Volume 45,Issue 2,2022 Table of Contents

1 Development and optimization of abrasive water-jet directional slitting machine for coal mine

LU Yiyu , QIN Xuqian , TANG Jiren , ZHANG Wenfeng , LING Yuanfei , LI Qian

2022, 45(2):1-13. DOI: 10.11835/j.issn.1000-582X.2020.270

[Abstract](451) [HTML](773) [PDF 5.49 M](603)

Abstract:
The N00 method is a highly efficient and resource saving mining method, and its key step is to quickly separate the gob roof and the roadway roof by making a slit between them. Based on the water jet theory and technology, a new idea of using abrasive jet directional cutting roof was proposed. The structural composition and working principle of the abrasive jet directional cutting system were studied, and the water jet nozzle, cutting nozzle, orienter, conveyor, abrasive were designed. Through experiments, the working parameters of the abrasive jet directional cutting were optimized. The roof cutting test was carried out on the S1201-Ⅱ working face of a mine in Shaanxi. The results show that under the conditions of jet pressure 25 MPa, nozzle diameter 1.5 mm, abrasive type yellow sand/quartz sand, abrasive mass concentration 3.5% and cutting speed 4.4 mm/s, the developed system is able to make slits at the same time in 4 holes of 7 000-8 000 mm deep within a cycle time (50 min).

2 Design of a new dehydration tube based on bionics and its dehydration law

ZHANG Aiqing , WU Aixiang , WANG Yiming , LI Jinyun

2022, 45(2):14-20. DOI: 10.11835/j.issn.1000-582X.2020.271

[Abstract](370) [HTML](714) [PDF 1.85 M](633)

Abstract:
The type of dehydration tube is one of the key factors influencing the dehydration technology of filling. This paper designs a new dehydration tube based on the analysis of the water absorption model of plant roots and its related test devices. The dehydration efficiency and the dehydration law of the new dehydration tube for unclassified tailings non-cemented filling are studied. The test results show that the root-like design of the dehydration tube can increase the water passing area and reduce the seepage distance of the dehydration tube. Compared with the ordinary dehydration tube, the new type reduces the dehydration time by 20%, and the cumulative dehydration volume increases by 10.3%. Using the tailing loss to evaluate the dehydration effect of dehydration tube, the new type of dehydration tube has a 45% reduction in tailing loss compared with the conventional dehydrating tube. The dehydration process of the unclassified tailings non-cemented filling can be divided into 2 zones, i.e. rapid and steady flow zones, and the rapid flow zone is the key for the improved dehydration efficiency of the new type pipe. Another important factor for the improved dehydration efficiency is the large number of uniformly distributed pore water-conducting zones formed on the unclassified tailings non-cemented filling and the inner surface of the test device.

3 Study on the mechanism of secondary dewatering for fine thickened tailings containing admixture

YANG Gangfeng , WANG Yong , WU Aixiang

2022, 45(2):21-28. DOI: 10.11835/j.issn.1000-582X.2021.251

[Abstract](363) [HTML](695) [PDF 1.66 M](589)

Abstract:
When the tailings still do not reach the expected mass fraction under the dewatering process conditions by vertical sand silo or deep cone thickener, the addition of admixture in the tailings is an effective means to achieve secondary rapid dewatering. Taking t the fine copper ore tailings whose bleeding ability was poor, and the mass fraction was still not up to standard after dewatering by the deep cone thickener as the example, the secondary dewatering experiment was carried out with three groups, one adding the A-type admixture another adding the B-type admixture, and the third one without adding admixture. The experimental results show that the bleeding amount of slurry with adding admixture is significantly greater than that without adding admixture after 1 h and 2 h. With the increase of bleeding time, the bleeding amount of slurry with adding admixture and without adding admixture is basically equal at 4 h. Through the regression equation of dewatering mass fraction and dewatering time in three cases, the mathematical model of secondary dewatering of concentrated tailings was obtained, i.e. the relationship between the secondary dewatering mass fraction and the dewatering time is exponential function. Finally, the mechanism of rapid dewatering and structural strengthening of tailings by adding admixture were analyzed. Adding admixture not only increased the mass fraction of tailings, but also improved the stability of tailings, which has potential engineering application value.

