Underground Conditions Research Articles

Study on the Ground Movement in an Open‐Pit Mine in the Case of Combined Surface and Underground Mining

The combined surface and underground mining method is typically used in an open‐pit mine for better production and profits. However, the improved scale of mining operations at the combined mining conditions results in even more intensive strata movement and massive ground damages. This paper assesses the progressive development of the characteristics of roof movement with the longwall face advance and its influence on the ground movement at the slope area using physical models. The identification of strata zones at the combined mining conditions is also included. The results show the following: (1) the failure of the competent strong roof creates an inverse arch‐shaped rock block structure, which compacts the loose rock fragments in the caved zone; (2) a bed separation occurs above the inverse structure at the top of the disturbed strata configuration and extends upward with the face advance until it approaches the continuous bending zone; (3) more intensive strata movement and ground damages are produced by the large‐scale multiseam mining operations, while regular and more distinct strata zones in the disturbed configuration are identified for less intensive single‐seam mining; and (4) the intensive and massive underground mining activities increase the slope strata movement at the surface mining side. This research suggests that a less intensive mining activity is preferred in the combined surface and underground mining conditions from the point of view of ground control.

Landslide investigation using electrical resistivity tomography (ERT) technique at the location of water channel PLTM Lambangan, Pagimana, Central Sulawesi

Mass movement phenomena that occur in the research area affect the destruction of water channel in the area of PLTM Lambangan that located at the location. This research aimed to investigate soil movement phenomena in order to determine control factors that causing soil prone to move, especially in the surface geological aspect and underground lithology condition in the research area. Investigation method applied is by underground geologic and geophysical surveys using electrical method, that is Electrical Resistivity Tomography (ERT) with Wenner Configuration. Results of investigation show that geological factors are quite related to the soil movement. Movement phenomena occur in the surface with hilly to steep cut topography (21-55%) with material sourced from alluviation of clastic sediment dan carbonatic rocks. The damaged area is people farming area where fibre root of plant adds water absorption capacity of the soil. Also, sliding materials show water seepage that indicates that the moving slope has been saturated. This condition supported by information from geoelectric survey which indicates that in general the under surface material potent to slide or move because of unconsolidated material with its resistivity values in the order of 16 – 43 m that estimated related to alluvial or saturated residual soil.

Risk Assessment for Karst Hazards at a Facility in Saudi Arabia—A Case Study

The boom in industrial and infrastructure construction in Saudi Arabia requires in-depth knowledge of the underground conditions to build a sustainable project. This paper gave a practical example of the challenges facing an existing facility built on a karstic limestone formation in 1970’s. Multiple geophysical techniques such as Microgravity, Electrical Resistivity Imaging, Vertical Seismic Velocity Profiling, Cross Hole Seismic Tomography, Ground Penetration Radar, Multi-Channel Analysis of Surface Waves, as well as boreholes and down-hole video imagery, were deployed through the journey of assessing the karst associated hazards of potential sinkholes or general subsidence. This paper described the karst processes, site geology, geophysical and geotechnical exploration program, and characterizes the subsurface karst conditions at the eastern province of Kingdom of Saudi Arabia. Results and findings of preliminary, geotechnical and geophysical investigations have been utilized to identify the major factors influencing the karst formation. Analyses and integration of obtained results to estimate the type and magnitude of risk affected the major components of industrial facility at the project site using well-known statistical approach were presented in this paper. Consequently number of remedial measures implemented to combating the experienced and expected karst hazards at the studied industrial facility placed in karstified landform are given. A model for using integrated geophysical and geotechnical techniques to assess karst-related risks to a facility was further explored herein.

Non-invasive prospection techniques and direct push sensing as high-resolution validation tools in wetland geoarchaeology – Artificial water supply at a Carolingian canal in South Germany?

