Underground Conditions Research Articles

Problems and solutions in underground mining of non-ferrous and precious metal deposits in Yakutia

The article considers the experience gained in underground mining in Yakutia in terms of geological conditions of local ore bodies, as well as the mining methods used and equipment employed. The main factors of permafrost, having positive and negative effects on the safety and efficiency of mining are identified. The research data on deterioration of underground mining conditions during transition to the subpermafrost levels are given. The solutions proposed make it possible to improve the efficiency of underground mining of ore bodies with lower content of commercial minerals, without infrastructure available and in complex geological conditions, including subpermafrost reserves.

Review of coal and gas outburst in Australian underground coal mines

Outburst of coal and gas represents a significant risk to the health and safety of mine personnel working in development and longwall production face areas. There have been over 878 outburst events recorded in twenty-two Australian underground coal mines. Most outburst incidents have been associated with abnormal geological conditions.Details of Australian outburst incidents and mining experience in conditions where gas content was above current threshold levels are presented and discussed. Mining experience suggests that for gas content below 9.0 m3/t, mining in carbon dioxide (CO2) rich seam gas conditions does not pose a greater risk of outburst than mining in CH4 rich seam gas conditions. Mining experience also suggests that where no abnormal geological structures are present that mining in areas with gas content greater than the current accepted threshold levels can be undertaken with no discernible increase in outburst risk. The current approach to determining gas content threshold limits in Australian mines has been effective in preventing injury from outburst, however operational experience suggests the current method is overly conservative and in some cases the threshold limits are low to the point that they provide no significant reduction in outburst risk. Other factors that affect outburst risk, such as gas pressure, coal toughness and stress and geological structures are presently not incorporated into outburst threshold limits adopted in Australian mines. These factors and the development of an outburst risk index applicable to Australian underground coal mining conditions are the subject of ongoing research.

Лучевое обследование новорожденных при общей терапевтической гипотермии

Purpose: Search of possible criteria of the diagnosis of occupational lung cancer in workers of uranium mines on the basis of the analysis of literary data.
 Material and methods: The analysis of literary data with the purpose of allocation of possible criteria and their use for the diagnosis of occupational lung cancer at 6 employees of uranium mines.
 Results: The following criteria for the diagnosis of occupationally caused lung cancer at workers of uranium mines are marked out:
 • Total effective dose of radiation exposure is more 200–250 mSv (40–50 WLM).
 • Period in underground conditions is not less than 10 years.
 • Dust content in a workplace is more than 1 mg/m3.
 • Hygienic assessment of working conditions – the 3rd class, 3.2–3.4 degree.
 • The latent period of development of a tumor is not less 10 years.
 • Development of primary and multiple synchronous or metachronous lung cancer.
 Also the diagnosis of occupational lung cancer the pulmonary anamnesis (frequent bronchitis, pneumonia, chronic bronchitis of the smoker) has to be considered.
 On the basis of the marked-out criteria documents of 6 employees of uranium mines, at which lung cancer has been revealed, are considered. On the basis of the carried-out analysis at 5 patients relation of a disease with professional activity has been established. One patient was denied this relation.
 Conclusion: Authors offer this expert approach to experts’ discussion as above-mentioned criteria is planned to be used by the pathologists who are carrying out observation of workers of uranium production and for the solution of questions of relation of a disease with professional activity of the patient.

Возможные критерии установления диагноза профессионального рака легкого у работников урановых шахт

Purpose: Search of possible criteria of the diagnosis of occupational lung cancer in workers of uranium mines on the basis of the analysis of literary data.
 Material and methods: The analysis of literary data with the purpose of allocation of possible criteria and their use for the diagnosis of occupational lung cancer at 6 employees of uranium mines.
 Results: The following criteria for the diagnosis of occupationally caused lung cancer at workers of uranium mines are marked out:
 • Total effective dose of radiation exposure is more 200–250 mSv (40–50 WLM).
 • Period in underground conditions is not less than 10 years.
 • Dust content in a workplace is more than 1 mg/m3.
 • Hygienic assessment of working conditions – the 3rd class, 3.2–3.4 degree.
 • The latent period of development of a tumor is not less 10 years.
 • Development of primary and multiple synchronous or metachronous lung cancer.
 Also the diagnosis of occupational lung cancer the pulmonary anamnesis (frequent bronchitis, pneumonia, chronic bronchitis of the smoker) has to be considered.
 On the basis of the marked-out criteria documents of 6 employees of uranium mines, at which lung cancer has been revealed, are considered. On the basis of the carried-out analysis at 5 patients relation of a disease with professional activity has been established. One patient was denied this relation.
 Conclusion: Authors offer this expert approach to experts’ discussion as above-mentioned criteria is planned to be used by the pathologists who are carrying out observation of workers of uranium production and for the solution of questions of relation of a disease with professional activity of the patient.

