期刊封面

更多>>

Online System Service

更多>>

About the Journal

更多>>
Journal:
Coal Geology & Exploration
Establishment year:
1973
 
Periodicity:
Biomonthly
Supervised by:
Xi’an Research Institute Co. Ltd., China Coal Technology and Engineering Group Corp.
Sponsored by：
Xi’an Research Institute Co. Ltd., China Coal Technology and Engineering Group Corp.
Editor-in-chief:
 DONG Shuning
 
Associate E ditor-in-chief:

 LIU Cheng, James W. LaMoreaux 

 

Executive Editor-in-chief:
JIN Xianglan 

 

ISSN:
1001-1986
CN:
61-1155/P
Web:
www.mdkt.cbpt.cnki.net

Download Center

更多>>

2021年04期目次

  • Experimental study on advanced real time detection system of seismic-while-excavating

    WANG Ji;QIN Si;WU Hai;ZHANG Qingqing;YU Junhui;SU Xiaoyun;Xi'an Research Institute Co.Ltd., China Coal Technology and Engineering Group Corp.;

    The construction of intelligent loal mine requires the employment of the intelligent geological exploration technology to detect and predict front area in the process of roadway tunneling. The real time detection system of seismic while excavating is constructed on the basis of on-line seismic monitoring stations. The acquired seismic data is inspired by vibration of the tunneling machine, and is transmitted on optical fiber network to the database server located on the ground. The processing software acquires current seismic data from the database, through the steps of screening, pulsing and migration, imaging the front and side area of roadway head by reflected in-seam wave. In order to verify the performance and effectiveness of this system, we installed the real time detection system in the 5106 air return roadway of the Yushupo Coal Mine, and took a tracking detection test for several months. The detection system collected real-time seismic data, imaging in real time while excavating. With the increasing of the tunneling length, daily detection results show that there is a hidden fault existing in working face 5106. The fault has been verified by later drilling and detection of reflected in-seam wave. That means this real time detection system has the ability to image the area in front and side of the roadway by seismic signal generated from the road-header. Therefore, the detection system realized the continuous tracking and real time monitoring of abnormal structures in front of roadway side without affecting the process of roadway tunneling. It meets the requirement of geological detection ability for an intelligent tunneling system.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 6400K]

  • Three-component seismic data acquisition system of coal mine based on MEMS and LwIP

    WANG Huaixiu;QIU Shuai;ZHU Guowei;CHEN Bo;School of Electrical and Information Engineering, Beijing University of Architecture;College of Geosciences and Surveying Engineering, China University of Mining and Technology(Beijing);State Key Laboratory of Coal Resources and Mining;

    Aiming at the problems of poor real-time data transmission and limited data transmission in current coal mine seismic data acquisition and transmission system and the requirement of multi wave and broadband data acquisition, a three-component full wave seismic data acquisition system based on MEMS and LwIP is designed. The system consists of MEMS three-component detector, data acquisition unit, high-performance explosion-proof router, high-performance embedded host, acquisition control software and host monitoring software. The MEMS acceleration chip VS1002 is used as the core of the detector, which has the characteristics of high sensitivity and wide-band response. The host monitoring software completes the monitoring, management and simple data processing functions of the full wave acquisition unit. Full wave data acquisition unit realizes data acquisition, conversion, storage and data output of three component seismic signal. The system adapts the distributed control mode, improves the anti-interference ability of the whole system and the quality of the collected signal to realizes the flexible combination and split of the system, and then enhances the application scope in coal mines. The field contrast experiment is carried out in the open-pit coal mine. The experimental results show that compared with the conventional seismic acquisition system, the system has the characteristics of strong anti-interference and response frequency bandwidth, and is capable of capturing the seismic signal with wide frequency band in the harsh environment.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 3526K]

  • Fault recognition based on principal component analysis and k-nearest neighbor algorithm

    ZOU Guangui;REN Ke;JI Yin;Ding Jianyu;ZHANG Shaomin;State Key Laboratory of Coal Resource and Safety Mining, China University of Mining and Technology(Beijing);College of Geoscience and Surveying Engineering, China University of Mining and Technology(Beijing);

    Faults are geological structures that can cause disasters and thereby affect the safety of coal mines. Insight into the distribution of faults is one of the main purposes of 3 D seismic exploration in coal mines. With respect to human-computer interaction in the interpretation of faults, the reliability of fault interpretation depends to a certain extent on the interpreter's knowledge. We propose an algorithm based on principal components and nearest neighbors to detect the distribution of faults along target horizons. The Yangdong Coal Mine of Fengfeng Mining Area is selected as the research area, and ten seismic attributes are extracted from the data obtained via three-dimensional seismic acquisition and high-precision processing of the mining area. Principal component analysis(PCA) is used to integrate the aforementioned ten seismic attributes into six integrated attributes. At the same time, the attribute information is combined with the fault information of 139 points determined from 15 wells and 3 roadways in the mining area to construct a known data set. Based on these data, two sets of data were constructed. The ratio of training to testing data for the first and second data set was 9∶1 and 3∶7, respectively. Using these data sets and the 10-fold cross-validation method, the accuracy of fault recognition based on the k-nearest neighbors(kNN) algorithm was determined to be 87.75% for data set 1 and 71.63% for data set 2. This indicates that the accuracy of fault identification is closely related to the number of data sets. In particular, when the number of training data sets is greater than that of the testing data sets, the accuracy of fault identification is higher. The attributes obtained after dimensionality reduction via PCA were used as inputs in the evaluation of the classification results of the KNN model, and the classification accuracy rates were calculated to be 89.23% for data set 1 and 73.79% for data set 2, respectively. This is because PCA reduces the dimensionality of the original input features, thus reducing the amount of calculation required and increasing the characterization capability of these features. The results show that a combination of the PCA and kNN methods can effectively identify fault distribution, and improve the efficiency of fault interpretation.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 2190K]

  • Depth correction technique of electrical marker based on electrical field component of CSAMT

    LIU Zuiliang;ZHANG Fenxuan;ZHANG Jifeng;ZHOU Guangyu;ZHAO Hui;ZHANG Xin;Huayang New Material Technology Group Co., Ltd.;Shaanxi Coalfield Geophysical Prospecting and Mapping Co.LTD.;College of Geology Engineering and Geomatics, Chang'an University;

    Controlled Source audio-frequency Magnetotellurics(CSAMT) is an important geophysical method to detect water-rich areas and goafs in coal strata. However, the detection depth error is relatively large. Therefore, the electrical marker layer is used for depth correction to achieve the purpose of accurate interpretation of strata in this paper. A method for calculating all time apparent resistivity based on single component of electric field is proposed. The apparent resistivity can be obtained by translation algorithm, which is simple and fast without iteration. The relationship between the differential extremum of the apparent resistivity and the electrical marker layer is analyzed, and the electrical marker layer is identified by the well logging resistivity curve, then the depth correction coefficient is calculated by the ratio. Finally, the correction depth of any measuring point is obtained by interpolation in the whole region. Depth correction is carried out for the survey line R280 data of working face 31004, Xinyuan Coal Mine, and the results show that the corrected depth is in better agreement with the actual formation. Through comparison and verification of the known of known water-filled goaf boundary, water spraying point and borehole data, the desired goals are achieved. This method provides a new idea for fine data processing and interpretation by CSAMT in coal strata.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 4754K]

  • Application of in-seam wave technology in geological anomaly detection of Yangquan Mining Area

    FAN Deyuan;WU Guoqing;MA Yanlong;Huayang New Material Technology Group Co., Ltd.;Xi'an Research Institute Co.Ltd.,China Coal Technology and Engineering Group Corp.;

