Search Documents

A description is given of a detailed examination of a coal bore core and of attempts to predict properties of equivalent "as-mined" coal using the bore core data so obtained. The accuracy of the prediction was measured by testing independently a large sample of coal which was produced under near mining conditions from a site adjacent to the bore core. Very encouraging results were obtained particularly in the prediction of size and ash distributions and washability characteristics of run-of-mine Coal.

Jan 1, 1972

By M Ireland

Extensive use of diesel-powered mobile equipment in modern mines for materials handling, such as load-haul-dump machines, constitute a significant source of heat, exhaust gases and diesel particulate matter. Provision of sufficient quantities of fresh, cool air are required to remove such atmospheric contaminants from the environment for miners, particularly at depths where ventilation constraints and associated operating costs have an increasingly adverse impact. An alternative solution to diesel equipment to combat economic, environmental, social and health challenges, are battery electric vehicles (BEV), with the potential to expand production and substantially reduce ventilation and cooling demand, subsequently reducing operating costs. In this context, this paper focuses on the introduction of a battery electric loader to a diesel fleet at one of the deepest underground mines in Australia, the CSA Mine, a high-grade copper operation in Cobar, New South Wales. Analysis of a trial battery electric loader compared to existing diesel machines is performed with regards to infrastructure, technical and operational issues. Key benefits of battery electric vehicles over conventional diesel-powered vehicles are discussed, including lower energy consumption and greater efficiency, reduction of emissions and heat, reduced need for ventilation and lower operating costs. Challenges of introducing BEVs into an operation, along with the results from the comparative study are addressed under impacts to energy consumption, equipment selection, effects on ventilation and cooling, mine design and economic viability for future fleet implementation scenarios whilst meeting production targets.

Mar 29, 2023

By T Wambeke, J Benndorf

A risk-robust development of a heavy mineral resource requires an assessment of the geological uncertainty and spatial variability of the key factors impacting the mining and processing operation. Attributes of interest are the total heavy mineral grade, the slime content and the amount of oversized particles. The modelling of a mineral sand deposit presents two main challenges. Firstly, the exact location of the geological boundaries are obscure due to the complex interaction of the deposit formation processes. Secondly, the properties of interest exhibit a rather complex transitional behaviour across the so-called soft boundaries. Traditionally, the modelling exercise is restricted to a consecutive stochastic simulation of distinct geological facies and orebody properties. This results in different zones separated by hard boundaries, ignoring the typical transitional behaviour.This contribution presents an alternative approach which models the entire sand body as a single domain while accounting for the complex trends present. Error curves are used to infer covariance model parameters without the need of a prior removal of the trend. The principle is based on minimising the differences between empirical and theoretical errors resulting from two methods of prediction calculated for different rings of influence. The added value results from the unambiguous decomposition of the spatial variation into a deterministic trend and a stochastic residual. The trend model neither overfits nor underfits the data. The calculated residuals are thus unbiased and the uncertainty can be correctly assessed.The effort results in a characterisation of the resource uncertainty which provides a more realistic image of the spatial variability of the key properties in and across the geological domains of an existing heavy mineral sand deposit.CITATION:Wambeke, T and Benndorf, J, 2014. Optimal inference of modelling parameters to simulate complex trends across soft boundaries – a case study in heavy mineral sands, in Proceedings Orebody Modelling and Strategic Mine Planning Symposium 2014 , pp 73–84 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 24, 2014

By B Miles, D J. Williams, J Ahn, T A. Vangsness

The flooding of open strip coal mines in the Bowen Basin and Hunter Valley Coalfields of Eastern Australia has the potential to soften the spoil and floor materials to produce “mud”. This mud can act as a slip plane or weak zone when spoil is dumped into it, resulting in geotechnical instabilities. It is therefore important to understand the mechanisms and degree of degradation likely to occur within coal mine spoil of different qualities.To investigate this, five clay mineral-rich coal mine spoil samples were collected from the Bowen Basin, and each sample was subjected to wetting and drying cycles to simulate degradation that could be expected on wetting-up in situ, with their particle size distribution analysed both before and after degradation. These results were compared with the results of a modified slake durability test, in which the entire sample was tested.The paper presents the results of the accelerated degradation and modified slake durability tests on each of the five spoil samples. These results were related to the physical and geochemical characteristics of the samples, which highlighted their importance. The modified slake durability test may be used to rapidly simulate the expected in situ degradation of coal mine spoil on wetting-up, enabling susceptible spoil materials to readily be identified.CITATION:Vangsness, T A, Williams, D J, Ahn, J and Miles, B, 2018. Accelerated degradation and modified slake durability testing of clay mineral-rich coal mine spoil, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 83–96 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By W P. Darcey

