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ISRM VietRock International Workshop
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.
No.2 Construction Mining Co. Ltd, Quang Ninh, Viet Nam * minhducvimsat@yahoo.com (corresponding author's E-mail) Abstract The Underground mines are exploiting in too more depth, all of most less than limits depth. However, the swelling foundation had happened that caused destruction pit. This paper showed the study of swelling foundation and some solutions handle, use structure support in conditions swelling pressure destruction pit at some mines in Quang Ninh region.
Abstract Landslide and subsidence in waste dump is a major problem which most mining industry countries is facing, Viet Nam is not an exception. To reduce the effects of disasters such as subsidence, there have had many developed subsidence prediction methods. In this paper, prediction function of Knothe was presented. Based on Knothe function, the authors built a subsidence prediction module and applied it for Nam Deo Nai waste dump, Quang Ninh, Viet Nam. The predicted values from this module was compared to the actually measured data, the smallest difference of subsidence is -0.003 m, equivalent to 5.3%, the largest difference is 0.011 m, equivalent to 4.3%. The small disparity between the largest and smallest difference shows the result has a high convergence. As the final result, it is found that the developed module is powerful and effective tool for waste rock dumps subsidence prediction. 1. Introduction Many waste rock dumps can be considered as a potential source of environmental problems, such as subsidence, erosion and landslide, which lead to significantly negative impacts on surrounding areas where have many civil works as house, school, etc (Fig. 1a). There have been many serious incidences due to landslide at waste dumps of Vietnam National Coal – Mineral Industries Holding Corporation Limited (Vinacomin). For example, ten houses were buried due to the landslide occurring at the rock waste dump of Phan Me coal mine (Thai Nguyen Iron and Steel Joint stock Corporation) in early morning 15/4/2013 (Fig. 1b) (Vnexpress.net, 2013). Vinacomin has taken many solutions in order to increase the stability of waste dumps, such as dumping by benches, dumping by surface, building the system of walls at the food of waste dump and planting trees, etc. However, it is necessary that waste dumps are monitored frequently and then the warnings of environmental hazards are informed earlier. Therefore, many monitoring works have been built in large waste dumps by mining companies owned by Vinacomin.
- Asia > Vietnam > Quảng Ninh Province (0.25)
- Asia > Vietnam > Thái Nguyên Province > Thái Nguyên (0.25)
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)).
Abstract As the main engineering geological problems of the Xiangjiaba hydropower dam foundation, the deflection core fracture zone which not only affects the dam foundation stress and deformation, but also cause a potential threat to seepage stability. After the Xiangjiaba hydropower dam impounding and generating electricity and running, under the action of high water head for a long time, to ensure the seepage stability of the foundation curtain deflection core fracture zone of the sluicing dam section, for solving technical problem of drilling and collapsing hole, segmented closed, pressure grouting, repeat splitting lifting, ineffective perfusion and so on, that using by the process method, mechanisms, control standards of combined grouting process of " fixed hole and sealing up " and " high pressure impact extrusion" to research and practice, so that the deflection core fracture zone impermeability has been significantly improved, reaching the design impermeable technical requirements, provides technical support and reference to implement seepage control for other similar projects. 1. Introduction Xiangjiaba Hydropower Station is the last planning step of the Jinsha River, the dam is located in junction Yibin County in Sichuan Province and Shuifu County in Yunnan Province. Engineering hub is mainly water retaining structure, flood discharge energy dissipation buildings, blunt desilting buildings, diversion and power generation systems after the left bank dam, underground diversion and power generation systems on the right bank, navigation structures and irrigation water intakes and etc. Which weir dam is a concrete gravity dam, the largest dam height is 162m. Hydropower normal water level elevation is 380m, dead water level elevation is 370m, total reservoir capacity is 5.163 billion m, regulating capacity is 903 million m, which is incomplete season regulating reservoir. Power plant installed capacity is 6400MW, guaranteed output is 2009MW, annual average generating capacity is 30.747 billion kW·h, irrigated area is 3754800acres.
