Physical modeling of high extraction columns in block cave mining

Construction and development of the Grasberg Block Cave (GBC) mine continues to progress, with undercutting commencing in late 2018.As an experienced operator of block cave mines, PT Freeport Indonesia (PTFI) works to improve the planning and execution of undercutting.The GBC mine, with its large size and complex geotechnical conditions, requires increased focus on initiating and sustaining caving.For the past two years, PTFI has worked on developing a software tool for detailed undercut planning.The tool utilises cave management rules, the geologic block model, and ring shapes to produce detailed tonnage and grade schedules.Additionally, further analytical processing of the tool's output data allows examination of the feasibility and required resources to implement the undercutting plan.As a constraint-based scheduling application, the tool provides a high degree of flexibility in adapting quickly to changing assumptions.Factors affecting GBC undercutting include high tonnage rates, mine development resources, and variable rock mass conditions.Of primary concern, with production targets between 130,000 and 160,000 tpd, drawbells must open at a sufficient pace to achieve acceptable caving production ramp-up and then maintain throughput targets.Detailed undercut scheduling alleviates those concerns by optimising production block start dates, caving rules, and ring designs, to drive cave production with an achievable drawbelling rate.These detailed schedules also enable vetting of mine development plans, construction plans, and resource requirements.The GBC geotechnical environment requires undercutting strategies to adapt accordingly.Poor rock mass conditions, large panel boundaries, and high-stress conditions all affect undercut start points, caving directions, and other design decisions.The ability to produce realistic, detailed schedules enables further study of the impacts with 3D numerical modelling.Results from numerical modelling have helped refine not only the caving strategy, but also the overall mine design.The importance of the undercutting plan for successful caving of the large footprint, high tonnage rate GBC mine remains a priority.In conjunction with the geotechnical engineers and operations personnel, the mine planning team utilises the newly developed undercut planning tool to adapt and improve undercutting plans as more informed data becomes available.The geotechnical and operational challenges to mining the GBC necessitate the methods and approach to planning discussed in this paper.

Microplastic analysis in sediments of the Elbe River by electrostatic separation and differential scanning calorimetry

SummaryThe recent phase‐out of herbicide use on public pavements in Flanders has triggered the development of alternative strategies for weed prevention and control. In this study, growth chamber experiments investigated the ability of various water permeable joint filling materials for pavements to prevent weed growth. Joint fillers included in the tests comprised five innovative (iron slag sand, polymeric bound sand and three sodium silicate enriched fillers) and eight standard joint fillers (four fine materials, for example, sea sand, white sand, sandstone and fine limestone, and four coarse materials based on porphyry and limestone). Their ability to suppress weeds was investigated by examining seedling emergence and biomass production of seven test species in pure or organically polluted (5%, 10%, 20%, 40% and 80% compost by volume) filler substrate. Selected test species were dominant, hard‐to‐control weeds found on pavements. Seedling emergence and weed biomass were lowest in iron slag sand, polymeric bound sand and most sodium silicate enriched fillers, irrespective of pollution level or test species. Within standard joint fillers, pure white sand, sandstone and the coarse materials also reduced biomass, but their inhibitory effect dropped quickly once organically polluted, in contrast to fine limestone and sea sand for which weed suppression lasted longer (up to 40% compost by volume). Weed suppression of joint fillers was species specific. Our results show that there is potential for preventing weed growth using fillers that prevent the growth of a wide spectrum of plant species over a long period.

Vertical stratification of benthic samples at three stations on the Credit and Humber rivers revealed significant between-layer differences in the physical structure of riffles and abundances of larvae and pupal cases of Cheumatopsyche Wallengren and four species of Hydropsyche Pictet (Trichoptera: Hydropsychidae). Rock size and total rock surface area decreased from the top layer to the bottom (surface areas of pebbles excluded). Larvae of all five instars of H. sparna Ross were significantly more abundant (P < 0.05) in the top layer than in the bottom, but pupal cases were more numerous in the middle and bottom layers. Similar patterns were found for larvae and pupal cases of Hydropsyche bronta Ross, Hydropsyche slossonae Banks, and Cheumatopsyche. Pupal cases as well as larvae of Hydropsyche morosa Hagen were more numerous in the top layer. Depth and current conditions influenced sedimentation. Mean current velocities and total accumulation of fine material were greater at downstream stations. Significant variation in deposition of fine and coarse materials was found within the riffle at each station, suggesting that local streambed conditions govern sediment deposition at the microhabitat level.