Jabiru Metals completed a feasibility study on the Jaguar Base Metal Project in July 2005. The study was based on conventional truck haulage via a decline. Conveyor haulage was considered but not in sufficient detail to provide a meaningful comparison. The current study investigates the cost and productivity of alternative ore transport systems for the Jaguar project. The options considered are conventional underground truck, conveyor, road train, rigid frame truck, monorail haulage and shaft hoisting. Shaft hoisting was not considered in detail due to the high capital outlay for such a relatively short mine life of less than six years. This study goes beyond the common approach of evaluating haulage systems in isolation; it includes development costs, timing of ore production and costs associated with mine services as well as administration and milling costs. The results of this study indicate that the best haulage option for the Jaguar project is conventional truck using the Hitachi AH400 trucks. The net present value (NPV) for this option is A$8.13 million higher than the next best option namely the Kiruna E635 electric truck. The conveyor option has the lowest operating cost per tonne of ore but the longer development time negatively impacts on its NPV. The monorail option is considered impractical due to the number and length of trains required to achieve production targets.

Mar 21, 2011

By K G. Harding, A Osman, A du Toit, F K. Crundwell, C M. Sheridan

"Most mineral processing plants have high water requirements for their operational activities. These plants often function in an environment where water is becoming increasingly scarce. An increase in population will result in an increased demand for water; potentially beyond the limits of supply and hence increased competition for the resource. In South Africa, Gauteng and the North West Province are likely to be first to experience a shortage of potable water.In order to avoid a water crisis, efforts must be made to ensure the effective management of water resources and the minimisation of wastage. Hydrometallurgical plants have a responsibility to society and the environment to operate in a sustainable manner - reducing their water requirements will certainly assist towards developing a sustainable footprint.This project improved site water management by: surveying the potable water and storm water systems with a view to assessing the current water accountability and determining methods to improve accountability determining the monthly and yearly water balance for the site and presenting it in the form of a water balance sheet drawing up an input-output and operational model in accordance with the Minerals Council of AustraliaÆs æWater Accounting Framework for the Minerals IndustryÆ calculating the water footprints of the refinery identifying ways in which water savings could be achieved recommending management systems for water usage monitoring.This work was conducted in South Africa. The value of this work lies in that it established the current baseline and assisted in developing management systems that can reduce water usage sustainably.CITATION:Osman, A, Crundwell, F K, Harding, K G, Sheridan, C M and du Toit, A, 2013. Water accountability and efficiency at a base metals refinery, in Proceedings Water in Mining 2013, pp 277-286 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Nov 26, 2013

The character of alluvial gold deposits presents severe difficulties, and sometimes limitations, on the extent to which metallurgical efficiency can be measured. Very little monitoring of metallurgical performance is practised. An indication of performance is often extracted from the comparison of production to the estimate. This is a dubious practice. The recovery efficiency of conventional practices, viz sluices, tables and jigs, falls off sharply below 0.2 mm. Field evaluation procedures tend to simulate these conventional practices. Thus the presence of fine gold may not be detected, particularly if obscured by clay. There is increasing evidence that fine gold could, in places, be present in sufficient concentrations to be economic. Most gold in paleoplacers is finer than 0.1 mm. There are established practices elsewhere in the mineral industry that may physically recover gold down to 5 microns in size and which could find application for fine alluvial gold.