4 Safe and green exploitation model and demonstration projects of deep outburst mine based on the integration of gas control, extraction and utilization

ZHANG Jianguo , WANG Man , YUAN Miao , LIU Qingjun , LI Deng , WANG Xiaochuan

2022, 45(2):29-40. DOI: 10.11835/j.issn.1000-582X.2020.260

[Abstract](409) [HTML](710) [PDF 5.68 M](638)

Abstract:
This paper analyzed the main problems in gas control and recycling in deep outburst mines in China and summarized the state of gas control, gas extraction, gas utilization and heat damage control. Taking Shoushan No. 1 Mine as an example, a closed loop system architecture of gas treatment-gas extraction-gas power generation-centralized refrigeration-heat damage control was proposed to realize safe, efficient and green development of deep outburst mines. The comprehensive gas control technology of "One side, Many lanes" in coal seam with single mining height and low permeability outburst in Shoushan mode was studied. An integrated pipeline system for gas extraction and gas dynamic control technology were developed to realize efficient collaboration of gas management and drainage. The combined operation process of gas power generation equipment and refrigeration equipment was analyzed to realize effective treatment of heat damage in deep wells. The demonstration project of power grid connection and mine cooling in Shoushan No.1 Mine was established to realize the unification of comprehensive management and recycling of gas resources, forming a safe, efficient and green development mode of deep outburst mines and providing reference for similar mine development in China.

5 Investigation on correlation between energy dissipation and fractal characteristics of fragments of preflawed sandstone

LIU Xianghua , ZHANG Ke , WU Wenyuan

2022, 45(2):41-51. DOI: 10.11835/j.issn.1000-582X.2020.273

[Abstract](420) [HTML](1023) [PDF 2.32 M](818)

Abstract:
This paper aims to investigate the correlation between the energy dissipation and fractal characteristics of fragments of preflawed sandstone. First, the uniaxial compression tests on preflawed sandstone with different flaw inclinations were conducted to analyze the energy evolution characteristics of preflawed sandstone during loading. Based on fractal theory, the size distribution characteristics of fragments after final failure were quantitatively characterized. The study shows that the compressive strength and the dissipation strain energy of specimen first decrease and then increase with the increase of flaw inclination and the data fitting suggests a positive correlation between them. The fragment size distribution of fragments under the uniaxial compression tests has obvious fractal property. The fractal dimensions of specimens with different flaw inclinations are in the range of 2.58-2.64. The trend of fractal dimension changing with flaw inclination is similar to that of compressive strength, and fractal dimension and compressive strength are approximately linearly related. The higher the compressive strength of the specimen is, the more the dissipative strain energy releases during failure. At this time, the more severe failure the specimen has, the greater the proportion of micro and fine particles is, resulting in the increase of fractal dimension. The regression analysis shows the relationship between dissipation strain energy and fractal dimension is linear positive correlation.

6 A new improved soft and hard threshold method and its application in seismic data denoising

LIU Jian , QIN Feilong , CHENG Yali

2022, 45(2):52-57. DOI: 10.11835/j.issn.1000-582X.2020.274

[Abstract](393) [HTML](878) [PDF 2.46 M](715)

Abstract:
The collected field seismic data are accompanied by random noise interference, which needs to be eliminated by wavelet threshold denoising method. However, the soft and hard thresholding methods have some shortcomings in noise reduction. In this paper, a new threshold denoising algorithm is proposed to perform seismic data denoising. Firstly, a new threshold denoising method is designed based on the principle of soft and hard threshold method, and the relevant characteristics of the new algorithm are studied. Then, the wavelet base of the new threshold algorithm is defined as sym 3, and the denoising effect of the new method is evaluated by root mean square error (RMSE) and signal-to-noise ratio (SNR) through simulation experiments. Finally, the new threshold denoising method is applied to actual seismic data denoising. The results show that the improved threshold denoising method can remove random interference in seismic data, and the denoising effect is better than that of the old soft and hard threshold method.

7 Analysis on the superposition effect of stress and the failure law of surrounding rock during the last mining period of pre-excavation return channel

HE Yanjun , ZHANG Jinshan , CHEN Kai , WANG Shuai , SHI Zhanshan , LI Jianwei

2022, 45(2):58-67. DOI: 10.11835/j.issn.1000-582X.2020.262

[Abstract](391) [HTML](442) [PDF 9.38 M](650)

Abstract:
In order to obtain the control method of the pre-excavation return channel surrounding rock failure in the last mining, the superposition effect of the concentrated stress around the return channel and the mining supporting pressure, and the law of surrounding rock failure were analyzed through numerical simulation, and the field verification was carried out. The results show that with the decrease of the distance between the working face and the return channel, the superimposed stress increases gradually and is transferred to the positive side of the return channel, and the failure of the return channel moves from the front side to the working face. Because of the stress superposition effect, when the working face is 20 m away from the return channel, the plastic failure of roof changes from sparse failure to dense failure. Before the failure of coal pillar between the working face and the return channel, the deformation and failure of the back channel mainly occurr at the front side of the return channel. The damage of the front side is more serious than that of the auxiliary side when the coal pillar is less than 5 m. When the coal pillars are completely destroyed, the roof lost support, resulting in roof rotation, and the scope of the roof and floor damage increases correspondingly. It is suggested that the key to control the large deformation of the return channel is to control the stability of the front side of the return channel.

