矿业科学学报

Experimental study on the proportion of similar materials for different geological structures of coal seams

Gong Yufei, Zhu Guowei, Jiang Yupu, Shi Dongjing

2022, 7(3): 267-274. doi: 10.19606/j.cnki.jmst.2022.03.001

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Abstract:
This paper based on coal strata structure of mine working face, a one-to-one physical model of coal and rock concealed disaster-causing abnormal body is designed and constructed which is used to study the geophysical response characteristics of coal strata and hidden geological anomalies.Selected pulverized coal, gravel and sand, cement as raw materials to study similar material ratio and manufacturing process experiment of coal seams, roofs and floors, collapse columns and faults in Xinyuan Mining by applying the orthogonal design method.In addition, a variety of parameters on physical property were tested.Based on the experimental data of physical parameters such as wave velocity, resistivity and dielectric constant, the optimal construction ratio of each geological structure in the underground physical model was determined by comparing the original coal samples and the comprehensive detection results.Coal powder, sand and cement contents of 55 %, 10 % and 25 % were selected for coal seam simulation; The sand cement ratio is 3 and gypsum cement ratio is 2∶8 for the roof of coal seam; The ratio of sand cement ratio is 2.5 and gypsum cement ratio is 3∶7 for coal seam floor; The test proportions of sand 57.5 %, coal 10 %, gypsum 4.5 % and cement 18 % were selected for the collapse column.The above provides quantitative support for laboratory construction of mining detection equipment technology test platform of the project.

The evolution law of pore characteristics and pore bulk modulus for overpressured coal-bearing formation in Yuwang Minefield

Che Yuyan, Zou Guangui, Yin Caiyun, Zeng Hu, She Jiasheng

2022, 7(3): 275-285. doi: 10.19606/j.cnki.jmst.2022.03.002

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Abstract:
The abnormal high pressure in coal and coalbed methane exploitation will bring danger to exploitation, thus threatening the safety of personnel and property.Six coal samples collected from Yuwang colliery in Yunnan province were analyzed by CT scanning and low-temperature liquid nitrogen adsorption experiment.Analysis reveals the characteristic parameters of pore radius, pore throat radius and pore volume-pore diameter differential distribution of overpressured coal samples.Meanwhile, the pore bulk modulus of overpressured coal samples under different confining pressures is derived based on the mechanism of the Gassmann model.The results show that the porosity of Yuwang colliery overpressured stratum can reach 10 %, and the mesoporous pore shape is mainly spherical and cylindrical.The shear wave velocity of dry coal samples increases nonlinearly with confining pressure.The pore bulk modulus of saturated coal sample remains proportional to confining pressure, but increases rapidly when the water saturation exceeds 90 % with the same confining pressure.

Evolution characteristics of elastic energy storage of marble under creep loading

Li Dongyang, Lu Jingyi, Liu Bo, Wang Shijie, Li Saige

2022, 7(3): 286-295. doi: 10.19606/j.cnki.jmst.2022.03.003

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Abstract:
In order to study the energy absorption and transformation characteristics of marble, the release of strain energy and dissipation mechanism during creep process, this paper tested the stress-strain relationship of marble under uniaxial cyclic loading and multi-level creep cyclic loading respectively, and calculated their elastic energy density curves.The power function is used to fit the relationship between elastic energy density and stress of marble.By comparing the test data of the two loading modes, the results showed that the elastic energy density curves of uniaxial cyclic loading and multi-level creep cyclic loading were basically coincident, and they have the same elastic energy density curves, which means neither the creep loading mode nor the uniaxial cyclic loading mode will affect the elastic energy density curve of the marble.Comparing the ratio of elastic energy to external power in two loading modes, the results showed that the marble materials all went through three stages: compaction, stabilization and deterioration.After creep cyclic loading, the elastic energy storage capacity of marble would decrease to 43 % of uniaxial cyclic loading.Correspondingly, its strength also decreased obviously, which was 62 % of uniaxial cyclic loading.If the long-term bearing issue of this kind of marble is taken into account, the maximum stress value should be controlled below the stress that corresponds to the end point of the compaction stage of material.

