scholarly journals UG2 pillar strength: Verification of the PlatMine formula

2021 ◽  
Vol 121 (8) ◽  
pp. 1-8
Author(s):  
B.P. Watson ◽  
W. Theron ◽  
N. Fernandes ◽  
W.O. Kekana ◽  
M.P. Mahlangu ◽  
...  
Keyword(s):  
Back Analysis ◽  
Strain Curve ◽  
Platinum Group Metals ◽  
Direct Result ◽  
Stress And Strain ◽  
Stress Strain Curve ◽  
Pillar Design ◽  
Pillar Strength ◽  
Group 2 ◽  
Strength Formula

The research described in this paper was done to confirm the Upper Group 2 (UG2) PlatMine peak pillar strength formula (Watson et al., 2007), which was determined from a back-analysis of failed and unfailed pillars. Underground measurements were made on a stable pillar that was loaded by firstly reducing it's length and then by mining the surrounding pillars until pillar failure took place. The pillar was instrumented with suitably positioned strain cells and closure meters, which allowed both the average pillar stress and strain to be determined. The paper describes the methodology applied to identify a suitable position for the instrumentation, as well as the results. A stress/strain curve is presented for a UG2 pillar with a w/h ratio of 2.0, at Booysendal Platinum Mine. The measured pillar strength was similar to the predicted strength using the PlatMine pillar strength formula for UG2 pillars. The PlatMine formula has been successfully implemented on Booysendal Platinum Mine, and about 3 670 pillars have been cut without a single failure. An additional revenue of US$1.3 billion was calculated for the 25-year life of the mine as a direct result of the improved pillar design, given the January 2020 platinum group metals basket price. An extended life of mine and better mining efficiencies will also be realized.

scholarly journals PlatMine pillar strength formula for the UG2 Reef

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.

Experimental Setup for the Determination of Mechanical Solder Materials Properties at Elevated Temperatures

2010 ◽  
Vol 638-642 ◽  
pp. 3793-3798
Author(s):  
Wolfgang H. Müller ◽  
Holger Worrack ◽  
Jens Sterthaus
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Elevated Temperatures ◽  
Young's Modulus ◽  
Linear Optimization ◽  
Strain Curve ◽  
Stress And Strain ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Non Linear

The fabrication of microelectronic and micromechanical devices leads to the use of only very small amounts of matter, which can behave quite differently than the corresponding bulk. Clearly, the materials will age and it is important to gather information on the (changing) material characteristics. In particular, Young’s modulus, yield stress, and hardness are of great interest. Moreover, a complete stress-strain curve is desirable for a detailed material characterization and simulation of a component, e.g., by Finite Elements (FE). However, since the amount of matter is so small and it is the intention to describe its behavior as realistic as possible, miniature tests are used for measuring the mechanical properties. In this paper two miniature tests are presented for this purpose, a mini-uniaxial-tension-test and a nanoindenter experiment. In the tensile test the axial load is prescribed and the corresponding extension of the specimen length is recorded, both of which determines the stress-strain- curve directly. The stress-strain curves are analyzed by assuming a non-linear relationship between stress and strain of the Ramberg-Osgood type and by fitting the corresponding parameters to the experimental data (obtained for various microelectronic solders) by means of a non-linear optimization routine. For a detailed analysis of very local mechanical properties nanoindentation is used, resulting primarily in load vs. indentation-depth data. According to the procedure of Oliver and Pharr this data can be used to obtain hardness and Young’s modulus but not a complete stress-strain curve, at least not directly. In order to obtain such a stress-strain-curve, the nanoindentation experiment is combined with FE and the coefficients involved in the corresponding constitutive equations for stress and strain are obtained by means of the inverse method. The stress-strain curves from nanoindentation and tensile tests are compared for two mate-rials (aluminum and steel). Differences are explained in terms of the locality of the measurement. Finally, material properties at elevated temperature are of particular interest in order to characterize the materials even more completely. We describe the setup for hot stage nanoindentation tests in context with first results for selected materials.