8 Stability analysis of high stage backfill based on improved CRITIC-G1 method combined with weighted cloud model

WANG Shi , WEI Meiliang , SONG Xuepeng , LIU Wu , SONG Lin

2022, 45(2):68-80. DOI: 10.11835/j.issn.1000-582X.2020.259

[Abstract](417) [HTML](919) [PDF 11.80 M](992)

Abstract:
The process of high-stage filling stability risk assessment is characterized with fuzziness and randomness. A high-stage filling stability evaluation model with the introduction of the cloud model theory is proposed in this paper. Taking four domestic deep mines including Anqing Copper Mine as the research objects, 16 influential factors, such as slump, lateral exposure area, filling slurry slope, and filling effect, were selected as risk assessment indicators. The cloud model parameters of each index belonging to different risk levels were calculated with the help of cloud theory. At the same time, based on the improved CRITIC-G1 method, the subjective and objective weights of the evaluation indexes were optimized and integrated into the comprehensive weights of the indexes. Then, the comprehensive certainty degree of the backfill stability was calculated by using the forward Gaussian cloud generator, and the stability grade of the filling body of four mines was finally determined. The results show that the risk levels of Anqing Copper Mine, Lilou Iron Mine, Dongguashan Copper Mine and Sijiaying Iron Mine are grade IV, grade IV, grade III, and grade II, respectively, and the filling body of Sijiaying Iron Mine is relatively stable. Compared with other mathematical models, the proposed model not only ensures the accuracy of the results, but also uses cloud numbers to represent the fuzziness and randomness so as to obtain the stability grade of the filling body under the coupling effect of different evaluation indexes. The model realizes the visualization of the classification, and has certain reliability, providing a new method for the risk assessment of the stability of high-stage filling body.

9 Water-rock interaction simulation of artificial recharge in the groundwater over-exploited area of the Hutuo River Basin

GENG Xinxin , ZHANG Feng'e , ZHU Pucheng , MA Linna , CHEN Li , GUO Chunyan

2022, 45(2):81-93. DOI: 10.11835/j.issn.1000-582X.2020.268

[Abstract](380) [HTML](760) [PDF 9.29 M](595)

Abstract:
The water-rock interaction in the recharge water and groundwater mixed zone of aquifer under artificial recharge is the key process that determines the evolution of groundwater quality and leads to the chemical clogging of aquifer. To study the effect of artificial recharge on the groundwater quality evolution in the groundwater over-exploited area of the Hutuo River Basin, taking the groundwater artificia recharge site in Shijiazhuang as an example and using the Shijin irrigation canal water as the recharge water, we revealed the mechanism of water-rock interaction of surface water and groundwater mixed zone in the aquifer by carrying out the laboratory experiments and reverse hydrogeochemical simulation. The results show that the evolution characteristics of total dissolved solids(TDS) in the mixed zone firstly increase and then slowly decrease. The larger the proportion of surface water mixed with water is and the smaller the particle size of medium is, the larger the variation amplitude of TDS is. The change of main ion concentrations is controlled by mixing action, carbonic acid balance, dissolution-precipitation, cation exchange and nitrification. Among them, the concentrations of K⁺, Ca²⁺and SO₄^2- are mainly controlled by dissolution-precipitation, the concentrations of Na⁺, Cl^-, HCO₃^-, NO₃^- are mainly controlled by mixing action, and the concentration of Mg²⁺ is mainly controlled by cation exchange. In the water-rock reaction, the dissolved minerals include anhydrite, albite, K-feldspar and halite, whereas the precipitated minerals included calcite, calcium montmorillonite and quartz. Moreover, in the aquifer with larger proportion of surface water and finer particle size of medium, the calcite precipitation is greater, indicating that there is a high risk of carbonate chemical clogging in the recharge aquifer with fine particle size when the surface water is the recharge source.

