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Yang, Wenhua (xi’an University of Science and Technology / Key Laboratory of Western Mines and Hazard Prevention) | Lai, Xingping (xi’an University of Science and Technology / Key Laboratory of Western Mines and Hazard Prevention) | Wang, Ningbo (National Energy Group Xinjiang Energy Company) | Shan, Pengfei (xi’an University of Science and Technology / Key Laboratory of Western Mines and Hazard Prevention) | Zhang, Shuai (xi’an University of Science and Technology / Key Laboratory of Western Mines and Hazard Prevention) | Ren, Jie (xi’an University of Science and Technology / Key Laboratory of Western Mines and Hazard Prevention)
Under the condition of fully mechanized horizontal sublevel caving mining in steeply inclined and extra-thick seam, the problem of disaster caused by strong rock pressure is becoming increasingly prominent, which seriously restricts the safe production of the mine. It is urgent to study its mechanism to provide theoretical basis for the prevention and control of rock pressure. In this study, numerical simulation experiments are carried out to reveal the change characteristics of stress field, displacement field and plastic zone of the whole model after single slice mining in steep seam. Then, combined with the coal seam occurrence characteristics and mining methods, using the knowledge of mine pressure and rock mechanics, the structure model of stope overburden is obtained. The results show that under the complicated geological occurrence conditions of steeply inclined seams, it is difficult for roof strata to collapse in time under the condition of self-weight after mining, and a large area of roof suspension is formed. Under the combined action of transfer stress and bending stress of suspended roof, a triangular stress concentration area (SFC=2.5-3) is formed in the stope rock mass 6m-45m away from the roof roadway along the coal seam inclination, which makes the stress of roadway support system increase sharply and causes the occurrence of floor heave and side heave and other rock pressure phenomena. With the mining level extending to the deep, the stress concentration degree increases, and the rock pressure appearance also increases. When the stress reaches the ultimate tensile strength of roof strata, the roof collapses in a large area instantaneously, forming a strong rock pressure event. According to the structure and stress characteristics of overburden caving, the electromagnetic radiation intensity of coal and rock mass is obviously reduced by adopting multi-level roof blasting weakening technology of surface and underground, which reduces the stress concentration in coal and rock mass of working face, effectively controls the rock pressure problem of working face, and ensures the safety production of working face.
Manned vehicle transportation is one of the most important aspects of the oil and gas industry. The oil industry is dependent on the expertise that trucking providers bring, and would not have the ability to function otherwise. There are multiple types of trucks that must be utilized in drilling tasks to complete a job properly. One key factor to consider in land transportation safety is the driver. The major considerations include qualifications, training, and health.
ABSTRACT: Jinchuan mine is the largest underground nickel mine in China, There is highly stressed surrounding rock in this mine. The problem of highly fractured roadway support in the mine is serious. In the paper, according to mechanical principle of imitation soil nail reinforcement on highly fractured roadway support, the coupling reinforcing technology of prestressed hollow rock bolt-TECCO wire mesh-grouting concrete is proposed. In this supporting system, the prestressed rock bolt perform as the deep roots of plants into shallow rock to reinforce deep stability of the bedrock, the wire mesh just like be the shallow roots of plants, and the random distribution of grouting is the branch roots of plants. The on-site support test shows that the technology of prestressed hollow rock bolt-TECCO wire mesh-grouting not only improves the strength and rigidity of the supporting structure, but also provides a “first softening” for highly stressed broken roadway. After 20 days of roadway support, the deformation rate of surrounding rock is less than 0.05mm/d, the largest subsidence of the roof of the roadway is 37.6mm, and the largest relative displacement of the two gangs is 62.8mm, which indicates that the support method can effectively control the deformation of the roadway.
JinChuan Nickel Mine, the largest nickel base in China, has been depleted of rich ore resources. The mining scale of poor ore resources has gradually expanded and the geological conditions have become more complicated. The vertical depth of some major projects from the mine is 1200m below the surface, which is a large and complex metal deposit which is not widely seen in the world [Wang. et al., 2015]. Mining area is the horizontal tectonic stress-based high stress area, according to known stress measurements [Cao. et al., 2015]. When the depth is 1000m, the maximum horizontal principal stress should near 50MPa, and the minimum horizontal principal stress should near 20MPa. Such a large tectonic stress causes the engineering geological conditions of the mining area to be complex, the rock mass is fragmented, the deformation and destruction of the newly driven roadway is very serious, and the support and maintenance costs of the roadway are both high. Therefore, a large number of roadway support tests have been carried out in the Mine, but also achieved some short-term results, but eventually the roadway support difficulties, roadway maintenance costs are high. Spray anchor net support system, which imitation the mechanical principle of plant root reinforcement, significantly improve the roadway support effect reducing roadway maintenance costs, reducing the intensity of labour, but also improve the working environment underground. At the same time, it made JinChuan mine poor ore resources safe, efficient and low-cost mining proceed smoothly.
