矿业科学学报

3D seismic prediction of low rank coalbed methane enrichment area in the southern margin of Junggar Basin

Xu Maoxuan, Du Wenfeng, He Yunlan, Yang Feng

2023, 8(5): 593-599. doi: 10.19606/j.cnki.jmst.2023.05.001

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Abstract:
In order to investigate and evaluate the potential of CBM Resources in the southern margin of the Junggar Basin, this study conducted 3D seismic exploration in the Hutubi block. The seismic acquisition design tailors to wide azimuth, small receiver distance and high folds, the seismic geometry design includes 16 lines, 6 shots and 160 receivers. Given the serious static problems in mountainous terrain and imaging accuracy of steep dip coal seam in the seismic data processing, a high-resolution 3D seismic data processing flow is therefore established to meet the prediction requirement of coalbed methane enrichment area. The dividing principle of the coalbed methane enrichment area and the classification model of favorable area are proposed in line with the main seismic geological factors affecting coalbed methane enrichment, such as the coal seam depth, the faults characteristics, the coal seam thickness, the coal seam roof lithology and the coal seam gas content. Based on 3D seismic data, this study combined seismic data interpretation and seismic attribute analysis to obtain data on coal seam thickness, coal seam roof lithology, and coal seam gas content by using seismic lithology inversion results. Under the constraints of logging, this study made predictions of the B4 coalbed methane enrichment area in the research area, and put forward suggestions for deploying coal bed gas production borehole.

Controlling factors of reservoir in platform margin zone of Lianglitage Formation in Katake Uplift, Tarim Basin

Sha Xuguang, Jiang Zhongzheng, Li Yulan, Sun Zhipeng

2023, 8(5): 600-612. doi: 10.19606/j.cnki.jmst.2023.05.002

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Abstract:
In order to study the different types and formation causes of reservoirs in the marginal zone of the Lianglitage Formation in the Katake Uplift, this study analyzed the marginal zone sedimentary reservoir characteristics, and their main controlling factors by utilizing a plethora of data sources including thin sections, core samples, FMI logging, and seismic data. The results show that the high-energy reef-flat facies of the Lianglitage Formation are distributed in a strip along the No.1 fault zone, exhibiting perplexing distribution patterns. The marginal zone also displays varying sedimentation patterns from east to west, which can be divided into three types of margin facies: fault-controlled narrow and steep, sedimentary steep slope, and sedimentary wide-gentle. Corresponding to these are three types of reservoirs: fracture-pore type, fracture-pore and pore type, and low-permeability fracture type. There are differences in the contribution of three constructive diagenetic processes, including quasi-syngenetic karstification, shallow-burial fresh water dissolution, and structural damage, to the formation of reservoirs in different locations of the marginal zone. The main controlling factors for the formation of the fault-controlled narrow and steep margin facies reef-flat superimposed bodies, karstification period faults, and late-stage fault activity. The sedimentary steep slope margin facies are found to be reef-flat superimposed bodies and northeast-trending strike-slip faults. The sedimentary wide-gentle margin facies are found to be karstification period fault activity and late-stage strike-slip faults. These results offer evidences for the exploration of marine carbonate reservoirs.

Prediction of coal-gas compound dynamic disaster based on convolutional neural network

Wang Kai, Li Kangnan, Du Feng, Zhang Xiang, Wang Yanhai, Zhou Jiaxu

2023, 8(5): 613-622. doi: 10.19606/j.cnki.jmst.2023.05.003

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Abstract:
As deep mining becomes prevalent in China's coal mining industry, coal-gas compound dynamic disasters pose increasing threat to the safety production of coal mines. This paper adopts the field data of Pingmei No. 8 coal mine for analysis, with the attempt to predict coal-gas compound dynamic disaster through convolutional neural network. Following the routine of the big data processing, we first employed Box-plot analysis and multiple interpolation method(MI)to clean the data. Combined with grey relation analysis(GRA), we established a coal-gas compound dynamic disaster index system. Then, principal component analysis(PCA)is used for dimensionality reduction of the data. Combined with the convolution neural network(CNN)in deep learning, we established the coal-gas compound dynamic disaster prediction model based on BMGP-CNN. The field data is used to compare and verify this model with BP, random forest(RF), support vector machine(SVM)and artificial neural network(ANN). It is found that BMGP-CNN model yields prediction results with satisfactory accuracy and quick convergence. The results offer implications for the prediction and prevention of coal-gas compound dynamic disasters.