10 Study on background CO screening and spontaneous combustion prediction in monitoring data of super long coal roadway

LI Teng , LI Zongxiang , WANG Jiren , YANG Fuqiang , ZHANG Chunhua , JIA Jinzhang

2022, 45(2):94-102. DOI: 10.11835/j.issn.1000-582X.2020.264

[Abstract](339) [HTML](536) [PDF 5.13 M](544)

Abstract:
To realize early prediction of spontaneous combustion of overlong double coal roadway, this paper proposes a CO trend analysis method based on the big data of the underground monitoring system when the spontaneous combustion mark-gas analysis method is invalid. Meanwhile, to screen out and remove fluctuation disturbance of CO caused by underground diesel vehicle exhaust, the concept of background CO volume fraction which can only reflect the relatively slow oxidation of coal is put forward. The background CO volume fraction screening method is established on the basis that for an independent ventilated investigation area of a mine, there is always an extreme moment that no diesel vehicle works (or exhaust gas does not interfere all diesel car) in a long enough time, and the CO volume fraction value is recorded by the monitoring system. Through the comparison of the screening results of a 0.125-day time unit cycle and a 0.5-day time unit cycle, it is found that as the time unit increases, the CO volume fraction curve becomes lower, the fluctuation decreases, and the background CO volume fraction curve becomes clearer, suggesting the objective existence of background CO volume fraction. Taking a part of the shortest spontaneous combustion period as the examination period, the spontaneous combustion of coal pillars is predicted based on the trend development of the background CO volume fraction. Combined with the experience of Hongqingliang coal mine, the CO increasing trend(increasing rate k₁^*=0.607×10^-6 d^-1) is obtained as the critical index of spontaneous combustion risk prejudgment. The spontaneous combustion risk warning is divided into three levels. When k₁≥k₁^*, it is first-level warning, which triggers key inspections, and upgrades the daily comprehensive inspection to the targeted inspection with more manpower and material resources. When k₁1<k₁^*, it is second-level alert, which requires to find out the causes. When k₁≤0, there is no spontaneous combustion risk. The predicted results meet the engineering requirements.

11 Experimental study on complex resistivity test of coal

LEI Dongji , ZHOU Meng , MENG Hui , ZHAO Chenguang

2022, 45(2):103-113. DOI: 10.11835/j.issn.1000-582X.2020.267

[Abstract](373) [HTML](921) [PDF 6.66 M](644)

Abstract:
The purpose of complex resistivity measurement of coal in laboratory is to provide reliable data of complex resistivity for further field application. The measurement accuracy of coal complex resistivity is affected by many factors, and electrode plate is one of the most important factors. The thickness and the size of electrode plate will affect the result of coal complex resistivity measurement, so the change of electrode plate is of great significance to the accuracy of measurement parameters. In this paper, the complex resistivity of the electrode material with three different thicknesses is measured by using the copper material with better conductivity as the electrode plate. The influence of the thickness of electrode plate on the induced polarization effect is analyzed. The influence of different sizes of electrode plates(diameter of 1 cm, 2 cm, 3 cm, 4 cm and 5 cm) on the measurement of the complex resistivity of coal is tested, and the Cole-Cole model is used for data fitting. The results show that 1) the polarization effect of the electrode plate itself and the bonding degree between the electrode plate and the end face of the coal sample are the main factors affecting the measurement error of the complex resistivity of the coal sample, and the error of the conductive copper paper is the smallest among the three electrode materials. 2) For the same coal sample, the change of the area of the electrode plate only has a great influence on the amplitude of the complex resistivity, and the influence of the area on the induced polarization of the coal sample can be ignored.

12 Electro-hydraulic control system for automatic anti-sticking of coal mine drilling rig

LI Dongmin , ZHU Shiming , ZHAO Yuanzhi , WANG Tong , ZHONG Peisi , XIA Shangfei

2022, 45(2):114-124. DOI: 10.11835/j.issn.1000-582X.2020.258

[Abstract](374) [HTML](752) [PDF 4.07 M](603)

Abstract:
Due to the complex and changeable geological conditions of the soft coal seam, sticking accidents often occur during the drilling construction of the drilling rig, which greatly reduces the work efficiency and seriously threatens the personal safety of workers. To solve these problems, an automatic anti-sticking electro-hydraulic control system is proposed. By analyzing the influencing factors of sticking, the rotary pressure of drilling rig is used to describe the state of sticking, and the threshold of slewing pressure sticking is set. According to the working principle of drilling rig and sticking mechanism, the anti-sticking hydraulic circuit based on the load flow independent distribution system(LUDV) is established. The automatic anti-sticking controller is established by PID and signal selector, and the seeker optimization algorithm(SOA) is used to adjust PID parameters. The system simulation test is carried out with AMESim. The results show that when the rotary pressure reaches 20 MPa, the drilling rig automatically pulls back; when the rotary pressure reaches 22 MPa, the drilling rig slewing pressure remains stable and a large slewing power is maintained to overcome the external load resistance and avoid sticking accidents, verifying the effectiveness of the automatic anti-sticking electro-hydraulic control system.

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