    By reviewing the application history of in-seam wave seismic detection technology in Yangquan Mining Area in recent years, this paper summarizes the characteristics of in-seam wave in Yangquan Mining Area, and analyzes the in-seam wave detection effect of geological anomalies such as faults and collapse columns in Yangquan Mining Area. The characteristics of in-seam waves in various regions are summarized, and the propagation patterns and the interpretation methods of in-seam wave in the regions are proposed. The results show that there are more than 200 working faces adopted in-seam seismic detection in Yangquan Mining Area, among which 58 working faces are used in No.15 coal seam, which mainly solves the detection problems of geological abnormal bodies such as faults, collapse columns, deflection, roof and floor breakage, and the overall accuracy rate of detection results is more than 82.2%. The characteristics of in-seam waves in Yangquan Mining Area are as follows. In-seam wave development is moderate to good in coal seams of 3-6 m thickness. In the south of Shanxi where the coal thickness is less than 2 m, in-seam wave is generally developed. The Airy velocity of in-seam waves are 960-1 000 m/s, and there is little difference in different regions. The Airy frequency is related to coal thickness, and the thicker the coal seam, the lower the Airy frequency. In the same coal seams, differences of velocity and frequency is not significant. According to the results of mining verification, the effect of detection from different coal seams and regions are quite different. For detection of geological anomalies by in-seam waves, suggestions are given from data collection, processing and comprehensive interpretation. The detection methods need be strengthened in the future to detect more geological disasters such as structural coal, gas enrichment areas, and stress anomalies. With extension of its application, in-seam wave technology will provides reliable geological protection for safe production and promote transparency for working faces of coal mines.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 4036K]

  • Evaluation on the resolution ability of underground transient electromagnetic instrument to disaster-causing water bodies

    ZHAO Zhongnan;XU Yangcheng;WU Yanqing;TAN Qingqing;KANG Yueming;WANG Yao;State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University;School of Resources and Safety Engineering, Chongqing University;College of Advanced Manufacturing Engineering, Chongqing University of Posts and Telecommunications;

    The downhole transient electromagnetic detection technology is an effective method to detect the disaster-causing water body in front of the tunneling. It is an important means to evaluate the instrument's resolution ability to disaster-causing water from the aspect of hardware for the instrument to be used correctly in underground mines. By comparing the magnitude relationship between the absolute difference of the secondary field, the resolution of the instrument and the background noise after superposition, the hardware conditions and evaluation basis for distinguishing the water-bearing hazards are analyzed. A calculation method for evaluating the resolution ability of underground transient electromagnetic to disaster-causing water body from the aspect of hardware is put forward. A three-dimensional geological model is established based on the structure of the disaster-causing water body, and the relationship between the trapezoidal wave turn-off and the negative step wave turn-off secondary field induced voltage was deduced, and the full-space three-dimensional finite difference parallel was adopted on the GPU. The algorithm calculates the secondary field response of the disaster-causing water body. The turn-off time and background noise of a transient electromagnetic instrument are measured. According to the hardware discrimination basis of the disaster-causing water body, the ability of the underground transient electromagnetic instrument to distinguish water-conducting subsidence column and water-filled goaf was evaluated from the hardware aspect. The development of downhole transient electromagnetic detection instruments and accurate on-site detection provide technical reference, which is of great research significance.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 3450K]

  • Love wave full waveform inversion via Pseudo-Hessian gradient pre-conditioning operator

    GUAN Jianbo;LI Yu;YIN Caiyun;YANG Zhi;JIN Chaobin;ZHAO Meng;YANG Hang;School of Geological Engineering and Geomatics, Chang'an University;Key Laboratory of Western China Mineral Resources and Geological Engineering, Chang'an University;Huaneng Coal Technology Research Co., Ltd.;

    The construction of near surface shear wave velocity is an important step in multi-component seismic data processing in coalfield. Compared with the multichannel analysis of surface wave, the full waveform inversion(FWI) has higher resolution in the construction of near surface shear wave velocity model. However, in the gradient-based FWI, the gradient operator is not scaled with increasing depth due to the narrow frequency band of seismic records, the non-uniform coverage of the wavefield, and the double scattering. The parameters of the deep model cannot be updated significantly. The Hessen operator of the objective function contains curvature information, which can clearly predict the defocusing phenomenon and the artifacts generated by double scattering in the gradient operator. The inverse Hessen operator can be used as a deconvolution operator to realize gradient pre-conditioning and enhance the illumination ability of the deep model. However, the explicit calculation of Hessian operator is very difficult because it has huge dimensions. Based on this, inverse scattering theory is referred to, the expression of the pseudo-Hessian operator of the objective function of full-waveform inversion is given, and a pre-conditioned gradient-based FWI method is developed. The proposed method was applied to the reconstruction tests of the fault model, subsidence model, and undulating interface model, respectively. The inversion results show that, compared with the classic conjugate gradient-based FWI, the pre-conditioned conjugate gradient method based on the pseudo-Hessian operator can accelerate the convergence rate and improve the inversion accuracy.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 2180K]

  • Research status and prospect of fault activation under coal mining conditions

    TIAN Yutong;ZHANG Pingsong;WU Rongxin;LIU Chang;State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines, Anhui University of Science and Technology;School of Earth and Environment, Anhui University of Science and Technology;

    Fault activation under mining conditions is easy to induce dynamic geological disasters such as rock burst and floor water inrush. How to carry out advanced prevention and early warning for a series of dynamic geological disasters caused by the activation of stope faults has always been a scientific and technical problem faced by coal mine safety mining. This paper summarizes the research status of stope fault activation at home and abroad from three aspects of numerical simulation, similar physical simulation and field test. Focusing on the monitoring and early warning methods of fault activation, including microseismic monitoring technology, acoustic emission technology, apparent resistivity monitoring technology, optical fiber sensing technology, water injection test, etc., the main existing testing and evaluation methods are summarized from the aspects of method principle, research status, technical characteristics and so on. Combined with the current coal mining in complex fault areas in China, the formation mechanism and internal relationship of several typical dynamic geological disasters induced by fault activation are analyzed. At present, the research on multi-dimensional and multi-scale whole process fine monitoring technology of fault activation induced by mining is still insufficient. Based on the requirements of precision and intelligence of coal mining, it is pointed out that the research on coal mining in complex fault area should develop in the direction of multi field coupling, fine model construction, multi means comprehensive exploration, intelligent early warning, etc. It is considered that further research on the basic theory of fault activation, fine simulation, multi-dimensional multi field multi-scale monitoring and early warning technology system can provide a solid foundation for the mine geological guarantee work under the guidance of intelligent coal mine.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 4829K]

  • Research on the model of accurate exploitation and utilization of underground space resources in closed/abandoned mines

    LIU Qinjie;WANG Jinjiang;YANG Ke;DI Shengjun;DONG Zhiyong;State Key Laboratory of Mining Response and Disaster and Prevention and Control in Deep Coal Mines;School of Mining Engineering, Anhui University of Science and Technology;Shanxi Coking Coal Group Co., Ltd.;

    With the continuous development and utilization of green coal resources, the problem of abandoned mines at the end of the full cycle of coal mine development and utilization has gradually emerged, and the subsequent development and utilization of underground space resources in closed/abandoned mines has become an urgent problem to be solved. Based on the statistical analysis of the status quo of underground space resources in closed/abandoned mines in China and the difference in the location and form of underground space caused by mining demand, the underground space resources of closed/abandoned mines are classified into goaf space resources and roadway space resources, chamber space resources; the use of space resources as a single energy accumulation site and the use of closed/abandoned mine underground space resources in multiple directions and multiple fields to coordinate the development and utilization of the resources were explored; and thereout a model of the classification, the grading and accurate utilization of the underground space of the closed/abandoned mines was proposed to build the accurate development and utilization system model with survey analysis, initial judgement of engineering analogy, detailed assessment of model building, software decision-making system as the main process. The accurate utilization pattern and the system model for the accurate development and utilization were used to analyze further the patterns of the single and multiple development and utilization so as to provide the reference for the researches and practices of the underground space resources of the closed/abandoned mines.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 4805K]