The prospection of (geo-)archaeological sites yield important knowledge about the concept and the utilisation of pre-historical and historical infrastructure. The satisfactory conduction of classical prospection methods like archaeological excavations or geoarchaeological vibra-coring might be challenging in the case of large sites or difficult underground conditions. This is particularly problematic in wetlands featuring a high groundwater table and high compaction rates of organic layers.In this study, we provide an alternative and non- to minimal-invasive exploration approach to discover hydro-engineering structures for artificial water supply in the surrounding of a Carolingian summit canal in South Germany. The Early Medieval Fossa Carolina was intended 792/793 CE to bridge the Central European watershed between Rhine-Main and Danube catchments. As the canal was constructed as a summit canal, an artificial water supply at the highest levels seemed very likely or even obligatory. In order to explore these obligatory hydro-engineering features, we use a wide range of on-site and off-site tools in a spatial hierarchical way. Our approach includes the large-scale SQUID magnetic survey and the sighting of historical maps. Furthermore, we integrate high-resolution direct push colour logs, and subsequent vibra-coring for small-scale stratigraphical verification and sedimentological analyses.The SQUID magnetic survey and related depth models discover two pronounced linear anomalies that might represent potential artificial water inlets in the North-Eastern and Northern Sections of the canal. I) In the North-Eastern Section, direct push colour logs, vibra-coring and 14C dating provide no evidence for a Carolingian hydro-engineering feature but reveal a natural lenticular structure of Early Holocene age. II) The linear magnetic anomaly in the Northern Section can be excluded with high probability as a hydro-engineering structure as well. Here, direct push colour logs, vibra-coring, 14C dating and the comparison with a historic map reveal evidence for a historic gravel road. Thus, we have nicely verified the magnetic information but have no prove for an artificial Carolingian water inlet from the Swabian Rezat River that contradicts with assumptions of former studies.

Assessment of risks of tunneling project in Iran using artificial bee colony algorithm

The soft computing techniques have been widely applied to model and analyze the complex and uncertain problems. This paper aims to develop a novel model for the risk assessment of tunneling projects using artificial bee colony algorithm. To this end, the risk of the second part of the Emamzade Hashem tunnel was assessed and analyzed in seven sections after testing geotechnical characteristics. Five geotechnical and hydrological properties of study zone are considered for the clustering of geological units in front of tunneling project including length of tunnel, uniaxial compressive strength, rock mass rating, tunneling index Q, density and underground water condition. These sections were classified in two low-risk and high-risk groups based on their geotechnical characteristics and using clustering technique. It was resulted that three sections with lithologies Durood Formation, Mobarak Formation, and Ruteh Formation are placed in the high risk group and the other sections with lithologies Baroot Formation, Elika Formation, Dacite tuff of Eocene, and Shear Tuff, and Lava Eocene are placed in the low risk group. In addition, the underground water condition and density with 0.722 and 1 Euclidean distances have the highest and lowest impacts in the high risk group, respectively. Therefore, comparing the obtained results of modelling and actual excavation data demonstrated that this technique can be applied as a powerful tool for modeling risks of tunnel and underground constructions.

Formation of working conditions and the problems of hygienic assessment of industrial environmental factors in railway tunnels

Tunnels are an integral part of the ways and artificial constructions of the railway. Objective assessment of working conditions is important, because current regulations fail to allow to give a definite hygienic assessment of some factors of the production environment of the tunnels. Objective: to reveal the peculiarities of the formation of working conditions in railway tunnels with the subsequent hygienic assessment for the development of preventive measures. Measurement of the factors of working process and working environment is carried out with the use of the certified equipment for the approved the hygienic and sanitary-chemical methods in workplaces in tunnels of the East-Siberian railway. Specific conditions were shown to be formed due to constructive solutions, climate and geographical location, the length of railway tunnels, the composition of the rocks through which the tunnel, the nature of the maintenance tunnels, ventilation system, repetition rate and type of passing rolling stock. All employees from occupational groups from examined tunnels were established to be exposed to high concentrations of aerosols with predominantly fibrogenic action, noise levels, adverse climate (low positive and negative temperatures, high relative humidity and mobility of air), the lack of natural lighting, low levels of artificial light, hard exertion of labor (dynamic physical load, working position, the slopes of the body, movement in space). Additionally, high levels of the vibration, nonionizing and ionizing radiation were typical for jobs of the Baikal and the North-Muya tunnel. There is proposed the algorithm of hygienic assessment of the microclimate, light environment at the working places depending on the time of the works in the underground conditions and constructional features of tunnels, methods of accounting personnel dose rates from natural sources.