Numerical modelling of vertical borehole heat exchangers performance under Lithuanian Quaternary conditions

The vertical borehole heat exchangers were surrounded by the heterogeneous multilayered geological environment and groundwater flow that affected the performance of borehole plants. In this paper, the field investigation of vertical borehole ground heat exchangers in capital city Vilnius (Visoriai), Lithuania is presented. The numerical heat transfer model considering seven different geological strata was developed using the cylindrical heat sink model for vertical borehole inside by solving the soil mass and heat transfer equations with groundwater flow. The numerical multilayered ground vertical borehole heat transfer model was calculated and validated by in-situ thermal response test data. The numerical model results were also compared with the homogeneous finite difference model expressed by the temperature response functions (well known as “g-functions”). The practical realization of g-functions was designed in the Earth Energy Designer as a practical tool for geoengineers designing the vertical borehole plants. The temperature profiles at borehole wall at different heating times were presented and explored together with relative errors. The numerical model will be used as a practical tool for the Lithuanian Geological Survey under the Ministry of Environment to estimate the underground conditions for the consumption of shallow geothermal energy.

Full waveform inversion based on inequality constraint for cross-hole radar

Cross-hole radar is an effective method for geophysical exploration of underground geological conditions. Besides cross-hole radar, some geological information can be obtained by other methods, such as preliminary geological survey, geologic drilling and long-distance geophysical prospecting. This information can work as priori information to help interpret cross-hole radar detection data. Full waveform inversion (FWI) is an advanced inversion method for cross-hole radar, having higher resolution than the ray tomography method. However, traditional FWI for cross-hole radar takes less advantage of the prior information. Therefore, the introduction of the priori information into FWI is worthy of in-depth study to improve inversion quality. Here we use a special penalty function to impose inequality constraint on the objective function, and then calculate a new update step length value different from the traditional FWI. We use this method to introduce the priori information and improve the accuracy and stability of FWI. The reasonable value range of weight coefficients is discussed, which can control the strength of inequality constraint. Several inversion examples are designed to validate the effect of this improved FWI method. The inversion examples for synthetic and field data show that FWI based on inequality constraint for cross-hole radar has better inversion effect than the traditional FWI. To a certain extent, the introduction of inequality constraint can constrain inversion process, improve the inversion stability and provide higher precision inversion results.

The model of energy efficiency transportation of thermal and electric energy in the underground heat collector

The paper deals with modeling of the underground heat collector thermal conditions for utilities, calculating variations in temperature taking place in the soil mass around the collector as well as temperature variations in the air space of the latter. This leads to the reduction in the cost of heat and electricity transportation and a significant cost cutting of heat that is electricity supply of urban areas. The dependences of the thermal soil massiveness on the laying depth of the collector and changes in soil temperature in the course of time are presented.

The Present And Future Of Virtual and Augmented Reality In Geotechnical Engineering: This Technology Has Gone Way Beyond Gaming!

One of the greatest challenges with subsurface construction has always been our relative inability to visualize underground conditions that are often comprised of spatially variable soil and rock strata, existing utilities, and complex foundations. In recent years, however, advances in computer science, virtual reality (VR), and augmented reality (AR) technologies are transforming foundation and geotechnical engineering by greatly improving our ability to visualize complex subsurface conditions in three dimensions. This article examines the state of geotechnical applications in VR and AR, and describes areas where visualization technologies can transform our practice into Immersive Geotechnical Engineering.

