Volume 43,Issue 4,2020 Table of Contents

1 Numerical simulation and structure optimization of a local reverse-circulation fishing tool based on computational fluid dynamics technology

ZHANG Huali , YANG Sheng , LI Qing , LI Yufei , LUO Wei , TANG Jiren

2020, 43(4):1-10. DOI: 10.11835/j.issn.1000-582X.2020.04.001

[Abstract](989) [HTML](482) [PDF 28.24 M](1055)

Abstract:
To solve the problems of single fishing object, insufficient reverse-circulation energy and low debris recovery rate of existing local reverse-circulation fishing tools, a new local reverse-circulation fishing tool, which integrates collection and fishing, is proposed. The flow field of the tool is simulated by computational fluid dynamics (CFD), and the mechanism of reverse-circulation formation of the tool is revealed, on the basis of which the numerical simulation of the tool structure optimization is carried out. The results show that the reverse-circulation system is formed by the entrainment of the high pressure water jet formed by the nozzle, and the performance of the tool can be improved by increasing the number of nozzles appropriately. The performance of the local reverse-circulation fishing tool increases first and then decreases with the increase of the nozzle diameter, and further increasing the nozzle diameter results in the failure to form an effective reverse-circulation system. The change of nozzle geometry affects the performance of the local reverse-circulation fishing tool, which is the best with a conical nozzle, but the required displacement is relatively large. The research results can provide reference for the optimization design of local reverse-circulation fishing tools and theoretical guidance for the on-site operation of local reverse-circulation fishing tools.

2 Quantitative assessment of water richness in mining area of river basin by transient electromagnetic method

MU Yi , LI Hongjie , LI Wen , LI Ling , XU Hui , JIANG Peng , LI Jianghua , QIU Hao , LI Jian , WANG Guoku

2020, 43(4):11-24. DOI: 10.11835/j.issn.1000-582X.2020.101

[Abstract](594) [HTML](567) [PDF 32.89 M](799)

Abstract:
In order to ascertain the scope and extent of the impact river infiltration on the exposed goaf and backfill area, we used the transient electromagnetic method to detect underground mining goaf and open-pit mining backfill near the Huhe Wusu Ditch and Ulan Moron in Ordos. According to the different distance from the river, the electrical response characteristics were analyzed from the unidimensional, planar, and three-dimensional perspectives. Combined with the results of drilling pumping test in the geophysical exploration area, the feasibility of quantitative detection of water richness by transient electromagnetic method was discussed. The results show that the transient electromagnetic method can accurately survey the water-rich range and intensity of geological anomalies at a shallow buried depth not exceeding 150 m in the river basin. The high-resistance characteristics of the non-aqueous (or weakly-water-bearing) goaf near the river are obvious while the low-resistance characteristics of the water-filled backfill near the river are also obvious. The nearby rivers had a great influence on the backfilling area, to the lateral distance up to 500 m. The backfilling area presented a clear water-rich "funnel". Both the lateral influence range and the water-rich intensity decreased with depth, which was basically consistent with the space scope of the open-air stripping backfill. And the nearby rivers had less impact on the goaf and the upper rock with the lateral distance less than 80 m, vertically mainly affecting the upper aquifer of the goaf, and the goaf was basically free of water, or weakly aquiferous. The relationship between the unit water inflow and the apparent resistivity of the drilling was established, and the use of transient electromagnetic method to quantitatively detect the unit water inflow and water-richness level was explored.

3 A method for evaluating shale fracability based on shear slip fractures under plane strain and intergranular fracture

JI Guofa , LI Shichen , LI Kuidong , LI Shaoming , LIU Wei , XIONG Likun

2020, 43(4):25-32. DOI: 10.11835/j.issn.1000-582X.2019.255

[Abstract](631) [HTML](662) [PDF 6.56 M](941)

Abstract:
Horizontal well fracturing combines the artificial fracture and a large number of structural weak surface, such as natural fracture or bedding, forming a complex network, an important section of which is shear slip fracture. Therefore, it will be of great significance to search for shale fracability. With the plane strain and intergranular fracture condition of real shale failure taken into account, and with the focus on the microscopic morphology of shear slip fracture, a method for calculating fracture toughness of shear slip fracture under plane strain was established. Compared with the experimental results, the average error of the method was 2.93%. Based on the logging data and fracture toughness index of a horizontal shale gas well, the whole wellbore continuous profile of fracability evaluation was drawn. By comparing the production after hydraulic fracturing, the reliability of this method was verified, which provided a theoretical reference for efficient development of shale gas.

