RQD range and the threshold value

الملخص EN

The ROD is the easiest method of calculating the desingation of the rock masses for design purposes.

The threshold value of 100mm is used so far to calculate ROD, with no scientific or physical basis for choosing this value.

If the ROD calculation is based on this value it could give an ambiguous evaluation of the actual ROD of the rock mass in concern, and different threshold values could lead to different RQD's.

In this paper, various threshold values were chosen from 10mm to 100mm to calculate the effect of ROD using a written computer program utilizing Monte Carlo method.

The criterion used in the assessment of threshold value is its change with the ROD range which is defined as the difference between maximum and minimum ROD values that occur during a simulation of ROD by Monte Carlo technique.

The result appears as an inverse parabolic relationship between ROD range difference and the threshold value.

This research recommends use of a threshold value between 10mm to40mm to calculate the actual ROD of the rock mass which lead to a minimum expected error.