Tests of Geometry of the Powered Roof Support Section

A powered roof support is a basic protection mean for longwall excavations in which highly efficient mining is carried out. The support operates properly when its individual sections are spragged correctly in a working and their operating parameters meet specific requirements. The geometry of the section, and in particular, the correct position of the floor base and the canopy, have a significant impact on the parameters and effectiveness of its work. Disturbances in this area, in many cases, are the cause of damage and improper operation of the support. Therefore, a new method of testing the position of the section in a longwall was developed based on an analysis of its geometry. The basis of this method are inclinometers (angle sensors) mounted on the main structural elements of the section. Recorded values of the angles of inclination of these elements and the developed analytical models are used to determine the positioning of the section in a longwall. The main purpose of the research was to develop a method that would allow, in the simplest possible way, the analysis of section geometry in real conditions. A simplified analytical model was used to determine the actual geometry of the section. It was used then as a basis of an analysis of possible states of the position of the section in the mining wall, including the surrounding rock mass. The results were applied during tests of the section carried out in a testing station and in real (underground) conditions. The developed measuring system helped to determine selected geometrical parameters of the section during these tests. The purpose of the research was to verify the developed model and demonstrate that the geometry of the section has a significant impact on its uneven loading. The obtained results, especially from underground tests, confirmed that during operation the support sections are twisted, which may cause overloading of their construction and disturbance of the operation process. The developed method of testing the geometry of the section is a new approach to analyzing the work of the powered roof support operating in variable mining and geological conditions. The developed method of testing the position of the section based on the angle of inclination of its individual elements is undoubtedly a new approach to this research area. The results obtained should be successfully used in practice to optimize the support section and when selecting support for specific working conditions.

Evaluation of the propensity of strain burst in brittle granite based on post-peak energy analysis

The increasing demand for resources and depletion of near ground mineral resources caused deeper mining operations under high-stress rock mass conditions. As a result of this, strain burst, which is the sudden release of stored strain energy in the surrounding rock mass, has become more prevalent and created a considerable threat to workers and construction equipment. It is, therefore, imperative to understand how strain burst mechanism and stored excess strain energy are affected due to the high confinement in deep underground conditions. For this purpose, post-peak energy distributions for brittle rocks were investigated using a newly developed energy calculation method associated with acoustic emission (AE). A series of quasi-static uniaxial and triaxial compression tests controlled by the circumferential expansion were conducted. Snap-back behaviour known as Class-II behaviour associated with energy evolution and the material response under self-sustaining failure were analysed on granites under a wide range of confining pressures (0–60 MPa). The experimental results underline that the energy evolution characteristics are strongly linked to confinement. Stored elastic strain energy (dUE), energy consumed by dominating cohesion weakening (dΦCW) and energy dissipated during mobilisation of frictional failure (dΦFM) showed a rising trend as the confining pressure was increased. An intrinsic ejection velocity was proposed to express the propensity of strain burst that was purely determined by the excess strain energy released from Class II rock.

ОСНОВНЫЕ ИТОГИ И ПЕРСПЕКТИВЫ СЕМЕНОВОДСТВА КОРМОВЫХ ТРАВ В ФГУП «ПОЙМА»

Presents the historical aspects and the current state of breeding and seed production in the Federal State Unitary Enterprise "Poima", as well as the prospects for the production of seeds of forage herbs, including their higher reproduction in order to provide farmers and other consumers with high-quality seed. The stages of seed production of perennial grasses in the economy are reflected, the analysis and the importance of seed production for agricultural production, as well as prospects. Special attention is paid to the creation and reproduction of high-yielding varieties of perennial grasses for floodplain conditions, such as awnless brome, fescue, timothy-grass, cocksfoot and other species. It is noted that the special variety of fescue meadow hayfields and pasture ecotype Krasnopoimskaya 92, well adapted to the conditions of flooding in the underground conditions, as well as when growing it on watershed areas, is of great importance in modern conditions of forage production. The article also notes a great prospect of developing tetraploid variety of ryegrass annual Rapid in the system of feed production in floodplain conditions, which can replace to a large extent in the Central, Northern and North-Western regions of unstable productivity of corn, even its early-maturing hybrids. In addition, the publication presents the basic agrotechnical methods of cultivation of seeds of such most sought-after perennial grasses as perennial ryegrass, festulolium, fescue reed, allowing them to obtain high and stable yields.