4 On the solution to large-scale open-pit mine production planning problem based on AHCP algorithm

GU Qinghua , LI Junfei , LU Caiwu

2020, 43(4):33-46. DOI: 10.11835/j.issn.1000-582X.2019.257

[Abstract](557) [HTML](936) [PDF 13.67 M](739)

Abstract:
With the expansion of the scale of open pit mines, the problems of preparing production plans has increased dramatically, leaving it difficult for traditional methods to obtain high-quality solutions in a reasonable time. In response to the above questions, a method combining agglomerative hierarchical clustering algorithm with penalties (AHCP) and binary intrusive weed algorithm (BIWO) is designed in this paper, according to the characteristics of mining, to solve the large-scale open pit mine production planning problem. Firstly, the block deposit model is aggregated according to AHCP algorithm. Then, the state of these units in each period is taken as variables to establish a 0-1 integer programming (IP) model. Finally, the IP model is solved by the BIWO algorithm. Experimental results show that AHCP algorithm can significantly improve the ability of BIWO algorithm in solving large-scale open pit production planning problems. The method in this paper can reduce the overall solution time by nearly 90% while ensuring the quality of the solution.

5 Preliminary feasibility analysis of abandoned coal goafs as PHES reservoirs

WANG Li , LI Zongze , CHEN Jie , JIANG Deyi , DU Junsheng

2020, 43(4):47-54. DOI: 10.11835/j.issn.1000-582X.2019.261

[Abstract](846) [HTML](967) [PDF 11.75 M](943)

Abstract:
Clean energy, such as wind power and solar power, has been greatly developed in China, whose installed capacity has ranked the first in the world. However, the shortage of the matched storage facilities causes a lot of wind, solar and electricity abandonment. Pumped-hydro energy storage (PHS) plants currently dominate the energy storage market in China. Utilizing abandoned coal mine goafs as PHS reservoirs can not only enhance the efficient utilization of clean energy, but also reuse the wastes and protect the underground water resources. This paper investigates the preliminary feasibility of goafs as PHS underground reservoirs in terms of storable space and safe distance. The results show that as the permeability of goaf increases, the effective capacity of reservoirs rises. With the permeability above 8×10^-8 m², the effective coefficient(the ratio of effective capacity to total capacity) of underground goaf-reservoir can reach 0.8. A smaller horizontal distance between two reservoirs will lead to a larger leakage rate of the upper one and the acceptable distance for a typical coal mine geology is suggested.The results can provide a reference for the construction of coal mine PHES plants.

6 Effects of superplasticizers and fly ash on rheological properties of cemented tailings backfill

SHENG Yuhang , LI Guangbo , JIANG Haiqiang

2020, 43(4):55-63. DOI: 10.11835/j.issn.1000-582X.2019.260

[Abstract](584) [HTML](491) [PDF 9.91 M](760)

Abstract:
The workability of cemented tailings backfill (CTB) is significantly affected by its rheological properties. The influence of fly ash and superplasticizers (SPs) including polycarboxylate (PC), polynaphthalenesulfonate(PNS) and polymelaminesulfonate(PMS) on the rheological properties of CTB mixtures was quantitatively analyzed by using Brookfield RST-SST rheometer in this paper. The results show that regardless of SP type, the addition of superplasticizer will reduce the yield stress and plastic viscosity of CTBs, and the rheological properties are improved with increasing SP dosage. PC is found to be the most effective SP in improving the rheological properties of fresh CTB. However, as hydration time increases, the effect of SPs on the yield stress and plastic viscosity of CTB decreases. With the increase of fly ash content, the yield stress and plastic viscosity of CTBs also show a decreasing trend, due to "morphological effect" of fly ash. The mixture of SP and fly ash has a synergistic effect on the rheological properties of CTB, the modification effect of which is much better compared to that of single mix of SP or fly ash.

7 The study of GPD and its application in mineral prediction

QIN Feilong , LIU Jian , YAN Wenyong

2020, 43(4):64-72. DOI: 10.11835/j.issn.1000-582X.2019.251

[Abstract](675) [HTML](707) [PDF 10.38 M](826)

Abstract:
This paper is aimed at exploring the method of mineral resources prediction. Though study we found that the anomalous distribution of geochemical elements was consistent with the generalized Pareto distribution (GPD) of extreme value theory, on the basis of which a new algorithm called the GPD model of geological anomaly was designed. In the new model, the parameters and threshold selection of GPD were discussed and proved. The proposed GPD model of the geological anomaly was applied to identify anomalies in the actual mining area. The results show that the model can effectively identify the geochemical anomaly region of the study area, and the delineated anomaly region coincides with the distribution of ore bodies of actual engineering exploration. The application of the GPD model will be instrumental to the delineation of new prospecting targets.