Jan 1, 1984

By D Bradshaw, R Dunne, S Farrokhpay

It is well known that clays affect the flotation performance, and many of the refractory gold ores around the world contain clay minerals. Therefore, an ore sample from the Carlin Trend was selected for this study as these ores contain large quantities of clays. The presence of clay minerals in an ore makes it susceptible to a range of variables, such as the solution chemistry determined by pH and the chemistry of the rheology modifiers. The viscosity of the ore slurry was measured as a function of solid concentration and particle size distribution, in addition to using different rheology modifiers and pH regulators. The results were correlated with the ore flotation performance. It was found that various reagents known commonly as dispersants or rheology modifiers have different effects on the ore slurry viscosity. This study revealed that the gold flotation recovery can be improved by changing the pulp rheology.CITATION:Farrokhpay, S, Bradshaw, D and Dunne, R, 2013. Rheological investigation of the flotation performance of a high clay containing gold ore from Carlin Trend, in Proceedings World Gold 2013, pp 333-340 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

The Australian coal industry has undergone sevenfold growth over the last 30 years and since 1985 has been the world's largest coal exporter. Three quarters of Australia's coal production is exported so its future is dependent on it remaining internationally competitive with other energy sources and other coal exporting countries. Coal is likely to increase its share of the energy market during the nine- ties as oil prices increase, new coal-fired capacity is commissioned and some form of nuclear energy is developed which is of acceptable safety standards to the community for use in the 21st century. Gas may take a part of coal's anticipated market share by the Year 2000. While coal exports will increase from China, Colombia, Indonesia and Venezuela and satisfy some of this additional coal demand Australia will also expand its export production, due to its existing advantages. The United States, Canada, South Africa, Poland and USSR seem unlikely to enjoy the same degrees of expansion and some, particularly Poland and USSR, will decline. Australia will always find it difficult to compete in the more distant markets due to levels of ocean freight, although its high quality coals will tend to partly offset such disadvantage.

Jan 1, 1988

By D M. Frantois-Bongarton

"A few situations are first reviewed where practical shortcuts lead to acceptable solutions where none seemed to be possible. These include: The solving of many complex sampling optimisation problems with the simple approach of the worst case policy (WCP). A simple approach to single-stage sampling problems will be mentioned at continuation. In the plants, minimising the impact of border effects in incorrect samplers, so that the resulting samples are approximately correct and acceptable in practice because the bias risk attached to them is controlled. Examples are given, as well as practical tools and a general methodology.Finally, some sources of undue conservatism are reviewed with general recommendations aiming at eliminating them.CITATION:Frantois-Bongarton, D M, 2012. Practical considerations and shortcuts in sampling, in Proceedings Sampling 2012, pp 171-174 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Aug 21, 2012

By V Louchnikov

Ever increasing depth of mineral extraction presents a challenging environment for hard rock underground mines. High in situ stresses and associated seismicity with potential rock burst hazards are the major decisive factors contributing to the choice of a ground support regime. Conventional ground support systems, designed primarily for static loads, are not always capable of providing safe working conditions for underground personnel in seismically active mines. Systems specifically developed to resist dynamic loading and allowing for larger deformations are therefore preferred alternatives. High-tensile chain-link mesh has a proven record of successful use in open cut operations in various rockfall barrier installations due to its high energy absorption capacity. It has also been used in underground operations in various parts of the world. Its application in Australian underground mining, however, is limited due to the high labour intensity. This paper describes a method of mechanised installation of a chain-link mesh as trialled at Golden Grove, a base metals underground mine in Western Australia. A purpose-built mechanised roll mesh handler, developed in Australia, was used in this trial. The handler is compatible with all standard multi-boom underground drill rigs and is operated utilising the hydraulic circuit normally used for the feed arrangement.A number of operational benefits have been identified during the trial, the main two being:•improved safety of underground personnel due to the reduced amount of manual handling, and•increased productivity due to the decreased cycle time (the trial suggests a 40 - 50 per cent reduction in time over the weld mesh installation method).Although the energy-absorbing mesh combined with yielding rock bolts is a ground support system of choice for rock burst prone conditions, the operational upsides recognised during the trial imply that this product can also be competitively used in less demanding ground conditions where customarily weld mesh or shotcrete are used as a primary surface support.

