: stefano.bondua@unibo.it