Strength of massive to moderately jointed hard rock masses

The Hoek-Brown (HB) failure criterion and the geological strength index (GSI) were developed for the estimation of rock mass strength in jointed and blocky ground where rock mass failure is dominated by sliding along open joints and rotation of rock blocks. In massive, veined and moderately jointed rock in which rock blocks cannot form without failure of intact rock, the approach to obtain HB parameters must be modified. Typical situations when these modifications are required include the design of pillars, excavation and cavern stability, strainburst potential assessment, and tunnel support in deep underground conditions (around σ1/σci > 0.15, where σ1 is the major principal compressive stress and σci is the unconfined compressive strength of the homogeneous rock) in hard brittle rocks with GSI ≥ 65. In this article, the strength of massive to moderately jointed hard rock masses is investigated, and an approach is presented to estimate the rock mass strength envelope using laboratory data from uniaxial and triaxial compressive strength tests without reliance on the HB-GSI equations. The data from tests on specimens obtained from massive to moderately jointed heterogeneous (veined) rock masses are used to obtain the rock and rock mass strengths at confining stress ranges that are relevant for deep tunnelling and mining; and a methodology is presented for this purpose from laboratory data alone. By directly obtaining the equivalent HB rock mass strength envelope for massive to moderately jointed rock from laboratory tests, the HB-GSI rock mass strength estimation approach is complemented for conditions where the GSI-equations are not applicable. Guidance is also provided on how to apply the proposed approach when laboratory test data are not or not yet available.

RESEARCH CONCERNING OF THE ATTRIBUTION TO THE CONCEPT OF "WORK WITH INCREASED RISK" TRANSFER OF EMPLOYEES IN MINES TO THE PLACE OF PERFORMING WORK

Development of coal deposits in Ukraine is carried out in complicated mining and geological conditions in the presence of high parameters of gas formation, mountain pressure, temperature of enclosing rocks, danger of appearance of sudden coal emissions, rock and gas and the ability of minerals to spontaneous combustion. Being found in mining work places (permanent or temporary stay), as well as while moving to the place of performing work, there is an influence possibility on an employee of hazardous and harmful production factors that by their origin can be of industrial or natural nature. The analysis of accidents in the mining industry demonstrates that accidents occur with the miners who are in the mine, not only while performing a task at the work place, as well as during a descent into the mine leaving the cage on the working horizon, during the movement of mine workings on foot or underground transport to the work place. The research concerning of the attribution to the concept of "work with high risk "of stay of the workers in mine workings while of moving to the place of performing works during carrying out forensic engineering and technical examinations regarding investigation on causes and consequences of emergencies in the mining and underground conditions is carried out. Investigating normative documents and regulations and other sources regarding the regulation of underground works, it possible to conclude that underground staying, namely moving to a workplace by mine working is an operational need, when the worker is located in a dangerous area where he can be exposed to action of hazardous and/or a harmful production factor of natural or anthropogenic origin, therefore the movement of workers in mine workings to the place of performing works is classified as "work with increased danger".

FIGHTNING SUBLIMATION AND CRYSTALLIZATION OF COAL MATTER

The processes of sublimation and crystallization of coal matter in underground conditions are considered and described. One of the solutions to the problem of the occurrence of large volumes of gas in emissions in coal mines was proposed. It is shown that the quasicrystals of coal, described in the middle of the 1980s by the author of the article, can have an increased specific surface area. The sizes of quasicrystals reach microns and nanometers. They are the link between the crystalline and amorphous forms of matter. Gas-dynamic and thermal phenomena, in the presence of disturbed zones with a sufficient number of quasicrystals with a large specific surface area, can lead to the process of sublimation of coal. Gas-dynamic phenomena at shallow depths with considerable humidity and methane content can lead to the process of crystallization and the formation of gas hydrates. Sublimation has an exothermic effect and is realized with an increase in entropy. Crystallization has an endothermic effect and is realized with decreasing entropy. A real proof of sublimation can be considered as the resonance release of different gases in the process of burning of coals. The absence of resonant emission of gases indicates a transition of combustion to the process of decay. Cold and hot emissions are a consequence of the implementation of sublimation and crystallization processes. Cold emission is characterized by the presence of frost on the emission cone. The hot release has an exogenous character and is characterized by an elevated temperature. An example is given of the spontaneous formation of gas hydrates in the case of a fault in the soil of mining. The possibility of isolating disturbed zones and gas accumulations is the basis for controlling gas-dynamic processes.