  • Study on exploitation and utilization mode of tourism resources of the underground space in abandoned mines

    HAN Yun;LIU Qinjie;WU Benniu;YANG Ke;DONG Zhiyong;School of Mining Engineering, Anhui University of Science and Technology;State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines;Institute of Energy, Hefei Comprehensive National Science Center;Shanxi Coking Coal Group Co., Ltd.;

    With the deepening of the coal industry capacity policy, a large number of mines are closed or abandoned, but there are still a lot of available resources. How to develop and utilize them has become a major problem in the transformation and development of the coal industry. On the basis of analyzing the current situation of domestic abandoned mine industrial tourism development and the problems of underground space tourism development, learning from the experience of foreign abandoned mine tourism development mode, the characteristics of abandoned mine underground space tourism resources were summarized and analyzed. This paper explores the development and utilization mode of underground space tourism resources in abandoned mines, and puts forward three senses and five characteristics design method based on vision, touch and hearing, and knowledge, appreciation, participation, entertainment and interest. In view of the existing problems in the development and utilization of underground space resources in abandoned mines, the corresponding countermeasures are given, that is, attach great importance to the development of abandoned mine tourism resources, improve the traditional single tourism mode, strengthen the experience-based tourism design, and modern functional transformation of underground space. It provides a reference for maximizing the utilization of underground space resources, serving national development and construction, social security and economic development.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 4768K]

  • Key problems and countermeasures of CBM development through surface boreholes in abandoned coal mines of Shanxi Province

    WANG Zheng;LI Guofu;ZHOU Xianjun;HU Shengyong;LI Rifu;CHEN Wenke;JIAO Pengshuai;LI Chao;LI Jiangbiao;State Key Laboratory of Coal and Coalbed Methane Co-Mining;Yi'an Lanyan Coal and Coalbed Methane Co-Mining Technology Co., Ltd.;College of Safety and Emergency Management Engineering, Taiyuan University of Technology;Chongqing Research Institute Co.Ltd., China Coal Technology and Engineering Group Corp.;Shanxi Lanyan Coalbed Methane Group Co.Ltd.;Shanxi Coal Geology Surveys Research Institute;

    With the effective implementation of China's coal capacity reduction policy, a number of resource-depleted and under-developed mines will be abandoned. The plenty of coalbed methane resources still existing in abandoned mines, could be developed and utilized to realize clean, safe, efficient and low-carbon development of coal industry, promote safe production of coal mines, optimize energy structure, and achieve greenhouse gas emission reduction. Based on the relevant research of Shanxi Province Coal-based Key Science and Technology Targeting Project(Coalbed Methane Industry Chain), the author systematically expounds the key problems faced by coalbed methane development in abandoned coal mines, such as inaccurate resource evaluation, unsound drilling system, lack of surface and underground co-extraction, etc. In view of these problems, the following countermeasures are proposed: Accurate geological exploration of abandoned mines is an important basis for the design of surface drilling trajectory in goaf, especially for abandoned mines with backward coal mining technology such as blasting mining. In order to effectively reduce the risk of drilling into coal pillars, the precision of geophysical exploration should reach meter level. “L” –shaped coalbed methane surface boreholes are the best choice in abandoned mines, that is, selecting a certain distance of safe coal pillar around the goaf as the location of L-shaped boreholes and supporting special drilling technology. Coal mining enterprises should consider the development and utilization of abandoned mine resources during the whole life cycle planning of coal mines in advance, especially ensure the unblocked CBM pumping channels before the mine is abandoned, so as to realize the new combined mining mode of “one borehole for multi-purpose” of CBM boreholes and improve the CBM development efficiency of abandoned mines. Adopt backfire prevention device, various sensors and other devices, and set automatic alarm halt limit value for key parameters, so that coalbed methane surface extraction process in abandoned mine is safe and efficient; In order to improve the overall development and utilization value, it is necessary to adopt the corresponding cascading utilization mode for coalbed methane with different concentration in abandoned mines. Taking the abandoned mines in Shanxi Province as a demonstration area, the research and understanding has important guiding and demonstrative significance for promoting the development and utilization of coalbed methane in abandoned mines in the coal mining areas of China.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 2003K]

  • Technology of across-goaf drainage of coalbed methane from a lower coal seam group and its primary application: Taking Sihe mine field as an example

    LI Junjun;LI Guofu;HAO Haijin;HAO Chunsheng;WANG Zheng;State Key Laboratory of Coal and Coalbed Methane Co-Mining;Yi'an Lanyan Coal and Coalbed Methane Co-Mining Technology Co.Ltd.;Shanxi Lanyan Coalbed Methane Group Co.Ltd.;

    After many years of coal mining, a large area of goaf had been formed in the No.3 coal seam of Sihe mine field in Jincheng mining area, the pressure relief in a large area increased the permeability of the lower coal seams(seams No.9 and No.15), however, due to the limitation of goaf barrier and surface pre-extraction technology of coalbed methane, the coalbed methane of the lower coal seam group had not been effectively extracted, in order to ensure the safe production of the coal mine and the release of production capacity, based on the characteristics of goaf, a new technology of drilling, completion and fracturing in goaf was developed, focusing on the analysis of construction parameters and production capacity in the later stage, and the application effect of coalbed methane extraction technology cross the goaf in the lower coal seam group was evaluated. The results show that when the surface drilling is used to develop coalbed methane resources in the goaf, well location optimization and wellbore structure optimization should be carried out first, which can effectively ensure the success rate of drilling. The nitrogen replacement casing drilling technology and low pressure leakage grouting reinforcement technology can not only effectively reduce the risk of spontaneous combustion and even explosion of coalbed methane in the goaf, but also ensure the cementing quality of goaf section. The fracturing parameters of coal seam under goaf were optimized and the fracturing technology of coalbed methane wells with different well locations was designed to effectively extend the fracture length and avoid fracturing accidents such as fracturing through. Fine drainage control measures can effectively expand the drainage radius and improve the single well productivity. The drainage practices of more than 100 CBM wells across goaf show that the maximum gas production of a single well reached 8 832 m3/d, and the daily average gas production was up to 2 694 m3, which verifies the feasibility of the across-goal CBM extraction technology of the lower coal seam group and can be popularized and applied.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 3316K]

  • Development characteristics of coal microfracture and coal petrology control under cyclic high voltage electrical pulse

    LI Hengle;QIN Yong;ZHOU Xiaoting;ZHANG Yongmin;CHEN Yilin;School of Environmental and Biological Engineering, Henan University of Engineering;Key Laboratory of Coalbed Methane Resources & Reservoir Formation Process, Ministry of Education, China University of Mining and Technology;School of Earth Sciences, East China University of Technology;School of Electrical Engineering, Xi'an Jiaotong University;

    Based on the open experimental platform of cycle high voltage electrical pulse generator, the impact cracking experiments of three kinds of coal samples with different metamorphic degrees, namely, fat coal, lean coal and anthracite were carried out under two kinds of energy loading methods: metal wire and energetic material. Then, the characteristics of coal rank and load response of microfracture were analyzed by the polarizing microscope, and the relationship between microfracture evolution and macerals was studied. The results show that the increasing trend between the density of microcracks and the impact times is nonlinear, which can be roughly divided into three stages: slow increase in the initial stage, rapid increase in the middle stage, and stabilization in the later stage in the first place. This means that the cracking effect is not better with more cyclic impacts, and there is an optimal impact number. Second, the microfracture density in coal under wire loading is more developed than that under energetic material loading. In general, the development degree of micro fissures in fat coal is higher than that in lean coal, and that in lean coal is higher than that in anthracite. It shows that the cyclic high-voltage electrical pulse has “double bottom effect” in fracturing effect. Namely, when both low energy loading condition and low rank coal are available, the cracking effect is better. Third, there are some differences and emphases in the development of microfractures among the macerals. Vitrinite is the most developed, followed by inertinite, and exinite is the least developed. This is mainly due to the advantages of vitrinite, such as volume content(space dominance), original fissure density(location advantage) and brittleness(mechanical superiority). Fourth, the microcracks in the macerals can be classified into four main types: through the macerals, confined within the macerals, developing along the boundary of the macerals, showing oblique morphology and progressive tensile shear extension. Finally, these conclusions are of important theoretical significance for further revealing the microscopic mechanism of coal seam fracture induced by cyclic high voltage electric pulse, clarifying the target coal seam in the engineering practice, optimizing the working process parameters and improving the operation results.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 6013K]

