Rock mass rating - IS 12070, IS 13365, IS 11315

RQD is a modified core recovery percentage in which all the pieces of sound core over 10 cm long are counted as recovery, and are expressed as a percentage of the length drilled. The smaller pieces resulting from closer jointing, faulting or weathering are discounted.

Rock mass rating is given to rock as per deciding factors given in IS 13365 ,
1. Class
2.Classification of rock mass
3.Average stand-up time
4. Cohesion of rock mass (kg/cm2)
5. Angle of internal friction.

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