The influence of CO2 saturation time on the coal gas flow: Fractured bituminous coal

The permeability reduction due to the coal matrix swelling induced by the adsorption of CO2 is the major concern during enhanced coalbed methane recovery (ECBM) as well as CO2 sequestration in coal reservoir. Many problems arise in the context of this process regarding the coal permeability variations, and very few studies have been made with consideration of long-term CO2 saturations on gas flow behaviour alterations. The main objective of this study is therefore to examine the influence of both subcritical and supercritical CO2 flooding durations on N2 and CO2 permeability variation of naturally fractured low volatile bituminous coal under various tri-axial conditions. Five CO2 flooding durations, up to 65 h, both subcritical (6 MPa) and supercritical (14, 20 MPa), were introduced to the sample under three confinements, respectively. Results show that for 11 MPa and 17 MPa confining environment, most permeability reduction occurs during the first CO2 flooding process, and supercritical CO2 flooding causes significant higher N2 permeability reduction (from 14.38% to 50.18%) than subcritical CO2 (from 4.11% to 11.25%). The permeability reduction rate decreases with time but this reduction continues even after a total of 153 h flooding. Longer permeability reduction process is observed upon supercritical CO2 adsorption due to the much higher viscosity of supercritical CO2. Under deep underground condition (>1 km), CO2 exhibits a N2-like flow behaviour because of the dominant poroelastic effect. The influence of CO2 flooding on permeability alterations has been significantly compromised with much smaller permeability reduction after 20 MPa CO2 flooding compared with 14 MPa CO2 flooding (7.33% and 38.75% for 7 MPa CO2 injection pressure, respectively), along with no apparent permeability reduction for the further CO2 flooding scenarios.

Analytical Study on the Flexural Behavior of Reinforced Concrete Beam with Mineral Admixture under Calcium Leaching Degradation

Calcium leaching degradation could be happened in reinforcement concrete member due to the contact with pure water in underground condition. Thus, it is needed to evaluate the resistance of calcium leaching for concrete mixed with mineral admixtures. So, in this paper, to evaluate the flexural behavior in RC member with mineral admixture under calcium leaching degradation, we investigated the effect of calcium leaching using the non-linear finite-element program. From the results, the load capacity and flexible rigidity of a degraded RC member decrease when the degradation level increases with leaching period. And, regardless of the type of mineral admixtures, finite-element-method analysis effectively showed the characteristics of calcium leaching damaged RC beam.

Research on Quantitative Demand of Underground Space Development for Urban Rail Transit Station Areas: A Case Study of Metro Line 1 in Xuzhou, China

Under the background of the rapid development of urban rail transit in China, the development demand of urban underground space has also greatly increased especially in the rail transit station areas. In this paper, taking the high-speed railway station area of Xuzhou Metro Line 1 as an example, the underground space development demand evaluation is conducted by considering the principle of urban underground space stock planning, the local underground space development conditions, as well as the special planning of the local urban constructions. Using the Analytic Hierarchy Process (AHP), a specific weight indicator scale is employed after the rationality of different weight indicator scales being compared. And then the weight indicator of different function types, i.e., commercial, parking, road, etc., are calculated and laterly utilized to forecast the recent development demand of underground space in the station area. Moreover, the steps to forecast the underground space development demand in rail transit station area are proposed, which can provide a reference for the forecasting of underground space development demand in the urban rail transit station areas.

A BIOLOGICAL WATER QUALITY ASSESSMENT BASED ON PHYTOBENTHOS AND MACROINVERTEBRATES AT THREE STATIONS ON THE RIVER NERETVA

UDK: 556.115:574.587(282.249 Neretva)
 This paper presents the research results of benthos community (phytobenthos and macroinvertebrates) on three locations of the Neretva River: Glavatičevo, Žitomislići and Višići. According to typology of rivers, the site Glavatičevo belongs undertype 10a, while sites Žitomislići and Višići are undertype JIVT (heavily modified water bodies). Research of the benthos community has been done in December 2016 with the simultaneous monitoring chemical parameters of water. All research states showed a great number and a high diversity of benthic taxa, although sampling was spent in December. The saprobic values of benthos community at the site Glavatičevo indicates to oligosaprobic level, the water unloaded with organic substances. The site Žitomislići points to oligo/betamesosaprobic level, the water a bit loaded with organic substances. The site Višići according to phytobenthos demonstrates to oligo/betamesosaprobic level, while according to benthic macroinvertebrates point to betamesosaprobic level (the water loaded with organic substances). Based on saprobic values and chemical parameters of water in keeping with The decision on the characterization of the surface and underground water, reference conditions and parameters for the detection of water state and water monitoring (Official newspapers FBiH, No. 1/14), a maximum ecological potential has been registered on sites Žitomislići and Višići, while a high ecological status has been registered on the site Glavatičevo.

