Significance and Use
The classification systems included in this standard and their respective applications are as follows:
Rock Mass Rating System (RMR) or Geomechanics Classification—This system has been applied to tunneling, hard-rock mining, coal mining, stability of rock slopes, rock foundations, borability, rippability, dredgability, weatherability, and rock bolting.
Rock Structure Rating System (RSR)—This system has been used in tunnel support and excavation and in other ground support work in mining and construction.
The Q System or Norwegian Geotechnical Institute System (NGI)—This system has been applied to work on tunnels and chambers, rippability, excavatability, hydraulic erodibility, and seismic stability of roof-rock.
The Unified Rock Classification System (URCS)—This system has been applied to work on foundations, methods of excavation, slope stability, uses of earth materials, blasting characteristics of earth materials, and transmission of groundwater.
The Rock Material Field Classification System (RMFCS)—This system has been used mainly for applications involving shallow excavation, particularly with regard to hydraulic erodibility in earth spillways, excavatability, construction quality of rock, fluid transmission, and rock-mass stability (11).
The New Austrian Tunneling Method (NATM)—This system is used for both conventional (cyclical, such as drill-and-blast) and continuous (tunnel-boring machine or TBM) tunneling. This is a tunneling procedure in which design is extended into the construction phase by continued monitoring of rock displacement. Support requirements are revised to achieve stability (6).
Note 2—The Austrian code (7) specifies methods of payment based on coding of excavation volume and means of support.
The Coal Mine Roof Rating (CMRR)—This system applies to bedded coal-measure rocks, in particular with regard to their structural competence as influenced by discontinuities in the rock mass. The basic building blocks of CMRR are unit ratings. The units are rock intervals defined by their geotechnical properties, and are at least 0.15 m (6 in.) thick. The unit ratings are combined into roof ratings, using additional geotechnical characteristics (8).
Japanese Rock Mass Classification Systems—The Japanese Society of Engineering Geology has recognized seven major classification systems in use in Japan (9). These are summarized in 4.1.8.1-4.1.8.7, without additional details in this guide.
Rock-Mass Classification for Railway Tunnels by Railway Technical Research Institute—Rock-masses are classified based on the values of P-wave velocity, unconfined compressive strength and unit weight. Support patterns for tunnels, such as shotcreting and rock bolting, is recommended depending upon the rock-mass classification obtained.
Rock-Mass Classification for Tunnels and Slopes by Japan Highway Public Corporation—This system classifies the rock-mass using RQD, P-wave velocity, unconfined compressive strength and unit weight.
Rock-Mass Classification for Dam Foundations by Public Works Research Institute, Ministry of Construction—In this system, the rock-masses are classified by observing spacing of joints, conditions of joints and strength of rock pieces.
Rock-Mass Classification for Water Tunnel Design by The Ministry of Agriculture, Forestry and Fisheries—The rock-mass is classified into four categories based on values of P-wave velocity, compressive strength and Poisson ratio as well as rock type.
Rock-Mass Classification by Central Research Institute of Electric Power Industry—This system classifies rock-mass based on rock type and weathering characteristics.
Rock-Mass Classification by Electric-Power Development Company—This system is somewhat similar to the system developed by the Central Research Institute of Electric Power Industry (see 4.1.8.5). The three factors used for classifying rock-mass are weathering, hardness and joint spacing.
Rock-Mass Classification for Weathered Granite for Bridge Foundation by Honshu-Shikoku Bridge Authority—This system uses results of visual observations of rock-mass in situ, geophysical logging, laboratory tests on rock samples, pressuremeter tests or other forms of in-situ tests or a combination thereof, to estimate strength and stiffness.
Other classification systems are described in detail in the general references listed in the appendix.
Using this standard, the classifier should be able to decide which system appears to be most appropriate for the specified engineering purpose at hand. The next step should be the study of the source literature on the selected classification system and on case histories documenting the application of that system to real-world situations and the degree of success of each such application. Appropriate but by no means exhaustive references for this purpose are provided in the appendix and in STP 984 (1). The classifier should realize that taking the step of consulting the source literature might lead to abandonment of the initially selected classification system and selection of another system, to be followed again by study of the appropriate source literature.
Note 3—The quality of the results produced by this standard is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing, sampling, inspection, etc. Users of this standard are cautioned that compliance with Practice D3740 does not in itself ensure reliable results. Reliable results depend on many factors. Practice D3740 provides a means for evaluating some of these factors.
Scope
1.1 These guides offer the selection of a suitable system of classification of rock mass for specific engineering purposes, such as tunneling and shaft-sinking, excavation of rock chambers, ground support, modification and stabilization of rock slopes, and preparation of foundations and abutments. These classification systems may also be of use in work on rippability of rock, quality of construction materials, and erosion resistance. Although widely used classification systems are treated in this standard, systems not included here may be more appropriate in some situations, and may be added to subsequent editions of this standard.
1.2 The valid, effective use of this standard is contingent upon the prior complete definition of the engineering purposes to be served and on the complete and competent definition of the geology and hydrology of the engineering site. Further, the person or persons using this standard must have had field experience in studying rock-mass behavior. An appropriate reference for geological mapping in the underground is provided by Guide D4879.
1.3 This standard identifies the essential characteristics of seven classification systems. It does not include detailed guidance for application to all engineering purposes for which a particular system might be validly used. Detailed descriptions of the first five systems are presented in STP 984 (1), with abundant references to source literature. Details of two other classification systems and a listing of seven Japanese systems are also presented.
1.4 The range of applications of each of the systems has grown since its inception. This standard summarizes the major fields of application up to this time of each of the seven classification systems.
1.5 The values stated in SI units are to be regarded as the standard. The values given in parentheses are mathematical conversions to inch-pounds units that are provided for information only and are not considered standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
1.7 This standard offers an organized collection of information or a series of options and does not recommend a specific course of action. This document cannot replace education ore experience and should be used in conjunction with professional judgement. Not all aspects of this standard may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project's many unique aspects. The word “Standard” in the title of this document means only that the document has been approved through the ASTM consensus process.