지하수 열원 지중 열교환기의 열적 특성에 관한 실험적 연구

In order to enhance the utilization of underground heat including underground water, the comparison between the existing high density polyethylene underground heat exchanger and the newly developed metal heat exchanger was conducted to suggest the potential use of geothermal energy corresponding to the geological characteristics of Jeju Island. When the acquired heat of the underground loop system test condition of the KS B 8292 water-water geothermal heat pump unit was compared by installing heat exchanger of HDPE material and the heat exchanger of STS material under the same bore hole condition, the total heat area of the heat exchanger of STS material was about 15% less than HDPE, but the acquired heat was estimated to be about 4 times or more.

Mikrostruktur des Salzburger Seetons – Charakterisierung basierend auf Drucksondierungen

AbstractPiezocone penetration tests (CPTu tests) allow continuous measurements of the tip resistance, the sleeve friction and the pore water pressure over depth. Furthermore, they minimize the required time as well as costs for a soil characterization. Due to the difficulty related to undisturbed sample recovery of soils (i.e. of weak silty fine‐grained sediments) for laboratory testing, in situ investigations are becoming increasingly popular in geotechnical engineering. The article illustrates results of cone penetration tests, executed at three test sites in the city of Salzburg. It is shown that CPT‐based soil behaviour type charts according to Robertson lead to a realistic characterization of the underground conditions. The grain size distribution of the Salzburger Seeton varies between fine sand‐silt mixtures, which are found in the upper parts, to clayey silts in greater depths. According to CPT‐based soil behaviour type charts of Robertson clayey silts behave clay‐like contractive and are characterized by homogeneous properties with increasing depth. Qtn‐IG diagrams underline that the Salzburger Seeton with a high clay content presents a weak microstructure. On the other hand, the upper Seeton layers, which can be classified as silt‐sand mixtures and silty sands respectively, show a stronger bounding between the particles.

On the Application of Multi-frequency Ground-Penetrating Radar Method for Mapping Underground Pipe

Ground penetrating radar (GPR) method is commonly used to map underground pipe network due to its ability to map objects on shallow area and its minimum effect to surrounding area, although the resolution and depth of interest of mapping really depend on the antenna’s frequency. To improve the resolution of object that is going to be detected, more than one antenna frequencies are used in a measurement in the same line and multiple-frequency compositing is performed to combine those radargrams to simplify the analysis. This research will use and compare three compositing methods ability, i.e. simple summation, comparison of average radargram amplitude spectrum of each radargram, and least-square weighting according to Berlage wavelet analysis - called also Optimal Spectral Whitening (OSW), to map a big pipe with metal casing that surrounded with some metal cables from 200 MHz and 400 MHz radargram datasets. Comparisons of those three methods mentioned above were performed through the analysis of each radargram and sample trace analysis on some positions to show the ability of each method in separating boundary of each medium. The analysis showed that multiple-frequency compositing was able to improve resolution for showing underground condition, with OSW method had better ability compared to other methods.

Laboratory-Based Investigation into Stress Corrosion Cracking of Cable Bolts.

Cable-bolt failures due to stress corrosion cracking (SCC) could significantly compromise the sustainability and long-term stability of underground constructions. To fully understand the SCC of cable bolts, a two-step methodology was implemented: (i) long-term cable-bolt coupon tests using mineralogical materials collected from underground mines; and (ii) accelerated full-scale cable-bolt tests using an acidified solution. In the long-term tests, a novel three-point bending coupon was designed. The effects of mineralogical materials on SCC were evaluated under the simulated underground bolting conditions through the application of “corrosion cells”. For accelerated tests, SCC resistance of different type of cable bolts was examined using the new designed tensile-loading apparatus under the periodically increasing strain-rate loading mechanism. It was identified that mineralogical materials and applied stress intensity accelerated the corrosion process of the cable bolts. The number of wires and wire surface conditions in different types of cable bolt directly affected SCC susceptibility. The cable bolts with a greater number of wires provided higher resistance to SCC. The developed experimental methodologies can be applied to study SCC in other reinforcement materials and the results can be used to design optimal support systems in different environmental and geotechnical conditions.