Mar 21, 2011

By A Tawadrous, D S. Preece

Cave mining is of interest to the mining community as it offers a chance to extract large, deep orebodies with low operating costs and high production rates. It allows for extracting large low-grade orebodies, which may not have previously been considered for mining. Cave mining is done either top down (ie sublevel caving) or bottom up (ie block/panel caving). Both approaches rely on gravity, stresses and weakness of the rock to fracture and achieve a controlled collapse.Block caving starts at the base of the orebody. It progresses upward and across through continuous collapse of the roof. To achieve this, a critical hydraulic radius must be exceeded. This is accomplished by blasting drawbells, through which the caved ore passes to the production level. An entire level above the drawbells (undercut level) is excavated to help initiate the cave. The undercut level ensures the connection between drawbells and achievement of the required hydraulic radius.Conventionally, drawbells are generated by drilling and blasting several times from the production level as well as the undercut level. Mucking between each shot is required to generate enough void space for the rock to swell. The need for several blasts necessitates some downtime between each blast. Also, the cost of developing and maintaining the undercut level can constitute up to 35 per cent of the cost of mining the panel.A new blasting technique was developed to create the drawbells in a single blast from the production level. The technique ensures the connection of the drawbell to the neighbouring ones, thus, the critical hydraulic radius is reached and propagation of the cave achieved without the need for the undercut level. The technique has the potential to reduce the capital cost of a block caving operation, increase its feasibility and reduce time to reach the ore and consequently the payback period. This paper presents the modelling of a traditional drawbell excavation process, the philosophy of the developed technique, the modelling of that new design and its implementation.CITATION:Tawadrous, A and Preece, D S, 2015. A novel blasting technique to create drawbells and eliminate the undercut level in block cave mining, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 617–624 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By T Peters

The Kibali Gold Mine is currently comprised of several open pits, a 3.5 Mtpa underground mine and a 7.5 Mtpa processing plant. Development of the underground operation commenced in December 2012, with initial access established through twin surface declines, followed by the commencement of a blind sink 8 m diameter rock hoist shaft in March 2013. Stope production started in December 2014 with ore and waste trucked to surface. The 755 m deep blind shaft sink was completed in August 2015 together with the cutting and equipping of three main station levels. Two of these levels provide access for the establishment of the underground materials handling system as well as the main dewatering system for the mine. This paper covers the process of determining the optimal location of the Kibali hoisting shaft relative to project-specific critical factors, and then focuses on the design and implementation journey associated with the off-shaft development that essentially encompasses the Material Handling System (MHS) for the mine. The journey starts from the findings of the previous owners Feasibility Study (FS), a subsequent Optimised FS, followed by detailed engineering through to implementation. It was identified during implementation that a significant change in the designed off-shaft layout was required following detailed underground geotechnical and hydrogeological investigations. In addition, the paper provides details on the MHS performance since commissioning to steady state, and on key learnings relating to the overall project process.

Mar 29, 2023

By D Roldpo, M Vidigal, J F. C L Costa

The local cumulative distribution function (lcdf) of a selective mine unit (SMU) can be estimated by conditional simulations using the statistics derived from the sample points, generating multiple equally probable scenarios. Conditional simulations permit the evaluation of the lcdf at any support, taking into account the spatial variability, ie the variogram, and the two statistical moments, mean and variance, of the conditioning samples. The SMU ore losses and dilution depend on the mining method and mining equipment selectiveness that, in its turn, depends on the predicted block size. A new approach to predict ore loss and dilution was developed in this study. Monte Carlo simulation is used to randomly generate a grade value derived from the lcdf at the mining stage (Zs_mc(t)) in order to make a decision about the SMU destination, ie processing plant (ORE) or waste dump (WASTE). If Zs_mc(t) is lower or equal to the cut-off (Z_cut-off) the block is ORE and, conversely, if Zs_mc(t) is higher than the cut-off (Z_cut-off) the block is WASTE. Considering these binary destinations ORE/WASTE, at the mining time t, and combining each realisation of the simulated random function Zcs_i (X), there are four possibilities for each SMU simulated value: 1. the block was simulated as ore and is actually ore (OO), 2. the block was simulated as ore and is actually waste (OW),3. the block was simulated as waste and is actually ore (WO), and 4. the block was simulated as waste and is actually waste (WW).The dilution factor is given by possibility 3 (WO), while the ore loss factor is represented by possibility 2 (OW). These results comprise the classical classification and reconciliation plots used in the mining industry. The new procedure proposed in this paper is based on the use of all the equally probable simulations to define the ore loss and dilution factors. An application of this methodology was carried out at Vale's iron mine in Brazil. The grade of silica was simulated and 50 multiple equally probable 3D models were generated. The mean and the standard deviation of the ore tonnage (OO + WO) for the 50 realisations, was 233 Mt and 0.5 Mt, respectively. The mean grade increased for the diluted ore (OO + WO) as well as their respective coefficient of variation (CV). The CV increases from 62 per cent in the undiluted ore (OO), to 101 per cent in the ore, considering the dilution factor (OO + WO). The mean ore loss (OW) was 10 Mt and the waste tonnage dilution (WO) was 9 Mt.