- Asia > China > Yunnan Province (0.24)
- Asia > China > Sichuan Province (0.24)
- Energy > Renewable > Hydroelectric (1.00)
- Energy > Power Industry (1.00)
- Energy > Oil & Gas > Upstream (1.00)
Abstract OSV (On-Site Visualization) is a monitoring system in which measured information is shared visually on a real time basis at site. It was introduced by Akutagawa in 2006 and it has been applied at various construction sites in Japan and overseas projects. Through OSV application on various overseas projects, it has been recognized that a major problem with OSV system is the high cost of electrically driven OSV devices needed to cover many locations for a more effective OSV operation. Based on the above observation, low cost OSV were developed and trial installation was conducted at the slope of National Highway in Vietnam. Hanoi Metro Line 2 has been implemented since Mar 2011 under Japanese ODA and the construction works start in 2015. Because the underground station has deep open excavation works located at downtown in Hanoi, the careful construction operation with instrumentation and monitoring are required. In this paper, the plan of various type of OSV installation on Hanoi Metro Line 2 is proposed and the effectiveness of OSV monitoring is examined. 1. Introduction Recently the installation of safety monitoring systems at construction sites has become mandatory and everyone recognizes the importance and requirement of safety. However the ratio of injuries and fatalities have not been reduced so much in Japan as well as other countries. A new approach for the safety monitoring of infrastructure and visually sharing the measured information on a real time basis was proposed by Akutagawa in 2006 and has been implemented in more than 50 construction sites including overseas projects in New Delhi and Bangalore3) - 6) to improve safety management practices. This new approach is derived by utilizing an On-Site Visualization system, whereby light emitting sensors are used as the key technology for monitoring and giving simultaneous visual presentation of the measured information of structure and ground movement information on site. Fig. 1 shows typical light emitting sensors developed for the implementation of the OSV by which the various phenomena and movements can be monitored and visualized on site in real time. The monitoring items can be listed as follows at normal construction site.
- Construction & Engineering (1.00)
- Energy (0.95)
- Transportation > Ground > Rail (0.83)
Geotechnical Issues on Application of Highwall Mining System in Indonesia
Sasaoka, T. (Kyushu University) | Shimada, H. (Kyushu University) | Hamanaka, A. (Kyushu University) | Sulistianto, B. (Institute Technology Bandung) | Ichinose, M. (Center of Urban Infrastructure, Environment and Resources) | Matsui, K. (Kyushu University)
Abstract Indonesia is the second largest coal exporter to Japan. Almost all the coal is produced from open cut mines. However, a great deal of coal is left in the highwalls of the mined-out pits. The use of highwall mining systems has increasingly come into play in the US and Australia, when overburden depth exceeds economical recovery in open cut mine. However, the stability of the highwalls is always a major safety concern in such mining. This paper describes the characteristics of the highwall mining system and discusses the appropriate highwall mining system for use in Indonesia. 1. Introduction Indonesia produces over 400 Mt of clean coal and is the second largest coal exporter to Japan, accounting for about 32 Mt of coal annually. Over 99% of the coal produced in Indonesia comes from surface mines. More open cut mines will be developed and more coal will be mined in order to fill the great demand both in Indonesia and the rest of the world. In open cut mines in Indonesia, there are many sites where mining operations have developed long highwalls which have been abandoned due to the current economics. Mining operations have been transferred to lower stripping ratio blocks of coal or overlying seams. In some cases, coal lies buried beneath spoil heaps or is covered with mud and water. It is estimated that there is a great deal of coal beneath abandoned and working highwalls. Considering these situations, it seems to be worth introducing highwall mining systems into Indonesian open cut mines. Final highwalls of open cut mines can form the starting point for other mining methods, such as highwall or underground mining. In its basic application, highwall mining is a technique utilized after an open cut portion of a reserve has been mined, sometimes prior to the introduction of underground mining (Seib, 1993). In this system, the coal seam is mined by remotely operated equipment, such as an auger machine or a modified continuous miner incorporated into a highwall mining system. Major issues of highwall mining systems are less coal recovery due to leaving coal as the pillars and the instability of openings and highwalls due to the pillar and roof failures. This paper describes the characteristics of the highwall mining system and discusses the appropriate highwall mining system for Indonesia.
Abstract For the design of the foundation level and stability assessment of concrete dams three criteria with respect to the rock-mass are important to establish as soon as possible for a safe and economic dam design; the rock shear strength parameters, concrete-rock shear strength parameters and modulus of deformation. In this respect timely in-situ testing carried out according to international standard is considered best practice. The Lai Chau dam is situated in northern Vietnam and is the upper most dam in a cascade of hydropower dams along the Song Da. The site geology is of a composite granitoid intrusive body of grano-diorite, quartz-diorite and diorite, which has been syn-tectonically intruded and extensively tectonised post intrusion. In the technical design stage dam foundation levels are initially defined based on weathering. Vietnamese weathering classification systems describe 5 weathered weathering Vietnamese weathering classification systems describes 5 weathered grades from IA1 (completely weathered rock) through to IIB (fresh rock). For the Lai Chau Project two exploratory adits; HN-1 (length: 260 m) and HN-2 (length: 200 m) were carried out at the proposed dam axis in the left and right abutments respectively. The rock mass of the weathering grade IIA (slightly weathered) was considered the most appropriate foundation material. However, tests were also carried out in rock masses of weathering grade IB (moderately weathered) and IIB (fresh). A comprehensive in-situ testing program (rock-rock shear and concrete-rock shear tests and modulus tests) was performed in the rock-mass on the various weathering grades to establish the parameters associated with the identified weathering grades. On the basis of these tests an optimized foundation design was possible with foundation in IIA in the river section and in IB on the upper parts of the abutments. As a result excavation and RCC volume could at design stage be minimized. 1. Introduction The dam for the Lai Chau HPP (under construction) is the most upstream of a cascade system on the Song Da within Vietnam (see Fig. 1 for location). Downstream the Son La dam (2012) and the Hoa Binh dam (1994) have already been constructed. The completion of the Lai Chau HPP will result in a total installed power capacity of 5'520 MW on the Song Da mainstream. For the Lai Chau dam an RCC (roller compacted concrete) gravity type dam was chosen as the most economic. The maximum dam height is131 m. The original dam design called for a maximum height of 137 m. A higher quality rock mass in the river section allowed for excavation to be stopped 6 m higher. The installed power capacity is 1'200 MW with 3 Francis turbines. Construction of the Lai Chau dam started in 2011 and is due to be completed in 2015.
