矿业科学学报

Study on microbial cemented backfill mining technology

Deng Xuejie, Liu Hao, Zhang Jixiong, Zhao Yile, Li Yu, Bian Liguo, Tian Xiuguo, Xie Jin

2023, 8(4): 439-451. doi: 10.19606/j.cnki.jmst.2023.04.001

Abstract(290) HTML (135) PDF(66)

Abstract:
The microbial induced carbonate precipitation(MICP) technology is proposed in the field of backfill mining to tackle high emission and high energy consumption in the current backfill system.Specifically, mechanical properties of microbial cemented backfill materials are investigated, and a proposal of microbial cemented backfill mining technology is presented in this paper.Results show that the strength of mixed and grouted microbial cemented backfill first increases and then decreases with the increase of cementation solution concentration and bacterial solution dosage.The average strength is 0.88 MPa and 17.95 MPa respectively.The effective CaCO₃ crystal in the microbial backfill material is the key to its consolidation.The CaCO₃ crystal of the mixing sample exists in the form of calcite and vaterite, and mainly calcite in the grouted sample.Microbial cemented backfill mining technology has significant environmental benefits such as energy conservation and emission reduction.There is happy prospect for this technology under current environmental needs and policies.

Mechanical mechanism of large deformation and support control for jointed thin soft rock tunnel in Southwest China

Tao Zhigang, Li Mengnan, Zhang Bo, Li Huiru, Shi Guangcheng

2023, 8(4): 452-463. doi: 10.19606/j.cnki.jmst.2023.04.002

Abstract(208) HTML (70) PDF(34)

Abstract:
This study analyzes the large deformation failure mode and mechanical mechanism of tunnel surrounding rock, with an aim to lessen the damage of high ground stress soft rock tunnel support structure and large deformation of surrounding rock in southwest mountainous area, with Yunnan Changning Tunnel as example for analysis, This paper investigates NPR anchor cable stress compensation support for soft rock tunnel.First, we analyzed the geological conditions and causes of failure of the tunnel through field survey and indoor test.Then, we looked at the main control factors affecting the stability of surrounding rock and the failure mode of surrounding rock of Changning Tunnel.Next, this study proposed the stress compensation support technology with NPR anchor cable as the core.Finally, we analyzed the control effect of surrounding rock of Changning Tunnel under the condition of NPR anchor mesh coupling support through field test.Results show that the main failure modes of the surrounding rock of Changning Tunnel are the compression bending of rock strata and the shear slip between layers.The stress compensation support technology with NPR anchor cable as the core works to effectively control the large deformation of the tunnel surrounding rock in the initial support.The maximum deformation of the tunnel surrounding rock is controlled from 2 150 mm to less than 100 mm, which demonstrates significant control effect.The research results can provide reference for the prevention and control of large deformation of soft rock tunnel.

Experimental study on dissolution effect and water purification mechanism of broken coal and rock mass in goaf

Wang Fangtian, Hao Wenhua, Zhang Cun, Sun Nuan, Xiong Jibing, Fan Changhao

2023, 8(4): 464-473. doi: 10.19606/j.cnki.jmst.2023.04.003

Abstract(173) HTML (24) PDF(21)

Abstract:
Research on the dissolution effect and the water purification mechanism of fractured coal and rock mass in the goaf area of underground reservoir is the key to realizing the safe and efficient operation of underground reservoir in mine.This paper takes the underground water reservoir formed by the mining of 31409 working face in Jinjie coal mine as example, and selects the broken coal rock mass in the mining area and deionized water for the experimental study of pollutant release law.We analyse the law of dissolution action of broken coal rock mass in the mining area, and explore the mechanism of the influence broken coal rock mass exerts on the characteristics of the water body.We discover the law of pollutant release of broken coal rock mass under different temperature and weathering degrees, and analyse precipitation and dissolution that occurs during the water purification process in underground water reservoir.The water-rock interaction of dissolution, the adsorption and precipitation of clay mineral surfaces and soluble organic matter in the rock body constitute the water purification characteristics of the groundwater reservoir, with dissolution, adsorption and precipitation each playing a dominant role in influencing mine water quality at different time scales.

