Status and Prospects of Underground Thick Coal Seam Mining Methods

ABSTRACT: Australia has very large thick seam coal resources. As a result, there has been ongoing research conducted by UNSW and others into suitable mining methods that are capable of safe, efficient and productive resource recovery. The significant production improvements achieved in the Chinese coal mining industry over the last decade, as a result of development and application of the LTCC method, has prompted Australian mines to examine the method and its potential, for Australian application. This paper presents the key issues and latest findings from recent thick seam mining research conducted by UNSW into various mining methods, but particularly, the Chinese LTCC method. In respect to LTCC, geotechnical factors such as coal strength and rock mass characteristics are considered with respect to caving potential and face support performance. The caving and coal clearance simulation/optimization research includes evaluation of a range of front and rear conveyor capacities relative to different caving strategies, as well as alternate panel conveying options

Analysis of a spatial Lotka-Volterra model with a finite range predator-prey interaction

We perform an analysis of a recent spatial version of the classical Lotka-Volterra model, where a finite scale controls individuals' interaction. We study the behavior of the predator-prey dynamics in physical spaces higher than one, showing how spatial patterns can emerge for some values of the interaction range and of the diffusion parameter.Comment: 7 pages, 7 figure

Discussions on rockburst and dynamic ground support in deep mines

The paper is a summary of discussions on four topics in rockburst and dynamic ground support. Topic1 is the mechanisms of rockburst. Rockburst events are classified into two categories in accordancewith the triggering mechanisms, i.e. strain burst and fault-slip burst. Strain burst occurs on rocksurfaces when the tangential stress exceeds the rock strength in hard and brittle rocks. Fault-slip burstis triggered by fault-slip induced seismicity. Topic 2 is prediction and forecasting of rockburst events.Prediction for a rockburst event must tell the location, timing and magnitude of the event. Forecastingcould simply foresee the probability of some of the three parameters. It is extremely challenging topredict rockbursts and large seismic events with current knowledge and technologies, but forecastingis possible, for example the possible locations of strain burst in an underground opening. At present,the approach using seismic monitoring and numerical modelling is a promising forecasting method.Topic 3 is preconditioning methods. The current preconditioning methods are blasting, relief-holedrilling and hydrofracturing. Defusing fault-slip seismicity is difficult and challenging but has beenachieved. In very deep locations (>3000 m), the fracturing could extend from the excavation face to adeep location ahead of the face and therefore preconditioning is usually not required. Topic 4 is dy-namic ground support against rockburst. Dynamic ground support requires that the support system bestrong enough to sustain the momentum of the ejecting rock on one hand and tough enough on theother hand to absorb the strain and seismic energies released from the rock mass. The current dynamicsupport systems in underground mining are composed of yielding tendons andflexible surfaceretaining elements like mesh/screen and straps. Yielding props and engineered timber props are alsoused for dynamic support.publishedVersionc2019 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CCBY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Humans Strengthen Bottom-Up Effects and Weaken Trophic Cascades in a Terrestrial Food Web

Ongoing debate about whether food webs are primarily regulated by predators or by primary plant productivity, cast as top-down and bottom-up effects, respectively, may becoming superfluous. Given that most of the world\u27s ecosystems are human dominated we broadened this dichotomy by considering human effects in a terrestrial food-web. We studied a multiple human-use landscape in southwest Alberta, Canada, as opposed to protected areas where previous terrestrial food-web studies have been conducted. We used structural equation models (SEMs) to assess the strength and direction of relationships between the density and distribution of: (1) humans, measured using a density index; (2) wolves (Canis lupus), elk (Cervus elpahus) and domestic cattle (Bos taurus), measured using resource selection functions, and; (3) forage quality, quantity and utilization (measured at vegetation sampling plots). Relationships were evaluated by taking advantage of temporal and spatial variation in human density, including day versus night, and two landscapes with the highest and lowest human density in the study area. Here we show that forage-mediated effects of humans had primacy over predator-mediated effects in the food web. In our parsimonious SEM, occurrence of humans was most correlated with occurrence of forage (beta = 0.637, p \u3c 0.0001). Elk and cattle distribution were correlated with forage (elk day: beta = 0.400, p \u3c 0.0001; elk night: beta = 0.369, p \u3c 0.0001; cattle day: beta = 0.403, p \u3c 0.0001; cattle, night: beta = 0.436, p \u3c 0.0001), and the distribution of elk or cattle and wolves were positively correlated during daytime (elk: beta = 0.293, p \u3c 0.0001, cattle: beta = 0.303, p \u3c 0.0001) and night-time (elk: beta = 0.460, p \u3c 0.0001, cattle: beta = 0.482, p \u3c 0.0001). Our results contrast with research conducted in protected areas that suggested human effects in the food web are primarily predator-mediated. Instead, human influence on vegetation may strengthen bottom-up predominance and weaken top-down trophic cascades in ecosystems. We suggest that human influences on ecosystems may usurp top-down and bottom-up effects

Biotic and Abiotic Associations with Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi) in the North Fork Flathead River Basin in northwestern Montana, USA and southeastern British Columbia, CAN under current and future climate scenarios.

Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi; WCT) populations are declining across much of their native range due to threats such as habitat degradation, competition with non-native species, and climate change. Understanding how habitat characteristics impact distributions of nonhybridized WCT populations throughout a relatively pristine core conservation area is needed to inform management and conservation efforts. We investigated whether abiotic (e.g., gradient) and biotic (i.e., Bull Trout – Salvelinus confluentus) variables predicted WCT presence and predicted how future stream temperature projections for the area might be expected to alter distributions. We compared logistic regression models of WCT presence throughout tributaries of the North Fork Flathead River in Montana, USA and British Columbia, CAN models using a variety of metrics (e.g., Akaike Information Criterion). WCT were widespread throughout the 293 reaches analyzed (present in 69.3% of reaches). Their presence was predicted by gradient, summer temperature, and an interaction of pool density and Bull Trout. Using this regression model and climate projections under both moderate and extreme emissions scenarios, WCT presence is predicted to increase by 13.0% and 14.1% respectively in 2075 from current distributions based on changes in temperature alone. When changes in Bull Trout distributions and temperatures are considered, WCT distributions are predicted to increase by 13.4% and 17.5% under the moderate and high emissions scenario, respectively. This conservation area is predicted to continue to serve as a WCT stronghold, if other threats can be contained

Step by step: reconstruction of terrestrial animal movement paths by dead-reckoning

Background: Research on wild animal ecology is increasingly employing GPS telemetry in order to determine animal movement. However, GPS systems record position intermittently, providing no information on latent position or track tortuosity. High frequency GPS have high power requirements, which necessitates large batteries (often effectively precluding their use on small animals) or reduced deployment duration. Dead-reckoning is an alternative approach which has the potential to ‘fill in the gaps’ between less resolute forms of telemetry without incurring the power costs. However, although this method has been used in aquatic environments, no explicit demonstration of terrestrial dead-reckoning has been presented.Results: We perform a simple validation experiment to assess the rate of error accumulation in terrestrial dead-reckoning. In addition, examples of successful implementation of dead-reckoning are given using data from the domestic dog Canus lupus, horse Equus ferus, cow Bos taurus and wild badger Meles meles.Conclusions: This study documents how terrestrial dead-reckoning can be undertaken, describing derivation of heading from tri-axial accelerometer and tri-axial magnetometer data, correction for hard and soft iron distortions on the magnetometer output, and presenting a novel correction procedure to marry dead-reckoned paths to ground-truthed positions. This study is the first explicit demonstration of terrestrial dead-reckoning, which provides a workable method of deriving the paths of animals on a step-by-step scale. The wider implications of this method for the understanding of animal movement ecology are discussed

Stress corrosion cracking of rockbolts: An in-situ testing approach

Premature failure of rockbolts due to stress corrosion cracking (SCC) is an unresolved global issue in underground structures, particularly underground mines. To date, SCC of rockbolts has been produced in laboratory-based studies under laboratory conditions, however no attempt to produce SCC in-situ in actual underground coal mine conditions has previously been made. In this study, an innovative testing methodology was used in which a rockbolt coupon was developed with multiple stressed sections. The test coupon could be placed in-situ within a borehole in an underground mine, exposing it to the borehole environment, the surrounding rock strata and the groundwater. In-situ coupons were made from both 1355 and HSAC840 grade rockbolt steels and installed within a typical rockbolted horizon where known SCC failure of rockbolts had occurred. SCC occurred in the 1355 grade in-situ coupons, but not in the HSAC840 grade ones despite service failures of HSAC840 rockbolts having occurred in the same underground mine. The difference in behaviour of the HSAC840 coupons and in-service rockbolts is most likely due to different stress regimes acting on the coupons and the rockbolts. Localised corrosion was observed on both steels although analysis of the groundwater indicated that it had low corrosivity. Microbiological analysis showed that a range of bacteria known to be involved in corrosion were present on the rockbolt coupons and in the underground environment. This suggested that the occurrence of localised corrosion and SCC in low corrosivity groundwater could be due to the presence of microbial organisms, in particular, sulphate reducing bacteria. The results of this study provide detailed insights into the SCC of rockbolts in the underground environment. The method developed here can be used to study other reinforcement elements and stressed settings for stress corrosion cracking

Integrating resource selection into spatial capture-recapture models for large carnivores

Wildlife managers need reliable methods to estimate large carnivore densities and population trends; yet large carnivores are elusive, difficult to detect, and occur at low densities making traditional approaches intractable. Recent advances in spatial capture-recapture (SCR) models have provided new approaches for monitoring trends in wildlife abundance and these methods are particularly applicable to large carnivores. We applied SCR models in a Bayesian framework to estimate mountain lion densities in the Bitterroot Mountains of west central Montana. We incorporate an existing resource selection function (RSF) as a density co-variate to account for heterogeneity in habitat use across the study area and include data collected from harvested lions. We identify individuals through DNA samples collected by (1) biopsy darting mountain lions detected in systematic surveys of a study area, (2) opportunistically collecting hair and scat samples, and (3) sampling all harvested mountain lions. We included 80 DNA samples collected from 62 individuals in the analysis. Including information on predicted habitat use as a co-variate on the distribution of activity centers reduced the median estimated density by 44% the standard deviation by 7% and the width of 95% credible intervals by 10% as compared to standard SCR models. Within the two management units of interest, we estimated a median mountain lion density of 4.5 mountain lions/100 km2 (95% CI=2.9, 7.7) and 5.2 mountain lions/100 km2 (95% CI=3.4, 9.1). Including harvested individuals (dead recovery) did not create a significant bias in the detection process by introducing individuals that could not be detected after removal. However, the dead recovery component of the model did have a substantial effect on results by increasing sample size. The ability to account for heterogeneity in habitat use provides a useful extension to SCR models, and will enhance the ability of wildlife managers to reliably and economically estimate density of wildlife populations, particularly large carnivores