Wang, D. S. (University of Science and Technology Beijing) | Chang, J. P. (University of Science and Technology Beijing) | Yin, Z. M. (University of Science and Technology Beijing) | Fei, F. (Shouyun Mining Co. Ltd.)
ABSTRACT: Complex goaf system at Shouyun Mine is assembled by two upper and lower levels and steep left and right two blocks, the roof cover of goaf system is shallow. The stability of the goaf system are analyzed and predicted by using FLAC 3D numerical simulation. The study shows that the state of crushing destruction limit is achieved at the two corners of roof plates, and gradually expands into a deep extension of the arch. The tensile stress distributes in the central roofs, but tensile failure will not occur; the displacement of surrounding rock at goaf system is bigger than that of other rocks, but the overall goaf system is stable. The goaf roof safe thickness is comprehensively determined by considering a variety of factors; The goaf system is treated by using fan-shaped deep holes blasting in upper treat tunnels and open deep holes compression blasting, an overlying rock protection layer of sublevel caving was formed by filling goaf areas with breakout rock; the safety of goaf handling and conversion of mining methods were organically integrated.
Mines of metal mineral resources in China have entered the transition period from open-pit to underground mining. To enhance the production of underground mining and improve the recovery rate of ore in the early stage, the ore nearby slope is generally mined by using of stope method; the produced goaf may bring serious problems to deep ore body mining in the transiting process of open pit to underground mining (Swift & Reddish 2002). In recent years, the study of mine goaf is increasingly deepened, and a lot of progress in the stability assessment, detection and engineering handle of the goaf has been made.
ABSTRACT: In construction process of large underground caverns, huge quantity computation is involved in feedback analysis of loosened zone of surrounding rock, corresponding estimate values are needed for keeping in step with excavation schedule. At first, elastic modular estimate type of surrounding rock at measure point is deduced from the classic deformation formula of circular tunnel, and an estimation method for correlation parameter is confirmed according to data reading characteristic of multipoint extensometers. Then, after excavation of top layer in main cavern, when loose zone hasn't been measured, initial test of the algorithm is carried out and its feasibility is verified. Furthermore, computation way of displacement pattern is improved. Finally, the method is applied to feedback analysis of main cavern after excavation of next layers, and it is shown that the method's computation precision meets demand of practical engineering. So that, the estimation method with brief computation and reliable estimate results, will be hopefully applied in more other large underground cavern projects in the future.
Loosened zone model is a kind of basic cavern supporting theory (Dong et al. 1994, Meng et al. 2010), in which loosened rock mass around cavern is regarded as a part of supporting structure, can availably reduce supporting cost of cavern. One of important parameter among loosened zone parameters is its depth, which is belong to key parameters for design, such as bolt length and spout layer thickness. Its concrete numerical value should be confirmed by field test, with familiar method such as ultrasound, seismic wave and acoustic emission as well as comprehensive analysis (Peng et al. 2008, Yang et al. 2012, Toshio et al. 2003, Fan et al. 2011, Zhou et al. 2011, Liu et al. 2006). Embedded multipoint extensometers are installed in advance of excavation, interior distortion in surround rock of cavern can be then perfectly measured, so loosened extent and degree of surround rock can be reflected in principle at last. But, for limitation on measure point arrange density and distribution of space, formerly corresponding method is auxiliary (Toshio et al. 2003) or for qualitative analysis (Liu et al. 2006). It is difficult to give satisfactory estimate value individually because of limited precision and reliability.
Wang, J. C. (State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences) | Wang, C. Y. (State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences)
ABSTRACT: Despite the significance of coral reefs as resources for development and research, only a limited amount of drilling surveys have been done on coral reefs, and obtaining comprehensive geological information remains difficultly to obtained. In the Chenhang Island survey, the digital borehole camera technology was utilized for the first time in China to provide guidance and acquire firsthand information of coral reefs, including anomalies in the rock body (e.g. fissures, cavities, traces of biological activities, interfaces, foreign strata and substances, color variations, etc), which also helped determine the causes of low or zero coring rates. In addition, data acquired by borehole camera can be used to evaluate the integrity of coral reefs. It can be concluded that: (1) the borehole camera system is an accurate and effective tool for determining the geological characteristics of coral reefs; (2) the system can serve important purposes in the geological survey of coral reefs.
The coral reefs are soil and rock structures formed from the remains of scleractinian corals, shaped by geological forces over a long period (Wei et al. 2008). Their great potential as a natural and military resource lends importance to the geological survey of coral reefs. In the drilling of Chenhang Island in Xisha (Paracel) Islands, we used deep boreholes to obtain rock cores from coral reefs and model their geological structures. The data can be used in the research of climate and environmental changes on a million-year time scale, the study of coral reefs' development and their interaction with the environment, as well as the exploitation of coral reefs for military purposes. The scientific and engineering values of such data would be significant.