Analysis on roof sag of pre-driven recovery room based on energy calculation

Wang Bonan, Gu Shuancheng, Li Jun

2023, 8(5): 623-632. doi: 10.19606/j.cnki.jmst.2023.05.004

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Abstract:
The fully mechanized mining face adopting pre-driven recovery room is prone to large roof deformation at the final mining stage, which will lead to support crushing accidents. Based on the three main roof failure forms after longwall face entered recovery room, this paper established different mechanical models for roof sag of the recovery room. By analyzing energy release and work process in roof deformation, this paper obtained the immediate roof sag of recovery room under different main roof failure forms. Taking the large roof deformation and support crushing accident of recovery room in the N14201 longwall face of Zhangjiamao Coal Mine as example for analysis, this paper analyzed the influencing factors of the models and found that the main roof break position, the thickness of key block and its overlying strata, the rotation angle of key block and the supporting intensity have significant impact on the roof sag of recovery room. The research results confirmed that the reason for the support crushing accident in N14201 longwall face of Zhangjiamao Coal Mine: the main roof is broken within 4~6 m above the protective coal pillar, and the main key stratum is broken and unstable due to the mining of upper 3^-1 coal seam.

The triaxial compressive mechanical properties and failure characteristics of backfill-rock combined bodies with different interface angles

Xu Wenbin, Chen Wei

2023, 8(5): 633-641. doi: 10.19606/j.cnki.jmst.2023.05.005

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Abstract:
This study proposes to explore the effect of interface angles β on the triaxial mechanical properties of backfill and surrounding rock combined bodies(backfill-rock combined bodies)by conducting a triaxial compression experiment of backfill-rock combined bodies with interface angles β of 0°, 15°, 30°, 45° and 60°. This paper compared and analyzed the mechanical properties, failure characteristics and strength evolution patterns of the combined bodies with different interface angles. The experimental results show that: When β≤30°, the stress-strain curve of the combined bodies can be divided into four stages: pore compaction, elastic deformation, plastic deformation and failure development. Its failure characteristics are mainly compression shear failure of the backfill. With the increase of the interface angles, the combined bodies stress drops steeply after reaching the peak strength, without significant plastic deformation or failure development stage. Its failure characteristics gradually change from compression shear failure inside the backfill to sliding failure along the interface. The peak strength of the combined bodies first increases and then decreases with the increase of the interface angles, and peak strength reaches a maximum value when β=30°. Based on the theory of single weak plane, the interface critical angles for sliding failure of the combined bodies is 57° to 68°. Where β=60°, the combined bodies occurred sliding failure surface along the interface, and the results from theoretical calculation confirm the experimental results.

Numerical simulation study of rock breaking mechanism by high voltage electric pulse

