Pit Boundaries Research Articles

Инструмент оптимизации выемочных единиц на открытых горных работах для блочных моделей месторождений

The MINEFRAME mining and geological information system features an algorithm and a software module to create bench-wise mining units for surface mining operations, which optimizes losses and dilution with due account for the spatial variability of the ore and gangue rock composition. The software module is based on both wireframe and pure block models, and takes into account a given development direction. The algorithm defines the mineable reserves of the deposit as a set of mining unit models. The module determines the expected levels of rational loss and dilution for each mining units of the bench, for each ore body, for the bench and for the open pit in general. The mining units also become the reference points for the design of blasting operations and the basis for the development of special measures to modify the parameters of the mining system locally. The obtained mineable reserves can be used in defining the pit boundaries and planning mining operations, and the contours of mining units will guide the design of the blast blocks. The algorithm can also be used to clarify the pit boundaries in the footwall of a sloping deposit and for economic comparison of the development options.

Studying rock mass jointing to provide bench stability while Northern Katpar deposit developing in Kazakhstan

Purpose is to identify the basic joint systems, their characteristics, distribution within the rock mass, and determine impact of the joints on the bench stability. Methods. The risks of strain emergence in the form of blocks sliding along weakness surfaces within the local areas were determined based upon the definition of rock stability loss. The results of large-scale measurements of jointing were processed using circular and bar diagrams as well as stereographic grids. In the context of the paper, kinematic analysis was implemented through Dips Rocscience Inc. Software. Findings. Five basic joint systems have been identified; joints of 2nd and 5th systems are the most commonly encountered among them. The results of the jointing determination within the open pit boundaries have been represented as well as the open pit wall stability in terms of each site inclusive of consideration of potential strains along the sliding surface. Originality. For the first time, zoning of the open pit wall in terms of slide types has been performed. It has been identified that potential shear of a prismatic block is 33%; at the same time, 66% are bench destruction with the block toppling. The risk of wedge-shaped block shear is minimal. Practical implications. The research findings may be helpful to define and select both parameters and conditions of safe mineral extraction under the specific mining and geological conditions. In turn, the abovementioned will help reduce the risk of accidence while providing scientifically substantiated approach to select quarrying sequence, techniques, and system.

Evaluation of rockburst risk in deep tunnels considering structural planes based on energy dissipation rate criterion and numerical simulation

Risk evaluation of rockbursts is crucial for ensuring the safety and stability of deep-tunnel construction. Structural planes play an important role in the potential for rockbursts to occur, and more related studies are needed. In this paper, a new rockburst criterion based on energy dissipation rate (EDR) index was developed and the role of structural planes in rockburst potential was studied. Firstly, a method of generating structural planes and a viscoplastic constitutive model with internal variables were introduced for numerical simulation using FLAC3D. Then, tunnelling under different hydrostatic pressures was simulated to obtain the values of EDR index and stress-strength/strength-stress ratio indices, and EDR criterion was estimated based on stress-strength/strength-stress ratio criteria. The results show that EDR criterion is: 0∼1 Pa/s (no risk), 1∼3 Pa/s (low risk), 3∼6 Pa/s (medium risk), >6 Pa/s (high risk). Subsequently, the case study of rockbursts in the drainage tunnel of Jinping II hydropower station was conducted considering a nearby fault to validate EDR criterion. The simulation results using EDR are basically consistent with actual rockbursts in terms of the potential location, intensity and time. Finally, the numerical simulations of tunnel excavation considering a joint set with different dip angles were implemented, and the influences of joints on rockbursts were investigated using EDR. Analysis results show that rockbursts are prone to occur on tunnel walls parallel and perpendicular to joints; potential rockburst locations are controlled by local joints and are less affected by geostress distribution. Joints may increase the intensity, delay the occurrence time, and control the pit boundaries of rockbursts. Obtained EDR contours can be used to infer damaged zones of strainbursts and strain-structure slip rockbursts and understand inducing mechanism of rockbursts in Jinping II drainage tunnel. The findings of this study provide insight into the role of structural planes on rockbursts. The presented methodology can be applied to rockburst evaluation and prevention during the construction of deep tunnels.