Yu, W. J. (Hunan University of Science and Technology, Xiangtan) | Du, S. H. (Hunan University of Science and Technology, Xiangtan) | Feng, T. (Hunan University of Science and Technology, Xiangtan) | Wang, W. J. (Hunan University of Science and Technology, Xiangtan)
ABSTRACT: There were many small and medium coal mines in South China, and its geological conditions was very complex, so it could often found that there have large deformations during application in these coal mines and become very difficult to support. In view of the roadway deformation and control issues under complicated geological conditions, several mining area, such as Qujiang Coal Mine and Baise coal mines, geological conditions, roadway deformation characteristics of coal mines and outstanding problems of roadway support after in South China were summarized; and a series of field investigations, industrial test and supporting design research were carried out. According to the deformation characteristics of roadway surrounding rock in typical mines, industrial test of control technologies in high stress and large deformation rock, small coal pillar roadway and soft inflating half coal roadway were respectively illustrated. This study could provide theoretical and practical support in control technology for the same kind roadway, and it was of great significance to promote the development of science and technology of coal mines in South China.
Compared to large coal mines in North mine, the supporting technology of soft rock roadway in South mine in china was relatively backward, and it was mainly include the following aspects: the design was not reasonable, supporting form was simple, the strength of supporting materials was low and the construction quality was poor. Moreover, all of these did not get enough attention of scientific research for a long time. In recent years, Hunan University of Science and Technology had temped up with many coal mines comprehensively, inventing the “pre-stressing force and large stiffness truss cable beam“ as the comprehensive control core measures, and the high resistance to pressure release and high strength supporting technology with high strength bolt, strong anchor, and grouting. These techniques were used in the field, and its effect was obvious. The results can provide theoretical and practical support in control technology for the same kind of roadway, and it was of great significance to promote the development of science and technology of coal mines in South China.
Ma, H. T. (China Academy of Safety Science and Technology, Beijing) | Wang, J. A. (University of Science and Technology Beijing) | Liu, Y. F. (China Academy of Safety Science and Technology, Beijing) | Liu, S. J. (University of Science and Technology Beijing)
ABSTRACT: Bolt and wall rock should be regarded as a whole in the tunnel stability analysis. Based on the principle of bolt-rock combined action, a monitoring system of bolt stress and wall rock strain was developed, and a judging standard for the warning level of the rock stability was put forward, including the rock movement, rock moving velocity, rock moving acceleration, and the stress variation rate of bolt. The method was used in the PanGuShan mine, and an early-warning was made for some dangerous area. Based on the data acquisition of stress and strain of bolt, the system realized online monitoring by underground wireless transmission, it would be useful for the prevention of ground pressure disaster.
Pangushan Bismuth & Tungsten Mine is the only production site of Pangushan Jiangxi Tungsten Industry Co., Ltd. The Mine is located 33 kilometers south of the city of Yudu County, Jiangxi Province, and it's under the administrative jurisdiction of Pangushan Town in Yudu County of Jiangxi. Composed by three sets of veins, the mine is developed with joints, and there are seven groups of distributed faults. In June 1966 and July 1967, destructive activities of ground pressure occurred in the upper part of the mine, causing serious losses. After it was converted to deep mining since the 1990s, ground pressure activities occurred frequently, and in the mid-sections of 535 m-485 m and 485 m-335 m, the active blocks in vertical goaf are big enough to pose serious threats.
Based on the above, anchorage supports were adopted to places that may affect the stability of rocks in Pangushan tungsten mine, reinforced by security rock pillars and other methods. At the same time, the ground pressure of key areas was monitored through sophisticated methods. By analyzing the monitoring data of Pangushan tungsten mine, a complete set of system for monitoring and warning ground pressure has been developed and it is of great significance for preventing harms caused by ground pressure.
ABSTRACT: Durability of concrete shaft wall has seriously endangered the safety of mining in salt environment. Based on the background of Tongting Coal Mine project, the corrosion behavior of concrete under structural loads was studied. In order to simulate the practice of shaft lining concrete, accelerated corrosion of concrete tests are adopted to simulate the real corrosion environment of concrete, and using the ultrasonic detection method, which could obtain the evolution law of the corrosion thickness of concrete by the time. Through micro structure images, quantitative explication of concrete corrosion thickness is analyzed. Compared with the experimental results, the factors of concrete corrosion are discussed.