Liu Weiji, Zhang Youjian, Zhu Xiaohua, Feng Wenrong

2023, 8(5): 642-653. doi: 10.19606/j.cnki.jmst.2023.05.006

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Abstract:
High-voltage electric pulse(HVEP)drilling has become a new and efficient rock breaking method, which is also the research focus in the field of drilling speed increase. To probe into rock breaking mechanism of high voltage electric pulse, this study establishes a two-dimensional numerical model of multi-physical field coupling electric breakdown of single pair of electrodes. The model reproduces the generation of plasma channels in homogeneous red sandstone from the coupling of current field, electric breakdown field and circuit field. This paper analyzes the effect of electrode pair angle, voltage and electrode spacing on rock electrical breakdown(that is, the formation of plasma channel in rock). The model includes the circuit structure parameters of pulse tool, the occurrence and development of electrical breakdown, and the relationship between electrical breakdown intensity and time. Results indicate that the plasma channel begins to sprout from the partial area near the top of the discharge electrode and develops towards the partial weak dielectric strength. With the voltage value of loading pulse increasing gradually, the time of electrical breakdown decreases gradually; comparatively, the equivalent failure volume of rock model increases gradually, and there is a positive correlation between them. On the precondition that the rock can be electrically broken, increasing the electrode spacing can improve the rock breaking efficiency of high voltage electric pulse. The equivalent failure volume of rock shows significant fluctuations during the gradual increase of electrode inclination angle of discharge electrode, and its extreme value mostly appears in the range of electrode inclination angle of 35°~ 55°. To further promote the industrial application of high-voltage electric pulse rock breaking, this paper proposes a three-dimensional numerical model of multi-physical field coupling dynamic electric breakdown of red sandstone based on two-dimensional model, reproducing the appearance of the fracture crater in the rock during the rock breaking process with electrode bit. At the same time, the self-designed coaxial electrode bit is selected for experiments of electric breakdown, and the laboratory experimental results of electric breakdown confirm the simulation experimental results.

A new method for nondestructive testing of mudstone moisture migration process by nuclear magnetic resonance

Li Dongyang, Zhou Xingchen, Liu Bo, Zhang Qianli, Liu Jingyu

2023, 8(5): 654-662. doi: 10.19606/j.cnki.jmst.2023.05.007

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Abstract:
When traditional methods are used to test soil moisture migration of rock and soil, the undisturbed soil is often broken and reshaped, which will change the structure of rock and soil and affect the authenticity of the test results. In order to solve this problem, a new testing method is proposed by using the characteristics of nuclear magnetic resonance(NMR)technology for nondestructive measurement of moisture in materials. Firstly, the calibration experiment was carried out to establish a functional relationship between the NMR signal amplitude and the position of a soil sample with unit water mass in a non-uniform magnetic field of 0~0.05 T. Second, a one-dimensional infiltration experiment and NMR test were conducted to record the infiltration time, water mass increase and NMR signal under different test positions. Then, using the functional relationship obtained in the calibration experiment, approximations of the moisture mass and its spatial distribution in the sample were obtained by comparing the theoretical signal and the measured signals. Finally, the mudstone sample was cut into several parts to perform a verification experiment by oven drying, and the results showed that the error in water content was 4.05 % or less.

Fractal model of shear-induced rough fracture flow by cross-scale description of its geometry

Xue Dongjie, Hou Mengdong, Cheng Jianchao, Jia Zhen, Liu Yintong, Xin Cui, Xu Yanzhuo, Wang Lujun

2023, 8(5): 663-676. doi: 10.19606/j.cnki.jmst.2023.05.008

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Abstract:
The Beishan area in Gansu province is the main pre-selected site for deep geological disposal of high-level radioactive waste, it therefore bears implications for the study of fracture seepage characteristics of granite caused by shear failure. This paper investigated the fractal modeling of the geometric and seepage characteristics of granite fracture sections under shear conditions, with the aim to explore the effect of the geometric characteristics of multi-scale rough fractures on the evolution of nonlinear seepage field in Beishan granite. Results show that the roughness height and aperture of rough fractures have complete self-similarity in the process of model scale change, whose distribution are always consistent in the process of spatial scale change. The seepage velocity field, gradient field and divergence field only demonstrate the continuation of local characteristics, in particular, the corresponding quantity fields at different scales are subject to normal distribution. As the observation scale increases, the spatial fluctuation in the field gradually decreases, the sharp mutations in the three fields gradually disappear and are smoothed. This indicates that the larger the observation scale, the greater the probability that the seepage of rough fracture is misjudged as the seepage of parallel plate, therefore the seepage characteristics of rough section would be more accurately described by taking the geometric scale into account.