Pit-floored craters and layered terrains in the circum-Hellas region, Mars: Morphology, topography, stratigraphy, and relation to Late Noachian–Early Hesperian climate

Pit-floored craters (PFCs) have been observed in the highlands surrounding the Hellas impact basin on Mars. The pits consist of large irregularly shaped depressions (∼10s of km wide and ∼100s of m deep), often with steep layered walls and terraced interiors. We analyze a previously recognized population of circum-Hellas PFCs and nearby layered terrains using high-resolution visible imagery and stereo topography data and compare them to current models of Noachian–Hesperian geologic and climatic evolution. We find little evidence for regionally integrated fluvial runoff or crater rim breaching; crater interiors instead display fine-scale layering potentially related to pyroclastic, aeolian, or glacial deposition. Steep pit scarps, terraced pit floors, and a lack of traditional sediment transport pathways implicate sublimation of ice and removal into the atmosphere as the major pit-forming process. Radiating ridges interpreted as inverted fluvial channels emanating from raised pit boundaries further suggest water ice as a dominant crater floor fill material. Latitudinal distinctions in PFC morphology and evidence for both recent and past crater mantling and degradation events suggest a climate-controlled origin and evolution of circum-Hellas layered terrains dominated by the emplacement and removal of snow and ice. • Pit-floored craters (PFCs) and layered terrains are observed around Hellas basin. • Layered PFC walls are potentially related to ancient ice and dust deposition. • PFCs were likely formed through sublimation of ice to the atmosphere. • Origin, evolution of circum-Hellas layered terrains was modulated by early climate.

Основные этапы и результаты исследований по разработке методологических основ стратегии развития горнотехнических систем при освоении глубокозалегающих месторождений твердых полезных ископаемых

Specific features of mining deep-seated deposits charcterized with complex structure require a step-by-step change in parameters of the technological processes due to the clarification of the qualitative characteristics of minerals as well as the physical and mechanical properties of rocks. A new methodological approach to addressing the challenges associated with subsurface development is proposed based on the principles of consistency and complexity combined with the interdisciplinary and innovative approach and supplemented by introduction of the 'transient process' concept. The following most significant scientific, technological, organizational and technical issues that require investigation have been identified: 1) assessment of the volume and quality of reserves; 2) justification of the open pit boundaries and its depth; 3) the sequence of forming the open pit space and its working zone in relation to the development of the open pit transport system; 4) transition from the surface to the underground (combined) mining system. A scientific and methodological formulation of the solution to the problems of developing the existing mining operations is proposed, which consists of the following three sections: 1) development of a long-term strategy of innovative and technological development that would include solution of complex tasks; 2) formulation of approaches to development of mining technology, including optimization of technological process parameters; 3) working out a set of organizational and economic measures and managerial actions to prevent crisis situations or recover from them, including redundancy and resource management, situation-based technical and economic analysis and elimination of bottlenecks.

Synthetic Rock Mass Modelling and Geotechnical Mapping: An Open Pit Mine Case Study in Anisotropic Rock

ABSTRACT Most pit boundaries at Sishen Mine in South Africa consist of Banded Iron Formation (BIF), which exhibits anisotropic behaviour on a rock mass scale. A generally applicable approach is to apply Synthetic Rock Mass (SRM) modelling to characterise rock mass anisotropy. To characterise the rock mass for slope stability analysis, the persistence of bedding planes is very important. Subsequently, a sensitivity analysis on the effect that bedding persistence has on rock mass strength, was performed. Results indicate that bedding plane sizes less than the sample dimensions, produce higher strengths due to the influence of rock bridges. SRM modelling therefore demonstrates that persistence is a critical factor in rock mass strength analysis and subsequent slope stability analyses. The definition of SRMs is completely reliant on data provided by high quality, bench-scale structural mapping. The importance of geotechnical mapping is discussed, as it is currently the only way to accurately determine persistence. The Sishen study is a case in point that geotechnical mapping remains an essential function to obtain the appropriate rock mass characteristics for slope design. Routine mapping exercises, performed by well-trained geotechnical engineers, will therefore remain critical to acquire the necessary input parameters to advance the cutting edge SRM approach.

