Digging Conditions Research Articles

An analysis of digging anchor machine stability and track wear under digging conditions

To analyse the stability of a digging anchor machine under digging conditions, the dynamics model of the anchor machine and the interaction mechanics model between its tracks and the roadway floor are constructed with a Sandvik MB670-1 digging anchor machine in the context of the Zhang Jiamao 5–2 coal seam of the Shaanxi Coal and Chemical Industry Group. The discrete element method (DEM) and multibody dynamics (MBD) two-way coupling algorithm is used to simulate the cutting process of a full coal seam and coal rock containing gangue by using a digging anchor machine in a roadway. The changes in the cutting depth of the digging anchor machine drum, the sliding distance of the track and the stress‒strain pattern of the roadway floor are obtained. Finally, through shear slip testing, the stress distribution and deformation pattern of the roadway floor under different grouser parameters of the digging anchor machine track shoe, as well as the wear characteristics of the track shoe, are obtained. The results of this study can provide a theoretical basis for the control and reliability of the digging anchor machine and the life fatigue prediction of its tracks.

Energy efficiency assessment of electric shovel operating in opencast mine

Electric shovels are used for loading in opencast mines. Energy efficiency assessment of electric shovel is important to minimise its electrical energy usage. Specific power consumption (SPC) has been used as performance indicator to assess energy efficiency of shovel. A modelling framework is developed for estimating SPC of electric shovel from operating time and power measured for each process. The model is illustrated with a case study of 42 cu. m. P & H shovel operating in a large opencast mine of India. The SPC of shovel is optimized for actual operating cycle time components (idle time and digging time). Results of field measurements show that digging operation consumes maximum power in comparison to other operations of electric shovel in a cycle. The model has been used to assess the energy saving potential of electric shovel by using the real time operational data. The minimum SPC of electric shovel is 0.12 kWh/cum for zero idle time and the energy saving potential is 13.45%. The optimization of SPC has also been done for different digging conditions. The model developed can help to set a target for energy consumption of electric shovel operating in a mine.

P‐10.2: Characteristic and hollowing‐out Pattern with Debonding Layer in Mechanical separation

A thermo‐stable Debonding layer (DBL) is applied between the glass substrate and polyimide (PI) layer to weaken the adhesion. Through the investigation of the TFT characteristic after mechanical separation under different speed and digging conditions, the optimized process condition has been summarized for the mechanical lift off of the flexible OLED display to avoid inducing more defects.

Digging Trajectory Optimization for Cable Shovel Robotic Excavation Based on a Multi-Objective Genetic Algorithm

As one of the most essential earth-moving equipment, cable shovels significantly influence the efficiency and economy in the open-pit mining industry. The optimal digging trajectory planning for each cycle is the base for achieving effective and energy-saving operation, especially for robotic excavation, in which case, the digging trajectory can be precisely tracked. In this paper, to serve the vision of cable shovel automation, a two-phase multi-objective genetic algorithm was established for optimal digging trajectory planning. To be more specific, the optimization took digging time and energy consumption per payload as objects with the constraints of the limitations of the driving system and geometrical conditions. The WK-55-type cable shovel was applied for the validation of the effectiveness of the multi-objective optimization method for digging trajectories. The digging performance of the WK-55 cable shovel was tested in the Anjialing mining site to establish the constraints. Besides, the digging parameters of the material were selected based on the tested data to make the optimization in line with the condition of the real digging operations. The optimization results for different digging conditions indicate that the digging time decreased from an average of 20 s to 10 s after the first phase optimization, and the energy consumption per payload reduced by 13.28% after the second phase optimization, which validated the effectiveness and adaptivity of the optimization algorithm established in this paper.

Diggability assessment in open pit mines: a review

Loading efficiency has a critical role in increasing production and reducing cost of mining operations. Inefficient loading can significantly increase operational costs. The term diggability index is used to indicate ease of excavation. It also can be related to loading equipment performance and subsequently quality of blast. Several indicators have been defined in the past to assess diggability. This paper mainly focuses on the review of loading equipment based diggability assessment methods. The review highlights that although several indicators for different purposes were proposed in the literature, no universally accepted approach for diggability assessment has been defined which could produce reliable and repeatable results for assessing the muck-pile digging conditions. In addition to muck-pile characteristics and blast quality, operator practice and machine type and conditions have been found to have a significant effect on diggability. Therefore, it is necessary to investigate their effect in any diggability assessment study.

