Study On Highway Slope Rock Mass Rating In South-West Mountain Area, China

On account of limited time of highway construction, we can hardly explore geologic status and rock mass mechanic character for all slopes in detail, before a stability analysis. Slope rock mass rating system, a convenient method, sees a bright future in the field of highway slope stability evaluation. More than 100 highway slopes collected from south-west area of China are analyzed statistically in this paper. A new slope stability system HSMR (Highway Slope Mass Rating), improved from SMR-CSMR, is given here.1). There are many difficulties in getting parameters when using Q system. In addition, the compound of strike, angle of gradient and discontinuities were not taken into consideration. Therefore, the system is hard to appraise slope stability precisely. In SMR system, the relation between discontinuities and slope freeing face was considered, so was excavating method. However, slope height was omitted in this system. As a result, SMR is 5-10 point lower than that of actual stability. Based on SMR, CSMR system has adopted slope height coefficient, to show the relation between slope height and slope stability. However, the coefficient is unreasonable to highway slope, so CSMR is higher on average.2). After a mechanical analysis, slope height coefficient was updated by statistical means. The amended coefficient is more effective for evaluating the effect of highway slope height. For the first time, multiple lithology factor, was brought into slope stability rating system. The values of different discontinuities' coefficients were partly modified. HSMR system for highway rock slope was presented here.3). A quantitative relation between befitting gradient and HSMR was established by statistic means, and a corresponding gradient to different stability level was suggested. Through a analysis of possible failure styles relative to different stability levels, this paper gave some detailed systematized advice on slope support patterns, which are widely used in highway engineering.4). Standardizing detailed rules about slope stability rating, what made for a uniform standard, and helps to an objective result. Accordingly, reliability of this system was ensured.5). Verifying typical samples showed that HSMR is preciser than other rock mass rating systems when estimating highway slope stability, besides, support patterns and befitting gradient suggested provide engineer a effective reference to rock slope design. Characterized by convenience, HSMR system can satisfy preliminary stability evaluation to highway slope well.