  • Coal body structure identification by logging based on coal accumulation environment zoning and its application in Mabidong Block, Qinshui Basin

    ZHANG Jianguo;HAN Sheng;ZHANG Cong;CHEN Yanjun;Shanxi CBM Exploration and Development Branch of Huabei Oilfield Company,PetroChina;Exploration and Development Research Institute of Huabei Oilfield Company,PetroChina;

    Identification of coal body structure by logging curves is an efficient and economical geophysical method. However, due to the influence of sedimentary environment and coal reservoir property, logging curves have multiple solutions, leading to an unclear logging response of coal body structure. And the identification rules acquired in one place cannot be applied in another place. Therefore, before starting logging discrimination, it is necessary to control the factors influencing well logging apart from coal structure. This essay takes an example from No.3 coal seam in Mabidong Block, Qinshui Basin. Firstly, coal cores are relocated to their logging depth by the positive correlation between ash content and gamma logging curves. And then, the coal-accumulating environment is divided by the ratio of vitrinite content to inertinite content. After that, the logging curves of similar environment are selected preferably. The result shows that resistivity logging serial curves can indicate the changes in coal body structure clearly, while acoustic wave logging cannot because of its shallow penetration depth. Finally, the Random Forest Model built by the chosen curves is used to predict other wells' coal body structure. The predicted results and the measured fracturing curves show that the results are in good agreement with the measured data. According to the application, the method can predicate the allocation of coal body structure, instruct hydraulic fracturing, which reduces development cost, and provide guidance to the logging response study on multi-regional coal body structure.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 6358K]

  • Sequence stratigraphy and coal accumulation of barrier coastal system under epicontinental-sea environment: A case study of the Late Paleozoic Taiyuan Formation in Bohai Bay Area

    CHANG Jia;CHEN Shiyue;WANG Qiong;PU Xiugang;YANG Huaiyu;School of Geosciences, China University of Petroleum(East China);The Third Institute of Geology and Mineral Resources of Shandong Province;PetroChina Dagang Oilfield Company;Research Institute of Petroleum Exploration and Development,Shengli Oilfield Company,SINOPEC;

    The Bohai Bay Area, located in the east of North China, is an important area for coal production in China. There are many coal seams available for industrial exploitation in the Late Paleozoic, among which the marine coal seams developed in the epicontinental-sea environment are the most widely distributed. In order to study the sedimentary sequence and coal accumulation model of the barrier coastal system in the epicontinental-sea environment, this paper studies the sedimentology and sequence stratigraphy of the Late Paleozoic Taiyuan Formation in the Bohai Bay Area, combining with drilling and field profile data. Based on the identification of lithology and sedimentary facies, the study of sequence stratigraphy is carried out to reveal the coal accumulation model of the barrier coastal system in the sequence stratigraphic framework. Taiyuan Formation is mainly composed of yellowish brown, gray black mudstone and yellow green and gray white sandstone, with several layers of marine limestone and coal seams. The sedimentary facies are mainly tidal flat facies, lagoon facies, barrier island facies and platform facies. Against the background of the barrier coastal system, the base level and the sedimentary interface are basically the same, and the sequence boundary is mostly sedimentary interface. According to the two types of subaerial unconformities(SU) including sedimentary facies transition surface and incised valley scour surface and transgressive direction transition surface(TDS), Taiyuan Formation can be divided into Sq1, Sq2 and Sq3. The third order sequence is divided into LST, TST and HST system tracts by maximum flooding surface(MFS) and maximum regression surface(MRS), representing eight fourth order sequences. During the period of Sq1, the internal area of the basin fails to provide a stable coal accumulation environment, and the thickness of the coal seams is relatively thin. During the Sq2 period, the influence of sea level on the Area increases, the coal accumulation reaches the peak, and the overall thickness of the coal seams increases and connects into slices. During the period of Sq3, the coal accumulation relatively weakens, and the distribution range of coal accumulation centers contracts, developing in isolation. The statistics of cumulative thickness of the coal seams in drilling data reveal that thick coal seams are mainly developed in the eastern part of Jizhong depression area, Huanghua depression area and Jiyang depression area. The coal accumulation model of Taiyuan Formation in the study area can be divided into five stages: LST, early TST, middle TST, late TST and HST. Under the control of the growth rate of accommodation space and peat accumulation rate, peat flat and lagoon are favorable coal accumulation centers.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 6735K]

  • Spatial-temporal distribution of outburst accidents from 2001 to 2020 in China and suggestions for prevention and control

    ZHANG Chaolin;WANG Enyuan;WANG Yibo;ZHOU Xifang;Key Laboratory of Gas and Fire Control for Coal Mines of Ministry of Education, China University of Mining and Technology;School of Safety Engineering, China University of Mining and Technology;

    Prevention and control of coal and gas outburst is a prerequisite to ensure the safe and efficient mining of coal mines and the stable supply of national energy. Two outburst accidents(Zuoquan Coal Mine outburst accident on March 25 and Dongfeng Coal Mine outburst accident on April 9) occurred in 2021 resulting in 12 deaths, indicating that there is still a very difficult way to go before we achieve the goal of "zero outburst". In view of the current situation of unclear outburst mechanism and frequent outburst accidents, this paper makes statistics data of outburst accidents in China from 2001 to 2020. There were 484 outburst accidents and 3 195 deaths in the past 20 years. Although the outburst accidents have been effectively controlled in recent years, they are still at a relatively high level and more prominent in coal mine accidents. The spatial-temporal distribution law of outburst accidents in China from 2011 to 2020 is further analyzed from the aspects of the grade, place and time of outburst accidents. The results show that there were 93 outburst accidents and 645 deaths in 12 provinces, among which the major outburst accidents continue to dominate, and the death toll of extraordinarily major outburst accidents remains high throughout the year, and the proportion of general outburst accidents increases gradually. The outburst accidents are characterized by “wide and concentrated distribution, more cases and more serious in the south of China”. Guizhou Province, Hunan Province, Yunnan Province and Henan Province are the most serious provinces, accounting for 68% and 79% of the total number of accidents and death toll. The outburst accidents mainly occur in May to July and November to December every year, on the 4 th-6 th, 15 th-17 th and 28 th-29 th of each month, 1-2 o'clock, 5-6 o'clock, 10-12 o'clock and 17-20 o'clock every day. The outburst accidents present the periodic development law of high and low alternation. From the perspective of safety management, the outburst prevention measures must be implemented in every day and every shift of production, and the safety management should be strengthened in the period of low incidence of outburst accidents. The long-term virtuous cycle of “enhancing safety awareness-low incidence of accidents-enhancing safety awareness” is the core concept of outburst prevention and control.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 3622K]

  • Distribution characteristics of heavy minerals in the sandstone of Zhiluo Formation of northern Ordos Basin and its implication

    ZHANG Yuanyuan;ZHANG Pengfei;NIE Fengjun;YAN Pengbing;ZHANG Zhibo;YAN Zhaobin;ZHANG Xin;Geological Party No.208,CNNC;Institute of Sedimentary Geology, Chengdu University of Technology;State Key Laboratory of Nuclear Resources and Environment, East China University of Technology;School of Resources and Geosciences, China University of Mining and Technology;