GRAPHIC RECONSTRUCTION OF A KASHINO DWELLING DATING BACK TO THE EARLY IRON AGE

The article presents the results of archaeological studies carried out at the Yakushkino 3 settlement attributed to the Kashino culture of the Early Iron Age (subtaiga Tobol area, Western Siberia). The settlement was preliminary dated at the 4th–3rd centuries BC. In this work, the authors set out to study the house-building tradition of the Ka-shino culture using the Yakushkino 3 settlement as an example, create its graphic visualisation; identify certain characteristics of the structure defining the nature of the settlement — seasonal use or place of permanent resi-dence, which indicate the adaptation strategies of the population. In 2016–2017, two structures connected by a passage were studied at the settlement. The former is interpreted as a residential structure, whereas the latter is thought to have been used for utility purposes. The multi-chamber residential structure (ca 48 m2) was chosen for the reconstruction. To this end, the authors employed the method of theoretical reconstructions. Drawing on the planigraphy and stratigraphy of the excavation site, the main elements (foundation pit boundaries, pits, ditches, etc.) of the structure were identified. The authors defined the layout of the structure on the basis of the character-istic arrangement of structural elements; identified techniques used in the construction of walls and roofs; deter-mined the possible use of certain building materials; as well as suggested interior variants. Finally, a graphic image of the structure was created. As a result of the study, the following assumptions were made. The structure con-sisted of 4 near-square rooms: the main central chamber (1) — 25 m2; chamber 2 — 12.5 m2; chamber 3 — 6.75 m2; chamber 4 — 3.5 m2. The second chamber was divided into two unequal parts, with ceramics being concentrated in its larger part, which could serve as a kitchen or a dining area. Chambers 3 and 4 could be used as bedrooms or as utility rooms. There was no hearth in the structure. The structure had a frame, with vertical posts providing support for the roof beams and being part of the frame-wall construction. The walls could be constructed of wicker boards or erected by leaning poles against the upper beam of the frame. The roof could be gable, covered with reeds and poles. Against the background of uniform buildings of the Early Iron Age, Kashino dwellings are cha-racterised by one common structural detail that was traced in the layout of the dwelling from the Yakushkino 3 settlement — additional chambers (utility or sleeping rooms) attached to the main room without an additional cor-ridor. This fact distinguishes these buildings from the dwellings of the Sargatka or Gorokhovo cultures of the Early Iron Age (Western Siberia). The absence of a hearth and the lightness of the construction suggests that the dwel-ling from the Yakushkino 3 settlement was used in the spring-autumn period.

Açık Ocak Üretim Planlaması için Örnek Bir Uygulama

Madenler, milyonlarca yılda oluşan, tüketildiğinde yenilenemeyen kaynaklardır. Bu nedenle; ülkenin ihtiyaçları göz önüne alınarak, kaynak kaybına yol açmadan, çevreyle barışık, akılcı, ekonomik kurallara göre ve işçi sağlığı-iş güvenliği esasları çerçevesinde, kamu yararı öncelikli olacak şekilde etkin bir planlama ile üretilmelidir [1]. Etkin bir planlama ise; değişen maliyet ve ürün değerine en hızlı şekilde uyum sağlayarak, rezervden elde edilebilecek net bugünkü değeri en yüksek üretimi sağlamalıdır.Bu çalışmada bir açık ocağın ocak ömrü boyunca maksimum kâr ile üretim yapmasını sağlayacak ilerleme yönleri bilgisayar programı (MICROMINE 11.0 ve SURPAC 6.5.1) yardımıyla araştırılmıştır. Sahada yapılan sondajlardan elde edilen verilerle veri tabanı oluşturulmuştur. Jeoistatistiksel analizler (istatistik ve variogram analizleri) ile tenör-tonaj hesaplamaları yapılmış ve kriging yöntemi ile cevherin yataktaki dağılımı tespit edilmiştir. Kazı ve zenginleştirme aşamaları için öngörülen maliyetler belirlenmiştir. Cevher fiyatı değiştirilerek iç içe ocaklar serisi oluşturulmuş, oluşan ocak sınırlarındaki değişimler incelenerek cevher üretim sırası belirlenmiştir. 

A Rho-actin signaling pathway shapes cell wall boundaries in Arabidopsis xylem vessels

Patterned cell wall deposition is crucial for cell shapes and functions. In Arabidopsis xylem vessels, ROP11 GTPase locally inhibits cell wall deposition through microtubule disassembly, inducing pits in cell walls. Here, we show that an additional ROP signaling pathway promotes cell wall growth at pit boundaries. Two proteins, Boundary of ROP domain1 (BDR1) and Wallin (WAL), localize to pit boundaries and regulate cell wall growth. WAL interacts with F-actin and promotes actin assembly at pit boundaries while BDR1 is a ROP effector. BDR1 interacts with WAL, suggesting that WAL could be recruited to the plasma membrane by a ROP-dependent mechanism. These results demonstrate that BDR1 and WAL mediate a ROP-actin pathway that shapes pit boundaries. The study reveals a distinct machinery in which two closely associated ROP pathways oppositely regulate cell wall deposition patterns for the establishment of tiny but highly specialized cell wall domains.