Effects of dip angle and length of open joints on dynamic properties of materials like rock

Kang Yiqiang, Zhang Xiang, Jia Wenhao, Zhao Zhiwei, Li Jin, Fang Shizheng

2022, 7(3): 296-303. doi: 10.19606/j.cnki.jmst.2022.03.004

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Abstract:
In order to investigate the influence of tensioned joints on the dynamic mechanical properties of rock-like materials under impact loading, investigated the stress wave propagation characteristics, peak bearing capacity, damage pattern and damage law based on energy theory under dynamic loading for intact specimens and cement mortar specimens containing joints of different angles and lengths with the help of a split Hopkinson compression bar device.The results show that the specimens will be damaged by forming a set of tensile cracking surfaces along the axial direction through the joint surface and a set of cracking surfaces almost parallel to the end face of the specimen.Under the experimental loading rate, when the joint length increases from 5 mm to 30 mm, the more obvious the reflection effect on the wave, the smaller the peak bearing capacity of the specimen, and the smaller the damage.When the joint angle increases from 0° to 90°, the smaller the reflection effect on the stress wave, and the smaller the damage value of the specimen.The peak bearing capacity of the specimen decreases with the increase of the joint angle and then increases.When the joint angle is 60°, the peak bearing capacity of the specimen reaches the minimum, and when the joint angle is 90°, the peak bearing capacity of the specimen reaches the maximum.

Experimental study on the energy evolution characteristics of high-concentration cemented backfill in coal mine

Yang Baogui, Yang Haigang

2022, 7(3): 304-312. doi: 10.19606/j.cnki.jmst.2022.03.005

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Abstract:
In order to study the energy evolution characteristics of high concentration cemented backfill in coal mine, conventional triaxial compression tests of high-concentration cemented backfill under different confining pressures were carried out with the help of RTR-2000 triaxial dynamic test system for high pressure rocks.This paper analyzed the evolution law of the strain energy and the confining pressure effect during the deformation and failure of the specimens.The results show that: (1) for the specimen whose confining pressure is not 0, the ratio of dissipated strain energy corresponding to peak strength to absorbed strain energy is more than 70 %. Before the specimens reached the peak strength, they have undergone severe plastic deformation and failure.(2) in the process of deformation and failure of specimens, the absorbed strain energy increases rapidly, the elastic strain energy accumulates first and then releases, reaching the energy storage limit at peak strength, and the dissipated strain energy begins to increase rapidly from the stage of yield deformation.(3) under the condition of the same axial strain, the larger the confining pressure is, the larger the absorbed strain energy and elastic strain energy of the specimens are.The dissipated strain energy of the specimen with high confining pressure will exceed that of the specimen with low confining pressure as the axial strain increases.The confining pressure can greatly improve the stress level of the specimens, limit the radial deformation of the specimens, improve the energy storage capacity of the specimens, and restrain the deformation and failure of the specimens.

Parameter optimization of alkali injection prevention and field application in coal seam of high hydrogen sulfide roadway

Ai Chunming, Zhou Qinyuan, Xia Ji, Wang Dapeng, Mu Xiaozhi, Li Kun

2022, 7(3): 313-321. doi: 10.19606/j.cnki.jmst.2022.03.006

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Abstract:
Exceeding the limit of underground hydrogen sulfide not only harms operators, but also damages underground equipment.The concentration of hydrogen sulfide in water in a coal mine roadway in Shanxi is 228.19 mg/m³, and 45.64 mg/m³in the air, rendering it a high hydrogen sulfide coal mine.The method of coal seam drilling and alkali injection is used to control hydrogen sulfide.In order to determine the optimal parameters of alkali injection, this paper uses COMSOL Multiphysics software to carry out single-hole and double-hole alkali injection numerical simulations on the process and effect of coal seam alkali injection to treat hydrogen sulfide.The simulation results of single-hole and double-hole alkali injection show that: the farther away from the drilling center, the lower the alkali injection pressure on the coal seam.The longer the alkali injection time, the larger the diffusion range of the alkali solution.And the diffusion speed of the alkali solution gradually decreases as the diffusion range becomes larger.When the distance of double-hole alkali injection is too close, the cross-flow will cause the diffusion range of the alkali solution to become smaller at the same time.The optimal simulation scheme is as follows: the hole distance is 10 m, the pressure is 8 MPa, and the alkali injection time is 48 h.After alkali injection at the 13103 working face, a 28 d on-site data monitoring was carried out.The maximum hydrogen sulfide concentration in the return air flow was 9.13 mg/m³, which did not exceed the limit during the mining, indicating that the optimal alkali injection parameters can guide the coal seam alkali injection work.