The traditional use of extruded polystyrene (XPS) rigid foam insulation has been to control heat flow between building living space and outside environment; however, new information reveals additional ways XPS rigid foam insulation can be used in heavy load roadway, railbed, and airfield applications. The objective of this paper is to provide engineers with a better understanding of the behavior of rigid foam as an engineered insulation material to support transportation infrastructure in cold regions. Numerous aspects of foam application and performance are discussed in this paper. Aspects include equivalent thermal resistance of foam vs. soil, normalized stress-strain curves of various rigid foam ultimate compressive strengths, cost comparisons between rigid foam and fill, and recent testing results of rigid foam when applied loadings exceed the ultimate compressive strength under repeated loadings. Testing approach was designed to consider loading associated with heavy equipment active in oil and mining operations. Historic design recommendations for use of rigid foam in bearing considerations has been the inclusion of a sustained dead load from which a reduced live load is then utilized. The reduced live load presents challenges in roadway and runway applciations as more fill is required to reduce applied surface loads to lower values, thus disqualifying XPS as a viable insulation solution to support pavement structures under heavy live loads. With the introduction of new data, analysis, and interpretation, XPS is shown to provide a cost-effective thermal barrier between the subgrade and road surface for heavy loads when compared to fill that is sourced far from the construction site. The recent testing of both extruded and expanded polystyrene under heavy and repeated loadings, with thermal resistance comparisons, leads to additional understanding of rigid foam as an engineering material.
3D laser scanning is a unique technology used for the description and subsequent modeling of real shape of spatially complex underground mining environment. Groundbreaking was its application in the pilot deployment of the Room and Pillar method at the CSM mine, where this method was used for the first time within the Upper Silesian Coal Basin, also known to have one of the most difficult mining and geomechanical conditions in the world. Very difficult mining conditions at depth over 800 m warranted searching for complex geotechnical tool or method that would capture all changes without distortion. Despite some shortcomings, 3D laser scanning was selected, although there is still no suitable device for dusty and humid mining environment. During the pillar development phase, comprehensive geotechnical monitoring was undertaken including the frequent scanning of pillar movement using 3D laser scanning technology. Based on repeated time-separated measurements, spatio-temporal analyses of deformation changes during ongoing mining were carried out. These analyses captured dynamic changes in coal rib, roof and floor movements of designated roadways while developing the pillar panel. In addition, time dependent long term post-mining measurements quantified additional strata movements within the panel enabling assessment of the long term pillar and mine roadway stability. The time-lapse scanning indicated variable pillar rib movement with maximum measured displacements of 60 cm. The scans indicated that in most cases, the bottom of the seam displaced more than the top of the rib side due to low floor strength causing large floor heave of up to 100 cm. During the 3-year monitoring, more than 2 billion spatial points were captured that can be used for further analysis.
A considerable amount of coal reserves are located in protection pillars that lie under built-up region in active Czech mining areas of the Upper Silesian Coal Basin. The commonly used controlled caving longwall mining method is not applicable in these areas because significant deformation of the surface is not permitted. For this reason the modified room and pillar method with stable coal pillars has been tested in order to minimise strata convergence. The trial operation of room and pillar method has been implemented at the shaft protective pillar where no mining was carried out in the past. Mining depth of room and pillar trial ranged from 700 m to 900 m. It is perhaps the deepest room and pillar coal mining in the world.
