When assessing the slope stability, the SMR method is difficult for general road managers to use because it includes RMR estimation. In this study to simplify SMR estimation, GSI values are substituted for RMR parameters except rock strength and ground water condition. This new method is named KSMR(Korean Slope Mass Rating). The validation of this method was checked out through comparing the hazard classes estimated by KSMR and SMR. In spite of a high correlation between two methods, SMR estimation show a little difference compared to the real stability of slopes. This is because the slope height is not reflected in SMR. For the adjustment related to the slope height, the hazard classes estimated by KSMR and the subjective observation of experts were compared. The optimal adjustment value for slope height was induced using a genetic algorithm. When using the adjusted KSMR, the final hazard classes came to a little more close to those obtained from the experts.
When assessing the slope stability, it is almost impossible to perform a precise investigation for all the rock slopes due to limitation of professional experts and the budget required for this investigation. In order to maintain these rock slopes efficiently, it is required for the site engineer to evaluate the stability of slopes comprehensively for collecting fundamental information as a first step and by selecting any unstable slopes based on this information, to authorize a professional expert to carry out subsequent precise investigation as a second step. Though SMR, suggested by Romana[1, 2, 3], is being broadly implemented internationally as a method of assessing rock slopes stability, this method is not suitable for domestic rock slope conditions in some areas and it is hard for a layman to perform such assessment for the rock slopes comprehensively. This study, based on SMR, has developed a technique of KSMR (Korea Slope Mass Rating) that allows the site engineer to perform the assessment for rock slopes comprehensively with simplicity and reliability and this method was referred to experts for its feasibility verification. In addition, a statistical evaluation for the adjustment of KSMR related to the slope height was carried out under the support of three experts.
2. PROBLEMS WITH CURRENT METHODS
Though various assessment methods for rock slopes stability, as well as SMR, have been developed and are currently under implementation in U.S.A., Hongkong, Australia, etc. All these methods are, however, provided exclusively for the experts. Regarding RMR that determines the basic rating of SMR, it is somewhat difficult for a layman to assess and in particular, consideration of the slope height is excluded in this method. According to Romana et al., SMR is widely implemented internationally and in the case of China in particular, it is known to be utilized nation-wide. However, it is still difficult for the site engineer to use this method in determining input values and the shortcoming of this method is that the slope height is not considered.