Jan 1, 2009

To finalise the arrangement and details of the headframe to be erected over the new No. 3 Shaft, the haulage and winding equipment requirements were first determined, then tentative designs were prepared to cover the needs of general shaft servicing work for men and materials, mullock and ore handling, and the probable requirements of a breaker station to be built adjacent to the headframe, which would provide for the crushing of the run-of-mine ore down to a size which would be suitable for feeding on to the concentrating mill.

Jan 1, 1957

By T Wellman, G Sternadt, R Hingston

The 335 000 oz Wilber Deposit is located within the Meekatharra-Wydgee Archaean greenstone belt in the Murchison District of Western Australia. The deposit comprises high-grade gold mineralisation hosted within a steeply west-dipping quartz lode, which lies within a broader (20–60?m) north-east striking shear zone envelope. Locally, the northerly-trending host rock geology includes greenschist facies high-Mg basalt (albite, actinolite, chlorite, biotite, calcite, zoisite, muscovite and titanate) intruded by at least two generations of felsic to intermediate porphyries (albite, actinolite, zoisite, chlorite, sericite, biotite, quartz and titanate). The Archaean rocks are cross-cut by a number of east–west striking Proterozoic dolerite dykes (biotite (50 per cent), albite, carbonate, epidote, titanate and actinolite) that are interpreted to have intruded pre-existing regional structures. The entire mine package is cross-cut by a system of shallow north-east-striking, north-west-dipping, barren quartz veins that commonly contain large (up to 30 cm), euhedral, smokey quartz megacrysts.The north-east-trending lode lies within a 3 m wide shear zone and varies from a single discrete 0.5 to 4 m wide laminated, massive or brecciated quartz-carbonate vein to multiple laminated veins up to 1 m wide within the shear. The veins exhibit strong boudinage, with cross-cutting quartz-carbonate seal veins in the boudin necks. The boudin necks often contain pink calcite. The shear zone fabric wraps closely around the boudin necks proximal to the vein, becoming more lode parallel distal to the vein. The lode is offset by a north to north-north-west trending fault.Mineralisation occurs as free gold within the quartz carbonate veins, with accessory sulfides including pyrite ± chalcopyrite, ± galena ± sphalerite. Fuchsite is observed in the veins, as laminar wall rock inclusions, with visible gold commonly associated with the wall rock laminations.Gold grades range from less than 1 g/t within the hosting shear zone, either at the margins or interstitial to the veins, to approximately 30 g/t in the single vein, and up to greater than 60 g/t in the multiple vein areas. Gold is commonly visible and disseminated throughout laminated, breccia and massive quartz veins, although laminations show the highest concentration of gold grains.CITATION:Hingston, R, Wellman, T and Sternadt, G, 2014. The geology of the Wilber Deposit, Andy Well Gold Project, Murchison District, Western Australia, in Proceedings Ninth International Mining Geology Conference 2014 , pp 55–64 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By Nixon J. C, Reynolds C

