• Geomechanics and Engineering
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• v.27 no.5
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• pp.481-495
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• 2021

This article assesses and estimates the progressive failure mechanism of complex pit-rest secondary toppling of slopes that are located within the vicinity of the Gas Flare Site of Refinery No. 4 in South Pars Special Zone (SPSZ), southwest Iran. The finite element numerical procedure based on the Shear Strength Reduction (SSR) technique has been employed for the stability analysis. In this regard, several step modelling stages that were conducted to evaluate the slope stability status revealed that the main instability was situated on the left-hand side (western) slope in the Flare Site. The toppling was related to the rock column-overburden system in relation to the overburden pressure on the rock columns which led to the progressive instability of the slope. This load transfer from the overburden has most probably led to the separation of the rock column and to its rotation downstream of the slope in the form of a complex pit-rest secondary toppling. According to the numerical modelling, it was determined that the Strength Reduction Factor (SRF) decreased substantially from 5.68 to less than 0.320 upon progressive failure. The estimated shear and normal stresses in the block columns ranged from 1.74 MPa to 8.46 MPa, and from 1.47 MPa to 16.8 MPa, respectively. In addition, the normal and shear displacements in the block columns ranged from 0.00609 m to 0.173 m and from 0.0109 m to 0.793 m, respectively.

• The Journal of Engineering Geology
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• v.11 no.1
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• pp.13-23
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• 2001

Rock slope near the road or railroad is affected by the outside temperature and iterative freezing-thawing process during winter and early spring. The purpose of this study is to analyze the stability of rock slope which is iniluenced by deterioration due to the freezing-thawing. Method of analysis is homogenization method which find the strength property of discontinuous rock mass and as a strength failure criterion, Drucker-Prager failure criterion is used, The deterioration property of real rock is obtained by a freezing-thawing labordtory test of tuff and this quantitative property is used as a basic data of stability analysis of rock mass. To evaluate the deterioration depth due to the freezing-thawing in the field rock slope, one dimensional heat conductivity equation is used and as a a result we can find the depth of which is affected by a temperature. After determined the freezing-thawing depth of model slope, the pattern of rock mass strength value of model rock slope which excess the limit of self-load is analyzed.

• The Journal of Engineering Geology
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• v.25 no.1
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• pp.115-129
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• 2015

The cut-slope of a large-sectional tunnel portal is recognized as a potential area of weakness due to unstable stress distribution and possible permanent displacement. This paper presents a case study of a slope failure and remediation for a large-scale cut-slope at a tunnel portal. Extensive rock-slope brittle failure occurred along discontinuities in the rock mass after 46 mm of rainfall, which caused instability of the upper part of the cut-slope. Based on a geological survey and face mapping, the reason for failure is believed to be the presence of thin clay fill in discontinuities in the weathered rock mass and consequent saturationinduced joint weakening. The granite-gneiss rock mass has a high content of alkali-feldspar, indicating a vulnerability to weathering. Immediately before the slope failure, a sharp increase in displacement rate was indicated by settlement-time histories, and this observation can contribute to the safety management criteria for slope stability. In this case study, emergency remediation was performed to prevent further hazard and to facilitate reconstruction, and counterweight fill and concrete filling of voids were successfully applied. For ultimate remediation, the grid anchor-blocks were used for slope stabilization, and additional rock bolts and grouting were applied inside the tunnel. Limit-equilibrium slope stability analysis and analyses of strereographic projections confirmed the instability of the original slope and the effectiveness of reinforcing methods. After the application of reinforcing measures, instrumental monitoring indicated that the slope and the tunnel remained stable. This case study is expected to serve as a valuable reference for similar engineering cases of large-sectional slope stability.