- Geology > Rock Type > Igneous Rock (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.70)
- Geology > Structural Geology > Tectonics > Plate Tectonics (0.46)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (0.69)
- Data Science & Engineering Analytics > Information Management and Systems (0.67)
- Reservoir Description and Dynamics > Reservoir Characterization > Faults and fracture characterization (0.46)
Abstract The objective of this study is to determine shear strengths of factures under constant normal loads (CNL) and constant normal stiffness (CNS) conditions as affected by displacement rates. The rock specimens are prepared from Saraburi marble with the nominal dimensions of 100×100×180 mm. The fracture area is about 100×90 mm. The fractures are artificially made in the laboratory by tension induce method. The direct shear test is performed with constant normal stresses at 0.5, 1.0, 1.5 and 2.0 MPa using the triaxial loading frame. The applied shear displacement rates are 10 to 10 mm/s. The results indicate that the higher shear displacement rates have affected to the peak shear stresses are increase under CNL and CNS condition. The higher initial normal stresses have affected the shear strength and the normal displacement than the lower initial normal stresses for CNL and CNS condition. The CNS condition shows higher peak shear strength than the CNL condition. The higher initial normal stress and higher shear displacement rate give the higher peak shear strength. The CNS condition shows the effect of rock joint roughness more than the CNL condition. 1. Introduction The presence of joints in the rock can affect its mechanical behavior, depending on the underground situation. When dilation of the rock joint during shearing is constrained or partially constrained, an increase in the normal stress over the shear plane occurs, which substantially increases the shear resistance. An underground excavation is potentially unstable rock blocks are constrained between two parallel dilatant rocks (Indraratna et al., 1999). The sliding of such blocks inevitably increases the normal stress, and also, dilation becomes significant if the joint surfaces are rough.
Abstract The objective of this study is to experimentally investigate the rate-dependent shear strength of rock fractures by performing triaxial shear testing under various shear velocities and confinements. A polyaxial load frame is used to perform the shear tests on tension-induced fractures prepared in 50×50×87 mm rectangular blocks. The fracture area is 50×10 mm. The specimens are prepared from granite, marl and sandstone. The confining pressures vary from 1, 3, 7, 12 to 18 MPa. The axial stresses are applied under constant rates equivalent to the shear velocities on the fractures from 8.7×10 to 8.7×10 mm/s. The asperity amplitudes on the fracture planes are measured from laser-scanned profiles along the shear direction and used to estimate the joint roughness coefficients (JRC) of the fracture. The JRC's are averaged as 15, 8 and 6 for the granite, marl and sandstone. The test results indicate that the peak shear strengths under each confinement increases with shear velocities. The Barton's criterion is modified here to explicitly incorporate the shear velocity and confining pressure. 1. Introduction Understanding the nature behavior of rock mass is important in many geotechnical applications. The performance of engineering structures constructed in rock is concerned with the presence of fractures in rock when subjected to forces and displacements (Curran and Leong, 1983; Li et al., 2012). In rock masses, properties such as roughness, separation and joint aperture have considerable effects on shear strength of rock fractures. The shear behavior of rock fractures is usually estimated through direct shear tests (e.g., ASTM D5607–08) to determine the peak and residual strengths of the rock fractures. Its test configurations however pose some disadvantages that the magnitudes of the applied normal stress are limited by the uniaxial compressive strength of the rock and that the fractures are sheared under unconfined conditions. The triaxial shear testing (Brady and Brown, 2006; Jaeger et al., 2007) has been developed to simulate the frictional resistance of rock fractures under confinements. The normal stress at which the shear strengths are measured can be controlled by the applied axial stress and confining pressure.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.58)
- Geology > Rock Type > Igneous Rock > Granite (0.48)
- Geophysics > Seismic Surveying > Seismic Processing (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling (1.00)