Influence of roof cutting parameters on stability of surrounding rock of gob-side entry retaining

Sheng Fengtian, Zhang Yong, Wei Wensheng, Duan Yuqing, Mao Kaibin

2022, 7(3): 322-332. doi: 10.19606/j.cnki.jmst.2022.03.007

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Abstract:
As one of the core issues of roof cutting pressure relief gob-side entry retaining technology, roof cutting parameters have a great influence on the stability of surrounding rock.Taking the 1226 working face of Shuguang Mine as the engineering background, the reference values of cutting top height and cutting top Angle are 7.1~9.5 m and 11.4° respectively through theoretical analysis.Through numerical simulation, the roof collapse form, roof subsidence and stress distribution of solid coal side are analyzed when the roof cutting height is 4 m, 7 m, 10 m, 13 m and the roof cutting Angle is 0°, 10°, 15°, 20° and 30° respectively from two angles of roof cutting effect and surrounding rock deformation.The results show that the optimal cutting top parameters are the cutting top height 10 m and the cutting top Angle 15°.The optimum hole spacing, blasting method and charge quantity are determined by field blasting test.The surrounding rock deformation of the rear roadway of the working face was monitored after the roadway retaining.The deformation of the surrounding rock of the roadway was small and the effect of the roadway retaining was good.

Characteristic of the water-conducting fracture zone development in thick overburden working face with extra-large mining height in western mining area

Zhang Cun, Ren Zhaopeng, Han Penghua, He Xiang, Chen Jianhang, Guo Liang

2022, 7(3): 333-343. doi: 10.19606/j.cnki.jmst.2022.03.008

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Abstract:
In order to obtain the fracture development characteristics of the working face with extra-large mining height under the condition of thick overburden and medium mining depth in mining areas in China's western regions, this paper adopted a comparative study by combining empirical equations, numerical simulation and field measurement in the panel 12401 of the Shangwan coal mine.The results show that the empirical equations drawn from data from the typical geological conditions of mining areas in eastern and western China are difficult to apply to this panel with extra-large mining height, thick overburden and medium buried depth.The prediction values of the empirical equations based on data from the geological condition in the western mining regions are generally higher, which are significantly smaller in the eastern mining regions.The value predicted by the numerical simulation based on the damage constitutive model is closer to the measured value than those derived from using empirical equations, with a relative error of less than 5 %.The paper obtained the characteristics of the water-conducting fracture zone development: due to the existence of soft and hard rock in the overburden, the water-conducting fracture zone develops upward as a step, and the shape changes from "arch"(three-dimensional "shell") to "saddle"(three-dimensional "basin shape") with the variation of mining degree.

Statistical method of coal mine violations based on text classification technology

Li Jing, Zhang Zhizhen, Du Xuan, Wang Zhen, Liu Ziwei, Xin Yanli

2022, 7(3): 344-353. doi: 10.19606/j.cnki.jmst.2022.03.009

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Abstract:
As a high-risk industry, coal mining enterprises have a complex record of violations.In order to efficiently, accurately and intelligently retrieve and manage an enterprise's illegal record and reduce the occurrence of illegal behaviors.A database of 13, 935 violations in a mine in recent three years is taken as a sample.The illegal actions are divided into 3 categories and 23 subcategories.And based on the computer text classification technology, the illegal text data classifier is built.Its process includes text preprocessing of Jieba word segmentation, vector space model construction, feature value selection of TF-IDF model, and similarity calculation process.Finally, a visual classification statistics and presentation system was constructed in Python environment, and the classified statistics were carried out.The results showed that the proportion of illegal operation is 64 %, which is the highest among all illegal behavior, followed by illegal action, and illegal command accounted for the smallest proportion.At the same time, the key subcategories of high frequency, medium frequency and low frequency were analyzed to provide quantitative support for accident prevention.