Research on the influence of light intensity on digital image correlation measurement accuracy in the testing of concrete

Yang Denghui, Huang Chen, Fan Ping, Lü Jian, Wei Peng, Yang Liyun

2023, 8(5): 677-687. doi: 10.19606/j.cnki.jmst.2023.05.009

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Abstract:
When the surface strain field of concrete structure is measured by digital image correlation(DIC)technology under complex light conditions, the decorrelation effect of the pattern will be caused by the variation in light intensity. For this problem, the optimal light intensity suitable for DIC calculating and analyzing is studied, and the influence of light intensity variation on the measurement accuracy and calculation efficiency of DIC is explored by the traditional 2D-DIC measurement system. The experimental result shows that the average gray level of 190 is the optimal light intensity. The picture is used as the reference image at the optimal light intensity. The strain error increases exponentially when the light intensity increases, and the strain error increases linearly when the light intensity decreases. The computation time and the matching rate of calculation points are insensitive to the slight range fluctuation of light intensity, while the computation time of DIC will increase 1 to 3 times, and about 25 % of calculation points will match failed because of the extreme variation of light intensity. The accuracy of experimental results is verified by Combining them with the image quality assessment index. In order to get high-quality images, the green band-pass filter imaging system is established in this paper. It can stabilize the image's brightness and contrast when the external light varies seriously. The strain error and calculation efficiency are all close to the optimal light intensity when external ambient light changes seriously. Compared with the traditional 2D-DIC measurement system, The green band-pass filter imaging system can be better applied to measure in the outdoor environment.

BP neural network prediction model of floor failure depth in North China coalfield

Xing Chaorui, Li Lei, Wang Libin, Liu Yulong

2023, 8(5): 688-694. doi: 10.19606/j.cnki.jmst.2023.05.010

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Abstract:
North China coalfields are seriously affected by bottom aquifers. In order to accurately the depth of damage at the working face, this paper combined actual measurement with neural network prediction model in analysis. Firstly, DC method with special electrode cable is employed to observe the bottom plate damage depth of 15091 in the comprehensive mining face of Jiulishan mine; secondly, based on large-scale data, genetic algorithm is applied to optimize BP neural network. The prediction model of bottom plate damage depth is set up by optimizing parameters. The mean square error of the prediction model was 0.011, the average percentage error was 5.983 %, and the prediction error based on prediction set was below 10 %. These results indicate that the model can be used for predicting the bottom slab damage depth. Finally, the prediction model was used to analyze the effect of mining thickness and top cutting pressure relief on the depth of damage of the working face floor. Results show that under stratified mining, the depth of damage of the bottom slab is reduced by 77.84 % under cut top pressure relief than uncut top pressure relief; under integrated mining, the depth of damage of the bottom slab is reduced by 59.17 % under cut top pressure relief than uncut top pressure relief; and the effect of mining thickness on the depth of damage of the bottom slab is positively correlated.

Study on parameters optimization of unmanned aerial vehicle and ecological remediation of buckwheat stained with DSE

Bi Yinli, Zhang Longjie, Bai Xuerui

2023, 8(5): 695-703. doi: 10.19606/j.cnki.jmst.2023.05.011

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Abstract:
The complex and changeable terrain, subsidence topography and land fissures of mining area in northern Shaanxi make it difficult for mechanical restoration of ecological environment. Based on M8A20A eight-rotor UAV platform, this study investigated the effects of the optimal parameters on aerial seeding, and the ecological restoration of buckwheat by DSE infection and aerial seeding. Results showed that the flight parameters had significant effects on the available width and uniformity of buckwheat seeds. The optimal parameters of aerial seeding includehigh speed, flight height of 2.5 m, flight speed of 4.0 m/s and operating distance of 6.0 m. Compared with the control group, plant height, ground diameter and above-ground biomass of the buckwheat infected with Dark Septate Endophytes(DSE)increased by 11%、25%、49%, respectively. In addition, the DSE infection could increase the SPADR and photosynthetic rate of buckwheat, promoting the root to grow and improving the yield and quality of buckwheat. This UAV aerial seeding combined with growth promotion of DSE infection could offer reference for ecological restoration of complex terrain in the western mining areas.