Nie, Baisheng (China University of Mining and Technology) | Ma, Yankun (China University of Mining and Technology) | Chen, Jigang (China University of Mining and Technology) | Qiao, Yun (China University of Mining and Technology) | Yu, Hongyang (China University of Mining and Technology)
N2105 mining face of Yuwu coal mine, in Shanxi Provence of China, are in conditions of low bursting of coal stratum, roof and floor. Combined action of static and dynamic load on coal and rock can induce the occurrence of rockburst. The prevention of rockburst needs to be consider on two aspects: (1) change the mechanical properties of coal and rock to weaken the capability to store elastic energy, (2) modify the stress state of coal and rock to decrease the degree of stress concentration. The prevention measures of pre-split blasting and destress drilling were put forward. A numerical model established by FLAC3D was investigates the stress evolution in surrounding rock and coal pillar during the implemen-tation of prevention measures. The pre-split measure reduces the disturbance of roof fractur-ing and destress drilling measure can bring down the degree of stress concentration. In field test, sandstone strata with height from 23 m to 32 m was target region for pre-split blasting and the drilling borehole in pillar range from 20 m to 30 m in length. The implementation of comprehensive measures guaranteed N2105 working face was in normal production and advanced 1200 m securely.
Rockburst hazard have been a major safety concern in underground coal mining for recent decades (Jiang, 2012; Wang, 2017). Rockburst occurs with a sudden and violent failure of coal mass and rock to releases elastic energy. A large amount of coal and rock are expelled into roadway or working tace where men and machinery are present (Jiang, 2012). With the depletion of mineral resources in near surface ground, mining exploitation at great depth become an inevitable trend and the occurrences of rockburst significantly increase and seri-ously threaten safety production (Li, 2013).
Application of Longwall mining method in underground results in generation of gob area, millions of cube meter in space. Longwall mining is characterized by variation of mining-induced stress, frequent disturbances to surrounding rock and macroscopic failure region. Cai suggests that the kernel function of the measure is to reduce rock stress concentration and disturbance energy accumulation in rock mass (Cai, 2016). Geomechanical methods, comprising destress drill, distress blasting and seams watering, are used in Ostrava-Karviná Coalfield. Multiple measures were adopted to prevent rockburst by Wang et al., including the prediction and early warning measures, stress relief by blasting in advance, optimized blasting design and optimized tunnel support (Wang, 2012). A technology of directional hydraulic fracturing was used to cut groove in hard roof for rockburst prevention by He and Dou et al. (He, 2012). In the Polish part of the USCB, torpedo blasting are performed to decrease local stress concentrations and to fracture roof rocks to minimize the impact of high-energy tremors on excavations (Wojtecki, 2017). Zhu and Lu et el. studied prevention of rock burst by Guide holes based on numerical simulation (Zhu, 2009). He et al. developed the constant-resistance and large-deformation bolt to control and prevent rockburst (He, 2015).
The offshore energy industry continues to grow worldwide into new frontiers using larger than ever, marine equipment. Much of this equipment is infrastructure fabricated at yards located inland from traditional marine terminals which then requires specialized road transports to be used. Concurrently, Marine Assurance agencies are being called upon to act as the verification agency for these transports with one of their primary goals being to ensure the safe transport of the equipment.
Despite the relatively high number of marine equipment public road transports, the importance of robust securing of cargo is often underestimated in the industry. Additionally, the required operational Quality Assurance/ Quality Control (QAQC) procedures to be applied for a successful and safe operation are often disregarded. One of the main contributors to these issues is the lack of common guidelines recognized across the industry. The correct understanding of the requirements for the road transport will permit reliable and cost-effective operations to be performed in a timely manner.
The public looks to safety professionals for guidance as experts in risk avoidance and hazard mitigation. This is reasonable as they are ostensibly trained in that area and, thus, in a better position to evaluate the risks inherent in different activities and to assess what can and should be done to alleviate or reduce those risks to an acceptable level. As such, it behooves safety professionals to be aware of not only safety-related heuristics that are presented to the public, but also the research that underlies that guidance to assess the appropriateness of the various safety rules that are promulgated to address potential hazards. In the real world, however, ostensible safety experts often simply accept these rules as representing appropriate, normal or typical behavior based on longevity, common sense or the simple frequency with which they are expressed.
One example of this (with which most parents are likely familiar) is the “5-second rule”: the idea that food dropped onto the floor and quickly retrieved is still safe enough to eat. The rationale seems to be that bacteria requires a longer time to transfer from the floor surface to the food. In a study by researchers at Rutgers University involving multiple foods, surfaces and contact durations over 2,500 measurements, it was discovered that, while longer contact times result in more bacteria transfer, other factors (e.g., nature of the food, surface onto which it is dropped) are of equal or greater importance (Miranda & Schaffner, 2016). The study concluded that bacteria were found to instantaneously contaminate the dropped food, debunking the idea that eating food quickly retrieved from the floor was safe.