The shaft wall is the guarantee of the mine safety produces. Since 1990s, the reinforcement layer and initial shaft lining emerge a large number of water seepage in Tongting Coal Mine, bedrock section wall also appeared some outlet points. The circumferential length through the water takes 112 to 113 of borehole wall circumference. Under the long-term water erosion, the well wall concrete present expansion destruction, loss of its strength, and even induce concrete peeling, which not only have a dangerous for personnel and equipment, shaft wall safety is also worrying.
Non-destructive testing technique of concrete is an effective way for quantitative measurement its structure, widely used in the healthy monitoring and condition assessment of existing concrete macro/micro structures. As one of the most important aspects of ultrasonic monitoring, it has the good direction, strong penetrability, high energy conversion, and reflection, refraction and wave conversion when meet damage interface of corrosion concrete, harmless to the human body, strong adapt ability, high sensitivity, light equipment, flexible use, speed inspection, so it has particularly unique advantages in the field of nondestructive testing (Liang & Mu 2005, Lin 2002). This paper is aim to study corrosion characteristics of concrete shaft lining by ultrasonic detection in salt environment, simulating the shaft concrete experienced in coal mining.
Jiang, H. (University of Science and Technology Beijing) | Ji, H. G. (University of Science and Technology Beijing) | You, S. (University of Science and Technology Beijing) | Tian, X. L. (University of Science and Technology Beijing)
ABSTRACT: Rock burst is one of the Dynamic disasters in coal mining and other deep underground engineering as well as a hot-spot topic which the rock force field focus on widely. Along with the increasing depth of coal mining, the frequency and harmfulness of rock burst is increasingly serious, it has become a major technical problem to be solved in mines of our country. The paper treated the situation of rock burst when coal roadway tunneling in YANBEI colliery as the engineering background, based on the event data collected and sorted of real-time monitoring on microseismic and rock burst, to conclude the characteristics of spatial distribution under rock burst, analyzing the correlation between rock burst and microseismic, concluded the correlation between their distributions. To evaluate the impact factors of position and magnitude of rock burst, distinguishing the type of rock burst in this field is the bottom board of tunnel with stress. It has important engineering value on the studying and predicting of the mechanism about rock burst.
With the increasing demand for mineral resources, human are constantly looking for the mineral resources which in the deep of Earth, the deep resource exploitation has been becoming a trend of mining development. Mining depth is increasing under this trend. Under a certain high stress condition in the deep, the rock which is surround roadway, gob and pillar is easy induced unstable failure occurs, the rock burst. It usually refers to the elastic energy in the rock under the disturbance release instantaneously, generating the mine dynamic phenomena, often accompanied by a loud noise, rock burst and other phenomena (Qi & Chen 2003). Rock burst is one kind of rock dynamic disasters all around the world, it is the most serious disaster in coal mine. It tends to cause deformation of the mining face, the destruction of equipments, and result in casualties, even when serious cause surface subsidence and local earthquakes. In the long-term study on the earthquake, seismologists have accumulated a wealth of experience and made many valuable results, particularly the geophysical methods including microseismic monitoring, positioning, etc., all the results are valuable assets during the study of rock burst (Zhao & Tang 2005). In this paper, according to the existing data about microseismic and rock burst events of the 250204 face of Yanbei mine, finding the positions of microseismic and shocks, summarizing the events’ distribution rule under different locations and magnitude.
Zhang, Z. C. (University of Science and Technology Beijing) | Guo, Q. F. (University of Science and Technology Beijing) | Peng, C. (University of Science and Technology Beijing) | Zhao, L. (University of Science and Technology Beijing) | Zhang, H. (China Silicon Corporation Ltd.)
ABSTRACT: A set of hydro-fracturing tests were conducted to obtain the geostress in II measuring segment of 2 boreholes ranging in depth from 164.92 to 373.98 mat locations of Gaocun Iron Mine of the Ma'anshan site in the east of China. Results of all hydro-fracturing tests showed that all of the HFT parameters increase with depth. Roughly, the relation among these parameters is SH > Sv > Sh. And the orientation of the maximum horizontal main stress is N326.5°W~N338.2°W with an average value of N332°W It shows that the orientation of the main stress is close to NNW, and the ratio of maximum horizontal principal stress (hc) to vertical principal stress (Sv) is 0.94~1.40 with an average value of 1.18 in 10 measuring points. Logging data and laboratory observations of core samples reveal the cracks oriented at N332°W±6°. This paper describes the various applications of the result of hydro fracturing. The gestures measurement results provide a solid basis for mining design.