Disturbing stability of interface by adopting phase-change temperature gradient to reduce ice adhesion strength

The study proposes a novel de-icing model that established a phase-change temperature gradient on an interface to alter the contact stability between the substrate surface and the ice cover. During the experiment, pits of the same size were machined on the surface of aluminum alloy and polymethyl methacrylate, which are both regarded as the experimental materials, and ethanol solutions with different freezing points were filled in the pits. The ice adhesion strength on each substrate was repeatedly measured under different conditions. The results show that the ice adhesion strength on a sample with a phase-change temperature gradient was significantly reduced when compared to the ice adhesion strength on a smooth sample. That meant that the proposed de-icing model had the excellent de-icing capability. Owing to the rigid constraints of the pit boundaries and different mass concentrations of the ethanol solutions, an ethanol solution filling in the pits at different positions had an intermittent impact on the elastic interface between the ice and substrate. This deformed the interface, and the accumulated ice was always subjected to an upward impingement load, which affected the contact stability of the interface and causing the accumulated ice to separate from the sample surface. The energy released from the solution at low temperature could be used to enhance the active de-icing of various components, and to advance the development of new de-icing methods and materials.

Development of methodology for determining open pit boundaries

Development of methodology for determining open pit boundaries

Технологическая оценка расширения границ карьера при разработке крутопадаю- щих месторождений в простих горно-геологических условиях

Технологическая оценка расширения границ карьера при разработке крутопадаю- щих месторождений в простих горно-геологических условиях

Combined method of opencast and underground mining of valuable ore

The efficiency of the combined opencast and underground mining of deposits directly depends on the overburden amount within the open pit boundaries. The amount of overburden to be removed, in its turn, is determined by the angles of the open pit slopes. At the same time, the influence of the open pit slope angle on the amount of the rock mass within the open-pit contours increases in an arithmetic progression with the mining depth. This fact confirms the direct relationship between the open pit slope angle and the efficiency of the mining operations from both an economic and ecological points of view. The article considers the technology for mining steeply inclined deposits of valuable ores by means of underground chambers mined out in advance with consolidating stowing to support unworked sides of an open pit called “well”. The chambers which can be not only vertical but also inclined at an angle of 60-80° serve to create an artificial fence (a ring concrete support). The work of the fence supporting the open pit side is markedly different from that of retaining walls of any type since the consolidating stowing mixture used to create the fence provides an ideal contact of the concrete wall with the enclosing rocks, thus making it impossible for an artificial fence to overturn. The proposed combined mining technology is expected to reduce considerably the number of the overburden operations, to minimize the damage caused by mining operations to the environment, and to increase the intensity of mine workings.

Технологическая оценка расширения границ карьера при разработке крутопадаю- щих месторождений в простих горно-геологических условиях

Технологическая оценка расширения границ карьера при разработке крутопадаю- щих месторождений в простих горно-геологических условиях

Assessment of Dewatering Requirements and their Anticipated Effects on Groundwater Resources: A Case Study from the Caldag Nickel Mine, Western Turkey

Dewatering requirements of three open pits located in western Turkey and the impact of dewatering on groundwater resources were evaluated using a three-dimensional numerical groundwater flow model. The groundwater was modeled using MODFLOW software and the dewatering was simulated using the MODFLOW Drain Package. The drain cell configurations were determined by pit boundaries; invert elevations of drains corresponded to the bench elevations in the mining schedule, which varied dynamically among the three pits. Transient model runs were conducted for the 21 years of mine life to calculate the monthly dewatering rates. Simulation results indicate that the average groundwater inflow to the excavations is 3.64 L/s, excluding the effects of direct rainfall into the pits and surface water flow from the benches. Long term (80 years) simulations were conducted to predict the amount of drawdown at the water supply wells in the area. The results indicate that 21 years of mining will not significantly impact the water levels in these wells. However, natural discharge from the springs near the pits will be exhausted by the dewatering.

Contribution of electrical tomography methods in geotechnical investigations at Mavropigi lignite open pit mine, Northern Greece

In this paper, the application of 2D and 3D electrical resistivity methods in geotechnical investigations is explored through a case study in Northern Greece. These two methods were employed at a lignite surface mining operation where fracture zones and discontinuities have been recently observed close to the pit boundaries. The main aim of the geophysical survey was to estimate the inclination of the contact between the Neogene and Schist/Carbonate formations near the southern limits of the pit, as well as to estimate the thickness of the carbonate rocks on top of the Schist formations to evaluate the stability of the southern slopes. Synthetic data were initially generated to help plan an efficient electrical tomography survey, in a region with complex geology and irregular terrain. Three configurations (Wenner–Schlumberger and dipole–dipole or pole–dipole) proved essential in such conditions and helped improving the resolution of the resistivity section. The sections were then calibrated by boreholes. Finally, the geophysical survey provided invaluable data regarding the geometry of the bedrock and possible faults, which was essential for the slope stability calculations.