    In recent years, the evaluation of sandstone-type uranium ore in Ordos Basin has made great progress, and the problems about provenance and uranium sources of the target layer have drawn the most attention for a long time. Based on the comprehensive analysis of heavy minerals, this paper discusses the source of detrital materials and ore-forming uranium sources in Zhiluo Formation of sandstone type uranium deposits in the northern Ordos Basin. The results show that the heavy mineral assemblages of Zhiluo Formation in the study area mainly include garnet, zircon, epidote, biotite, spinel, as well as a small amount of apatite, sphene, rutile and hornblende, tourmaline, ilmenite, which reflects the parent rock type of mainly intermediate and high-grade metamorphic rocks and intermediate acid magmatic rocks. The heavy mineral characteristic index reflects the characteristics of the garnet-bearing metamorphic rock as the main source rock type and proximal deposition. The comprehensive analysis shows that the main provenance areas of Zhiluo Formation are the Middle-Lower Archean Proterozoic Wulashan Rock Group, the Middle Proterozoic Zartai Group and intermediate acid intrusive bodies of various periods in Daqingshan and Wulashan regions in the northern part of the basin. Among them, the ancient basement metamorphic rocks and various periods intermediate acid magmatic rocks generally have high uranium content, with an obvious uranium migration along the NW-SE direction, providing the initial uranium source for the later uranium mineralization.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 5218K]

  • Mechanism and applicability of increasing coalbed methane well production by pre-positioned acid fracturing

    FAN Yao;China Coal Research Institute;Xi'an Research Institute Co.Ltd., China Coal Technology and Engineering Group Corp.;

    At present, the production shortfall and benefits decline of the coalbed methane reservoirs in China are the leading problems. In order to explore and study the economic and efficient stimulation technology suitable for the coalbed methane wells, this paper studies mechanism and applicable conditions on increasing coalbed methane well production by the pre-positioned acid fracturing technology, by drawing on the successful experiences of conventional oil and gas reservoir with this technology. The coal samples of No.4-2 coal seam in Jiaoping Mining Area were collected to evaluate the effect of improving fracturing with acid preposition. The changes of mineral composition and content before and after the experiment were analyzed by macroscopic observation, X-ray diffraction and scanning electron microscope energy dispersive spectrometry. The results indicate that the pre-positioned acid achieved remarkable effect in improving the connectivity between pores and fractures of coal reservoir and reducing the damage of fracturing fluid to coal seam. The main stimulation mechanisms is acid dissolving plugging and interstitial materials, and the auxiliary stimulation mechanisms include forming irregular acid dissolution surface and promoting CH4 desorption by CO2 generated from acid salt reaction. Pre-acid fracturing technology is suitable for increasing production and reforming of coal seams with high mineral content and poor permeability, and near the well zone plug removal. The coal seams with rich acid-soluble fillings such as calcite, dolomite, siderite and hematite are the first choice. While for coal seams containing high clay minerals or for the purpose of eliminating pollution near well, the negative effect caused by secondary sedimentation should be mainly considered. It is suggested to adopt secondary sediment prevention measures, combined with anti-filtration technology, low density proppant, low damage/high viscosity fracturing fluid and other countermeasures to solve the problems of secondary damage after pre-acid acidification and large filtration loss of fracturing fluid in coal seam.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 4684K]

  • Effects of different combined pretreatments on biogenic methane production by anaerobic digestion of lignite

    ZHANG Huaiwen;YAO Yiqing;XIE Changwen;College of Mechanical and Electronic Engineering, Northwest A&F University;Northwest Research Center of Rural Renewable Energy Exploitation and Utilization of Ministry of Agriculture, Northwest A&F University;China North Industries Group Corporation Limited;

    It is crucial to choose efficient and practical pretreatment for increasing methane production. However, the treatment effect is often unsatisfactory through a single pretreatment method. In particular, it has an uncertain influence on the methane production of lignite with complex composition. In order to explore the effect of fermenting methane from lignite through the different joint pretreatment, with 1.00% HCl + 5.00% H_2O_2(group 1), 6.00% NaOH + 5.00% H_2O_2(group 2), 1.00% HCl + 10.00 g(group 3), 6.00% NaOH + 10.00 g(group 4), and 5.00% H_2O_2 + 10.00 g ligninase(group 5) as the experimental groups, and with the unpretreated coal samples(group 6) as the control group, the experiments of methane production through anaerobic fermentation were carried out under suitable strain sources and environmental conditions. The colorimetry, the gas chromatography-mass spectrometry and the scanning election microscopy were used to analyze the saccharide, the volatile fatty acid content and the degradation characteristics n the process of joint pretreatment of methane so as to reveal its influence mechanism. The results showed the following:(1) Different joint pretreatment increased methane yield similarly. The treatment of groups 4 and 5 with the cumulative methane production up to 20.36 mL/g and 8.83 mL/g respectively, proved to be more effective for the degradation of coal. Compared with the group 6, the methane production of the two groups has increased by 24.24 and 10.51 times respectively.(2) The COD removal rate of each experimental group was higher than that of the control group, and the pH variation was also relatively small.(3) At the beginning of the reaction, the lowest polysaccharide content belonged to group 3(0.37 μg/mL), whereas the highest number fell into group 6(2.15 μg/mL). The polysaccharide content of the two groups showed the same variation tendency(first decreasing and then increasing).(4) The reducing sugar contents of experimental groups 2, 3, and 5 remained at relatively high level on the whole. At the end of the reaction, the carbohydrate content of each gas-producing group was not zero.(5) All the joint pretreatments promoted the degradation of acetate and butyrate, and improved the carbon conversion rate. This research demonstrated the effectiveness of enhancing biogenic methane from coal through the joint pretreatment. It is hoped that the methods and the findings of this study may shed light on the industrialization applications of biogas production from coal.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 2746K]

  • Construction and application of “eight in one” closed-loop management and control mode of roof water disaster in coal mines

    LIU Qingbao;DING Xiang;FENG Jie;ZHANG Kun;China Coal Xi'an Design Engineering Co., Ltd.;China Coal Energy Research Institute Co., Ltd.;

    The prevention and control of coal mine water disaster is one of the key points of mine safety control, but the lack of comprehensive, systemetic, controllable technology management restricts the safe and efficient mining of coal resources. To guide the prevention and control of coal mine water disaster in a scientific and effective approach, taking the water disaster of coal mine roof as an example, using the theoretical system of system engineering and closed-loop management, this paper proposes a closed-loop management and control mode of roof water disasters, including stereoscopic probe, prediction, tracking exploration and discharge, subsection drainage, pre-mining evaluation, step drainage, monitoring and early warning, summary and optimization. The mode covers the management and control of the whole process of hydrogeological condition exploration, water disaster prediction, roof water drainage, as well as water disaster monitoring and early-warning, and forms a feedback path from the water disaster control effect to each stage of the water disaster prevention and control process. That means a closed loop of water disaster prevention and control was formed, which ensures that the water prevention and control work has scientific basis and can be regulated. This mode can be applied to roof water management and control under deep and complicated hydrogeological conditions, realizing the collaborative innovation of water control technology and management philosophy. It ensures the safe and efficient coal mining and provides reference for the roof water disaster management and control of coal mining under deep and complicated hydrogeological conditions.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 4576K]

  • Hazard source effect and location experiment of concealed water disaster in coal seam floor

    LI Panfeng;China Coal Geology Group Co., Ltd.;