8 An improved CRITIC and cloud model evaluation method for predicting the wear risk of vertical filling pipes in deep well

WANG Shi , SONG Xuepeng , SHI Haitian

2020, 43(4):73-84. DOI: 10.11835/j.issn.1000-582X.2019.009

[Abstract](626) [HTML](429) [PDF 2.09 M](758)

Abstract:
To accurately predict wear degree of vertical filling pipe in deep mine, a cloud model has been established to assess the risk envolved. The paper has studied the case of four domestic enterprises, such as Longshou mining in Jinchuan. Fourteen elements, including the slurry volume fraction, were selected as risk assessment indexes. On the basis of to the cloud model theory, variable indicators were used to choose applicable digital characteristics. Taking the correlation between various indicators as well as internal variation of them into account, we introduced the improved CRITIC method to gain the index weight, and the pipeline wear risk grades were obtained by calculating the comprehensive determinacy of evaluation indicators. The results showed that the wear risk grades of vertical filling pipelines in Longshou Mine, Dongguashan Copper Mine, Suncun Mine and Gaofeng Mine in Guangxi were Ⅱ, Ⅲ, Ⅳ and Ⅲ respectively. Compared with other assessment methods, the computational model transforms ambiguity and randomness into a quantitative value of certainty, achieving a qualitative-to-quantitative mapping, providing an innovation for similar research of wear degree of vertical filling pipe in deep mine.

9 Finite element simulation of coal body failure in coal and gas outburst process

JI Chen , JIAN Kailin , HAO Zhong

2020, 43(4):85-93. DOI: 10.11835/j.issn.1000-582X.2020.04.009

[Abstract](475) [HTML](607) [PDF 6.75 M](1025)

Abstract:
The failure of coal mass in the process of coal and gas outburst, which is difficult to calculate by finite element software at present, is studied in this paper. The pre-processing module of ABAQUS is redeveloped by Python language. The coal mesh is re-divided by Python script program, and the zero-thickness cohesive unit is inserted. According to the principle of effective stress and the friction contact of ABAQUS based on Mohr-Coulomb criterion, the simulation of the influence of gas pressure on coal body is realized. The generation and expansion of coal fracture and the outburst process of coal body are simulated by using the cohesive unit. The actual simulation results conform to the experimental law, which proves that the secondary development technology of finite element method can well calculate the failure of coal mass in the process of coal and gas outburst. And it can also provide a reference to the application of Python secondary development in other fields.

10 Modification test and engineering application of high-water filling material in gob-side entry retaining

LI Xifan , XIONG Zuqiang , ZHANG Yaohui , SU Chengdong

2020, 43(4):94-106. DOI: 10.11835/j.issn.1000-582X.2019.252

[Abstract](462) [HTML](476) [PDF 19.69 M](696)

Abstract:
This paper aims to solve the poor toughness, small compressibility of high-water material. Based on the analysis of the failure characteristics of the backfilling body, the roadside backfilling body was divided into the yieldlayer and the support layer by the "yielding resistance" supporting mechanism. Orthogonal method was adopted to improve the high-water material performance, and the microstructure of the consolidated material before and after modification was compared. At the same time, simulation tests were conducted to obtain the optimal supporting conditions and material mechanical properties of backfilling body under lateral constraint conditions. The results showed that foaming agents and fibers had no effect on the formation of ettringite and other hydration products.The 28 days strength of the improved support layer consolidate body reached 12.18 MPa and the expansion rate of the yielding layer was 9.60%.The surface displacement of the optimal support combination under lateral constraint was 3.65%. The following industrial test indicated that the lateral surface displacement of filling body was only 229 mm, and the roof subsidence was controlled at about 216 mm. The high water material after modification can well meet the requirements of gob-side entry retaining.

11 Effects of chelating agent on coal properties

LU Kaixuan , XU Lianman

2020, 43(4):107-112. DOI: 10.11835/j.issn.1000-582X.2020.04.011

[Abstract](789) [HTML](743) [PDF 1.41 M](863)

Abstract:
During the deep mining period of a coal mine, the mechanical properties of coal body have changed, resulting in the decrease of injectability of coal seam, and the effect of water injection in coal seam gradually deteriorates over time. In this research, chelating agent is selected to increase the effect of coal seam water injection. The experimental analysis has shown that the injected low permeability coal seam contains a certain amount of minerals which can be dissolved into ions by the chelating agent tetrasodium iminodiasuccinate (IDS), unclogging the originally closed pores, and enhancing the fluidity of water in the coal seam. The leaching amount of mineral ions in the coal seam increases gradually with the increase of the concentration of chelating agent IDS. When the concentration of IDS is 2 000 mg/L, the performance-cost ratio is the highest; the rock burst tendency of coal samples decreases by the action of IDS; the metal ions in sulfur-bearing minerals (such as pyrite) are released after chelation, which reduces the sulfur content from the source. At the same time, IDS is a degradable and environment-friendly chelating agent, providing assistance for environmental protection. Adding chelating agent to coal seam water injection can provide reference for the prevention and control of compound dynamic disasters.

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