Research on appropriate borehole density for establishing reliable geological model based on quantitative uncertainty analysis

Geological structure is an important factor to explore the underground geological conditions for hydrogeological purpose. Borehole density has great influence on the accuracy and application of geological model. In this paper, Transition Probability Geostatistical Software (T-PROGS) has been used to simulate the four facies distribution of West Liao River Plain. And a quantitative uncertainty model of entropy method is introduced. For getting a reliable geological model with as few as the boreholes, two parts have been given. One is the vertical lithologic variability analysis, and the other is the model correct rate and uncertainty analysis. In geological modeling, the borehole data is too sparse to characterize the lateral heterogeneity, so the actual profiles are added. At last, many equal probability realizations of the geological model using 350 boreholes are built. Depending on the model calibration, uncertainty analysis and simulated profile comparison, the geological models are reliable. Thus, for the simple and single stratigraphy study area without complex fault structures and graben structures of several thousands to tens of thousands of square kilometer scale, establishing a reliable geological structure model requires one borehole at least within an average area of 120.81 km2. It is of great significance for decision maker to save manpower and material resources. And we present a workflow to build a 3D Markov chain using boreholes and actual profiles and develop a reliable geological model.

Underground sewer pipe condition assessment based on convolutional neural networks

Surveys for assessing the condition of sewer pipeline systems are mainly based on video surveillance or CCTV, which is a time-consuming process that relies heavily on human labor because an operator has to watch videos, looks for defects and decides the defect's type manually. Previous research required suitable handcrafted features that were inefficient in analyzing sewer pipeline condition, so a robust and efficient framework is crucial as it eliminates the time-consuming tasks and helps the operator access condition of sewer systems more efficiently. This study proposes a defect classification system on CCTV inspection videos based on convolutional neural networks (CNN). The dataset was manually constructed and validated by extracting the images from CCTV videos, and the images were labeled according to six predefined defects. The CNN model was fine-tuned before training, and trained on a total of 47,072 images (256 × 256 pixels). The highest recorded accuracy was at 96.33%. As a result, the presented framework will motivate the finding of a more robust model that automatically and precisely evaluates the condition of sewer pipeline systems using CCTV and encourages the integration of the proposed model in real applications.

H2O2-Enhanced Shale Gas Recovery under Different Thermal Conditions

The permeability of tight shale formations varies from micro-Darcy to nano-Darcy. Recently, hydrogen peroxide (H2O2) was tested as an oxidizer to remove the organic matter in the rock in order to increase shale permeability. In this study, shale particles were reacted with hydrogen peroxide solutions under different temperature and pressure conditions in order to “mimic” underground geology conditions. Then, low-temperature nitrogen adsorption and desorption experiments were conducted to measure the pore diameters and porosity of raw and treated shale samples. Moreover, scanning electron microscopy (SEM) images of the samples were analyzed to observe pore structure changes on the surface of shale samples. From the experiments, it was found that the organic matter, including extractable and solid organic matter, could react with H2O2 under high temperature and pressure conditions. The original blocked pores and pore throats were reopened after removing organic matter. With the increase of reaction temperature and pressure, the mean pore diameters of the shale samples decreased first and then increased afterwards. However, the volume and Brunauer–Emmett–Teller (BET) surface areas of the shale particles kept increasing with increasing reaction temperature and pressure. In addition to the effect of reaction temperature and pressure, the pore diameter increased significantly with the increasing reaction duration. As a result, H2O2 could be used to improve the shale permeability.

An estimation of Ufimian terrigenous reservoir lithology influence on oil recovery factor by steam stimulation basing on tube experiments

The settings, scale and geometry of lab facilities to simulate enhanced recovery methods play a significant role in the approximation of underground conditions of oil fields. The reliability more or less of the best replication of these conditions is a question of the reservoir engineer when forecasts are made for cases when enhanced recovery methods are applied. This paper presents the results of two experiments carried on in a steam flooding tube facility adding clay in one of them to assess the influence in temperature growth and production rates and onset times of a highly viscous oil field of the Tatarstan Republic. The results of the runs show that 4% (by weight) of clay content in the porous media has a strong effect on the overall oil recovery, reducing the temperature growth rate in average 73% when steam stimulation methods are used.