Three principal features of the ore at Captain's Flat, New South Wales, tend to complicate concentration of the valuable minerals, these being:1. The ore occurs in three more or less separate bodies which vary in texture and mineral ratios. Mining of constant proportions of the three sections, or adequate blending of the ore, is not fully effective, and consequently the flotation section is subjected to feedof varying texture.2. The mineral association in the heavily pyritic ore is extremely intimate. Composite particles exist even at 20 micron sizeI, and probably finer.3. The copper content of the ore averages_about 0,6%, which is high enough to justify recovery of the chalcopyrite in a separate concentrate. A review of the metallurgical history of the mine shows that this feature has been the cause of the several major changes in flowsheet of the flotation section since the commencement of milling.METALLURGICAL HISTORYThe mine started production in January 1939, at the rate of 250 tons per day of sulphide ore, assaying 0·68% Cu, 6·52% Pb, 10·8% Zn, and about 1 dwt. Au and 2 oz. Ag per ton.

Jan 1, 1952

By E M. Gama, L Resende

The tailings are waste from mineral processing operations. The type of tailings of iron ore processing are classified into sandy tailings and mud. Already the overburden are showing significant levels of useful mineral. Both iron ore`s waste have in your composition phyllosilicates/clay that indicates the potential for use in niche markets as paving and cement. According to several studies, there are various technologies in bench and pilot levels that could be used on a large scale but there is not an economic environment, tax, regulatory and tax set. Many of these technologies are associated with the reuse of tailings and overburden in construction. All these factors influence for that so many initiatives remain in search formats and cannot advance to the new business format. There is no way to set goals of reuse of this waste, as already occurs in China, if there is not a fiscal, tax and economic structure to support such measures. The way to foster and ensure that reuse of tailings and overburden is an incentive for promoting a culture of circular economy that would allow the emergence of an ecosystem between the private, public and Government sectors with the objective of accelerating and subsidize the entire network of reuse of this waste. The closure of the mine could be the tool used to ensure and boost this ecosystem of reutilization to align it with the vocation of the area of the mining law. Following this model, the end of the mining activity could provide a financial return to the local population, a more effective environmental compensation and a reduction in costs related to the closure of the mine. In this study are shown how the Vale is working in the reuse of tailings and overburden.CITATION:Resende, L and Gama, E M, 2018. The challenges of the reuse of tailings and overburden, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 117–125 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

Large areas of ground are permanently supported on coal pillars, both in extensive old workings and current drivages in active mining operations. Continued growth of civil infrastructure is resulting in more surface development above old bord and pillar mines and an increased need for mine development beneath existing surface structures and features. The result is a greater likelihood of conflict between miners, developers and regulatory bodies. However, over the last 40 years there has also been significant improvement in the general level of understanding of pillar behaviour and stability, both in Australia and overseas. This paper examines some of the issues to be considered when undermining surface structures or undertaking surface development above old workings. The Factor of Safety (FoS) methodology widely employed for the assessment of pillar stability is reviewed, including the key geometrical, geological and statistical concepts associated with the probability of pillar failure; local and international experiences are examined and significant parameters isolated. Common concerns are addressed in the context of actual practical experience, utilising a risk management approach. Recent advances in methods for the assessment of pillar stability are put forward, along with criteria for arriving at rational design outcomes.

Jan 1, 2005

By J P. Evert

Didipio gold-copper mine operation is situated in the island of Luzon, approximately 270 km north of Manila in the Philippines, in an area of high seasonal rainfall. The hydrogeological water flow model implied that there would be high connectivity between regional structures and underground operations. This model predicted that underground mine groundwater inflows were expected to quickly rise as the decline progressed to a peak of 510 L/s. Designing a capital pump station to deal with 510 L/s has its own challenges, however developing the decline down to the required level, always dealing with 300 L/s of water and constructing the pump station is extremely challenging and required a robust water management plan and mine design. When dealing with expected high volumes of water, underground mine design and scheduling plays a key role in protecting electrical infrastructure, equipment, secondary pumps, and the decline from flooding. A good drainage system and controlled dewatering plan is essential for safety and progress. This paper details the dewatering techniques and mine designs required to accomplish decline development with high water inflows as used in the Didipio project. It will describe the learnings and outcomes that are achievable with a flexible design, as new structures are mapped, and water intersections are increased. It also highlights the potential for adaptability in mine planning to provide evolving improvements or to evade problems that are expected from the constant reconciliation of data recorded during development.

Mar 29, 2023