Due to the high levels of uncertainty in underground coal mining operations, delays occur regularly which inadvertently reduce the utilisation of mining equipment. In most coal mines delay data is primarily sourced from shift reports, machine monitoring and production systems. The recording process is initiated commonly at the end of a shift to ensure the correct information is recorded for the managerial decision process. An issue that the Australian coal industry faces is the lack of a standardised delay recording process and delay classification system. Tools used within the industry to analyse delay data are mostly mine specific and offer no means of comparing the mine performance to the performance at other mine sites. This paper describes a VBA based delay data analysis tool UCDelay for underground coal mines. UCDelay is an add-in Excel module for classification of delay data into a standardised form.

Longwall mining accounts for more than 75% of underground coal production in Australia. It is a popular underground coal mining method worldwide, mainly due to its high extraction ratio, high productivity and increased safety due to improved powered support units. A longwall system requires significant capital investment, and it is necessary to minimise the financial risk associated with this investment. Minimisation of this financial risk requires a sound knowledge of the relationship between underlying operational/technical constraints and associated costs. A discrete simulation model using the Flexsim 3D virtual reality environment has been developed to assist management evaluate the impact of technical and operational constraints on longwall productivity. Using such a model, any set of operational scenarios can be evaluated to establish the optimum operational parameters for a longwall system.

This study investigates a glass-reinforced polymeric thin spray-on liner and its ability to reinforce substrate surface in underground excavations by the use of laboratory testing. Twenty-three hydrostone beams uncoated and coated with 5 mm thick fibre-reinforced polymer (FRP) coating were subjected to four-point bending tests to study their strength. The hydrostone beams coated with FRP experienced 1·3 times increase in strength when compared to the plain uncoated beams. Experiments also showed that in addition to the increased strength, the beams failure modes were also altered where the uncoated beams failed in tension while the polymer-coated specimens failed predominantly in shear. To study the influence of the FRP on fractured and notched surfaces, several beams with artificially induced rectangular and V-shaped notches were also tested. The results indicated that a single notch located at the bottom centre of the uncoated specimens led to strength reduction by 86% while polymer-coated notched beams had 13-fold increase in strength compared to a notched but uncoated specimen. The specimen strength further increased when the notch was infilled with the polymer material. Substantial reinforcement of rock substrate in an underground tunnel is possible with the application of this polymeric liner.

This study investigates a glass reinforced polymeric thin spray-on liner and its ability to reinforce substrate surface in underground excavations by the use of laboratory testings. Twenty-three hy...

To improve ground skin support in highly stressed underground mines, new types of thin spray-on liners (TSL) are currently under development to replace steel mesh. To test these products, three different types of support material were tested for their ability to resist buckling failure, a mode of failure typically experienced by strata in highly stressed mine roadways. Steel mesh, as currently used for skin support, and two types of glass fibre-reinforced polymeric TSL materials were tested and compared. One of the TSL materials FRP Y was specifically designed for coal mining application. Four hydrostone slabs, cast to promote buckling, were bolted together to mimic laminated roof strata, coated with each material and tested in compression. Test results indicated that due to the strong bond, specimens reinforced with TSL materials had greater stiffness and peak strength than specimens with no support or those supported with steel mesh. On average, the specimens supported with steel mesh were approximately 1.7 times stronger than the unsupported control specimens while the specimens supported with FRP X and FRP Y were 3.2 and 2.3 times stronger, respectively. Experiments clearly indicate that the bonding characteristics of the TSL material formed a composite layer with the rock skin thus increasing the specimen’s ability to resist rock skin failure.

The rate of underground coalmine roadway development is normally affected by multiple factors including the support cycle and operational delays. A simulation study of underground coal development rates together with associated roof support operations showed potential for a 30% performance increase utilising current support technology and faster coal transportation by the shuttle car to the boot end. In the case of the material supply requirements at the development face, the simulation results showed that the delivery rate of the material supply system has only a minor effect on the roadway development rate, regardless of either the duration or frequency of the supply operation.

Bunching usually occurs when faster trucks and slower trucks are mixed in a truck-shovel mining system. This paper presents the development of discrete-event simulation model to estimate the impacts of bunching on the productivity and efficiency of a truck-shovel system. The bunching effect on production, BEP, is defined to estimate the production sensitivity to the bunching effect on the truck fleet. The simulation results show that the mixed truck fleets with varying performance can cause significant bunching effect if the hauling trucks are from multiple loading sites or dumps. Depending on whether the fleet is over-trucked or under-trucked, the bunching has significant impact on both the fleet productivity and the equipment utilisation. Furthermore, the fleet with higher BEP takes a priority of overtaking the fleet with lower BEP to increase the productivity.