A data mining method based on unsupervised learning and spatiotemporal analysis for sheath current monitoring

Sheath current is one of the key indicators of underground power cable conditions. Considering the limitations of existing model-based methods for sheath current monitoring and difficulty in handling the increasing amount of unlabeled sheath current data accumulated by cable monitoring systems, we propose a data mining method based on unsupervised learning and spatiotemporal analysis of sheath currents for underground power cable monitoring. Tests based on real historical data demonstrate that the proposed method can effectively reveal unknown inherent patterns in unlabeled sheath current data.

Risk Management in Road Construction Projects: High Volume Roads

Road construction projects carry a significant amount of risk due to its spread over a wide geographical area and threat from underground conditions. Risk can be defined as an event of known uncertainty and this uncertainty is measured in terms of its probability of occurrence. Risk has significant effect on any one of the aspects of a project namely cost, time or scope of the project. Understanding risks in the early stages of a project will help project managers to reduce its impacts and complete the project in an improved and more efficient manner. This can be achieved through proper Risk Management. The process of Risk Management comprises of identification, analysis and application of methods to reduce the identified risk. Along with identification and analysis, it is also necessary to allocate the risk properly to the respective contracting parties such as owners, consultants, contractors etc., so that risk handling decisions can be taken properly with authorization and without any disputes. This study focuses on management of risk in road construction projects. The roads are categorized as “High-volume roads” and “Low-volume roads” and analysis is carried out for High-volume roads roads. Identification of risk factors is done through a questionnaire survey and assessment of risk is done considering both the probability of the occurrence of risk and impact of the risk factor using 5 point likert scale for high volume and low volume roads. From the two parameters ‘risk priority’ is calculated by multiplying the RII values of both the parameters and the risks are ranked according to the RII values of the ‘risk priority’. Further allocation of the risk is also done through the questionnaire according to the responses of the respondents for each risk factor. The allocation is done towards the owner, consultant, contractor or the risk is shared between them. This study would help project managers to better estimate risks prior to the commencement of a project and allows them to develop proper mitigation measures at an early stage of a project.

Sequential mineral transformation during underground coal gasification with the presence of coal partings

Underground coal gasification (UCG) can be adopted to convert unminable coal resources into synthesis gas for use in the production of electricity, fuels, and chemicals. UCG is a promising technology with many health, safety, and environmental advantages over conventional mining techniques. It is of great scientific significance to study the mineral transformation and identify the typical minerals in certain process conditions, because it may help to ensure the stable operation of the gasification processes and improve the utilization efficiency of coal seams. The presence of coal partings has an important impact on mineral transformation. In this paper, the UCG process has been subdivided into pyrolysis, reduction, and oxidation stages, and the progressive coal conversion products were prepared. Ulanqab lignite was used as the test coal. The minerals in the coal transformation products were identified by X-ray diffraction (XRD) and scanning electron microscopy coupled with an energy-dispersive spectrometer (SEM-EDS). The thermodynamic equilibrium simulation software, FactSage 7.2, was used to calculate the relevant phase diagram to assist in understanding the mineral transformations. The experimental results indicate that the different iron-bearing minerals occur in raw coal and non-coal partings which are nontronite (Na0.3Fe2Si4O10(OH)2.4H2O) and glauconite (K (Fe, Al)2(Si, Al)4O10(OH)2) respectively. Pyrrhotite is the main iron-bearing mineral in the pyrolysis products. In the reduction stage, the relative content of Al2O3 is increased due to the presence of non-coal partings, which reacts with FeO to produce hercynite (FeAl2O4) at a temperature above 1100 °C. When the temperature increases to 1300 °C, hercynite is converted to the thermodynamically-stable cordierite (Fe2Al4Si5O18). In the oxidation stage, mullite (Al6Si2O13) is produced when the oxidation temperature reaching 1300 °C, which could be used to reflect the underground reaction conditions in the coal seam. The phase diagram of (SiO2)6.2Al2O3-CaO-Fe2O3 proves that mullite and anorthite (CaAl2Si2O8) are the dominant minerals when the mole fraction of (SiO2)6.2Al2O3 is above 0.7. In addition, the ash melting point rises with an increase of Si and Al content in the presence of non-coal partings.