Experimental study on freeze-thaw damage and seepage characteristics of coal rock at different prefabrication temperatures

Qi Xiaoghan, Liu Yang, Yang Xuesong, Zhu Tongguang, Wang Pin, Hou Shuangrong

2023, 8(4): 474-486. doi: 10.19606/j.cnki.jmst.2023.04.004

Abstract(170) HTML (31) PDF(23)

Abstract:
This experimental study probes into the evolution patterns of fine damage and mechanical and seepage characteristics of coal rocks using the coal rock triaxial servo experiment system by employing three types of pretreatment methods, namely heating, freeze-thawing with liquid nitrogen and freeze-thawing with water, with an aim to investigate the effect of temperature on freeze-thaw damage and seepage characteristics of coal rocks.Results show that higher preheating temperature leads to more severe structural damage, damage to water-filled liquid nitrogen freeze-thawed coal samples at the same temperature is greater than that of liquid nitrogen freeze-thawed coal samples and heated coal samples only, the degree of damage is negatively correlated with the wave speed and positively correlated with the number of joint dimensions of the end face damage; coal samples with high triaxial compressive strength feature low pre-deformation under different pretreatment methods; all three pre-treatment methods lead to an increase in the number of internal pores and fractures in the coal sample, resulting in the formation of a network of fractures.Freezing and thawing the coal sample with warmed water and liquid nitrogen demonstrate more stronger effect than that of freezing and thawing with warmed liquid nitrogen only.Therefore, in engineering practice, preheating-water injection-liquid nitrogen injection freeze-thaw could be employed to achieve efficient coal seam penetration and improve the effect of gas extraction.

Study on the correlation of macro and meso parameters of parallel bond model sandstone

Wu Luyuan, Zhu Yongheng, Bai Haibo, Feng Yi, Li Hui, Su Chengdong

2023, 8(4): 487-501. doi: 10.19606/j.cnki.jmst.2023.04.005

Abstract(242) HTML (73) PDF(24)

Abstract:
In order to study the mechanical response and failure characteristics of sandstone at the meso level, this paper first carried out indoor rock compression test and PFC^2D uniaxial macro-meso parameter correlation numerical test based on parallel bond model.Then, the trial-and-error method is used to determine the order of the influence degree of each mesoscopic parameter on the macroscopic mechanical index, and the interaction analysis of significant factors is carried out.Finally, the regression analysis is used to establish the functional relationship between macroscopic and mesoscopic parameters.The main influencing factors of crack evolution and failure mode of rock samples are studied by using the control variable method.The results show that: ①The uniaxial compressive strength σ_c has a complex nonlinear relationship with parallel cohesion c, bond normal strength σ_c and bond internal friction angle φ.; ② Elastic modulus E has a polynomial relationship with bond modulus E ^* and bond stiffness ratio k ^*; ③ Poisson's ratio v is linear with k ^* and friction coefficient μ; ④The tensile strength σ_t has a good linear relationship with c and σ_c.; ⑤The crack evolution and failure mode of rock samples are mainly affected by the bond strength ratio σ_c/c, which is negatively correlated with the number of tensile cracks and positively correlated with the number of shear cracks. With σ_c/c increases, the failure mode of rock samples is characterized by tensile failure-conjugate failure-shear failure.The evolution law and failure form of uniaxial compression σ-ε in laboratory test and numerical simulation are basically the same.

Optimization and application of discontinuity detection in multi-frequency domain in ant-tracking

Yang Suju, Zhang Shijie, Yang Ruizhao, Shen Xiangcun, Li Yulan, Xia Yongtao

2023, 8(4): 502-511. doi: 10.19606/j.cnki.jmst.2023.04.006

Abstract(238) HTML (48) PDF(19)

Abstract:
The application of ant-tracking in seismic interpretation shows its advantages in fault characterization.However, this technology is limited by the quality of seismic data, the selection of ant-tracking input data, and multi-solution caused by single attribute.Thus, how to improve the accuracy of ant-tracking has been the hot issue and hard nut to crack in the industry.This paper takes well-block 1 in Shunbei area of Tarim Basin as the research object, and analyses the differences and application potential of chaos, variance, and the maximum positive curvature theories in fault detection.Besides, based on generalized S transform spectral decomposition, we compare discontinuity detection effects of chaos, variance and the maximum positive curvature attributes in different frequencies.Next, the data is processed after discontinuity detection with ant-tracking and optimize the best date for each frequency.Finally, RGB fusion is carried out after occurrence control.Results show that chaos in low frequency, variance in medium frequency and the maximum positive curvature in high frequency respond well with big, medium and small faults.The ant-tracking aided with multi-frequency domain and different fault detections can display multi-scale fracture distribution and enrich the underground geological information.

