3D Large Scale Physical Modelling for Studying Interactive Drawing and Drawpoint Spacing in Block Caving Mines

In block caving mines, the gravity flow of caved (broken) ore controls the amount of valuable material recovered and the extent to which it is diluted by caved waste rock. In addition, it also dictates the spacing, and thus the number of drawpoint required, which has a large impact on capital requirements for development of the mine. However, despite the large amount of research that has been carried out in the gravity flow field, 3D simulations of ore recovery and waste rock dilution can still not be done with confidence for conditions in a specific mine. Some mathematical models, in form of computer programs, have been developed. However these remain unvalidated due to the lack of validating data. It would be best to obtain this data from full scale tests. However experience has shown full scale tests to be very expensive, extremely time consuming and often the results from these tests have not yielded results that could be used effectively for the development of generally valid modelling approaches. Therefore, physical modelling remains as the only reliable way to do this task. It is the objective of this paper to describe the best method of physical modelling in order to produce reliable results which could be used to improve block caving mine design and validate mathematical models

Geostatistical Evaluation of Fracture Frequency and Crushing

International audienceThis work details how to estimate the Fracture Frequency (FF), ratio of a number of fractures divided by a sample length. The difficulty is that often, a part of the sample cannot be analyzed by the geologist because it is crushed, a characteristics of the rock strength that must also be considered for the Rock Mass Rating. After analyzing the usual practices, the paper describes the (geo)statistical link between fracturing and crushing and the resulting method to obtain a unbiased estimate of FF at a block or point support scale. Some concepts are introduced: "True" FF, "Crushed" FF, crushing probability and crushing proportion. The study is based on a real data set containing more than 13,000 samples. An appendix gives a very general formal demonstration on how to obtain an unbiased ratio estimation

Choice and substantiation of stable crown shapes in deep-level iron ore mining

Purpose. The aim of the paper is to select and substantiate stable shapes of crown pillars through determining regularities of rock pressure impacts on their stability depending on the crown shapes, mining depths and iron ore hardness. Methods. Stress and strain calculations are performed by the ANSYS 16.0 finite element analysis. Triangulation of the 3D model with a 2 m side is conducted to build stress and strain diagrams. In accordance with the conditions of the experiment, the models were created for horizontal, tent, arched and inclined stope crowns with the dip varying within a wide range. The assumed values of rock pressure on the ore massif conform to mining conditions of the Kryvyi Rih basin deposits at the depths of 1200 to 1700 m. Findings. The obtained values of maximum stresses in stope crowns were calculated in respect to mining depth, rock pressure, crown dip, iron ore hardness and relative curvature radius of the arched crowns. It was determined that vertical and inclined compensating rooms should be used in mining rich iron ores at great depths by sublevel caving systems. In case of the room-and-pillar systems used in mining rich iron ores at great depths, a key requirement is to apply tent and arched crowns which provide maximum stability under high rock pressure. Originality. The research proves that the integrated index of maximum stresses in crown pillars varies from –10 to +32 MPa at depths of over 1200 m and is in polynomial and logarithmic dependence on physical and mechanical properties of the ore mass. It also depends on the crown geometry and, in case of the arched crown, acquires minimal values allowing for stable crown pillar exposures at depths reaching 2000 m. Practical implications. The research results allowed to compile the methodological manual “Choice and substantiation of stable crown shapes in deep-level iron ore mining” for the underground mines of the PJSC “Sukha Balka” and “Rodina” mine of the PJSC “Kryvbaszalizrudkom”.Мета. Вибір та обґрунтування стійких форм стелин за рахунок встановлення закономірностей впливу гірського тиску на їх стійкість залежно від форми стелин, глибини розробки та міцності залізних руд. Методика. У даній роботі розрахунок напружень і деформацій гірського масиву виконано методом кінцевих елементів за допомогою програмного комплексу Ansys 16.0. Для побудови епюр напружень і деформацій методом кінцевих елементів над моделлю було проведено тріангуляцію 3D-моделі з розміром сторони 2 м. Згідно з умовами експерименту, були сформовані моделі з горизонтальною, шатровою, склепіннеподібною і похилою покрівлею камер, кут нахилу яких варіювався в широких межах. Прийняті величини тиску гірських порід на рудний масив відповідали гірничотехнічним умовам відпрацювання родовищ Криворізького басейну на глибинах від 1200 до 1700 м. Результати. Отримано розрахункові значення величин максимальних напружень в стелинах очисних камер залежно від глибини розробки, величини гірського тиску, кута нахилу стелини, міцності залізних руд і відносного радіуса кривизни склепіннеподібної стелини. Встановлено, що при відпрацюванні багатих залізних руд на великих глибинах системами підповерхового обвалення необхідно застосовувати вертикальні й похилі компенсаційні камери. Виявлено, що при відпрацюванні багатих залізних руд камерними системами розробки на значних глибинах ключовою вимогою, що забезпечує максимальну стійкість в умовах високого гірського тиску, є перехід на шатрові та склепінчасті стелини. Наукова новизна. Доведено, що інтегральний показник величини максимальних напружень у міжповерхових ціликах змінюється в межах від –10 до +32 МПа на глибинах понад 1200 м та знаходиться в поліноміально-логарифмічній залежності від фізико-механічних властивостей рудного масиву, залежить від геометричних параметрів склепіння і при його склепіннеподібній формі набуває мінімальних значень, дозволяючи формувати стійкі відслонення міжповерхових ціликів на глибинах до 2000 м. Практична значимість. Розроблено методичні рекомендації «Вибір та обґрунтування стійких форм стелин при видобутку залізних руд на великих глибинах» для умов шахт ПрАТ «Євраз Суха Балка» і шахти «Родіна» ПАТ «Кривбасзалізрудком».Цель. Выбор и обоснование устойчивых форм потолочин за счет установления закономерностей влияния горного давления на их устойчивость в зависимости от формы потолочин, глубины разработки и крепости железных руд. Методика. В данной работе расчет напряжений и деформаций горного массива выполнялся методом конечных элементов посредством программного комплекса Ansys 16.0. Для построения эпюр напряжений и деформаций методом конечных элементов над моделью было проведено триангуляцию 3D-модели с размером стороны 2 м. Согласно условиям эксперимента, были сформированы модели с горизонтальной, шатровой, сводообразной и наклонной кровлей камер, угол наклона которых варьировался в широких пределах. Принятые величины давления горных пород на рудный массив соответствовали горнотехническим условиям отработки месторождений Криворожского бассейна на глубинах от 1200 до 1700 м. Результаты. Получены расчетные значения величин максимальных напряжений в потолочинах очистных камер в зависимости от глубины разработки, величины горного давления, угла наклона потолочины, крепости железных руд и относительного радиуса кривизны сводообразных потолочин. Установлено, что при отработке богатых железных руд на больших глубинах системами подэтажного обрушения необходимо использовать вертикальные и наклонные компенсационные камеры. Выявлено, что при отработке богатых железных руд камерными системами разработки на значительных глубинах ключевым требованием, обеспечивающим максимальную устойчивость в условиях высокого горного давления, является переход на шатровые и сводчатые потолочины. Научная новизна. Доказано, что интегральный показатель величины максимальных напряжений в междуэтажных целиках меняется в пределах от –10 до +32 МПа на глубинах более 1200 м, находится в полиномиально-логарифмической зависимости от физико-механических свойств рудного массива, зависит от геометрических параметров потолочины и при ее сводообразной форме приобретает минимальные значения, позволяя формировать устойчивые обнажения междуэтажных целиков на глубинах до 2000 м. Практическая значимость. Разработаны методические рекомендации «Выбор и обоснование устойчивых форм потолочин при добыче железных руд на больших глубинах» для условий шахт ЧАО «Евраз Суха Балка» и шахты «Родина» ПАО «Кривбассжелезрудком».The authors would like to express their sincere gratitude to the management of PJSC “Sukha Balka” for assistance in conducting the research and implementing its results

