How To Measure Rock Quality Designation Index (RQD) | Procedure and Classification

The rock quality designation index (or RQD) is a widely used index to describe the quality of rock in rock mass. RQD is the ratio between the sum of the length of core samples that are equal to or greater than 10 cm to the total length of the core run. This video shows how it is done in practice. The measurement starts at 0:01:19 Only two pieces had the length of equal or greater than 10 cm; the other (smaller pieces) were ignored. The total run was 1 m (or 1000 mm). The calculations include two pieces: 190 mm (19cm) + 145 mm (14.5 cm).
RQD=(190+145)/1000=0.335 or 33.5% (Poor quality).
RQD is easy to obtain, and it is used in almost all rock mass qualification systems. For Rock Mass Rating (RMR), watch this video    • Rock Mass Rating (RMR) | Practical Ex...  . To see how to estimate RQD in the field, watch this video on rock wall discontinuity spacing    • How To Estimate RQD using Joint Count...  
Using an RQD value, the rock mass can be classified as follows:
RQD Rock mass quality
0- 25% Very poor
25-50% Poor
51-75% Fair
76-90% Good
91-100% Excellent
#engineering #geology #experiment #science
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