A three-dimensional modeling of multidirectional random wave diffraction by rectangular submarine pits

A three-dimensional modeling of multidirectional random-wave diffraction by a group of rectangular submarine pits is presented in this paper. The fluid domain is divided into N interior regions representing the pit area and an overall exterior region separated by the imaginary pit boundaries. In the interior region, the analytical expressions of the Fourier series expansion for velocity potentials in the pit regions have been derived with the unknown coefficients determined from a series of Green's function based boundary integral equations. The boundary integral approach has also been applied to obtain the velocity potential and free-surface elevation in the exterior region. The Pierson–Moskowitz (P–M) frequency spectrum was selected for the random wave simulation using the superposition of solutions of a finite number of decomposed wave components. Numerical results for the cases of regular waves and random waves are presented to examine the influences of the pit geometry and incident wave condition on the overall wave field. The general diffraction pattern of alternate bands of increase and decrease of relative wave height in front of the pit system can be observed. It is found that, in the shadow region, the relative wave height is reduced. As the number of pit increases, the effectiveness of reducing the relative wave height behind the multiple-pit system increases. However, the relative wave height within the pit area and in front of the leading pit shows increasing trend. It is noticed that under the random-wave condition, the level of increase and decrease of the relative wave height due to the existence of submarine pits is less pronounced than that observed from results in regular-wave condition.

Determination of Pit Boundaries in Step-by-Step Mining of Steeply Dipping Deposit. Part I

A new approach is proposed for solving the problem on determination of open pit boundaries in step-by-step mining of inclined and steeply dipping deposits.

3D inversion of a scalar radio magnetotelluric field data set

A radio magnetotelluric (MT) field data set, acquired in scalar mode, over a buried waste site has been successfully analyzed using a 3D MT inversion scheme using nonlinear conjugate gradients. The results of this analysis demonstrate the utility of the scheme where more than 4800 data points collected on multiple measurement profiles have been inverted simultaneously. The resulting image clearly detects the buried waste; when receiver profiles cross pit boundaries, the image maps the lateral extent of the pit. However, the base of the pit is poorly resolved, and depends upon the starting model used to launch the inversion. Hence, critical information on whether contamination is leaching into a resistive gravel bed lining the base of the pit, as well as the deeper geological horizons consisting of brown coal, clay, and tertiary sands, is inconclusive. Nevertheless, by incorporating within the inversion process a priori information of the background media that is host to the waste, sharper images of the base of the pit are obtained, which are in good agreement with borehole data. The 3D analysis applied in this paper overcomes previous limitations in the radio magnetotelluric (RMT) method using 2D data analysis and inversion. With 3D analysis, it is unnecessary to make assumptions regarding geological strike, and near‐surface statics can be accommodated in both source polarizations. Our findings also indicate that 2D MT interpretation can overestimate the pit's depth extent. This may lead to the erroneous conclusion that the geological horizons beneath the pit have been contaminated.

Etch pit development and growth on GaAs(110)

We used scanning tunneling microscopy to study etch pits that are formed at 650 K after exposure of GaAs(110) to ${\mathrm{Br}}_{2}$ at lower temperature. Dual bias imaging reveals that 80% of the pits that are one to two rows wide correspond to pairwise removal of Ga and As from surface lattice sites. These pits tend to grow along [11\ifmmode\bar\else\textasciimacron\fi{}0] and have ends that are equally likely to be bounded by either Ga or As atoms. In addition, there is etching across adjacent rows. The resulting pits cross several zigzag rows and have kinked [11\ifmmode\bar\else\textasciimacron\fi{}0] sides and irregular ends. When these pits grow larger, they increasingly exhibit kinked 〈11\ifmmode\bar\else\textasciimacron\fi{}2〉 boundaries and hexagonal appearances. Rebonding of As atoms at pit boundaries to exposed second-layer As atoms was observed, and an analysis of the pit boundaries indicates that there are equal numbers of As and Ga terminations. We suggest that etching along [11\ifmmode\bar\else\textasciimacron\fi{}0] involves removal of a Ga atom that was either a pit boundary atom or next to a rebonded As boundary atom and that such processes are equally accessible.