    The hydro-hazards, water-conductive collapse columns and water inrush from faults, hidden in coal seam floor have caused many coal mines flooded in North China, bringing huge economic losses and safety threats to enterprises. In order to study the hydrogeological effects of the hydro-hazards and hazards locating technology, the sand trough simulation experiments in which the hazard sources are located inside the measurement area are conducted based on the hydrogeological conditions of Carboniferous-Permian coalfields in North China. The experiments show that, when the hydraulic field becomes stable, the effects of collapse columns are manifested by the concentric circles of the water head, temperature and solute concentration contours, with the hazards located in the maximum contour circles. Water head contours are denser in the downstream of the hazard source than those in the upstream, while the contours of temperature and solute concentration are denser in the upstream than those in the downstream. The effects caused by hidden faults present parallel contours, and the hazards are between the two maximum parallel lines. Similarly, the density of water head contours increases in the downstream region of the hazard source, while the density decreases in the upstream region. The temperature and concentration contours are reversed.. The areas constrained by the maximum contours of water temperature and solute concentration for the two hazard sources are much bigger than those constrained by water head contours, and the real size of the hazard sources. Both the sources lay closely to the zone with denser contours. The graphic method and flow-field fitting method to search hazards are proposed in this paper according to the experiments, both of which have an error of no more than 6 m. The technology for hydrogeological effect detection is suitable for detecting water head, temperature and solute concentration in the hidden water-conductive collapse columns or faults in the thin limestone aquifer of Taiyuan Formation presented by Ordovician karst water in Carboniferous-Permian Coalfields in North China, providing a basis for locating and controlling groundwater hazards.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 1916K]

  • Water inflow forecasting method of deep buried coal working face in northern Ordos Basin, China

    YANG Jian;WANG Hao;LIANG Xiangyang;HUANG Hao;Xi'an Research Institute Co.Ltd., China Coal Technology and Engineering Group Corp.;Shaanxi Key Laboratory of Preventing and Controlling for Coal Mine Water Hazard;

    The Mesozoic strata are mainly fluvial deposits in the Jurassic deep buried area of northern Ordos Basin, which are characterized by multi-cycle evolution in stages, resulting in alternate distribution of the aquifer-bearing seams on the coal seam roof. As the surface is mostly covered by Mu Us Desert, the rainfall infiltration recharge coefficient is large, and the water storage capacity of Quaternary loosen stratum is strong. The sufficient water-filling recharge source causes the water-rich aquifers on the roof of coal seams, among which the main water-filled aquifer is Qilizhen sandstone aquifer. In this study, Qilizhen sandstone aquifer is taken as the key layer, and generalized as a direct water-filled aquifer. When the water level in a confined well is lower than the roof of the aquifer, there would be no pressure flow zone in the aquifer near the well, forming a confined-phreatic well. Segmentation method is used to calculate the flow to well, including non-pressurized and confined water areas. However, in mining process of the working face, the water level in the well has been reduced to the floor of the coal seam. The traditional formula of confined-phreatic wells is based on the assumption that the diameter of wells is small(<1 m). In mining process of the working face, with the destruction of the key water-filled aquifer(Qilizhen sandstone aquifer) by the water-conducting fracture zone of overburden, a huge drainage well is formed on the roof of the whole coal seam(102-103 m). As the radius of the well increases with the goaf, the traditional formula is inapplicable. Based on the confined-phreatic well formula in Groundwater Dynamics, combined with the evolution process of the drain wells in the goaf during deep coal mining in northern Ordos Basin, a confined-phreatic well formula suitable for drain wells under mining disturbance in deep buried areas is established. Taking the first mining face of Hulusu Coal Mine as the research object, this paper uses the relevant hydrogeological parameters obtained from geological exploration and underground exposure to calculate the water inflow. The calculation results show that in the initial stage of working face mining, the actual water inflow is relatively small as the water flowing fracture zone has not communicated with Qilizhen sandstone aquifer due to the insufficient development of the zone. In the middle and later stage, the water flowing fracture zone develops to Qilizhen sandstone aquifer, and the calculated water inflow is close to the actual value, which proves that the formula for calculating the water inflow at the working face of deep-buried coal can accurately predict the water inflow in the mining process of the working face in the study area. The formula established in this study is applicable to the roof water hazard areas of Jurassic Coalfields in Western China, and provides scientific basis for water hazard prevention and control for safe mining of coal resources in deep-buried coalfields.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 1635K]

  • Development and application of borehole sealing technology for water-sand inrush from Ordovician limestone aquifer in coal mine

    LI Xiaolong;Xi'an Research Institute Co.Ltd., China Coal Technology and Engineering Group Corp.;College of Geology and Environment, Xi'an University of Science and Technology;Shaanxi Key Laboratory of Prevention and Control Technology for Coal Mine Water Hazard;

    The technology for surface sand filling and underground grouting is adopted to control the karst collapse column of Ordovician limestone in Sangshuping Coal Mine. However, there are serious water-sand inrushes in three conventional inspection boreholes, so it is of great difficulty to seal them. Putting wooden wedges and reverse wire packers into the boreholes all fail. In order to solve this problem, the grouting sealing technology with pressure replacement is proposed in this paper. Firstly, water larger than the casing pipe volume is injected into the borehole to ensure a clear borehole and to avoid sand filling into the casing pipe, resulting in the sealing depth not reaching the stable rock layer below the casing. After that, a lower pumping volume is adopted to repeatedly inject cement slurry larger than the casing volume into the borehole. Finally, after the cement slurry is solidified, a small diameter bit is used to drill outside the casing to check the sealing quality of the large diameter boreholes. Three conventional inspection boreholes are successfully sealed. In the engineering practice, it is found that the water-cement ratio of the cement slurry for early grouting borehole sealing should be 1︰1, and the single setting time should be 3 to 4 days. Prolonging the cement setting time can improve the quality of borehole sealing. This borehole sealing technology is applicable to underground narrow space operation, which can prevent water-sand inrushes from the orifice, ensure the sealing quality and personnel safety, and provide a technical reference for sealing similar water-sand inrushes.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 1878K]

  • Prediction of the height of water flowing fractured zone based on PSO-BP neural network

    LOU Gaozhong;TAN Yi;School of Civil and Architectural Engineering, Anyang Institute of Technology;School of Energy Science and Engineering, Henan Polytechnic University;State Collaborative Innovation Center of Coal Work Safety and Clean-Efficiency Utilization;

    The height of water flowing fractured zone is the theoretical basis and key parameter of water-preserved mining in western mining areas of China. In recent years, BP neural network has been widely used to predict the height of water flowing fracture zone, but it has such defects as slow convergence speed and a tendency to fall into local minimum. In order to improve the prediction accuracy of the height of water flowing fractured zone, the weight values and thresholds of BP neural network were optimized by particle swarm optimization(PSO), and a prediction model was established based on PSO-BP neural network. Mining thickness, mining depth, inclined length of working face, dip angle of coal seam, overburden structural characteristics were chosen as the main influential factors of the height of water flowing fractured zone, and 22 measured data of the height of water flowing fractured zone were selected to train PSO-BP neural network. Then the trained PSO-BP neural network was used to predict two test samples, and the results were compared with the actual values, and with the predicting results of BP neural network prediction model and empirical formulas. The research results show that the average relative error of PSO-BP neural network prediction model is 1.55%, and that of BP neural network prediction model and the minimum relative error of empirical formulas are 4.8% and 9.4% respectively. The prediction accuracy of PSO-BP neural network is obviously significantly better than BP neural network and empirical formulas, and the variation of its absolute error and relative error are relatively stable, so PSO-BP neural network can effectively predict the height of water flowing fractured zone.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 1519K]

  • Hydraulic connection of aquifers in Barapukuria Coal Mine, Bangladesh

    YU Bo;WANG Hao;LIU Feng;LIU Ji;WANG Qiangmin;SHANG Hongbo;China Coal Research Institute;Xi'an Research Institute Co.Ltd., China Coal Technology and Engineering Group Corp.;Shaanxi Key Laboratory of Prevention and Control Technology for Coal Mine Water Hazard;

