RMR = IRS + RQD + distance + condition.
How to calculate rock mass rating?
The value of A + B = 46 and this means that for joints in good condition (slightly weathered and weathered) and a moderate water supply between 200 and 1000 gallons per minute, Table 3 gives the rating for C = 16. Hence the final value of the rock structure rating RSR = A + B + C = 62 .
What is Quality Index and how is it used to assess rock mass quality?
Rock classification The rock quality (Q) is a very sensitive index and its value varies between 0.001 and 1000 . The use of the Qsystem is especially recommended for tunnels and caverns with a vaulted ceiling. Rock masses are divided into nine categories based on the Q value (Table 8.9).
What are the three most common classifications of rock masses?
the development of the three most popular rock classification schemes, namely Q, RMR and GSI. Compression Potential (Singh and Geol, 1999).
What is rock strength?
The strength of a rock for foundation purposes is largely determined by the discontinuities in the rock. … The direction-independent stability assessment leads to a rock strength criterion based on classification data, e.g. intact rock strength, discontinuity distances and discontinuity conditions
How is the rock mass index calculated?
The RQD is determined from the rock cores or the volumetric fracture number. This is the percentage of rock core in one meter of drill. … Based on the RMR values for a given structure, the rock is classified into five grades: very good (RMR 100–81), good (80–61), fair (60–41), poor (40–21) and very bad (20).
What does rock mass assessment mean?
RMR combines the key geological influencing parameters and maps them with a comprehensive global rock quality index used for the design and construction of rock excavations such as tunnels, mines, embankments and foundations. …
How many rock classifications are there?
The RMR is determined as the algebraic sum of the scores for all parameters. Based on the RMR values for a given structure, the rock is classified into five grades: very good (RMR 100-81), good (80-61), moderate (60-41), poor (40-21), and very poor (20).
What are RMR and SMR?
Rock Mass Rating (RMR) has been widely used as a method of classifying the strength of rock masses. … RMR values are then correlated into Slope Mass Rating (SMR), which is a classification system of a rocky slope.
What is the Terzaghi Rock Mass Classification?
One of the first rock classification systems was developed by Terzaghi (1946). The RMR system includes rock mass data related to rock strength, RQD, discontinuity distance, discontinuity state, groundwater and an adjustment for orientation of discontinuities relative to excavation.
What are rock properties? Write a note on RQD classification of engineered rocks?
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 cores with a total core length greater than 100mm (4 inches).