ABSTRACT

To simplify SMR estimation GSI values were 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 ratings estimated using SMR method. 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 slope height is not reflected in SMR. For the adjustment of this factor, the hazard classes estimated by KSMR and the subjective observation of experts were compared. The optimal adjustment rating 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.

1 INTRODUCTION

According to Romana et al. (2003), SMR is widely implemented in the world and in the case of China in particular, it is known to be utilized nation-wide. However, it is 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.

In Korea, the stability assessment method for the individual slopes through physical stability analysis has been applied. Song and Lee (2005) have performed stability assessment and research on ways to prevent rock failure for several railway open-cut slopes. Lee (2003) has prepared a stability determination table with a somewhat low coefficient of correlation.

In this study, a new method based on SMR has been developed to allow the site engineer to perform the assessment for rock slopes comprehensively with simplicity and reliability. This method named KSMR (Korean Slope Mass Rating) was referred to three 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 the experts.

2 SIMPLIFICATION OF SMR
2.1 Adaption of modified GSI

GSI has been used to determine the value based on the range by selecting the sphere diagrammatically considering the structure and the surface conditions of the rock mass. However, in this case, if the original data are not conserved, it is difficult to figure out the selected sphere on which the corresponding GSI value was determined. For example, two different geological conditions such as very blocky rock with very good surface and massive rock with good surface can give the same GSI value.

The new method suggested in this study gives the average GSI value by selecting one of 6 grades for rock structure and one of 5 grades for surface condition, respectively. In order to obtain this correlation formula, optimized method was applied. Additionally, the maximum value of the modified GSI was adjusted to 70 which is the maximum value of RMR excluding rock strength and underground water conditions.

2.2 KSMR sheet

The assessment method of KSMR applying the modified GSI, rock base strength, underground water condition.

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