Back analysis of an excavated slope failure in highly fractured rock mass: the case study of Kargar slope failure (Iran) |
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| Authors: | Mostafa Sharifzadeh Mohsen Sharifi S Mohammad Delbari |
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| Institution: | (1) Department of Mining, Metallurgy and Petroleum Engineering, Amirkabir University of Technology, Hafez 424, 15875-4413 Tehran, Iran;(2) Parsehpaydar Consulting Company, Tehran, Iran |
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| Abstract: | This paper examines the failure of Kargar cut slope located at the south part of Esfahan subway using analytical and numerical
back analysis methods. The excavated trench has 27 m depth with near vertical walls due to the space limitation around it.
The geology of the area comprises weathered and heavily jointed shale and sandstone overlaid by alluvium deposits. Despite
the slope being supported by shotcrete and fully grouted rock bolts, a catastrophic failure occurred at the east wall. Due
to the uncertainty about the causes of failure initiation, back analyses have been performed via both the limit equilibrium
and numerical method for considering various probable mechanisms. In the back analysis with limit equilibrium method, the
rock mass is assumed as an equivalent continuum and Hoek–Brown failure criterion and geological strength index (GSI) are applied
to calculate the shear strength parameters. The results show that GSI value was 33 in the failed mass. In the numerical back
analysis, the distinct element method is applied to study the contribution of rock joints to the failure and progressive rock
mass strength degradation until failure. The results show that threshold values of joint cohesion and friction were 0.2 MPa
and 30°, respectively. Also the modeled slip surface being step-shaped agrees with the observed one. |
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