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Abstract Underground mining often causes negative effects such as subsidence on the mine surface. The impact of underground extraction activity is even more dangerous for the mine under the residential area. Surface subsidence from underground mining activity is a problem in most countries. With the purpose of reducing the harm and warning of underground mining impacts to surface, many subsidence forecasting methods have been developed. In this paper the authors introduce the theory of exponential function and its application in forecasting the surface deformation due to underground mining in Thong Nhat coal mine. Exponential function parameters are evaluated for 4 stations showing maximum RMSE of 62.5 mm. The maximum difference between predicted subsidence using these parameters and measured value is -84.5 mm, equivalently to 5.3%. 1. Introduction Consequences of underground is creating workings in the ground, rock lost equilibrium and tends to move to obtain new equilibrium, the movement spreading to the mine surface causes the formation of surface subsidence trough. The prediction of the consequences of mining is an important task for the mine surveyors. The prediction of surface subsidence enables to efficiently repair the mining damage and has a positive impact on the economic results of mining. Subsidence causes damage in different objects on the surface. Thus, the preliminary aim of mine surveyors is estimating the impact of underground mining on surface above mines. They started to measure the subsidence of points on the mine surface, in order to be able to control the subsidence process and to reduce the damages caused by the underground excavation activity. Several prediction methods have been developed such as empirical prediction methods, model prediction methods and prediction methods based on influential functions (T. Ambrožič & Turk, 2003). Each method has its own advantages and disadvantages and conditions for individual applications. However, empirical prediction methods have high reliability because of building from the surveying data.
Abstract Nowadays, the deformation monitoring of dam work has done mainly by conventional geodetic methods, these advantages are high accuracy but which only allows to monitor the movement of dam at the top. Thanks to developing techniques which are able to monitor the settlement of layer soils while parts of structures are building. This paper presents the magnetic disk using for monitoring movement of embankment at HuongDien hydroelectric plant, Hue province. 1. The principle of operation of magnetic disk method The magnetic disk, a kind of matter technical tool for monitoring the subsidence with layers, is firstly used to observe at a number of constructions such as hydroelectric dams, air platforms, roads, etc. These days, this instrument allows to measure and record data continuously, which is put into special positions to determine the subsidence in a continuous way (Ha, N.V (2013), Khanh. T (2010)). The magnetic disk surveying method bases on electromagnetic field between a top reading and a round magnet ring which is fixed at stable soil, where the height of observation marks, as follows: At the observation mark Pi (i=1,2,...,n) putting n magnetic disks with surface of disk is in the horizon, this surface creates a magnetic, when a wire fence is put on the disk, an electric current is created and detected by alarm accessories (alarm light, alarm ring). These signals help surveyors to determine when the wire fence lies on the surface of the disk. In the next step, the rule is rolled to measure a differential height between Pi and a reference datum (A) or another mark (O) which is fixed in a directional tunnel before (Fig. 1) (Ha, N.V (2013), Khanh. T (2010)).
In-situ Volume Change Monitoring for Deep Underlay Strata with Fiber Optical Technology
Kokubo, Tatsuo (Asano Taiseikiso Engineering Co., Ltd.) | Takenobu, Kazuyoshi (Asano Taiseikiso Engineering Co., Ltd.) | Ikeda, Hidefumi (Kanto Natural Gas Development Co., Ltd.) | Kunisue, Shoji (Kanto Natural Gas Development Co., Ltd.) | Nohara, Daisuke (Asahi Glass Co., Ltd.) | Ooba, Keiichi (Godo Shigen Sangyo Co. Ltd.)