This study investigates the geochemical characteristics of rare earth elements and yttrium (REE+Y) in the neutral mine drainage (NMD) and river water in the vicinity of the Anjir Tangeh coal washing plant, Mazandaran province, northern Iran. The NMD water had a neutral pH along with high sulphate and bicarbonate concentrations. The total concentrations of REE in the NMD water were lower than in the river water. According to the North American Shale Composite (NASC) normalised concentrations, the patterns of NMD showed heavy REE (HREE) enrichment while the river water represented middle REE (MREE) enhancement. Both negative europium (Eu) and positive gadolinium (Gd) anomalies were observed in the drainage and river water within the study area. The sum of REE concentration increased gradually downstream of the discharging point of the plant reject water, in contrast to decreasing of Al, Fe, Mn and Cu+Pb+Zn concentrations. The river sediment with high Fe concentrations was enriched with lanthanum (La) and cerium (Ce). The overall REE pattern of the NMD approximates those of coal except for the depletion in light REE (LREE) and the enrichment of Eu. Dominant inorganic REE species in the river water included Ln (CO3)2− and LnCO3+, while LnCO3+, Ln (CO3)2− and Ln (SO4) + were the main complexes in the NMD. The saturation index indicated that Al and Fe were both oversaturated in the drainage and river water, which can control the fractionation of REE by the sorption process. According to both hierarchical cluster analysis (HCA) and principal component analysis (PCA), pH, Al, and P were the significant parameters in the REE distribution.

In this study, hybrid models are designed to predict groundwater inflow to an advancing open pit mine and the hydraulic head (HH) in observation wells at different distances from the centre of the pit during its advance. Hybrid methods coupling artificial neural network (ANN) with genetic algorithm (GA) methods (ANN-GA), and simulated annealing (SA) methods (ANN-SA), were utilised. Ratios of depth of pit penetration in aquifer to aquifer thickness, pit bottom radius to its top radius, inverse of pit advance time and the HH in the observation wells to the distance of observation wells from the centre of the pit were used as inputs to the networks. To achieve the objective two hybrid models consisting of ANN-GA and ANN-SA with 4-5-3-1 arrangement were designed. In addition, by switching the last argument of the input layer with the argument of the output layer of two earlier models, two new models were developed to predict the HH in the observation wells for the period of the mining process. The accuracy and reliability of models are verified by field data, results of a numerical finite element model using SEEP/W, outputs of simple ANNs and some well-known analytical solutions. Predicted results obtained by the hybrid methods are closer to the field data compared to the outputs of analytical and simple ANN models. Results show that despite the use of fewer and simpler parameters by the hybrid models, the ANN-GA and to some extent the ANN-SA have the ability to compete with the numerical models. (C) 2016 Elsevier B.V. All rights reserved.

Thin spray-on liners (TSLs) have been attracting more and more attention as an alternative to the steel mesh in underground roadway support. In order to investigate and compare the compressive strength of glass fibre reinforced ToughSkin TSL developed at the University of Wollongong, a compression test was developed using the cube samples of 40 mm in size. The effect of a small amount of glass fibre in the polymer matrix was tested. The test results indicate that the compressive strength and the material stiffness of the cube samples increased with the increase of glass fibre. All of samples exhibited ductile stress strain curve as they had a yield point and a fracture point. The ductile ToughSkin yield characteristics are very important as sudden brittle failure is considered unsafe for mining practices.

Thin spray-on liners (TSLs) are attracting attention as effective rock support reinforcement in underground mines. They have the potential to increase roadway development rates and provide resistance at small rock surface displacements. To study the reinforcement provided by a TSL when applied onto a pillar surface, the support mechanism of TSL-coated rock samples was investigated, thereby providing a basis for studying the effect of TSL confinement on rock pillars. A polymeric material liner was applied to three types of rock (siltstone, sandstone and granite), and details of the sample preparation and loading procedures are presented. The results of rock failure tests indicate that significant strength improvement and enhancement of post-failure characteristics developed for the TSL-encapsulated samples. TSL reinforcement of the weaker rocks appears to be better than that of the stronger rocks. It is concluded that effective rock reinforcement occurs in the case when the tensile strength of the TSL material is greater than the tensile strength of the rock; the TSL reinforcement of stronger rock types may not be as effective. The test results obtained are consistent and conclusive.