Study on ecological quality evaluation of mining area based on remote sensing green index—Taking Yima mining area as an example

Peng Jinyan, Wang Shidong, Pan Jinyin

2023, 8(5): 704-713. doi: 10.19606/j.cnki.jmst.2023.05.012

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Abstract:
Mining and development of mining area poses significant impact on regional ecological quality. This study proposed a new remote sensing green index(RSGI)model more tailored for evaluating the ecological quality in the mining area by taking the Yima mining area as an example for analysis. The model was first applied to the ecological quality evaluation of the Yima mining area. Based on Landsat remote sensing images in 1991, 2011 and 2021, ENVI5.3 software was used to supervise the classification of remote sensing images and calculate the green index of remote sensing. The ecological quality of Yima Mining area in the past 30 years was evaluated from the perspective of time and space. Pearson correlation coefficient is used to analyze the correlation between ecological quality and ecological factors in mining area. Results showed that: ① From 1991 to 2021, the overall ecological quality was satisfactory, with the green space area reached more than 80 %. ② In 1991, 2011 and 2021, the RSGI values of Yima mining area were 0.90, 0.91 and 0.89, respectively. The ecological quality of Yima mining area showed initial increase and then a slow decline, and the overall ecological quality exhibits in a downward trend. ③ From 1991 to 2021, there were significant changes of eco-quality in towns and mining areas, with a downward trend observed in most regions. This indicates that the changes of eco-quality in Yima mining area is closely related to mining activities. ④ Areas with high remote sensing green index demonstrate larger proportion of cultivated land, forest land and grassland, and smaller proportion of buildings and impervious surface area. There is a significant correlation between remote sensing green index and other indexes. The research results provide reference for eco-environmental restoration and green mine construction in Yima mining area.

Suitability evaluation of underground space development in coal mining cities in Henan province

Shi Beining, Xiang Zhonglin

2023, 8(5): 714-724. doi: 10.19606/j.cnki.jmst.2023.05.013

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This study proposes to evaluate the suitability of underground space development and utilization in coal mining cities, with the aim to promote reasonable utilization of underground space left behind after the closure of coal mines and avoid resource waste. Specifically, it takes typical coal mining cities in Henan province(Zhengzhou, Pingdingshan, Sanmenxia, and Luoyang)with spatial resources exceeding 10000 m³ as examples for analysis, with the Analytic Hierarchy Process adopted to establish an evaluation system for the suitability of underground space development and utilization in coal mining cities. The evaluation system includes five major categories: safety factor, stability factor, spatial resource quantity, spatial environmental factor, and economic factor, coupled with 20 corresponding secondary indicators. Based on the aforementioned evaluation system and expert scoring method, the suitability for development of four typical coal mining cities in Henan province was ranked in a descending order of scores: Zhengzhou scored 25.59, Pingdingshan 23.21, Sanmenxia 8.86, and Luoyang 8.56. By conducting cross comparisons between cities, this study provides reference for the suitability evaluation of underground space in various coal mining cities both within Henan province and across the country.

Effect of calcination process and calcium-silica ratio on the composition and properties of hydraulic lime

Zhang Pengjuan, Song Xuefeng

2023, 8(5): 725-732. doi: 10.19606/j.cnki.jmst.2023.05.014

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Abstract:
The calcination process and the ratio of to calcium to silicon in raw materials are the key factors affecting the mineral composition and properties of natural water hard lime(NHL). This study prepared NHL was by different calcination processes using argillaceous limestone tailings with different chemical compositions as raw materials. This paper studied the mineral composition and compressive strength of the prepared NHL by a combination of orthogonal and single-factor tests, and analyzed the effect of calcination process and calcium-silica ratio on its performance. Results showed that: ① With the increase of calcination temperature, the content of CaO in NHL decreased, and the content of dicalcium silicate(Ca₂SiO₄, C₂S)increased in NHL. ② Calcination temperature had the most significant effect on the mineral composition and compressive strength of NHL, followed by holding time and heating rate. ③ In the calcination temperature range of 1 000~1 100 ℃, the natural hydrostatic lime prepared by the given argillaceous limestone tailings meets the requirements of NHL2 and NHL3.5 strength grades. ④ When the calcium-silicon ratio is in the range of 3.55~6.76, the compressive strength of NHL decreases and then increases with the increase of calcium-silicon ratio, while the CaO content shows continuous increases.

2023 Vol. 8, No. 5