Simplified Cost Models For Underground Mine Evaluation: A Handbook for Quick Prefeasibility Cost Estimates

This handbook provides simplified cost models for evaluating underground mines. Regression analysis is used to generate capital and operating cost equations for each model in the form Y = AXB, where Y is the cost estimated and X is the assumed production capacity in tonnes per day. A and B are constants determined by the regression analysis. Equations are developed for operating costs in five subcategories: equipment operation, supplies, hourly labor, administration, and sundries. Subcategories for capital costs are: equipment purchase, preproduction underground excavation, surface facilities, engineering & management, contingency, and working capital. Cost models are developed for eight underground mining methods

Determination of the indicators for ore recovery and ore dilution with laboratory research

Ore recovery and ore dilution are very important indicators in almost all mining exploitation methods, and are especially important in the sublevel caving mining method. In the sublevel caving mining method, there is an inverse proportion in the ore recovery and ore dilution, that is, by increasing one parameter the other is reduced, and vice versa. With each increased percent of ore dilution and reduction of ore recovery, there is a negative impact on the economic value of the ore reserves in the deposit, i.e., the content of metal in the ore is reduced, thereby increasing the production costs for treating the ore from loading to the final processing. In this paper will be presented laboratory methods in which the correlation between the coefficients of ore recovery and ore dilution in the sublevel caving mining method can be determined

Stability analysis of backfilling in subsiding area and optimization of the stoping sequence

AbstractIn underground mining by sublevel caving method, the deformation and damage of the surface induced by subsidence are the major challenging issues. The dynamic and soft backfilling body increases the safety risks in the subsiding area. In this paper, taking Zhangfushan iron mine as an example, the ore body and the general layout are focused on the safety of backfilling of mined-out area. Then, we use the ANSYS software to construct a three-dimensional (3D) model for the mining area in the Zhangfushan iron mine. According to the simulation results of the initial mining stages, the ore body is stoped step by step as suggested in the design. The stability of the backfilling is back analyzed based on the monitored displacements, considering the stress distribution to optimize the stoping sequence. The simulations show that a reasonable stoping sequence can minimize the concentration of high compressive stress and ensure the safety of stoping of the ore body

