Slope stability and rockfall Hazard analysis in open pit zinc mine
- Authors: Almandalawi, Maged , You, Greg , Dahlhaus, Peter , Dowling, Kim , Sabry, Mohannad
- Date: 2015
- Type: Text , Journal article
- Relation: International Journal of GEOMATE Vol. 8, no. 1 (2015), p. 1143-1150
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- Description: Rockfalls are a major safety hazard in open cut mines, particularly in large-scale deep pits. The geotechnical design relies on in-situ, site-specific, rock slope data to predict the trajectories and velocities of rockfalls that present a residual hazard in the mines. This paper presents slope stability analyses using both static general limit equilibrium methods and finite element stress analyses to estimate unstable areas and slope displacements in the mid-west slope at Glencore Zinc's Handlebar Hill Open Cut mine at Mt. Isa, Queensland, Australia. A conventional program -RocFall- was used for the slope rockfall risk assessment. Results indicate the possible slope benches involved in the initiation of rockfalls, and the maximum run-out distance, which could be defined as the pit's hazardous zone. A rockfall restraining system to absorb the impact energy of boulders and prevent them further falling was also modelled. © 2015, International Journal of GEOMATE.
Effect of faults on stability of partially saturated rock slope
- Authors: You, Greg , Jaggi, Nav , Al Mandalawi, Maged , Dowling, Kim , Dahlhaus, Peter
- Date: 2019
- Type: Text , Book
- Relation: Deep Rock Mechanics : From Research to Engineering
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- Description: The effect of three faults on the slope stability was studied for the Stage 1 open pit in an open cut mine in Australia. The faults were treated as joints using Barton's method, and the slope was under dry and partially saturated conditions. A finite element program in RocScience was used in the study, where the generalized Hoek-Brown criterion was employed for rock mass and the Mohr-coulomb criterion for the faults. It is found that the factor of safety of the slope decreased with the introduction of the fault structures. Furthermore, the fault structures created higher stress concentrations zones at the ends of the faults.
Kinematic assessment of slopes at handlebar hill open cut mine, Mt. Isa, Queensland, Australia
- Authors: Almandalawi, Maged , You, Greg , Dowling, Kim , Dahlhaus, Peter
- Date: 2016
- Type: Text , Journal article
- Relation: International Journal of GEOMATE Vol. 10, no. 1 (2016), p. 1575-1583
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- Description: A complete kinematic analysis was conducted for the west slope at the Handlebar Hill mine using the Rocscience/Dips 6.0 software. The west slope was divided into three zones: W1 (south-west), W2 (mid-west) and W3 (north-west), which were then subdivided into nine small elements to increase the certainty of parameters. This enabled the analysis to define the potential kinematics of motions of critical structures. Small scale joints, bedding, faults, shears along the discontinuities were plotted and the data were analysed systematically. The results indicated that the potential toppling mode created by discontinuities can lead to direct/flexural toppling failure. The kinematic feasibility also revealed that the intersections of the discontinuities within the critical zone can structurally control the wedge planar failure modes. The results will assist the mine geotechnical engineers to understand the potential slope failure mechanisms and their locations. © 2016, International Journal of GEOMATE.
Analysis of a combined circular–toppling slope failure in an open–pit
- Authors: Al Mandalawi, Maged , You, Greg , Dahlhaus, Peter , Dowling, Kim , Sabry, Mohannad
- Date: 2019
- Type: Text , Conference paper
- Relation: 2nd GeoMEast International Congress and Exhibition on Sustainable Civil Infrastructures, Egypt 2018 - The official international congress of the Soil-Structure Interaction Group in Egypt, SSIGE 2018 p. 10-30
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- Description: Most studies of rock slope failures on open–pit mines have considered either toppling or circular failure stability analysis. By comparison, complex circular–toppling failure has received much less attention in the published literature. This paper presents a study using a range of methods to investigate a failure that occurred in July 2008 in Handlebar Hill, an open–pit base metal mine, near Mt Isa, Australia. Circular failure is the typical slope failure mechanism in slopes with low–strength rocks, although direct/flexural toppling of jointed columns can also occur. The study reviews circular–toppling failure mechanisms in the context of the local geotechnical and geo–hydrological conditions, which include the interaction between fault contacts and the existing deformed rocks. General limit equilibrium methods are used to evaluate the sensitivity of slope models to rock strength parameters and the trigger mechanisms. Finite element methods are used to assess the failure mechanisms and slope displacement, and a kinematic approach is used to evaluate structurally controlled slope instability mechanisms. The results demonstrate that the most credible failure mechanism was shearing along a circular path through the upper weaker rocks (leached Magazine Shale) that in turn initiated secondary block toppling, and the progressive nature of the slope failure mechanism. The use of conventional and numerical techniques for back–analysis of the combined circular–toppling failure provided key insights into the failure mechanisms and factors controlling slope instability. © 2019, Springer Nature Switzerland AG.
