ABSTRACT

Slope Mass Rating is a worldwide used rock mass classification intended to characterize and classify rocky slopes. It uses basic RMR Bieniwaski's classification and is obtained by subtracting a factorial correction factor depending on the discontinuity and the slope face geometrical relationship (F1 ×F2 ×F3) and adding a correction factor depending on the excavation method (F4). Although these rock mass classifications were initially applied on the basis of discrete-defined parameters, several continuous functions have recently been proposed to compute parameters governing them. In this paper, an analysis of continuous SMR geometrical parameters (F1, F2 and F3) is performed in order to identify main controlling parameters in this geomechanical classification.

1 INTRODUCTION

Slope Mass Rating (SMR; Romana 1985) is a worldwide used rock mass classification intended to characterize and classify rocky slopes. It uses basic RMR Bieniwaski's classification (1989) and is obtained correcting it by means of four parameters depending on discontinuity and the slope face geometrical relationship and the employed excavation method. SMR index has been adapted to wedge failure (Anbalagan et al. 1992) and modified by means of continuous functions (Tomas et al. 2004, 2006, 2007) to avoid subjective interpretations by means of assigning a unique SMR value for every slope and discriminating among slopes that have the same discrete SMR index. The aim of this work is to perform a visual analysis of SMR geometrical parameters (F1, F2 and F3) using a nvision graphical representation method called "worlds within worlds" (Feiner & Beshers 1990) of the continuous functions proposed by Tomas et al. (2007) in order to identify the main controlling parameters of the continuous classification.

2 CONTINUOUS SMR

Function eq(4)is used for slopes with planar or wedge failure and expression eq(5) is used for toppling failure cases. C variable express dips relationship and is equivalent to β j −β s for planar failure, β i −β s for wedge failure and β j +β s for toppling failure.

3 VISUAL SENSIBILITY ANALYSES OF CONTINUOUS SMR

The sense of sight constitutes about 70% of objects perception. As a consequence this sense can be exploited in order to better understand the main parameters controlling rock mass classifications. Cai & Kaiser (2006) took multidimensional spaces visualization of several rock mass classifications (RMR, Q, RMi and GSI) in order to assist engineers in identifying their more important controlling parameters.

4 CONCLUSIONS

A four dimensional graphical visualization of continuous Slope Mass Rating (SMR) system using the "worlds within worlds" method has been presented in order to visualize the influence of the main parameters controllingSMR(i.e.RMRb, A, β j and β s). This visualization has helped us to better understand this rock mass classification and to establish several important conclusions. These are: For slopes affected by planar orwedge failures with β s lower than β j SMR can be calculating only correcting basic RMR by the excavation method, F4 (SMR≈RMRb +F4).

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