Path tracking of mining boom road-header using SVD-Unscented Kalman Filtering

Ji Xiaodong, Qu Yuanyuan, Fu Shichen, Zhang Minjun, Wu Miao

2022, 7(3): 354-363. doi: 10.19606/j.cnki.jmst.2022.03.010

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Abstract:
Facing the demand of autonomous path correction of the road-header working underground, a control law was designed and simplified based on the position and orientation deviation model of the road-header against its aimed walking trajectory.Reasonable Lyapunov function is constructed to prove the convergence of the position and orientation deviation that resulted from the designed control law.Based on a certain real time position and orientation detection strategy for the road-header, the possible errors exist during posture adjustments are summarized and classified into two parts: one is the main execution error of the road-header and it is presented by the slip rate of tracks; the other is the main observation error and it is identified as the position and orientation measurement errors.This paper proposed to take advantages of the statistical characteristics of these errors, which is obtained by a certain number of experiments or deductions instead of rigorous theoretical analysis.The SVD-unscented Kalman Filtering is used to modify the commands that are given originally by the controller so as to deduce and reduce the influence of process error and observation error in the process of position and orientation adjusting.The simulation results show that the proposed path tracking control strategy can effectively realize the transition of the road-header to the target roadway in limited adjustment period, and the corresponding recommended speeds of the driving wheels vary continuously and stably in the whole process.The negative influence of process error and observation error is effectively weakened by commands modification based on SVD-unscented Kalman Filtering.The obtained moving trajectory of the road-header coincides with the planned path very well during the adjustment, which is of great repeatability.This proves that the proposed strategy is of great potential to be applied experimentally in underground real road heading scenario.

Corrosion behavior of the new wear resistant steels Ti60 and ANM450 applied for middle plates of scraper conveyor

Teng Zi, Zhu Jin, Chen Huahui, Ma Feng

2022, 7(3): 364-370. doi: 10.19606/j.cnki.jmst.2022.03.011

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Abstract:
This paper looks into the microstructure and phase structure of the new wear-resistant steels Ti60 and ANM450 applied for middle plates of scraper conveyer.Their corrosion behaviors in deionized water, corrosion ion solution, scaling ion solution and simulated mine water were studied by weight loss method, electrochemical tests and XRD analysis.The results showed that the corrosion order was corrosion ion solution>simulated mine water>scaling ion solution>deionized water. The order of corrosion resistance was Ti60 > Hardox450 > ANM450.The corrosion products were Fe₂O₃、α -FeO(OH) and Fe (OH)₃, which indicated that iron was dissolved during the corrosion process.

The influence of functional groups in frothers on foaming performance and foam stability

Huang Bo, Zhou Maomao, Wang Ziyuan, Qin Lihui, Wang Yue, Xin Yayu

2022, 7(3): 371-380. doi: 10.19606/j.cnki.jmst.2022.03.012

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Abstract:
Flotation is an important method for the separation of fine materials.The type of frothers and the stability of the foam significantly affect flotation performance.In this paper, three foaming agents of alcohols (MIBC), esters (DEP) and ether alcohols (DGBE) are selected to investigate the effect of functional groups in frothers on foaming performance and foam stability.Foamscan was used in the experiment to determine the foaming performance and foam stability of the frothers, and the Tracker rheometer was used to determine surface tension and the viscoelastic modulus of the air-liquid interface.Results show that the foaming rate increases linearly with the decrease of surface tension.It reaches its peak/the maximum when the gas-liquid interface adsorbs the foaming agent to saturation, and when the adsorption of the foaming agent on the gas-liquid interface reaches saturation.The foaming rate of MIBC reaches its peak/the maximum and that of DGBE its trough/the minumum.When the concentration of the frother reaches the critical mass fraction, the foaming ability reaches its peak/the maximum, and the critical mass fractions of MIBC, DEP and DGBE are 1.1 %, 0.4 % and 0.8 %.The size of the bubbles decreases with the decrease of the surface tension of the solution, and the order of the average bubble size from large to small is: DGBE>DEP>MIBC.The ether alcohol frothers have the strongest foam stability, while the alcohol frothers have the worst foam stability.The foam is the most stable.when the mass fractions of MIBC, DEP and DGBE are 0.4 %, 0.5 % and 0.8 %.

Research on life cycle risk assessment of utility tunnel project base on AHP-Fuzzy

Zhang Xinwen

2022, 7(3): 381-388. doi: 10.19606/j.cnki.jmst.2022.03.013

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Abstract:
In order to comprehensively and objectively evaluate the risks faced by the underground comprehensive pipe corridor with large investment, wide coverage and long operation cycle, this paper takes a pipe corridor in Beijing as the object, based on the whole life cycle theory, identifies the risk factors in six stages of the whole life cycle of the pipe corridor, and establishes a risk index system consisting of 6 second-level and 43 third-level risk indicators. The comprehensive evaluation model of pipeline corridor risk based on AHP and Fuzzy was established, and the results were verified by weighted distribution method. The research results show that the overall risk of the whole life cycle of the studied pipe gallery belongs to the medium risk, of which the risk of abandonment stage is the highest, followed by construction and completion stage, operation stage, design stage, bidding stage and decision-making stage, and put forward targeted management measures.

2022 Vol. 7, No. 3