Assessment of the degree of reinforcement demand (DRD) for rock slope projects—principles and a case example application

The rational design of rock slope support is particularly important if the slope is steep, if safety is important, and if the design significantly affects project costs. Theoretically, slopes with stability factors smaller than 1.0 should be reinforced for maximum safety and efficiency. To optimize reinforcement design of a rock slope, an engineer should distinguish those locations needing critical, general, or even no reinforcement from other parts of the slope. The purpose of this paper is to present the concept of the degree of reinforcement demand (DRD) for rock slope projects and the quantitative procedures for the DRD assessment. The main influencing factors can be determined, classified and assigned based on knowledge from theoretical analyses, practical experiences and monitoring. To show variances in the DRD values with time and space, a rock slope to be assessed should be divided into a number of slope zones and the construction schedule into different periods. When geological conditions, mechanical properties of the rock mass, displacement measurements and/or construction have changed in a slope zone, the DRD value in this slope zone will increase or decrease. So for convenience in the DRD assessments, such changes in the main factors and measurements are analyzed via matrices. For example, the influencing factor matrix and the displacement ratio matrix, i.e. [A]k and [E]k, are, respectively, used to indicate possible modifications in the main factors and displacement measurements for all slope zones in the kth period. The DRD matrix, [R]k, can be obtained by multiplying [A]k and [E]k, and those elements along the leading diagonal of the matrix [R]k are the DRD values corresponding to different slope zones in the kth period. To demonstrate the feasibility of the DRD assessment, an application relating to the shiplock slope (including the lower-stream slope) of the Wuqiangxi hydropower station in China is described in this paper.