    In order to further identify the hydrogeological characteristics and hydraulic connection between aquifers of Barapukuria Coal Mine in Bangladesh, and provide a theoretical basis for the prevention and control of mine water disasters, this paper analyzes the hydraulic connection between Neogene UDT aquifer, Ⅵ coal roof aquifer and Ⅵ coal aquifer based on 19 sets of water quality test data, combined with the spatial distribution characteristics of aquifers, field structure characteristics, water level duration curve, hydrochemical type and hydrogen and oxygen isotope characteristics. The results show that the LDT aquifer in the northern part of the well field is partially missing, which provides conditions for the water supply of the UDT aquifer to the coal measure strata. The roof aquifer of coal seam in the north wing of the mine field is closely related to the water level change law of UDT aquifer, and the water level elevation is similar, which preliminarily proves that there is a hydraulic connection between the two. The water of each aquifer is HCO3-Ca·Na·Mg type, which is low salinity water, further proving that there is a hydraulic cycle between each aquifer. Cluster analysis results show that water quality of each aquifer has a certain degree of correlation, and the degree of hydraulic connection between aquifers is deduced. Hydrogen(δD)oxygen(δ18O) isotopic characteristics are distributed near the global atmospheric precipitation line, indicating that atmospheric precipitation is the common recharge source of aquifers. The research results can guide the prevention and control of water disaster in Ⅵ coal seam mining of Balapukuliya Coal Mine in Bangladesh.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 2543K]

  • Regularity and control of overburden and surface fractures in shallow-contiguous seams

    CAO Jian;HUANG Qingxiang;Institute of Mining and Coal, Inner Mongolia University of Science and Technology;School of Energy, Xi'an University of Science and Technology;

    The Shenfu-Dongsheng Coalfield in western country mainly occurs in shallow close multi-seam, and the thick loose layers on the overlying rock are distributed in a wide range. Mining in shallow-contiguous seams results in serious development of overlying rock and surface fractures, which aggravates the deterioration of the originally fragile ecological environment. In order to explore the mining-induced overburden and surface fractures development characteristics in shallow shallow-contiguous seams, and obtain its control method. Taking No.1~(-2) seam and No.2~(-2) seam mining in Ningtiaota Coal Mine as background, this paper obtains the development characteristics of fractures in shallow single seam mining and repeated mining through in-site statistic analysis, physical simulation and fractal theory. Besides, the control effect of pillar staggered distance to mining-induced fractures is revealed. The results show that the mining-induced surface fractures can be divided into two types, one is dynamic fractures which are parallel to the working face, and another is mining boundary surface fractures which contain open-off boundary surface fractures and pillar boundary surface fractures. The dynamic fractures can realize self-repairing after mining, while the mining boundary surface fractures can not realize self-repairing. After lower seam mining, the pillar boundary overburden and surface fractures development seriously, which are closely related to pillar staggered distance. After No.1~(-2) seam mining, the bedrock caving angle is 60°, and the soil layer caving angle is 65°, the width of surface fracture along coal pillar, 0.26 m. After lower No.2~(-2) seam mining, when the pillars are aligned, with pillar staggered distance of 20 m and 40 m, the width of overburden fractures are 0.81 m, 0.45 m and 0.22 m respectively, and the width of surface fractures are 0.65 m, 0.30 m and 0.12 m. Through determining the reasonable pillar staggered distance, development of the overburden and surface fractures can be controlled effectively. Finally, the reasonable pillar staggered distance should be greater than 40 m in No.1~(-2) and No.2~(-2) seams mining in Ningtiaota Coal Mine.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 10665K]

  • Improvement of shear strength and anti-disintegration performance of compacted loess

    ZHU Yanbo;LI Hongfei;JU Zhitong;LAN Hengxing;LIU Zhenqian;HAN Yutao;College of Geological Engineering and Geomatics, Chang'an University;

    In order to improve the mechanical properties and water stability of loess in land reclamation of gully-hill areas on the Loess Plateau, an experimental study on the strength and disintegration of loess improved by lime, Nano-SiO_2, polypropylene fiber and guar gum were carried out to compare and analyze their comprehensive improvement effect. The results show that the improvement effect of a single material is obvious in a certain aspect. For example, lime and Nano-SiO_2 can significantly improve the shear strength of loess by 36.3%-250.6% and 9.0%-99.7% respectively. However, their improvement effect is limited in disintegration resistance of loess. The two materials only delay the disintegration process of the sample, and have no effect on the disintegration amount. Polypropylene fiber and guar gum can significantly improve the disintegration resistance of loess. For example, guar gum can reduce the final disintegration rate of loess to less than 11.5%, and the final disintegration rate of polypropylene fiber improved soil is 11.2%-51.9% lower than that of unmodified soil. But the two materials are not effective in improving the loess strength, with the increase in strength ranging from 1.5%-22.9% and 2.8%-15.6% respectively. The composite improved materials can overcome the shortcomings of a single material in the improvement of the strength and disintegration resistance of the loess, improving the comprehensive performance of loess. The results show that 9% lime mixed with 0.6% polypropylene fiber and 2% Nano-SiO_2 mixed with 0.6% polypropylene fiber have the best improvement effect, increasing the shear strength of modified loess by 109.8% and 68.3% respectively and reducing its disintegration rate by 61.3% and 49.8% respectively.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 2971K]

  • Numerical study of Mabian landslide kinematics and impact intensity

    CHEN Xing;ZHAO Zhou;WEI Jiangbo;XU Chong;College of Geology and Environment, Xi'an University of Science and Technology;National Institute of Natural Hazards, Ministry of Emergency Management of China;

    study of landslide kinematics and impact intensity is of great significance for quantitative assessment of landslide risk. In this paper, the basic characteristics of Mabian landslide(occurred on May 5, 2018) in Leshan City, Sichuan Province were investigated. The support vector machine(SVM) model and particle flow method(PFC) were used to calibrate the meso-strength parameters of landslide rock and soil. Combined with the UAV data, the high-precision DEM of landslide area was generated. On this basis, the three-dimensional PFC model of Mabian landslide was reconstructed and simulated. The movement, accumulation and impact process of landslide are studied. The results show that: the movement of Mabian landslide lasted 32 seconds, main sliding time is 16 seconds, and the peak velocity is 10.2 m/s after 5 seconds; the movement trace of rock and soil in the middle and rear of the landslide is linear, while the middle and front of the landslide is in a diffusion state, and finally in a fan-shaped accumulation; the impact force of the landslide at the slope foot can reach 1.5×109 N, and the impact force presents the exponential attenuation characteristics with the increase of the movement distance. The results are basically consistent with the actual video interpretation results of landslide movement and accumulation, and the related research methods could provide references for quantitative risk assessment of landslide.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 11592K]

  • Study on the strength and microstructure of loess under freeze-thaw based on temperature path

    LONG Jianhui;ZHANG Lingling;XING Xianli;GUO Xiaojuan;College of Mining Engineering, Taiyuan University of Technology;

    In seasonal frozen soil regions, the essence of loess landslides induced by freeze-thaw cycles is the deterioration of the physical and mechanical properties of loess. It is necessary to find out the influence of temperature and water migration on the strength of loess under freeze-thaw cycles and its mechanism. Therefore, a new freeze-thaw cycle method is adopted, which is carried out based on the temperature path that the soil goes through each year, to study the law of the shear strength of the soil under the action of the freeze-thaw cycle with dynamic temperature changes and the influence of repeated freeze-thaw cycles on soil cohesion, internal friction angle and microstructure. The test results show that during a freeze-thaw cycle, the soil strength is negatively correlated with temperature, and low temperature has a greater impact on the soil strength. As the freeze-thaw cycles increase, the cohesion of the soil decreases exponentially, and the internal friction angle has little change. The microscopic test shows that with the increase of freeze-thaw cycles, the large particles in the soil are broken and the pores increase, indicating that the particles tend to be uniform, and the medium-sized(5-10 mm) pores account for the largest proportion. This study simulates the temperature change process of soil, providing a reference for the prevention and control of seasonal freeze-thaw loess landslides in this area.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 2832K]

