Rock mass classification systems are used for various engineering design and stability analysis. These are based on empirical relations between rock mass parameters and engineering applications, such as tunnels, slopes, foundations, and excavatability. The first rock mass classification system in

geotechnical engineering Geotechnical engineering is the branch of civil engineering concerned with the engineering behavior of earth materials. It uses the principles of soil mechanics and rock mechanics for the solution of its respective engineering problems. It als ...

was proposed in 1946 for tunnels with steel set support.

Design methods

In engineering in rock, three design strategies can be distinguished: analytical, empirical, and numerical. Empirical, i.e. rock mass classification, methods are extensively used for feasibility and pre-design studies, and often also for the final design.

Objectives

The objectives of rock mass classifications are (after Bieniawski 1989): # Identify the most significant parameters influencing the behaviour of a rock mass. # Divide a particular rock mass formulation into groups of similar behaviour – rock mass classes of varying quality. # Provide a basis of understanding the characteristics of each rock mass class # Relate the experience of rock conditions at one site to the conditions and experience encountered at others # Derive quantitative data and guidelines for engineering design # Provide common basis for communication between engineers and geologists

Benefits

The main benefits of rock mass classifications: # Improve the quality of site investigations by calling for the minimum input data as classification parameters. # Provide quantitative information for design purposes. # Enable better engineering judgement and more effective communication on a project. # Provide a basis for understanding the characteristics of each rock mass

Rock mass classification systems

Systems for tunneling: Quantitative

* Rock Mass Rating (RMR) * Q-system *

Mining rock mass rating Within geotechnical engineering, Laubscher developed the Mining Rock Mass Rating (MRMR) system by modifying the Rock Mass Rating (RMR) system of Z. T. Bieniawski. In the MRMR system the stability and support are determined with the following equatio ...

(MRMR)

Other systems: Qualitative

* New Austrian Tunnelling Method (NATM) * Size Strength classification

Systems for slope engineering

* Slope Mass Rating (SMR), Continuous Slope Mass Rating and Graphical Slope Mass Rating * Rock mass classification system for rock slopes *

Slope Stability Probability Classification Slope stability analysis is a static or dynamic, analytical or empirical method to evaluate the stability of earth and rock-fill dams, embankments, excavated slopes, and natural slopes in soil and rock. Slope stability refers to the condition of i ...

(SSPC)

Earlier systems

*Rock load classification method :The ''Rock load classification method'' is one of the first methodologies for rock mass classification for engineering. Karl von Terzaghi developed the methodology for tunnels supported by steel sets in the 1940s. By many regarded as obsolete as ideas about rock and rock mass mechanical behavior have since further developed and the methodology is not suitable for modern tunneling methods using shotcrete and rock bolts. :Reference: also in ''Soil Mechanics Series 25'', publication 418. Harvard University, Graduate School of Engineering. *Stand-up time classification :The ''Stand-up time classification'' by Lauffer is often regarded as the origin of the '' New Austrian Tunnelling Method'' ''(NATM)''. The original system as developed by Lauffer is nowadays by many regarded as obsolete but his ideas are incorporated in modern rock mechanics science, such as the relation between the span of a tunnel and the stand-up time, and notably in the New Austrian Tunnelling Method. :Reference: * Rock Quality Designation :The '' Rock Quality Designation'' index was developed by Deere in the 1960s to classify the quality of a rock core based on the integrety of borehole cores. Nowadays the classification system itself is not very often used, but the determination of the

RQD Core recovery parameters describe the quality of core recovered from a borehole. Total core recovery Total core recovery (TCR) is the borehole core recovery percentage. TCR is defined as the quotient: :TCR = \left(\frac\right)\times 100 % :l_\ma ...

as index for rock core quality is standard practice in any geotechnical rock drilling, and is used in many, more recent, rock mass classification systems, such as ''RMR'' and ''Q-system'' (see above). * Rock Structure Rating (RSR) :The Rock Structure Rating system is a quantitative method for describing quality of a rock mass and appropriate ground support, in particular, for steel-rib support, developed by Wickham, Tiedemann and Skinner in the 1970s.