JAMSKA EKSPLOATACIJA BOKSITA U ZAPADNIM DINARIDIMA KLJUČNE ČINJENICE I KOMENTARI

After a short information about the causes both for the deficiency of papers on bauxite underground mines and for the development of such mines, a concise sketch of the geologic structures of the bauxite regions in the Western Dinarids, inclusive the chemical composition of the bauxites, is given. The main portion of the paper is devoted to the description of the following bauxitic regions: Drniš (with the mines Kalun and Kumanovo), Obrovac (Dračevac, Ćukovac—Grižinice and Krš), Mostar (Orašnica, Tribošić, Trobukva, Dabrica), Jajce (Poljane, Crvene Stijene), Bosanska Krupa (Risovac), and Sinj (Visoka). Presented are the »bauxitic« history of the region as well as its mining characteristics, from the mode of opening to the used mining methods, with their adventages and disadvantages. Comments are made, but no conclusions drawn; the future remains open.Nakon kratke informacije kako o razlozima za nedostatak objavljenih radova o boksitnim podzemnim radovima i za otvaranje takvih rudnika, dat je sažet prikaz geološke građe boksitnih područja u zapadnim Dinaridima, uključivo kemijskog sastava boksita. Glavni dio studije posvećen je opisu sljedećih boksitnih područja: Drniš (s jamama Kalun i Kumanovo), Obrovac (Dračevac, Ćukovac—Grižnice i Krš), Mostar (Orašnica, Tribošić, Trobukva i Dabrica), Jajce (Poljane i Crvene Stijene), Bosanska Krupa (Risovac), i Sinj (Visoka). Izneseni su i »bok-sitaški« historijat pojedinog područja kao i njegove rudarske karakteristike, počev od načina otvaranja jama do otkopnih metoda, s njihovim prednostima i nedostacima. Dati su neki komentari, ali zaključka nema; budućnost ostaje otvorena

Application of seismic monitoring in caving mines

Comprehensive and reliable seismic analysis techniques can aid in achieving successful inference of rockmass behaviour in different stages of the caving process. This case study is based on field data from Telfer sublevel caving mine in Western Australia. A seismic monitoring database was collected during cave progression and breaking into an open pit 550 m above the first caving lift. Five seismic analyses were used for interpreting the seismic events. Interpretation of the seismic data identifies the main effects of the geological features on the rockmass behaviour and the cave evolution. Three spatial zones and four important time periods are defined through seismic data analysis. This thesis also investigates correlations between the seismic event rate, the rate of the seismogenic zone migration, mucking rate, Apparent Stress History, Cumulative Apparent Volume rate and cave behaviour, in order to determine failure mechanisms that control cave evolution at Telfer Gold mine.Master of Applied Science (M.A.Sc.) in Natural Resources Engineerin

LEŽIŠTA I MOGUĆNOSTI EKSPLOATACIJE BENTONITA U HRVATSKOJ

Bentonite is one of the materials that is planed to be used for buffering and backfilling in spent nuclear fuel repositories, within deep crystalline rock. There are several locations in Croatia that bentonite deposits and occurrences are found on. Some were exploited in past, and others were more or less explored. This paper presents overview of bentonite deposits, basic properties and potential resources, and mining practices in Croatia. Largest exploited deposits are found in area of Poljanska luka, Gornja Jelenska and Bednja. Surface and underground methods (drift and fill, sublevel caving) were used during exploitation. In the area of Svilaja and Lika are found potentially valuable deposits that were never exploited. Montmorilonite content ranges form 20-50% to 57-89%. Most deposits contain bentonite beds with thickness 0,4-1,6 m, and have plunge 10°-30°. Few exceptions are nearly horizontal and thick more than 5 m and even 12 m. One is declined at 70° and up to 40m thick. Proven reserves are about 2,3 Mt with some level of uncertainty. Average production per mine during exploitation period can be assumed to be several thousands t/y.Bentonit je materijal kojim se planira brtviti i zapunjavati podzemna odlagališta nuklearnog otpada u dubokim magmatskim strukturama. U Hrvatskoj postoji više lokacija ležišta ili pojava bentonita. Neka od njih su eksploatirana u prošlosti, dok su druga manje ili više istraživana. U radu je prikazan pregled ležišta bentonita, važnija svojstva i rezerve, te način eksploatacije u Hrvatskoj. Najveća ležišta nalaze se u područjima Poljanske luke, Gornje Jelenske i Bednje. Primjenjivale su se površinske i podzemne (stupno uz zapunjavanje, podetažno otkopavanje) metode eksploatacije. U području Svilaje i Like nađena su potencijalno vrijedna ležišta, koja nisu iskorištavana. Udio montmorilonita se kreće od 20-50% do 57-89%. Većina ležišta čine slojevi bentonita debljine 0,4-1,6 m, i pada 10°-30°. Iznimno su horizontalna i debljine veće od 5 m, pa čak i 12 m. Jedno ležište pada pod 70° i debljine je do 40 m. Dokazane rezeve čini otprilike 2,3 Mt bentonita, uz određenu razinu nesigurnosti. Prosječna proizvodnja po rudniku za vrijeme eksploatacije pretpostavlja se oko nekoliko tisuća tona godišnje