DOI: 10.7764/RDLC.17.1.23 The effect of fine particles on the zeolite shear strength is assessed for possible construction applications. A brief geological description of the zeolite is presented. Three groups of zeolite samples were prepared, namely a coarse material with no fines, a finer material with 3% of silt and a silty material with 15% of clay. Results from standard classification, compaction and compressibility tests are shown and explained. It was found that due to the low specific gravity, low values of density were obtained in compaction tests. Additionally, shear strength tests were performed, resulting in different response in terms of shear stress and horizontal and vertical displacements. The coarse zeolite followed a similar friction-dilation response as in feldspathic and quartz sands. However, addition of 3% of fines reduced significantly the zeolite shear strength. Furthermore, the finest material was tested under two different displacement rates, reflecting also marked differences in shear strength and stiffness.

The development of a general circulation model (GCM) of Mars' atmosphere allows questions to be addressed concerning the relationships between near‐surface winds and the distribution of wind‐related features and deposits. Predictions of wind surface stress as a function of season and dust optical depth are used to investigate the distribution and orientation of wind streaks, yardangs, and rock abundance on the surface. The occurrence and orientation of bright streaks are well accounted for by the GCM. Results suggest that bright streaks form during southern hemisphere summer by Hadley cell circulation, in which dust is raised in the southern hemisphere, carried northward at high altitudes, then deposited in the wake of craters and other topographic obstacles by the descending Hadley cell. The reduction in the number of bright streaks southward from 30°N is interpreted to reflect the depletion of dust by near‐surface winds blowing to the south. Although the winds responsible for the formation of the dark streaks are not well reproduced in all areas by GCM simulations, a band of high wind surface stresses in the southern subtropics corresponding to the latitude band where most of the dark streaks are found are predicted at the height of the dust storm season (southern hemisphere summer). Yardang orientations do not match the GCM simulations for any season; their orientation is attributed to either structural control in the rocks (such as joint patterns) or to a change in wind patterns from the time when the yardangs formed. The global distribution of rocks on the surface is correlated well with predicted wind stress, particularly during dust storm season; the rocky areas are sites of strong winds, suggesting that fine material is swept away by the wind, leaving rocks and coarser material behind.

At PT Freeport Indonesia’s Grasberg mining complex, the Grasberg open pit is scheduled to cease production in early 2019. Mining of the Grasberg deposit will then transition to the underlying Grasberg Block Cave (GBC) mine, with initial undercutting currently planned for late 2018. The GBC is projected to become the district’s flagship underground mine for the next two decades. Early-stage production areas at the GBC are hosted within a heterogeneous rock mass. The footprint will be subjected to variable abutment and cave loading conditions. Mine design and sequencing adjustments, combined with customised ground support options, continually evolve to improve footprint reliability and permit a favourable transition between open pit and underground operations. This paper provides a snapshot of strategies employed to promote the successful caving operation at the GBC mine.

