Modification of slope stability probability classification and its application to rock slopes in hydropower engineering regions

Abstract

Stability assessment of rock slopes in hydropower engineering regions is an important and complex issue. Rock mass classification systems are a good approach because they can thoroughly consider many factors influencing rock slope stability. The slope stability probability classification (SSPC) system is a novel method. However, it has two limitations when applied to rock slopes: 1) it is only suitable for slopes less than 45 m in height, and 2) there is great subjectivity and randomness in the estimation of intact rock strength. Therefore, this study presents two modifications of the SSPC system by adopting the Hoek-Brown strength criterion and an empirical formula for maximum slope height. Evaluation of results from of 34 typical rock slopes of the major hydropower engineering regions in China indicated that the accuracy rate of the modified SSPC for stability evaluation of these slopes was 61.8%, and the accuracy for stability evaluation of 10 slopes with non-structural control failure was 80%. The stability values of stable and unstable slopes obtained using the modified SSPC were different to those obtained using the Chinese Slope Mass Rating (CSMR) and modified CSMR systems. In addition, the identification accuracy rate of the modified SSPC was significantly higher than that of the CSMR and modified CSMR. Therefore, the modified SSPC can be applied to hydropower engineering regions, providing a new means of rapidly evaluating the slope stability of high rock slopes (slopes > 45 m in height) in these regions.

Stability Assessment of High and Steep Cutting Rock Slopes with the SSPC Method

“…To overcome the limitations previously, Hack (1998) [15] presented a new rock slope stability assessment approach (SSPC, slope stability probability classification), which has been used worldwide, especially in the research of road slopes in Spain [16], New Zealand, India [17], and Turkey [5,6,14] with good results. As a matter of fact, the method is generally suitable for slopes with a height of less than or equal to 45 m. Moreover, discontinuity property survey, weathering degree, and intact rock strength estimation involve high subjectivity and arbitrariness [14,17,18]. For these reasons, the SSPC method is rarely used in the high and steep cutting rock slopes [19].…”