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Slope Mass Rating or SMR is a rock mass classification scheme developed by Romana (1985, 1995) to describe the strength of an individual rock outcrop or slope. The system is founded upon the more widely used RMR scheme (Bieniawski 1989), which is modified with quantitative guidelines to the rate the influence of adverse joint orientations (e.g. joints dipping steeply out of the slope). Rock mass classification schemes are designed to account for a number of factors influencing the strength and deformability of a rock mass (e.g. joint orientations, fracture density, intact strength), and may be used to quantify the competence of an outcrop or particular geologic material. Scores typically range from 0 to 100, with 100 being the most competent rock mass. The term ''rock mass'' incorporates the influence of both intact material and discontinuities on the overall strength and behavior of a discontinuous rock medium. While it is relatively straightforward to test the mechanical properties of either intact rock or joints individually, describing their interaction is difficult and several empirical rating schemes (such as RMR and SMR) are available for this purpose. SMR uses the same first five scoring categories as RMR: 1. Uniaxial compressive strength of intact rock, 2. Rock Quality Designation (or RQD), 3. Joint spacing, 4. Joint condition (the sum of five sub-scores), and 5. Groundwater conditions. The final sixth category is a rating adjustment or penalization for adverse joint orientations, which is particularly important for evaluating the competence of a rock slope. SMR provides quantitative guidelines to evaluate this rating penalization in the form of four sub-categories, three that describe the relative rock slope and joint set geometries and a fourth which accounts for the method of slope excavation. SMR addresses both planar sliding and toppling failure modes, no additional consideration was made originally for sliding on multiple joint planes. However, Anbalagan et al.〔Anbalagan R, Sharma S, Raghuvanshi TK. Rock mass stability evaluation using modified SMR approach. In: Proceedings of 6th nat symp rock mech, Bangalore, India, 1992. p. 258–68.〕 adapted the original classification for wedge failure mode. The final SMR rating is obtained by means of next expression: SMR=RMRb+(F1×F2×F3)+F4 where: where RMRb is the RMR index resulting from Bieniawski’s Rock Mass Classification without any correction. F1 depends on the parallelism between discontinuity, αj (or the intersection line, αi, in the case of wedge failure) and slope dip direction. F2 depends on the discontinuity dip (βj) in the case of planar failure and the plunge, βi of the intersection line in wedge failure. As regards toppling failure, this parameter takes the value 1.0. This parameter is related to the probability of discontinuity shear strength. F3 depends on the relationship between slope (βs) and discontinuity (βj) dips (toppling or planar failure cases) or the immersion line dip (βi) (wedge failure case). This parameter retains the Bieniawski adjustment factors that vary from 0 to −60 points and express the probability of discontinuity outcropping on the slope face for planar and wedge failure. F4 is a correction factor that depends on the excavation method used. Tomás et al. (2007) proposed alternative continuous functions for the computation of F1, F2 and F3 correction parameters. These functions show maximum absolute differences with discrete functions lower than 7 points and significantly reduce subjective interpretations. Moreover, the proposed functions for SMR correction factors calculus reduce doubts about what score to assign to values near the border of the discrete classification. The proposed F1 continuous function that best fits discrete values is: F1=16/25-3/500×arctan(1/10(A-17)) where parameter A is the angle formed between the discontinuity and the slope strikes for planar and toppling failures modes and the angle formed between the intersection of the two discontinuities (the plunge direction) and the dip direction of the slope for wedge failure. Arctangent function is expressed in degrees. F2=9/16+1/195×arctan(17/100×B−5) where parameter B is the discontinuity dip in degrees for planar failure and the plunge of the intersection for wedge failure. For toppling failure mode F2 is equal to 1. Note that the arctangent function is also expressed in degrees. F3=−30+1/3×arctan(C) (for planar and wedge failure) F3=-13−1/7×arctan(C-120) (for toppling failure) where C depends on the relationship between slope and discontinuity dips (toppling or planar failure cases) or the slope dip and the immersion line dip for wedge failure case. Arctangent functions are expressed in degrees. Alternatively, Tomás et al. (2012) also proposed a graphical method based on the stereographic representation of the discontinuities and the slope to obtain correction parameters of the SMR (F1, F2 and F3). This method allows the SMR correction factors to be easily obtained for a simple slope or for several practical applications as linear infrastructures slopes, open pit mining or trench excavations. Riquelme et al. (2014) developed (SMRTool ), a free software which easily permits to compute SMR from the geomechanical data of the rock mass and the orientation of the slope and the discontinuities. ==See also== * Slope failure * Mass wasting * Rockfall 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「SMR classification」の詳細全文を読む スポンサード リンク
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