Grasberg open pit to Grasberg block cave transition wetmuck and mine design

This paper provides an update of the mine design, construction, caving progress and operations status of the Grasberg Block Cave (GBC) mine. Undercutting was initiated in September 2018 and drawbelling in December 2018. Undercutting is currently proceeding in three production blocks. Full production is expected in 2025, a 21-year time period between initial access development in 2004 to full production. Diluted ore reserves are about 959 million tonnes at a grade of 0.97% Cu and 0.73 g/t Au. The mine plan utilizes an El Teniente-style drawpoint layout on a 20 m x 30 m drawbell spacing, comprising some 2,400 drawpoints in a 720,000 m2 footprint. The drawpoint opening sequence comprises eight production blocks. Ore is transported via diesel-powered LHDs to a series of ore passes, then via loading chutes to a rail haulage system, which delivers the ore to a three-gyratory crusher complex. Crushed ore is transported to the mill stockpiles via dual inclined conveyors. Development and construction of the initial fixed facilities was completed in late 2018 and expansion of those facilities is ongoing to support production ramp up. Primary access for workers and materials is via the 6-km long AB adits. The service shaft for hoisting workers and materials from the AB adits’ level to the various operating levels was commissioned in 2016. The rail haulage central control system and initial haulage operating areas were commissioned in 2018. The first phase of the crusher/conveyor system was commissioned in mid-2018. Ventilation is provided through a series of large intake and exhaust drifts; four 5,000 kW main fans are operational, and a fifth fan will be commissioned in 2021. A 1,600 l/s pumping system will manage drainage from the mine. The initial stage of the pumping system is under construction and will be commissioned in 2020.

Here we present a modified version of the exploratory numerical model originally presented by Murray and Thieler (2004) and use it to further investigate the development of sorted bed forms on the inner continental shelf. The new version of the model is based on widely accepted parameterizations for hydrodynamics and sediment transport that are more detailed and empirically tested than the parameterizations used in the original model. The shallow water wave equations are replaced by the general equations, and changes in water depth related to morphological development are accounted for. This model reproduces the main results of the previous one, supporting the hypothesis that sorted bed forms are a self‐organized pattern and develop as a result of a coupling between bed composition and sediment flux. The sensitivity of the model predictions, evaluated in terms of the geometry of the sorted bed forms and their growth rate, with respect to external forcing variables and internal model parameterizations, shows increasing (decreasing) sorted bed form spacing (height) with increasing wave height and period. The opposite occurs for increasing water depths. More complicated behavior is observed when the ratio fine‐to‐coarse sediment diameter (or the percentage of fine and coarse material) is varied. The shape of the suspended sediment and current profiles and the formulation used to predict the geometry of wave‐generated ripples can significantly affect (or even inhibit) growth rates of sorted bed forms. Results from a sensitivity analysis show that there are deficiencies in the description of small‐scale processes that limit the ability to quantitatively predict sorted bed form evolution, highlighting gaps in our knowledge of sediment transport over mixed grain beds that need to be filled.

Lampung area has a basin, namely the Lampung Intermountain Basin which has the potential as a hydrocarbon system (Amin et al., 1994). The composition of the basin consists of various types of sedimentary rocks formed through sedimentation processes in different environments (Pettijohn et al., 1987). There is a group of sedimentary rocks exposed in the Bukit Barisan Strip, namely the Gading Formation (Amin et al., 1994). The Gading Formation has the same characteristics as the Talang Akar Formation which is used as a hydrocarbon reserve. In the Gading Formation there is sandstone lithology that has the potential as a reservoir rock. Analysis of Facies Association and depositional environment is an important part of oil and gas exploration, to provide information on the distribution and geological characteristics of oil and gas reserves in an area. Walker and James (1992) explained that facies is a rock body with several specific characteristics or characteristics that can be determined from lithology, biological structure, and sedimentary structure that show different facies aspects from other rock bodies, whether below, above, or around it. Facies association is a combination of two or more facies that form a rock body with a certain size. The research is located in the Rantautijang area, Pugung District, Tanggamus Regency, Lampung Province. The research uses a megascopic texture and lithology structure analysis method and stratigraphic cross-section measurements with a facies analysis approach, facies associations and determination of depositional environments. Stratigraphic cross-section measurements were carried out on the Gading Formation on the banks of the Way Tebu River. From the results of the research that has been carried out, namely the Facies in the Gading Formation are fine sandstone, conglomerate, medium sandstone, silt with a laminated structure, clay with a laminated structure, lensed shale, sandstone with a load cast structure. The channel fill facies association is composed of fine sandstone facies, conglomerate, medium sandstone and sandstone with a load cast structure. The floodplain facies association consists of laminated silt facies, laminated clay and lensed shale. The depositional environment is fluvial because it consists of fine and coarse material that is deposited.

