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The efficient excavatability of ground is an issue that has still to be fully resolved. Although many existing criteria currently address this problem, they do not coincide with respect to the question whether mechanical methods are better than drilling and blasting for a specific type of ground. This is undoubtedly due to the variety of parameters involved. In the present study, ground in which a cut was to be made was chosen in order to compare the different existing criteria, highlighting the differences between them. To carry out this study, numerous laboratory and field trials were conducted, including the performing of mechanical tests to select the optimum method for excavating the ground in the area under study.

The behaviour of different gases (He, N 2 and CH 4 ) in coal was analyzed using a device for treating raw coal, designed for taking samples in the mine. This device was subsequently used to transport the samples and inject them with the gases under study. Experiments were conducted under different pressures, and a clear relationship was found between the drop in pressure and the occupation of different storage levels. On analysing the pressure evolution it was found that helium rapidly stabilised due to the characteristics of this gas. As for the other gases, N 2 showed a percentage fall much lower than that of CH 4 . In order to compare the storage capacity of different materials with respect to these gases, experiments were performed with different materials which form the mine's ceiling and walls. It was shown that the fall in pressure is very inferior. A fitting equation relating the evolution of pressure with time is proposed which may be used to define the time needed for the gas to stabilize in the coal. A normalized equation, very similar to that proposed by Langmuir, is likewise obtained to characterize the adsorption and desorption processes.

This paper analyzes the stability of the Llerin rockfill dam using Barton–Kjaernsli's shear criterion. To fit the parameters of this criterion, a direct shear test was designed that allows in situ calculation, using large-size samples of the shear stress at which failure is produced for different normal loads. These experimental values are then used to obtain more reliable values for the friction angle and the equivalent roughness of the rockfill material. The rockfill of Llerin dam is formed by a suitably ground gonfolite limestone rockfill that serves as a contention dam for a lagoon of mine tailings. The experimental results obtained in in situ tests were compared with those predicted by the shear criterion, subsequently determining the safety coefficient of the rockfill dam using the SLOPE computer program. We conclude that the values estimated via in situ testing permit the behaviour of the containment dam to be predicted more accurately.

Underground coal mines have always had to control the presence of different gases in the mining environment. Among these gases, methane is the most important one, since it is inherent to coal. Despite of the technical developments in recent decades, methane hazards have not yet been fully avoided. This is partly due to the increasing depths of modern mines, where methane emissions are higher, and also to other mining-related circumstances, such as the increase in production rates and its consequences: difficulties in controlling the increasing methane levels, increasing mechanization, the use of explosives and not paying close attention to methane control systems. The main purposes of this paper are to establish site measurements using some critical parameters that are not part of the standard mining-control methods for risk assessment and to analyze the gas behavior of subvertical coal seams in deep mines in order to prevent gas incidents from occurring. The ultimate goal is the improvement in mining conditions and therefore in safety conditions. For this purpose, two different mines were instrumented for mine control and monitoring. Both mines belong to the Riosa–Olloniego coalfield, in the Asturias Central Basin, Spain and the areas instrumented are mined via subhorizontal sublevels at an actual depth of around 1000 m under the overburden of Mount Lusorio. During this research, a property favoring gas outbursts was site measured for the first time in an outburst-prone coal (8th Coalbed), gas pressure and its variations, which contributed to complete the data available from previous characterizations and to set some guidelines for assessing the potential outburst-prone areas. A gas-measurement-tube set has been designed for measuring gas pressure as well as its variation over time as a result of nearby workings and to calculate permeability. The paper establishes the effect of overlapping of works, but it also shows the efficacy of two preventive measures to be applied: high pressure water infusion and the exploitation of a protective coal seam (7th Coalbed), that must be mined preferably two complete sublevels before commencing the advance in the outburst-prone coalbed. Both measures constitute an improvement in the mining sequence and therefore in safety, and should be completed with a systematic measurement to control the risk: gas pressure in the 8th Coalbed in the area of influence of other workings, to establish the most suitable moment to renew the advance. Further researches could focus on ascertaining the permeability, not only in mined areas but also in areas of the mine that are still not affected by mining work and on tuning more finely the ranges of influence of overstress time and overlap distance of the workings of the 7th Coalbed in the 8th Coalbed.