Geostress is a natural stress that exists in the strata. Knowledge of Geo-stress is very important in many problems related to rocks in civil and mining engineering. Hydro-fracturing stress measurements for determining in situ stresses are used in different areas such as mine and tunnel construction, earthquake prediction, and oil and gas source designing all over the world (Goodman 1989, Cardy & Brown 1993, Ziaie et al. 2012, Haimson & Fairhust 1970, Haimson & Rummel 1970, Hubbert & Willis 1957, Shadizadeh et al. 2009).
Several studies have been carried out on hydraulic fracturing methods in China (Cai 2000, Gao & Ding 1990, Liu 1998, Wang 2000, Liu & Li 1991, Jing et al. 2007, Chen & Li 1998, Xiao & Luo 2005). They performed an extreme test program to find out the best layer to perform hydraulic fracturing tests. The stated the formation could be a good candidate for this.
The aim of this study is to analyze and assess the results of hydraulic fracturing tests at the Gaocun Iron mine, china, to determine the magnitude and orientation of the principal stresses.
Xu, M. G. (Xi'an University of Science and Technology) | Dong, K. Q. (Xi'an University of Science and Technology) | Pan, H. Y. (Xi'an University of Science and Technology) | Li, S. G. (Xi'an University of Science and Technology) | Han, J. Z. (Xi'an University of Science and Technology)
ABSTRACT: The existence of the overlying compound key strata would cause stress distribution in surrounding rock, breaking of the key strata and the periodic weighting of a mining face, which are also related to variation of the mining height. Based on the compound key strata theory, the simplified mechanical model of the compound key strata before breaking is established for the fully mechanized top coal caving mining of thick coal seam. Through calculation, the computational expressions of equivalent load of the upper strata and the ultimate breaking step of the key strata is obtained. By using the FLAC3D numerical software, the abutment pressure under the compound key strata during fully mechanized caving of thick coal seam is simulated, and the calculated breaking of the compound key strata, periodic weighting, stress concentration area etc. agree with in situ observation.
When there are two or more key layers of hard rock bed in overlying strata whichever upper or lower, the interaction in terms of the compound effect will affect the deformation and breaking behavior during coal mining (Miu et al. 1999). Qian, Miao, Mao etc (Miu et al. 1999, Mao et al. 1999, Sun et al. 2005), defined the basic concept of the compound key strata the compound effect, and simulated the influence of compound effect by discrete element, which provided foundation of discrimination of compound effect. The study (Mao et al. 1999) showed that the ultimate breaking length L of the key strata had an inverse relationship with the mining height b, indicating that mining height had significant influence on the breaking of the key strata, stress distribution of surrounding rock and periodic weighting. Based on the compound key strata theory, the affecting scope of abutment pressure and periodic weighting in the fully mechanized top coal caving mining face of thick coal seam under the compound key strata in Binchang are analyzed by using theoretical calculation and FLAC3D numerical simulation, the result agreed with field test data. This study provides a theoretical and instructive guide to select the support type, and so on.
ABSTRACT: Concrete socket is considered as a functional structure to improve the displacement and stress distribution, and enhance the stability of high arch dam and abutment, especially when geological condition of such large rock engineering is defective, but lack of particular clear mechanism description. The evaluation of concrete socket effect in this paper, resulting from numerical simulation for Baihetan arch dam is based on a particular nonlinear finite element method, in which Deformation Reinforcement Theory (DRT) is applied. The mechanism of action is clarified generally from two perspectives: the first one contains conventional parameters such as displacement, stress and volume of plastic zone; from the second one, Plastic Complementary Energy (PCE) of such as left bank, right bank and dam, is adopted to quantify the structure stability, and unbalance force is considered as measurement of local area failure, in a sense of characterizing the distance of local stress state beyond the yield surface during the overloading process. It is suggested that evaluation based on deformation reinforcement theory can also be a reliable reference of high arch dam design and construction.
Chinese history of high arch dam construction has lasted for more than 30 years, during which Ertan arch dam was completed and has been under normal operation so far, in addition, many other 300m level high arch dams such as Xiaowan, Xiluodu and Laxiwa are also under construction. Due to their unfavorable geological condition of the dam foundation and asymmetry of both sides of abutment, concrete socket is always designed to enhance dam body and adapt to adverse topographical and geological condition of foundation. In order to reduce the load on abutment rock mass and improve state of stress and strain of dam, the concrete socket located in riverbed or abutment is particularly assumed to be applicable, especially where geological condition of lower part of foundation is poorer than the upper part. It is clearly informed that concrete socket is set in international finished dam cases like Vaiont arch dam in Italy and Enguli arch dam in Georgia, and proposed dam case like Jingpin-1 high arch dam and Baihetan arch dam in China.