Reversing buoyancy in turbidity currents: developing a hypothesis for flow transformation and for deposit facies and architecture

Turbidity currents are turbulent, sediment-laden gravity currents which can be generated in relatively shallow shelf settings and travel downslope before spreading out across deep-water abyssal plains. Because of the natural stratification of the oceans and/or fresh water river inputs to the source area, the interstitial fluid within which the particles are suspended will often be less dense than the deep-water ambient fluid. Consequently, a turbidity current may initially be denser than the ambient sea water and propagate as a ground-hugging flow, but later reverse in buoyancy as its bulk density decreases through sedimentation to become lower than that of the ambient sea water. When this occurs, all or part of the turbidity current lofts to form a buoyant sediment-laden cloud from which further deposition occurs. Deposition from such lofting turbidity currents, containing a mixture of fine and coarse sediment suspended in light interstitial fluid, is explored through analogue laboratory experiments complemented by theoretical analysis using a 'box and cloud' model. Particular attention is paid to the overall deposit geometry and to the distributions of fine and coarse material within the deposit. A range of beds can be deposited by bimodal lofting turbidity currents. Lofting may encourage the formation of tabular beds with a rapid pinch-out rather than the gradually tapering beds more typical of waning turbidity currents. Lofting may also decouple the fates of the finer and coarser sediment: depending on the initial flow composition, the coarse fraction can be deposited prior to or during buoyancy reversal, while the fine fraction can be swept upwards and away by the lofting cloud. An important feature of the results is the non-uniqueness of the deposit architecture: different initial current compositions can generate deposits with very similar bed profiles and grading characteristics, highlighting the difficulty of reconstructing the nature of the parent flow from field data. It is proposed that deposit emplacement by lofting turbidity currents is common in the geological record and may explain a range of features observed in deep-water massive sands, thinly bedded turbidite sequences and linked debrites, depending on the parent flow and its subsequent development. For example, a lofting flow may lead to a well sorted, largely ungraded or weakly graded bed if the fines are transported away by the cloud. However, a poorly sorted, largely ungraded region may form if, during buoyancy reversal, high local concentrations and associated hindered settling effects develop at the base of the cloud.

The subgrade layer is the lowest pavement layer, which carries the loads transferred from the upper layers. Different researchers have studied the resilient modulus (Mr) of different subgrade soils for the fine-grained and coarse-grained soil types. The layer's resilient response mechanism was found to be different for those fine and coarse materials, and it is vital for improving the pavement performance and life constructed over it. The different parameters related to the soil that can affect the resilient modulus include moisture content, stress level, compaction degree, loading frequency, and matric suction characteristics. Due to the variability of the Mr result, a study is needed for each soil type and input parameter. The effects of these parameters on the Mr are reviewed and discussed in this paper. The results show that the water content beyond the optimum level and the increase in deviatoric stress decreased Mr. In contrast, the increase in confining stress, compaction degree, loading frequency, and matric suction was found to improve the Mr. During the wetting and drying of the soil, the Mr was improved in the drying process.

An increasing amount of waste is being disposed of as a result of growing industrialisation, endangering the environment. In the building industries of all the fly ash-producing nations, fly ash is used in structural and non-structural concrete in a variety of ways. Practically, high-volume flyash consumption is a significant advancement. Thus, an inquiry into high calcium fly ash-based geopolymer composites is started through this investigation, using class C fly ash obtained from the Thermal Power Station of Neyveli Lignite Corporation as a quantum waste. Geopolymer composites with diverse molarities for M30, M35 and M40 were experimented with characteristics of compressive, split tensile, flexural, water absorption, and rapid chloride ion penetration tests and correlated with standard concrete. The outcome established that a geopolymer composite with 12 molarity blended with crushed stone sand and pond ash bottom ash recycled coarse aggregate salvage marble coarse aggregate was optimal in characteristics. Investigation reveals that water absorption is relatively minimal in geopolymer composites compared to standard concrete. RCPT shows the geopolymer concrete has excellent chloride resistance over prolonged curing time. This study sees an opportunity to evaluate the effects of employing alternatives for both fine and coarse materials. Here, fly ash completely replaces the cement.