The aim of this study is to present a modification of the failure criteria of rock masses, separately considering the effect that the Bieniawski’s rock mass rating (RMR) has due to joints, as well as the RMR linked to compressive strength of the mass rock. This modification can be applied to three of the already existing criteria: that of Bieniawski–Yudhbir–Kalamaras, that of Sheorey, and that of Hoek–Brown, comparatively analysing the effects of the three modifications that have been proposed. The new, modified criterion will be validated with new data obtained in a marble mine exploited by means of rooms and pillars. The values observed and measured in the mine are compared to those obtained through numerical modelling of the pillars, using the Analisis Lagrangiano de Medios Continuos, Lagrangian Analysis of Continuous Media (ALMEC) program. Finally, several conclusions related to the application of these rock failure criteria to the analysis of mining excavation of rooms and pillars will be proposed.

This study presents a three-dimensional development of the n–k–g influence function with the aim of predicting subsidence phenomena and characterizing the shape and dimensions of the corresponding trough. The parameters “ n ” and “ k ” characterize the ground and “ g ” is related to the gravity. This function depends on two physical concepts: the first is gravity, which characterizes the forces acting on the ground, and the second, the convergence of the roof and floor of the mine workings due to the stress state of the ground. Caving in of the roof generates direct subsidence, and the swelling of the floor, indirect subsidence, which allow us to establish the shape of the trough. The physical concepts introduced are fundamental in the mathematical implementation of the n–k–g influence function, allowing a more intuitive interpretation of the subsidence trough and notably facilitating the work of calibration, validation and sensitivity analysis. These concepts likewise allow the scope of application of influence functions to be extended to non-horizontal seams, also taking into account the quality of the rock mass and the presence of preferential sliding directions, in both the roof and the floor of the seam. In the development of this paper, we shall first see the physical concepts considered, to then present the three-dimensional implementation of our n–k–g influence function. We shall see the results obtained when calibrating the proposed numerical model with real data obtained from subsidence measurements in a coalmine in the Coal Basin of Asturias, situated in the North of Spain.

Automatic mesh generators of 2D polygonal domains, especially those that use structured meshes, generate elements (triangles or quadrilaterals), which, in relatively complex models, tend to lose their equilateral form. In order to avoid this, the posterior smoothing of elements is necessary to obtain meshes with minimum geometrical distortions. In this paper, one of these smoothing techniques is developed for use in underground modelling. A system of equations is generated in a similar mode to structural analysis, where the degrees of freedom are the smoothed values of each node coordinate, and the local stiffness matrix is a measure of the geometrical connectivity of each element in the mesh. This facilitates the smoothing of non-convex domains with interior islands, which allows the imposition of directionally constrained nodes on the boundary of the domain. At present, this method is being utilized to compliment our mesh generation technique for the discretization of tunnels in 2D.

Roofing slate exploitations in Spain are concentrated within the regions of Valdeorras and La Cabrera. These progressively increased their production in the early sixties, and generated great volum...

A generic approach to subsidence prediction based on the influence function method is presented. The changes proposed to the classical approach are the result of a previous analysis stage where a generalization to the 3D problem was made. In addition other hypothesis in order to relax the structural principles of the classical model are suggested. The quantitative results of this process and a brief discussion of its method of employment is presented at the end of this paper

Optimal shape design is one of the branches of optimal structural design which uses as design variables aspects of the configuration of the system, its geometrical disposition and its dimensions.

Although the application of neural networks in quality control and maintenance is growing quickly from last years, they are just an incipient technology in the Mining Industry. At the same time, maintenance of the shift is probably the most important matter in Mining, considering that the shift could be the only way out for people and material in a colliery.

This paper presents an optimization method and a computer program for the study of the slate banks exploitation, which allows the bank cutting process in rock pieces to be simulated and their later sawing to be carried out. Such program analyzes the joints or natural discontinuity planes of each block (cleavage planes, fractures, kink-bands, microfolds, etc), together with the planes defined by the cutting and the free sides of the bank, and, according to these, determines the rock pieces stripping sequence, showing an estimate of the foreseeable efficiency. It also allows die rock pieces sawing to be designed according to die direction given by the intersection of the stratification and cleavage planes, in order to obtain die largest number of slate extracts of a given size. The program displays die results graphically through an AutoCad® graphics design program, using interchange files.