Abstract The Southern Kanto gas field, the largest field of natural gas dissolved in groundwater in Japan, is located in the Chiba Prefecture, eastern part of Japanese main island. In this gas field, 8 companies produce 460*10 m/y of natural gas. In addition, the iodine is extracted from the brine. Iodine is industrially useful and essential for the human body. About 30% of world production is produced in this area in recent years. On the other hand, land subsidence due to the gas-brine extraction from the strata has become a big issue to b solved since 1965. Natural gas and iodine producers in this area have made "The Land Subsidence Prevention Agreement" with the local government and have made an effort to prevent and minimize the land subsidence. Although the pumped up brine is inferred as the main cause of the subsidence from the early time, the geological mechanism of the subsidence, which includes the quantitative relationship between the volume change and extracted gas-brine's volume, has yet well known. As the measurement of the actual volume change of each stratum has become an important technological issue to reveal the mechanism, a new monitoring system has been developed jointly by them to identify the volume change of the target stratum. 1. Introduction "The Southern Kanto gas field", the largest field of natural gas dissolved in groundwater in Japan, is located in Chiba Prefecture, eastern part of Japanese Main Island. In this gas field, eight companies produce 460*106m3/year of natural gas. In addition, the iodine extracted from the brine is industrially used, about 30% of world production is produced in this area in recent years. On the other hand, land subsidence has become a big concern due to the gas-brine extraction from the strata since 1965. Natural gas and iodine producers in this area have made "The Land Subsidence Prevention Agreement" with the local government and have made an effort to prevent and minimize the land subsidence. These eight producers organized "Environment Committee of the Japan Natural Gas Association Keiyo Natural Gas Association (hereinafter the Environment Committee) " to address environmental concerns including land subsidence.
Abstract The Vietnam Coal and Minerals industrial group has currently invested in the development excavation of coal mine underground construction. Many modern equipment of world famous brands such as: Sandvik, Atlas Copco, Bolt tech... was put into execution. Manual labor of the workers have been replaced significantly. The advanced of construction and labor productivity has already improved. However, so far the performance of the new equipment actually has not been promoted. The reasons can be seen as: Using the device is not suitable for complex construction conditions in Vietnam; the investment is only a model, not focused; of the line equipment, only a modernized equipment (drill rig, excavator), the equipment remains the most backward; drainage maintenance, spare parts not meet the requirements. Even in many fields, the modern equipment no longer used and has been replaced by the more out of dated equipment. The fact is, if no solutions will increasingly hold back the development of the coal mining industry in Vietnam. According to the coal industry development plan in 2014–2020 period, coal production continued growth and expected 58 million tons by 2020. To achieve this task, there are a great of development have being constructed. According to the annual statistics, in order to exploit 20 to 30 million tons of coal by underground mining method in Vietnam today, Vietnam coal industry has to implement an average of 400,000 m the development. Through the initial survey, the general assessment above the construction in the Vietnam underground coal mines that the research on this problem, the solution at synchronization of the construction, improvement of technological scheme and labor organizations, to improve productivity, increasing of excavation advance should be necessary. 1. Introduction Coal Industry Group - Minerals of Vietnam (Vinacomin) currently has certain investments in the excavation equipment. Many modern equipment of famous world of brands such as Sandvik, Atlas Copco, Bolttech... was put into excavation implementation. Manual labor of the workers have been replaced significantly by mechanization. The advance of excavation and productivity have improved.
Abstract Stability and potential failure mode of tunnels and underground rock caverns are directly related to the magnitude and orientation of the in-situ rock stress. In some cases, the high horizontal in-situ stress is essential in maintaining cavern stability, whilst in other cases the high rock stress may bring forth additional difficulties in tunnel construction and rock support design. It is crucial to take into account the in-situ rock stress in designing of the shape and orientation of underground works and selecting of excavation methods and rock support. With a number of examples of real projects the paper describes the impact of the in-situ rock stress on the tunnel/cavern stability and corresponding rock support design. The hazardous effects resulting from spalling and rock burst associated with very high in-situ rock stress are addressed with the example of the world longest road tunnel – the Lærdal tunnel. 1. Introduction Stress-induced instability is one of major concerns for the safe construction and operation of tunnels and caverns. This is true for both soft rocks and jointed hard rocks. Jointing controlled rock falls are also controlled by the stress condition in addition to the jointing geometry since the sufficiently high normal stress will prevent the rock block from falling even the geometry is not favourable. The high horizontal stress may play a crucial role in maintaining stability of tunnels and caverns, which is particularly true for underground openings situated close to the ground surface. The Gjøvik Mountain Hall, which is 61m wide, 25m high and 95m long with the lowest rock cover of only 25 m, is an excellent example of using in-situ rock stress to maintain the cavern roof stability. Numerical analysis has demonstrated that it is the high horizontal stress that makes it possible to excavate such a large span cavern at such a shallow depth.