The Rock Quality Designation index (RQD) was developed by Deere (Deere et al 1967) to provide a quantitative estimate of rock mass quality from drill core logs.

RQD is defined as the percentage of intact core pieces longer than 100 mm (4 inches) in the total length of core.

The core should be at least 54.7 mm or 2.15 inches in diameter and should be drilled with a double-tube core barrel.

Palmstrom (1982) mengusulkan jika inti tidak tersedia, RQD dapat diperkirakan dari jumlah kekarkekar (joints) per satuan volume, di dalam mana jumlah kekar per meter untuk tiap kekar ditambahkan. Konversi untuk massa batuan yang bebas lempung adalah :

RQD = 115 3.3 Jv

Jv adalah jumlah total kekar per m3.

Hubungan antara indeks RQD dan kualitas teknik dari batuan adalah sebagai berikut (Deere, 1968) :

RQDKualitas Batuan< 2525 5050 7575 9090 - 100Sangat jelek (very poor)Jelek (poor)Sedang (fair)Baik (good)Sangat baik (very good)

Tabel Perbandingan dari RQD dan kebutuhan penyangga untuk terowongan dengan lebar 6 m a

No. Support orLocal BoltsPatem BoltsSteel RibsDeer et al,RQD 75 100RQD 50 75(1.51.8 mspacing)RQD 25-50 (0.91.5 mRQD 5075 (light ribs onon 1.51.8 mspacing as alternative to bolts)ROD 2550 (light to medium ribs on 0.91.5 m spacing as alternative to bolts)RQD 0-25 (medium to heavy circular ribs on 0.6 0.9 m spacing)spacing)Cecil (1970)RQD 82100RQD 5282 (alternatevely40-60 mmshotcrete)RQD 052 (ribs or reinforced shotcrete)Merrit(1972) RQD 72100RQD 023 (1.2 1.8 m(spacing)RQD 023

Stand Up Time

Stand up time is the length of time which an underground opening will stand unsupported after excavation.

Figure below illustrated span between face and the supports:

Relationship between active span and stand up time for different classes of rock mass

A = very good rockG = very poor rock

Relationship between Rock Load Factor (Terzaghi) and RQD (After Cording, Hendron and Deere)

Proposed use of RQD for choice of rock support system(After Merrit)