ABSTRACT:

There are numerous methods of empirical rock slope design presented in published literature. The methods rely on initial characterisation of the rock mass, typically Bieniawski's RMR or a close derivative, with factoring to allow for structure, blasting and weathering. Fundamentally an empirical method should be calibrated on the basis of slopes for which failure has occurred, i.e. limiting stability. Published data of case examples to confirm the applicability of each method is limited to low slope heights and/or stable slopes with little or no data for where rock mass failure has occurred. The authors have utilised case studies at several mining operations, where stability has been predominantly influenced by rock mass failure, to enable a review of several empirical rock slope design methods. The review highlights the merits of each methodology and summarises some of their limiting aspects.

EXISTING EMPIRICAL SLOPE DESIGN METHODS

Table 1 shows a summary of the various parameters requiring assessment for each of the empirical methods. Generally, each method consists of a basic rock mass rating and a series of adjustments. TableÊ1 provides the maximum and minimum weightings for each parameter and the factors (denoted by an asterix) included in the assessment.

Rock Mass Rating

The rock mass ratings discussed in this paper, with the exception of the BQ, have been based upon or are similar to Bieniawski's RMR. The RMR method has been updated a number of times. The two presented in Table 1 are from Bieniawski (1976), RMR76, and Bieniawski (1989), RMR89. The rock mass rating requires a summation of ratings assessed for each of the following parameters representing intact rock block strength, rock mass block size, defect condition and ground water. RMS, Selby (1980), includes defect orientation and weathering in the basic rock mass rating.

This content is only available via PDF.
You can access this article if you purchase or spend a download.