The groundwater inflow into a mine during its life and after ceasing operations is one of the most important concerns of the mining industry. This paper presents a hydrogeological assessment of the Irankuh Zn-Pb mine at 20 km south of Esfahan and 1 km northeast of Abnil in west-Central Iran. During mine excavation, the upper impervious bed of a confined aquifer was broken and water at high-pressure flowed into an open pit mine associated with the Kolahdarvazeh deposit. The inflow rates were 6.7 and 1.4 m3/s at the maximum and minimum quantities, respectively. Permeability, storage coefficient, thickness and initial head of the fully saturated confined aquifer were 3.5 × 10−4 m/s, 0.2, 30 m and 60 m, respectively. The hydraulic heads as a function of time were monitored at four observation wells in the vicinity of the pit over 19 weeks and at an observation well near a test well over 21 h. In addition, by measuring the rate of pumping out from the pit sump, at a constant head (usually equal to height of the pit floor), the real inflow rates to the pit were monitored. The main innovations of this work were to make comparison between numerical modelling using a finite element software called SEEP/W and actual data related to inflow and extend the applicability of the numerical model. This model was further used to estimate the hydraulic heads at the observation wells around the pit over 19 weeks during mining operations. Data from a pump-out test and observation wells were used for model calibration and verification. In order to evaluate the model efficiency, the modelling results of inflow quantity and hydraulic heads were compared to those from analytical solutions, as well as the field data. The mean percent error in relation to field data for the inflow quantity was 0.108. It varied between 1.16 and 1.46 for hydraulic head predictions, which are much lower values than the mean percent errors resulted from the analytical solutions (from 1.8 to 5.3 for inflow and from 2.16 to 3.5 for hydraulic head predictions). The analytical solutions underestimated the inflow compared to the numerical model for the time period of 2–19 weeks. The results presented in this paper can be used for developing an effective dewatering program.

Australian underground coal mines predominately use the longwill method for coal extraction. In longwall mining at least two parallel roadways known as gateroads are mined to delineate the sides of the longwall block, a longwall installation face is then driven connecting the gatheroads to enable the longwall mining equipment to be installed. Roadway development should ideally be ahead of the longwall so that the longwall equipment can be installed into the newly developed panel with minimal delay to coal production. A discrete event mode of roadway development can help asses how a particular configuration may perform with high levels of variability and uncertainty in operations. One of the major delays assoicated with roadway development is caused by the shuttle car due to its cyclic stop-start nature. Shuttle car travelling paths and machine interactions are normally constraint by the mine's roadway layout and mine safety issues. This paper presents simulations of shuttle car route operations which can be considered at the design stage to minimize the cycle time of a shuttle car as part of a general roadway developemnt simulation model developed using 3D flexsim.

A fibre reinforced polymeric thin spray-on liner (TSL) has been under development to substitute traditional steel mesh to control skin surface in underground excavations. Its application can largely reduce the labor intensity and significantly increase the mining advance rate. In order to better evaluate the shear-bond strength of polymer liner and thereby assess its geotechnical function in strata skin reinforcement, three shear bond testing procedures were trialed. The aim of the tests was to evaluate pure shear bond strength of TSL to the various strata types without the effect of normal stress and to choose the most appropriate test for future routine testing. The first test method utilized the standard double shear testing procedure using three rock cubes of the 40 mm side bonded together with 5 mm thick polymer layer. The second test method included a polymer ring 5 mm thick and 15 mm wide coated on the periphery of each cored sample. The polymer ring was then sheared off each rock core with a steel sleeve and shear bond strength determined. The third test method was identical to the second one except that the polymer ring was partitioned into three segments to eliminate the effect of normal stress onto the substrate. The results show that to obtain the expected shear bond from the double-sided shear testing method was difficult due to the bending of the sample. The second test method was not accurate as the polymer shrinkage during curing time induced the normal stress onto the substrate and therefore increased the measured shear bond values. The results from the third test method indicate that the resin shrinkage did not affect the shear bond values significantly as the shrinkage problem was minimised by leaving three gaps between the adjacent polymer segments. The third test method was considered to be the best testing approach.

Steel mesh is used as a passive skin confinement medium to supplement the active support provided by rock bolts for roof and rib control in underground coal mines. Thin spray-on liners (TSL) are believed to have the potential to take the place of steel mesh as the skin confinement medium in underground mines. To confirm this belief, large scale laboratory experiments were conducted to compare the behaviour of welded steel mesh and a TSL, when used in conjunction with rock bolts, in reinforcing strata with weak bedding planes and strata prone to guttering, two common rock conditions which exist in coal mines. It was found that while the peak load taken by the simulated rock mass with weak bedding planes acting as the control sample (no skin confinement) was 2494 kN, the corresponding value of the sample with 5 mm thick TSL reinforcement reached 2856 kN. The peak load of the steel mesh reinforced sample was only 2321 kN, but this was attributed to the fact that one of the rock bolts broke during the test. The TSL reinforced sample had a similar post-yield behaviour as the steel mesh reinforced one. The results of the large scale guttering test indicated that a TSL is better than steel mesh in restricting rock movement and thus inhibiting the formation of gutters in the roof.

Compared with welded steel mesh which is a passive support medium, Thin Spray-on Liners (TSL) have many advantages and it is believed that TSL have the potential to take the place of steel mesh support in underground coal mines. In this study, full scale tests were firstly conducted to determine the ultimate strength of a plain polymer liner and two types of plain steel mesh. In terms of load bearing capacity, it was found that the polymer liner was stronger than the mesh with thinner diameter wire and weaker than the mesh with thicker wire. The liner was much stiffer than both of the two steel mesh sizes. The polymer and steel mesh were further loaded with fractured concrete pieces. The results showed that the polymer-concrete composite not only achieved much greater maximum load but was also stiffer than the steel mesh-concrete test structure.