Application of vibration analysis of mining shovels for diggability assessment in open-pit operations

Over the past decades, technological advances and mining requirements have led to larger, more complex and more costly equipment. This trend in mining equipment has resulted in changing maintenance strategies from unplanned and scheduled maintenance to a condition-based maintenance (CBM) strategy. However, condition monitoring techniques used in CBM programmes are more than a maintenance management tool; they can provide the means to improve machine performance, production capacity and overall mine production. Vibration monitoring is usually the dominant technique of CBM programmes for critical machines such as electric rope shovels. It has been demonstrated that abnormal machine behaviour can be diagnosed using vibration monitoring techniques. However, this article aims to show the applicability of vibration monitoring of electric rope shovels for post-blast assessment rather than maintenance management. As a result, an electric rope shovel’s vibrations experienced by its boom during different operating conditions are measured by a tri-axial accelerometer mounted inside an enclosure on the side of shovel’s boom. The results show that the amount of apparent energy experienced by the tri-axial accelerometer can be used as an indirect measure of muck-pile digging conditions. Additionally, instantaneous and/or averaged vibration can be used as part of a system to monitor operator performance which potentially leads towards a machine with higher reliability, availability and maintainability and with higher productivity.

Past and Present Winter Feeding of Reindeer in Finland: Herders’ Adaptive Learning of Feeding Practices

The research examines reindeer feeding practices and herders’ learning of them in three herding co-operatives in Finland: Kuukas in the south, Oraniemi in the central area, and Hammastunturi in the north. In the southern and central co-operatives, from the late 19th century until the Second World War (1939 – 45), trees rich in lichens were cut to provide emergency forage. Harvesting lichens from trees and feeding associated with “tether calving” and “fence calving” have been common in the central and northern co-operatives. In the 1960s and 1970s, poor digging conditions resulted in reindeer losses, and pressure to feed reindeer increased further as forestry practices and overgrazing caused pastures to decline. Large-scale feeding entered daily practice in Kuukas and Oraniemi in the late 1980s and mid-1990s. The increased interaction between humans and reindeer brought about by regular feeding has made the animals tamer. In fact, they have adopted the permanent feeding areas as part of their pasture rotation. In Hammastunturi, herders entice reindeer from one pasture to another by providing supplementary forage. Knowledge about feeding developed in close concert with agriculture, and was transferred from south to north in the1980s and 1990s. We argue that feeding practices draw on traditional ecological knowledge, which includes old ways of herding cattle. Herders’ personal working practices and training are knowledge that is difficult to describe in words and must be learned by experience. Learning to feed reindeer requires not only familiarity with herding in practice (which implies profound knowledge about the animals, their nutrition, digestion, behavior, and handling), but also familiarity with the herding district and co-operation across generations.

Individual variation and prior experience affect the discrimination of a brood-parasite by its subsocial beetle host

In birds, host experience can modify response to parasites but nothing similar is known for insects. We studied two desert tenebrionid beetles, the subsocial host Parastizopus armaticeps and its obligate and ubiquitous brood-(clepto)parasite Eremostibes opacus, which mimics the host’s odour spectrum. Nearly 10% of host burrows in the field (n=214) remain unparasitised even after introducing E. opacus experimentally (n=22). In discrimination tests, 7% of naive host beetles eject the parasite, showing individual variation in olfactory discrimination ability. To test for effects of prior breeding experience, naive (“first time”) or experienced (“second time”) breeders with or without prior parasite contact were confined with E. opacus at breeding onset, their behaviour recorded and parasite number counted on breeding completion. More first- than second-time breeding pairs completely excluded the parasite and second-time breeders with no prior contact with E. opacus had fewer parasites than any others. These pairs increased burrow-guarding dramatically, mostly during early reproduction, this being the best predictor of parasite number. Prolonged guarding, however, must be traded-off against other brood-care behaviours. Hence, it might pay breeding pairs to take the risk of accepting some parasites breeding within their burrow, and we expect this effect will be more pronounced if poor feeding and digging conditions are taken into account. This might explain why apparently 90% of the P. armaticeps breeding burrows in the field contain at least one parasitic E. opacus.

