A New Approach of Adjustment Factor 2023 (NAAF23) for Modified Slope Mass Rating (M-SMR)

The Modified Slope Mass Rating (M-SMR) system is a SMR-based geomechanical classification system utilized for rock slope characterization in the Crocker Formation. The M-SMR rating is derived from the sum of the basic Rock Mass Rating (RMRb) and an adjustment factor. However, it has been observed that the parallelism correction parameter, F1, within both the M-SMR and SMR systems, can sometimes be overestimated, especially for toppling failures when the discontinuity dip direction (αj) is less than the slope dip direction (αs). This study was conducted on six rock-cut slopes to not only evaluate the production of a convincing F1 value but also to introduce a simplified New Approach of Adjustment Factor 2023 (NAAF23) diagram for the M-SMR. This adjustment factor (F) includes four correction parameters (F1, F2, F3, and F4), similar to those used in SMR, but modifies the calculation approach for F1. The calculation now involves subtracting the higher value from the lower value among the discontinuity dip, slope dip, or intersection line orientations. The symbols A, B, C, and D represent the subtracted values, with A and B used when the discontinuity dip direction is higher than the slope dip direction and vice versa, and C and D used when the intersection line is higher than the slope dip direction and vice versa. For plane failures, A or B becomes the value, while for wedge failures, C and D are used. For toppling failures, the formula is 180 − A or B if A or B is less than 180, and A or B − 180 if A or B is greater than 180, eliminating the need for absolute symbols. A comparison F1 calculation using SMR is also conducted. The results show that F1 values become more convincing when using NAAF23.