ABSTRACT: In underground coal mining practice, a majority of rocks are composed of clay minerals. When roadways are placed in them, clay minerals are exposed to water and humidity and will absorb water rapidly and generate pressures that can break apart the weakly bonded rock, leading to a progressive strength degradation and consequently a severe closure (i.e., squeezing) of the roadway. In this study, numerical simulation was carried out to investigate the mechanisms of roadway squeezing using UDEC Trigon approach. The strength degradation is simulated by gradually reducing the cohesion and tensile strength of the contacts between blocks in the UDEC Trigon model. The strength is not reduced everywhere throughout the model but only at failed (either in tension or in shear) contacts because moisture is considered to intrude into rock through cracks. When a contact fails, its cohesion and tensile strength are gradually reduced as a function of calculation time. The numerical study aims to realistically capture the squeezing process of the surrounding rock mass of roadway due to strength degradation.
In underground coal mining practice, a majority of rocks are composed of clay minerals, feldspar, quartz clastics, and a small fraction of other silicate and carbonate minerals. Shales probably are the most common and can be composed of 50-80% clay materials (Molinda and Klemetti 2008). Clay materials have a platy structure and can absorb water. Water absorption causes swelling, which may loosen bedding and break apart the flat- bedded material structure, resulting in rock deterioration (Huang et al. 1986). Considerable researches have been carried out to study the swelling characteristics of shale. The propensity for swelling is controlled by the mineralogical composition of the rock, for example the presence of swelling clay minerals and the higher the water absorption, the higher the degree of swelling (Olivertra 1990). Huang et al. (1995) carried out a series of laboratory tests and the results showed that the temperature of the shale had the least influence on swelling of shale, while the air humidity and the moisture activity index had a significant influence. Zhang et al. (2004) found that the low strength of shale is also correlated with low Young's modulus and low shear strength.
Li, J. L. (Institute of Rock and Soil Mechanics) | Shi, X. L. (Institute of Rock and Soil Mechanics) | Yang, C. H. (Institute of Rock and Soil Mechanics) | Li, Y. P. (Institute of Rock and Soil Mechanics) | Li, H. R. (Institute of Rock and Soil Mechanics) | Ge, X. B. (Institute of Rock and Soil Mechanics) | Yin, H. W. (Institute of Rock and Soil Mechanics)
ABSTRACT: The detection of the goaf area is the key to the treatment of the coal mine goaf. The underwater ultrasonic imaging technology is applied to detect the shape of the water filled goaf of coal mine for the first time in China. The basic principle of ultrasonic imaging technology is explained. The work process of the ultrasonic detection is introduced with a detection case of a coal mine goaf under a railway bridge in Shanxi, China. The ultrasonic reflection signatures of wall, fork and ground obstacle of the mine roadway have been discussed. The post-processing techniques of the ultrasonic detection are proposed to reconstruct the goaf shape from cloud data. Finally, the detection results are compared with the known exploratory drilling data. It shows that the ultrasonic goaf detection has a high accuracy, which can satisfy the requirement of the actual engineering. The detection results provides the key data for the treatment of the goaf area.
Due to the disordered over-exploitation of coal resources, there are plenty of coal mine goafs with unknown shapes in many areas of China (Han et al., 2011a). The exist of coal mine goaf is a safety problem, for it may cause land subsidence and ecological environment destruction, which may bring great damages to the economy and society development of themining area (Wang et al., 2015, Fan and Liu, 2017). The treatment of coal mine goaf have become a current urgent duty.
An accurate and effective detection of goaf area can ascertain the distribution of goaf roadways, which is the key data for the safety evaluation and hazard control of goaf treatment projects. At present, many detection methods have been used in the world, such as the transient electromagnetic method (Han et al., 2011b), high-density electrical methods (Wu et al., 2016), and shallow seismic reflection method (Thomas and Holzer, 1986). Most of these methods are indirect detection methods, which are used to determine the general range of the coal mine gaof area in most cases. The accuracy of these methods is not enough for the actual engineering requirements of the treatment of the coal mine goaf. The laser range imaging method (Ding, 2015) can directly detect the shape of roadway through a borehole, however, it can easily get disturbed by borehole water curtain. Otherwise, the laser can not pass through muddy water, thus the laser range imaging system can not work in water-filled goaf. Aiming at these problems, this paper proposes using the ultrasonic imaging technology to detect the water filled goaf of coal mine for the first time. The basic principle of ultrasonic imaging technology is explained. The work process, data analysis and detection effects of the ultrasonic imaging technology are discussed with an example of the detection of a coal mine goaf in Shanxi, China.