Finite element analysis of rock slope stability using shear strength reduction method
- Authors: You, Greg , Al Mandalawi, Maged , Soliman, Ahmed , Dowling, Kim , Dahlhaus, Peter
- Date: 2017
- Type: Text , Conference proceedings
- Relation: 1st GeoMEast International Congress and Exhibition on Sustainable Civil Infrastructures; Sharm El Sheikh, Egypt;15th-19th July 2017; published in Soil Testing, Soil Stability and Ground Improvement : Proceedings of the 1st GeoMEast International Congress and Exhibition, Egypt 2017 on Sustainable Civil Infrastructures (part of the Sustainable Civil Infrastructures book series) p. 227-235
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- Description: Finite element analysis incorporating the shear strength reduction method was applied to study the west slope stability of an open cut mine in Australia using Mohr–Coulomb and generalized Hoek–Brown criteria. The pit of the mine had multiphase excavations and reached 180 m in depth. The study investigated three slope configurations, namely, Stage 1 inter ramp slope 43°, Stage 2 inter ramp slope 49° and optimized Stage 2 slope 54°. When implementing the generalized Hoek–Brown failure criterion, the equivalent factor of safety was 1.96, 1.87 and 1.40 under dry slope for the three configurations, respectively. However, under partly saturated conditions, the optimised slope would have a factor of safety 1.16. Furthermore, the generalised Hoek–Brown criterion generated lower factors of safety than the Mohr–Coulomb failure criterion. The difference is related to an overestimation of the shear strength parameters by the linear Mohr–Coulomb criterion under low confining stresses compared with the non-linear Hoek–Brown.
Modelling and analyses of rock bridge fracture and step-path failure in open-pit mine rock slope
- Authors: Al Mandalawi, Maged , You, Greg , Dahlhaus, Peter , Dowling, Kim , Sabry, Mays
- Date: 2019
- Type: Text , Conference paper
- Relation: 2nd GeoMEast International Congress and Exhibition on Sustainable Civil Infrastructures, Egypt 2018 - The official international congress of the Soil-Structure Interaction Group in Egypt, SSIGE 2018, 24-28 November 2018 p. 198-226
- Full Text: false
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- Description: Rock Bridge fracturing and coalescence with pre-existing discontinuities in rock mass due to the initiation, propagation and interaction of these fractures refers to instability mode of step-path failure. Step-path failure is a typical type of instable mode of man-made and natural rock slopes. The continuum finite element method was applied to work on deeper insight into the propagation of tensile cracks which developing in the intact rock bridges that can finally coalesce to form step-path failure. In this paper, based on the intact rock fracturing hypothesis, two selected slope simulations from the Handlebar Hill open - pit mine near Mt. Isa in Queensland, Australia, modeled the process of fracturing and step-path failure through different pre-existing discontinuities. The empirical models of Bobet and Einstein (1998) and the progressively cracks development are observed within crack initiation, propagation and coalescence in the intact rock bridges. Proposed slope models of the mine included four joint-net distributions through the rock masses considering the geometry of structures (dip angles, spacing, lengths and orientation) illustrated the extension cracks from the flaw tips and propagated to the slope surface. Modes of intact rock bridges fracturing (shear, tensile and a combination of shear and tensile) have been observed. Tensile fracture is usually generated when the rock bridge angle is sub-vertical. Shear fracture can be initiated in less steep rock bridge angles. A combination of shear and tensile failure is normally generated in slopes with. Slope with explicit large-scale structures of steeper dip angles increased the yielding. Larger structures show much higher potential for yielding as the tensile stresses increasing. Major joint plane spacing resulted in less potential for relative deformations between neighboring structures and consequently reduced slope instability. The changes of length and spacing have more influence on slope stability than a change in the dip angle of the structures. © 2019, Springer Nature Switzerland AG.