• The Journal of Engineering Geology
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• v.20 no.2
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• pp.155-167
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• 2010

In analysis of slope stability, deterministic analysis which yields a factor of safety has been used until recently. However, probability of failure is considered as a more efficient method because it deals with the uncertainty and variability of rock mass. In both methods, a factor of safety or a probability of failure is calculated for a slope although characteristics of rock mass, such as characteristics of joints, weathering degree of rock and so on, are not uniform throughout the slope. In this paper, we divided a model slope into several zones depending on conditions of rock mass and joints, and probabilities of failure in each zone are calculated and compared with that calculated in whole slope. The persistence of joint was also used as a parameter in calculation of probability of failure. A rock slope located in Hongcheon, Gangwondo was selected and the probability of failure using zoning and persistence as parameter was calculated to confirm the applicability of model analysis.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.884-893
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• 2008

The purpose of this case study is cut-slope stability in pyroclastic-rock area. Pyroclastic-rock is very vulerable by Chemical and physical weathering. And risk increase of Pyroclastic-rock proportional to exposure time. This case of cut-slope located in Jeollabuk-do Jinan-gun and reserch order is topography character research, geological character research, field survey, measure method presentation.

• Tunnel and Underground Space
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• v.18 no.4
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• pp.289-299
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• 2008

Based on the case study on the causes for the failure of cutting slope composed of weathered rock and soil, the factors influencing the design of a cutting slope have been examined, This type of rock and soil is widely distributed on the region whose parent rock is granite. To analyze the stability of the cutting slope, the following series of progress has been conducted: (1) ground characterization by geological survey and ground investigation, (2) the safety factor examination by limit equilibrium analysis and numerical analysis and (3) the comparison and analysis of rainfall and failure history. As a result, the main factors to cause the failure is determined to be the decrease of shear strength in the upper parts whose ground condition is weakened during localized heavy rain. Moreover, the analysis indicates the failure is also closely related to the groundwater inflow path. On the base of this investigation, a reinforcement method is proposed to ensure the stability of the cutting slope.

• Tunnel and Underground Space
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• v.14 no.2
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• pp.133-141
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• 2004

Through the many site investigations, different methods for evaluating stability of rock slopes have been proposed. Those methods, however, may lead to different results depending on the subjective judgments associated with the selection of the evaluation items and the application of weighting factor. Accordingly, binary logistic regression analysis was carried out to ensure fair appliction of the weighting factor, leading to an equation for evaluating the stability of rock slopes.

• Tunnel and Underground Space
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• v.12 no.2
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• pp.83-91
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• 2002

Stability analysis of rocky embankment slopes is done by both the limit equilibrium method and the finite difference method. The height or the rocky embankment is approximately 40 m and the side slope is 1 vertical to 1.5 horizontal. The cohesion and internal friction angle of rock debris are assumed zero and 43$^{\circ}$, respectively. For finite difference analysis, strength reduction method is used to calculate the saft factor of the slope. As a result, the safety factor of the slope is discovered to be 1.4 by using either methods. Considering that the design criteria of the safety factor is 1.3, it can be judged that the rock fragments embankment slope is in a stable state.

• Tunnel and Underground Space
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• v.24 no.3
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• pp.187-200
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• 2014

After excavation or blasting, rock properties within an excavation damaged zone can be perpetually weakened on account of stress redistribution or blasting impact. In the present study, the excavation damaged zone is applied to a rock slope. The objective of this research is to compare the mechanical stability of the rock slope depending on the presence of the damaged zone using 2-dimensional modeling and analyze factors affecting factor-of-safety. From the modeling, it was founded that the mechanical stability of the rock slope is significantly dependent on the presence of the damaged zone. In particular, factor-of-safety with a consideration of the damaged zone decreased by approximately 49.4% in comparison with no damaged zone. Factor analysis by fractional factorial design was carried out on factor-of-safety. It showed that the key parameters affecting factor-of-safety are angle of the slope, cohesion, internal friction angle and height.

• Proceedings of the KSEEG Conference
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• 2001.04a
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• pp.206-207
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• 2001