Pillar strength prediction from representative sample of hard rock

Pillar stability is an important factor for safe working and from an economic standpoint in underground mines. This paper discusses the effect of blast damage on the strength of hard rock pillars using numerical models through a parametric study. The results indicate that blast damage has a significant impact on the strength of pillars with larger width-to-height (W/H) ratios. The blast damage causes softening of the rock at the pillar boundaries leading to the yielding of the pillars in brittle fashion beyond the blast damage zones. The models show that the decrease in pillar strength as a consequence of blasting is inversely correlated with increasing pillar height at a constant W/H ratio. Inclined pillars are less susceptible to blast damage, and the damage on the inclined sides has a greater impact on pillar strength than on the normal sides. A methodology to analyze the blast damage on hard rock pillars using FLAC3D is presented herein.

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PlatMine pillar strength formula for the UG2 Reef

Journal of the Southern African Institute of Mining and Metallurgy ◽

10.17159/2411-9717/1387/2021 ◽

2021 ◽

Vol 121 (8) ◽

pp. 1-12

Author(s):

B.P. Watson ◽

R.A. Lamos ◽

D.P. Roberts

Keyword(s):

South African ◽

Hard Rock ◽

Bushveld Complex ◽

Back Analysis ◽

The South ◽

The Past ◽

Pillar Strength ◽

Group 2 ◽

Strength Formula ◽

Hard Rock Mines

The Upper Group 2 (UG2) chromitite reef is a shallow-dipping stratiform tabular orebody in the South African Bushveld Complex, which strikes for hundreds of kilometres. Mining is extensive, with depths ranging from close-to-surface to 2 500 m. Pillars are widely used to support the open stopes and bords. Little work has been done in the past to determine the strength of pillars on the UG2 Reef and design was done using formulae developed for other hard-rock mines. This has led to oversized pillars with consequent sterilization of ore. In this paper we describe a back-analysis of stable and failed UG2 pillars on the Bushveld platinum mines, and provides a strength formula for UG2 pillars. The formula may be used cautiously on all Bushveld platinum mines with similar geotechnical, geometrical, and geomechanical conditions to the pillars in the database.

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Effect of discontinuity dip direction on hard rock pillar strength

Transactions ◽

10.19150/trans.8745 ◽

2018 ◽

Vol 344 (1) ◽

pp. 25-30

Author(s):

K.V. Jessu ◽

T.R. Kostecki ◽

A.J.S. Spearing ◽

G.S. Esterhuizen

Keyword(s):

Hard Rock ◽

Rock Pillar ◽

Pillar Strength

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Improved empirical hard rock pillar strength predictions using unconfined compressive strength as a proxy for brittleness

International Journal of Rock Mechanics and Mining Sciences ◽

10.1016/j.ijrmms.2021.104934 ◽

2021 ◽

Vol 148 ◽

pp. 104934

Author(s):

G. Walton ◽

S. Sinha

Keyword(s):

Compressive Strength ◽

Unconfined Compressive Strength ◽

Hard Rock ◽

Rock Pillar ◽

Pillar Strength

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Automation Surprise

Aviation Psychology and Applied Human Factors ◽

10.1027/2192-0923/a000113 ◽

2017 ◽

Vol 7 (1) ◽

pp. 28-41 ◽

Cited By ~ 4

Author(s):

Robert J. de Boer ◽

Karel Hurts

Keyword(s):

Flight Control ◽

Representative Sample ◽

Aviation Safety ◽

Control Mode ◽

Cognitive Errors ◽

Laboratory Studies ◽

Airline Pilots ◽

Flight Operations ◽

Widespread Phenomenon ◽

Few Data

Abstract. Automation surprise (AS) has often been associated with aviation safety incidents. Although numerous laboratory studies have been conducted, few data are available from routine flight operations. A survey among a representative sample of 200 Dutch airline pilots was used to determine the prevalence of AS and the severity of its consequences, and to test some of the factors leading to AS. Results show that AS is a relatively widespread phenomenon that occurs three times per year per pilot on average but rarely has serious consequences. In less than 10% of the AS cases that were reviewed, an undesired aircraft state was induced. Reportable occurrences are estimated to occur only once every 1–3 years per pilot. Factors leading to a higher prevalence of AS include less flying experience, increasing complexity of the flight control mode, and flight duty periods of over 8 hr. It is concluded that AS is a manifestation of system and interface complexity rather than cognitive errors.

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Association of Physical Morbidity and Health-Related Quality of Life in a Representative Sample of Older German People

European Journal of Health Psychology ◽

10.1027/2512-8442/a000019 ◽

2018 ◽

Vol 25 (4) ◽

pp. 140-151

Author(s):

Markus A. Wirtz ◽

Matthias Morfeld ◽

Elmar Brähler ◽

Andreas Hinz ◽

Heide Glaesmer

Keyword(s):

Quality Of Life ◽

Representative Sample ◽

Short Form ◽

Physical Symptoms ◽

German Population ◽

Health Related Quality ◽

Patient Reported ◽

Related Quality ◽

Health Related

Abstract. The association between health-related quality of life (HRQoL; Short-Form Health Survey-12; SF-12) and patient-reported morbidity-related symptoms measured by the Patient Health Questionnaire-15 (PHQ-15) is analyzed in a representative sample of older people in the general German population. Data from 1,659 people aged 60 to 85 years were obtained. Latent class analysis identified six classes of patients, which optimally categorize clusters of physical symptoms the participants reported: musculoskeletal impairments (39.8%), healthy (25.7%), musculoskeletal and respiratory/cardiac impairments (12.8%), musculoskeletal and respiratory impairments, along with bowel and digestion problems (12.9%), general impairments (4.9%), and general impairments with no bowel and digestion problems (4.8%). The participants’ SF-12 Physical Health Scores (η2 = .39) and their Mental Health Scores (η2 = .28) are highly associated with these latent classes. These associations remain virtually identical after controlling for age. The results provide evidence that profiles of patient-reported physical impairments correspond strongly with reduced HRQoL independently from aging processes.

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