Damage pattern scope prediction for well point dewatering on building foundations

In the well point construction process, it is necessary to control underground water effectively. The expected damage pattern scope within the influence radius of the depression cone of the well point can be determined according to noticeable ground and building settlement, as well as reference to the soil property changes due to the dewatering process with the aid of the formation mechanisms of underground water, based on underground water flow theory. This paper examines the Damage Pattern Scope expectation (DPS) and discusses some underground water conditions and practical key points by means of examining a laboratory pilot-scale model with light well point water lowering of different soil strata thickness, thus analysing the impact on the surrounding environment due to water lowering. The results showed that the water content and the void ratio of soil subjected to dewatering were reduced and that soil density and cohesion thus increases.

3D geological modelling – Through the example of Karawanken Tunnel project, northern section

AbstractBefore design and construction, particularly underground, it is essential to know the geological conditions well. Nowadays as in many other fields 3D modelling is a very powerful and helpful tool in geology and geotechnics. The advantages of 3D modelling in geology are convincing: In the past, 2D geological maps and sections were of common use and it could sometimes be difficult to conceive a 3D picture of the underground conditions from the 2D images. With modern software, geological 3D models can be generated easily. Once a 3D model is established, the underground situation is more comprehensible and inconsistencies in geological interpretation are immediately apparent. 2D sections can also be produced with little effort at any position. The model can also be used as a geological database for the project. All available geological and geotechnical information like maps, sections, borehole data and lab test results can be attached to the model. The generation of a geological 3D model will be explained through the example of the Karawanken Tunnel, northern section.

ACCURACY OF WORK TOOL POSITION MEASUREMENT BY MEANS OF A DRILLING MONITORING SYSTEM

The article presents examples of test results of an innovative, optical system of tool location identification in a workspace. This system was developed and produced as part of the research carried out in cooperation with KGHM Polska Miedź S.A. The article contains a general description of the system, basic components and the scientific basis underlying the development. The technical parameters of the system are also indicated as well as the ranges of required accuracy of the tool location determination, the achievement of which was a condition for the admission of the project to the implementation stage for operation. Based on the results of tests carried out both on the surface and in underground operation conditions, the project assumptions were confirmed and the system's accuracy ranges were determined. The very promising results obtained clearly indicate the validity of continuing work on the development of the tool location identification system in a wider range of machines.

Innovative Visualization System Designed to Monitor Parameters of Mining Systems Operation

Abstract Mining machines suitable for hard coal mining, due to the specifics of this industry must be characterized by very high technical parameters. In particular, it concerns their durability, reliability and availability. Currently used machines approved for operation in underground conditions meet such requirements. Nevertheless, during their operation it is reasonable to conduct supervision and control of work parameters. This applies to both machine manufacturers and users, which is especially important in the event of a failure. Mine employees should be able control of the entire operation process. This control can be effective thanks to a visualization system developed to monitor the working parameters of mining systems. The paper discusses the innovative system and presents the results of efficiency tests. They concerned the visualization of the operation of a powered roof support. The obtained results indicate that the assumed goal of the system has been achieved. The system is built on elements of industrial automation, which guarantees the reliability of the indicated values. Its graphic layout and selection of the presented parameters are also approved. It should also be emphasized that the system can work with currently operating systems and is easy to expand. According to the Authors, the system should find a wide application in practice.

Influence of duration and intensity of exposure to occupational hazards on mortality levels of coal miners

Th e article presents results of analytic epidemiologic study of mortality in coal miners cohort in Rostov region, who had occupational disease registered in various years. The cohort included 9980 males, the observation period was 26 years (01/01/1990–31/12/2015). Deep analysis of mortality with leading death causes in subgroups of coal miners differentiated by length of service in underground conditions. Standardized relative risk of death in the subgroups increased with longer length of service, with respiratory diseases, circulatory system diseases and malignancies.The authors studied mortality in subcohorts of the miners with leading and auxiliary occupations, whose work conditions differ in intensity of exposure to occupational hazards. For the workers with leading occupations, standardized relative risk of death with respiratory diseases, circulatory system diseases and malignancies was higher.