  • Characteristics analysis of the geothermal water in Heshan Coalfield based on hydrogeochemistry

    ZHAO Guanhua;Guangxi Administration of Coal Geology, China National Administration of Coal Geology;No.150 Exploration Team of Guangxi Coal Geology;

    In order to develop geothermal water resources in Heshan Coalfield, Guangxi Provence, the temperature of geothermal reservoir was estimated by quartz temperature scale method based on hydrogeochemistry, and the circulation depth of geothermal water was speculated to study the occurrence law of geothermal water. The results show that the recharge, runoff and discharge of underground hot water in Heshan Coalfield are controlled by karst structure, which is mainly along and across the stratum. It receives infiltration recharge from atmospheric precipitation and the water quality is HCO3-Ca·Mg type. By quartz geothermometers without steam loss, the thermal reservoir temperature is estimated to be about 80℃ and three types of water, namely, shallow groundwater, mixed water of shallow groundwater and deep groundwater circulating water and deep groundwater circulating water. Taking No.6 borehole data in the mine field as an example, the temperature of the thermal reservoir is 63.44℃ to 79.41℃, and the circulation depth is 2 541-2 704 m. The difference between the thermal reservoir temperature and the actual buried depth is small and the estimation result is highly reliable. The difference from the actual burial depth is small, indicating the high reliability of the estimation results. At the depth of 1 400 m and around, it is expected to explore geothermal water about 50℃. The metasilicic acid and temperature of underground hot water in Heshan coal field meet the medical requirements. No.3 and No.4 coal seams have low thermal conductivity and small porosity, which are good caprock for thermal reservoir. The lower member of Heshan Formation and Maokou Formation in the floor of No.4 coal seam are developed with solution fissures, which are good hot water reservoirs. The research results have certain exploration significance for the development and utilization prospect prediction of geothermal resources in coalfields.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 1868K]

  • Temporal and spatial evolution of surface thermal environment in Huainan Mining Area in the last decade

    FANG Liangcheng;CHEN Yongchun;AN Shikai;XU Yanfei;ZHAO Yuejiao;WANG Ning;LI Zhihui;ZHAO Ping;Huainan Mining Industry(Group) Co., Ltd.;Ping'an Coal Mining Engineering Technology Research Institute Co., Ltd.;School of Resources and Environmental Engineering,Hefei University of Technology;

    Land surface temperature(LST) is an important parameter to describe land surface processes and reflect land surface characteristics. It is of great significance to study the spatio-temporal evolution characteristics of surface temperature in the mining area in the last decade for understanding the influence of coal mining activities on the ecological environment. Huainan Mining Area is a typical high-phreatic mining area in eastern China. In order to explore the relationship between spatio-temporal heterogeneity of surface temperature and mining disturbance in this area, surface temperature inversion and underlying surface information extraction are carried out by using five periods of Landsat images from 2008 to 2018. Combined with the calculation of thermal landscape pattern index and urban heat island proportion index, the spatial and temporal evolution characteristics of surface thermal environment in Huainan Mining Area are analyzed. The results show that the surface temperature distribution pattern and its change are closely related to the underlying surface structure and its change in Huainan Mining Area. From 2008 to 2018, this mining area is mainly the middle temperature area, followed by the sub-low temperature and sub-high temperature area, with the area and proportion of the high temperature and low temperatures area being relatively low. Due to the construction of towns and mines, as well as the accumulation of coal gangue and mining subsidence water from coal mining, the area of construction land and water area is constantly increasing, and the vegetation area is constantly decreasing. Correspondingly, the low, sub-high and high temperature zones are increasing, and the middle and sub-low temperature zones are decreasing. On the whole, the urban heat island proportion index and the heat island effect are increasing. In the low temperature region, the patch fragmentation and complexity are decreasing and the dominance is increasing. The changes of patch fragmentation and complexity, landscape agglomeration and connectivity, diversity and evenness at other temperatures are divided into three stages: 2008-2013, 2013-2015 and 2015-2018. In 2013-2015, the intensity of human disturbance was higher. And the patch fragmentation and complexity increased, so did the landscape agglomeration and connectivity. The diversity and uniformity were reduced. The research results provide a scientific basis for the restoration and management of ecological environment and urban industrial planning in Huainan Mining Area.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 2953K]

  • Exploration method of underground geological anomaly and its application based on directional drilling

    FANG Jun;Xi'an Research Institute Co.Ltd., China Coal Technology and Engineering Group Corp.;

    The geological anomaly is the main hidden cause of mine disasters, and underground drilling engineering is an important technical means for exploration, verification and control of geological anomaly. In view of the shortcomings such as short distance, low accuracy and blind area of conventional drilling exploration, the exploration scheme of geological anomaly by underground directional drilling was introduced, and the identification characteristics such as spatial form, lithology and drilling were summarized. The trajectory layout principle of directional borehole was given, and the spatial calculation and positioning method of geological anomaly based on directional borehole was obtained. In addition, the influencing factors and solutions for the exploration precision of directional borehole were analyzed from four aspects: borehole layout spacing, borehole trajectory measurement and control accuracy, stratum and geological anomaly recognition accuracy, and geological anomaly development scale. The tests were carried out in Zhaogu No.2 Coal Mine and Meihuajing Coal Mine, coal seam stability of roadway strip is explored by main hole and branch hole with the exploration distance over 621 m. Water filling source in working face is explored by directional drilling group, with maximum water yield of single hole of 10.2 m3/h, then the water is discharged. The tests results show that the underground directional drilling has realized the accurate positioning of geological anomaly with the advantages of high exploration accuracy, long distance and short cycle, which provides technical support for disaster and accident prevention.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 3205K]

  • Introductions and applications of a self-locking wire-line coring system with a water-shielding bit and a circlip-shielded core barrel

    LIAO Yuansu;HU Qifeng;No.2 Geological Party of Jiangxi Nonferrous Metals Geological Exploration Bureau;

    The great progresses have been made in the research of wire-line coring system used in complex formations at home and abroad in recent years. However, the key technology problems that affect coring quality and drilling efficiency have not been well solved, such as the resistence caused by core clamping components when the core gets into the core-barrel and the mud pad at the bottom of jet bits. The common S95 wire-line coring system is selected as the example in our study. Adding stainless steel liner with 0.7 millimetres thickness in the inner core barrel separates circlip components. The methods of increasing the number of water holes at the bottom of jet bit and widening the drainage channels have been adopted in these tests. There are two kinds of core lifters alternatives, one is hairpin spring and the other is clip spring. A new type of wire-line coring system with three-ply core barrels has been developed for drilling in complex formation, which has the advantages of water shielding, circlip-shield and automatic core locking. This new kind of wire-line coring system with hairpin core lifter is tested in the broken formations with strong water sensitivity. The average roundtrip footage is 1.13 m and the core recovery is 94.48%, which is increased by more than 50 percent comparing with the core recovery rate of similar formation nearby. The test has been carried out in the muddy formation with developmental fractures by using the circlip core lifter. The core cutting is as reliable as the circlip used in the ordinary wire-line coring system. The tests show that the coring technology by using liner to separate the core clamping components is feasible, which solves the obstruction of the core clamping components to the soft and loose core, and which is effective to protect the core in original state. The water-shielding jet bit improves the flush effect at the bottom of the bit and reduces the damage of the mud pad on the drilling speed by calculating the reasonable drilling pump volume and the effective number of water holes. This new kind of wire-line coring system is easy to operate and is cheap to use. It is expected to be popular and applied in the current wire-line coring drilling crew in China, which is going to have a strong universality and wide application.

    2021 04 v.49;No.286 [Abstract][OnlineView][Download 4942K]