The Study on BFRP Binding Force of Secondary Compression Tests of Concrete Short Columns

2011 ◽  
Vol 418-420 ◽  
pp. 116-120
Author(s):  
Wei Ha Ma
Keyword(s):  
Initial Stress ◽  
Strain Curve ◽  
Peak Stress ◽  
Stress And Strain ◽  
Compression Tests ◽  
Secondary Stress ◽  
Stress Strain Curve ◽  
Binding Force ◽  
Short Columns ◽  
Strength And Deformation

This article has test researched on the BFRP constraint compression of the concrete short columns secondary stress axial compression , got C20, C25 reinforced concrete specimens of stress-strain curve test, studies show that strengthened specimens of strength and deformation of the increased significantly, and the degree of improve related with the size of initial stress. Through testing the processing and analysis of data, concludes that the calculation formula of peak stress and strain of the strengthening specimens under the secondary stress and can reflect the influence of different condition of initial stress .

Effect of Gamma-Irradiation towards Stress-Strain Curve of Single Die QFN Package

2011 ◽  
Vol 694 ◽  
pp. 620-624 ◽  
Author(s):  
Wan Yusmawati Wan Yusoff ◽  
Azman Jalar ◽  
Norinsan Kamil Othman ◽  
Irman Abdul Rahman
Keyword(s):  
Gamma Irradiation ◽  
Strain Curve ◽  
Stress And Strain ◽  
Flexural Stress ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Three Point Bending ◽  
Strain Behaviour ◽  
The Relationship ◽  
Different Doses

The aim of the research was to establish the relationship between stress-strain behaviour of single die Quad Flat No lead (SDQFN) and degradation by gamma irradiation. The SDQFN was exposed to Cobalt-60 with different doses from 0.5 Gy, 1.5 Gy, 5.0 Gy, 10.0 Gy and 50.0 kGy. The three-point bending technique was used to measure the flexural stress and strain of the package behaviour relations. After exposing with gamma radiation, the result showed the decreasing in the strength of the package behaviour of irradiated SDQFN when increasing the dose of gamma irradiation. The highest gamma irradiation dose used in this work produced the highest change in stress-strain behaviour of irradiated SDQFN.

Empirical Equations for Describing the Strain-Hardening Characteristics of Metals Subjected to Moderate Strains

1974 ◽  
Vol 96 (2) ◽  
pp. 123-126 ◽  
Author(s):  
C. Adams ◽  
J. G. Beese
Keyword(s):  
Strain Hardening ◽  
Elastic Recovery ◽  
Strain Curve ◽  
Stress And Strain ◽  
Accurate Assessment ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Initial Portion ◽  
Design Problems ◽  
Work Hardening Exponent

The strain-hardening characteristics of a metal have often been described by a power function which employs a work-hardening exponent, “n.” Usually the material is assumed to be rigid to the yield point and therefore the possibility of any elastic recovery is denied. The authors show that, particularly for the initial portion of a stress-strain curve, n is not a constant and therefore the curve cannot be described by one power law alone. A method is proposed for fitting equations to experimental stress-strain curves up to strain values of 0.05. The equations take into account possible elastic recovery. The equations should facilitate more accurate assessment of underload stress and strain distributions in various design problems.

Stress Analysis of Thin Elasto-Plastic Shells

1971 ◽  
Vol 93 (3) ◽  
pp. 851-861 ◽  
Author(s):  
Oles Lomacky ◽  
Barry Hyman
Keyword(s):  
Stress Analysis ◽  
Yield Criterion ◽  
Strain Curve ◽  
Normal Displacement ◽  
Flow Rule ◽  
Stress And Strain ◽  
Stress Strain Curve ◽  
Hardening Law ◽  
Concentration Factors ◽  
Special Case

The stress analysis of thin shells with large deflections loaded into the strain hardening range is presented. Plastic strain incompressibility is assumed. The two governing differential equations in terms of the stress function and the normal displacement are derived in a form where the corresponding equations of the elastic problem are modified only by the addition of the integrals of the plastic strains. The equations can be utilized in conjunction with any yield criterion, flow rule, and hardening law. The theory is applied to the problem of stress concentration around a circular opening in a pressurized spherical shell. A numerical solution is obtained by an iterative procedure using the finite difference technique for the special case of small displacements, bilinear stress strain curve, and deformation theory of plasticity. The speed of convergence for plastic stress and strain concentration factors was found to decrease with increasing pressure.

Sign in / Sign up

Export Citation Format

Share Document