A discussion on the adjustment parameters of the Slope Mass Rating (SMR) system for rock slopes

• A comprehensive summary of rock mass classification systems is presented.
• A review of the development of the SMR system is given.
• Corrections for adjustment parameters F1 and F3 in the SMR system is proposed.
• The corrections are also applicable to those derived from the SMR system.

Rock mass classification systems are common tools used in the design and construction of rock engineering. Numerous classification systems have been developed for rock slopes, of which the Slope Mass Rating (SMR) system is the most popular. Consequently, many rock slope classification systems have been derived from the SMR system. However, these systems are not good at determining the values of the two adjustment parameters F1 and F3, implying that the original SMR system may contain theory defects. In this paper, we propose some corrected methods for determining F1 and F3 and perform a series of analyses considering the three failure modes of rock slopes: plane, wedge, and toppling failures. The results of the discrepancy analysis from F1 illustrate that, with respect to each of the aforementioned three failure modes the calculated original SMR index is larger than, or equal to, the real value, and the designed slope is possibly in danger. The results of the discrepancy caused by the F3 illustrate that for each of the aforementioned three failure modes, the calculated original SMR index is smaller than, or equal to, the real value, and the designed slope might be conservative and not economical.