GRIZZLY BEAR DIGGING: EFFECTS ON SUBALPINE MEADOW PLANTS IN RELATION TO MINERAL NITROGEN AVAILABILITY

Grizzly bears (Ursus arctos horribilis) affect plant distributions and mineral nitrogen availability when they forage by digging for the bulbs of glacier lilies (Erythronium grandiflorum) growing in subalpine meadows of Glacier National Park, Montana, United States. Our working hypothesis is that grizzly bears structure plant communities and in- fluence nitrogen availability when they selectively dig for preferred plants. In this paper, we report on differences found in recently disturbed digs (<5 yr old) when compared to adjacent, undisturbed meadow. We used ion exchange resin bags to determine the availability of mineral nitrogen in grizzly bear digs compared to undisturbed meadow. Soil in digs contained significantly more ammonium-N and nitrate-N than adjacent, intact meadow. Glacier lily bulbs reve- getating bear digs had higher tissue nitrogen and water-soluble carbohydrate concentrations than lilies in undisturbed meadow. Mature glacier lilies in digs produced twice as many seeds as did those in adjacent meadow. Glacier lily seedlings establish best on bare mineral soil, which in these meadows is found primarily in bear digs. Therefore, grizzly bear digging may benefit old, deeply seated plants that survive digging and reproduce. Digs overlapped spatially, meaning that grizzly bears were returning to dig in patches disturbed in previous years, perhaps in response to easier digging conditions and more nutritious glacier lily bulbs. To test the idea that the observed increase in mineral nitrogen was due to the physical disturbance of grizzly bear digging and not bear choice of sites already high in nitrogen or bear excretion, we created experimental digs. Ammonium-N and nitrate-N levels in- creased significantly following our digging treatment, just as we had observed in the natural bear digs. Although we do not know how a bear chooses an initial digging site, this disturbance has the potential for influencing long- and short-term plant community structure.

Application of unconventional geoelectrical methods to the hydrogeological examination of the Mt. S. Croce rock formations (Umbria, Italy) involved in a railway tunnel project

he project of doubling and developing of the railway line Orte-Falconara, committed by the Italian State Railway Company to the COMAVI Consortium (Rome, Italy), envisaged building the Mt. S. Croce tunnel, about 3200 m long between the stations of Narni and Nera Montoro (Umbria, ltaly). During the last phase of the feasibility project, a geophysical research based on geoelectrical prospecting methods was carried out to complement other geognostic investigations with the following goals: a) to outline the complex geotectonic model of the rock system, which will be affected by the new railway layout; b) to gain information on the hydrogeologic features of the survey area, in relation to the existing geologic situation and the consequent effects on the digging conditions of the tunnel and on the operation conditions of the railway layout. The geophysical work was thus organized according to the following scheme: a) execution of dipole electrical sounding pro-files, to depict a series of significant tomographic pseudosections, both across and along the new railway layout; b) execution of self-potential measurements, to draw an anomaly map over the whole hydrogeological network system in the survey area. The research provided information which has helped to improve the geological-structural model of the area and disclosed the hydrogelogic network, conforming to the classified field surface manifestations. At present, further detailed field investigations are being carried out, which confirm all the results obtained by the geoelectrical survey.

Geotechnical Applications of Downhole Sonic and Neutron Logging for Surface Coal Mining

At BHP-Utah Coal Ltd minesites, sonic and neutron logs are obtained in about twenty percent of exploration drill holes to identify the geotechnical properties of the overburden rocks for blast design and diggability assessment. Applications in blast design range from the simple identification of massive, high-strength rock units through to the semi-quantitative measurement of rock strength from correlation with sonic log transit time. At Goonyella Mine a bucketwheel excavator is used to remove overburden, and the overburden diggability is determined from sonic logs. The onset of hard digging conditions is identified by a sonic transit time of 150 ms/ft (equivalent to 492 ms/m), and marginal digging conditions occur at 125 ms/ft (equivalent to 410 ms/m). Direct correlation between geophysically determined digging resistance and monitored production data from the bucketwheel excavator shows that the sonic log method of digging resistance measurement is superior to more conventional geomechanical testing of rock cores.

Identification of indurated siltstone layers in advance of oil sands mining

Abstract Indurated siltstone layers within both overburden and oil sands adversely affect rock handling productivity and maintenance at the Suncor mine. Drill performance monitoring and borehole geophysics have been used in the past to locate and characterize these hard layers at Suncor. The capabilities of both analog-and digital-based drill monitoring systems for the characterization of rock hardness are reviewed with reference to, Suncor and other mine studies. Particular reference is given to the alternative drilling-derived parameters to identify such zones and focuses on current studies at Suncor. This work relates to the development of diggability criteria and the subsequent ability to generate depth contour and thickness isopach plans for difficult bucket wheel and shovel digging conditions for mine planning.

Test on the Dynamic Mechanical Performance of the Power Shovel

As the power shovel must deal with the earth in its work, it receives severe impact loads which vary according to the digging conditions and operating method. These impact loads are very difficult to grasp theoretically and there have been only a few theses ever written on this subject. This report deals with analysis of oscillogram recordings taken on various factors concerning power shovels in actual work. The points clarified by this study were as follows. (1) Degree of impact torque applied on the power shovel during digging, swing and travelling. (2) Reduction of impact and improvement of working properties by wing a fluid power transmission device. (3) Adaptability of secondary impedance system motor for the shovel work of an electric power shovel.