Variation of pH value of leaching solution during steel slag dissolution

Fang Youdong, Zhao Shuaibing, Su Chang, Lü Ningning, Wang Haichuan

2023, 8(4): 512-518. doi: 10.19606/j.cnki.jmst.2023.04.007

Abstract(209) HTML (48) PDF(23)

Abstract:
This study explored the change law changing pattern of pH value of steel slag leaching solution in the process of steel slag dissolution with an aim to study the influence of steel slag on environment.Specifically, it analyzed the influence law of steel slag basicity, magnesium oxide content, water temperature, steel slag particle size, liquid-solid ratio and other factors on pH value of steel slag leaching solution and conducted a comparative test with on-site steel slag.Results show that the pH value of the leaching solution after steel slag dissolution is in the range of 10~12, and with the change of time, the pH value first increases and then decreases.Increasing the basicity of steel slag and the content of magnesium oxide can increase the pH value of the leaching solution.The increase of water temperature, steel slag size and liquid-solid ratio can reduce the pH value of the leaching solution.

Study on the strata displacement law of overlapping shield tunnels with different overlapping angles

Yang Zhiyong, Niu Yuzhe, Ding Yaowen, Qi Weiqiang, An Hongbin, Jiang Yusheng

2023, 8(4): 519-528. doi: 10.19606/j.cnki.jmst.2023.04.008

Abstract(153) HTML (43) PDF(21)

Abstract:
Based on the overlapping tunnel of Tel Aviv Red Line Light Rail Project in Israel, this study established a three-dimensional numerical model by using Rhino6 and FLAC^3D software on the basis of analysis of on-site monitoring data, to investigate the ground settlement and stratum displacement laws of shield overlapping tunnel at different overlapping angles.Results show that when the two tunnels gradually transit from horizontal to overlapping state, with the increase of overlapping angle of the two tunnels, the accumulated settlement at the measuring points in the middle of the two tunnels increases, but the accumulated settlement is not only affected by overlapping angle, but also closely related to the stratum traversing situation.Under the stratum condition of the project, when the overlapping angle is 60°, the accumulated surface settlement reaches the maximum because both tunnels pass through the loose reservoir K1 stratum.When the overlapping angle of the rear-built tunnel is less than 45° after excavation, the width of the settlement trough increases.When the overlapping angle is larger than 45° and smaller than 60°, the width of the settlement trough remains unchanged.The width of settlement trough decreases when the overlapping angle is larger than 60°.When the overlapping angle reaches 90°, the settlement trough is symmetrical on both sides.After excavation of tunnels on both sides, when the overlapping angle of the tunnels reaches 75°, the strata on both sides change the direction of movement.This research offer reference for the design and construction of overlapping tunnels.

Mine external fire monitoring method using the fusion of visible visual features

Fan Weiqiang, Li Xiaoyu, Liu Yi, Weng Zhi

2023, 8(4): 529-537. doi: 10.19606/j.cnki.jmst.2023.04.009

Abstract(124) HTML (27) PDF(18)

Abstract:
In order to overcome the problems of poor real-time performance, high false alarm rate and underreport alarm rate of mine external fire monitoring, a method of fire monitoring using the fusion of visible visual features is proposed.Firstly, the visual features corresponding to the video images of fire sources in different monitoring environments are analyzed, and the extraction methods of fire source texture, sharp corners, similarity coefficient and flicker frequency are designed.Then, an improved seed region growth algorithm is used to segment the suspected fire area, and different feature extraction methods are used to calculate the dynamic and static characteristics of the suspected fire area.Secondly, the extracted dynamic and static features are used to construct fire feature vectors.Finally, a fire monitoring model using BP neural network is constructed, and monitoring model is verified.The results show that the proposed fire monitoring method can effectively detect mine external fire in different scenes and distances.The correct rate and detection rate are 98.60% and 99.06%, respectively, the false detection rate is as low as 2.00%.It has strong anti-interference ability and robustness.

Propagation behavior of two collinear mode Ⅰ cracks driven by explosive gas

Yang Liyun, Dong Pengxiang, Wang Qirui, Wang Qingcheng

2023, 8(4): 538-547. doi: 10.19606/j.cnki.jmst.2023.04.010

Abstract(126) HTML (30) PDF(12)

Abstract:
In smooth pre-splitting blasting, two collinear cracks extending opposite to each other between adjacent holes will first avoid each other and then attract each other, resulting in crack propagation path that often presents hooked or butterfly-shaped loops.Based on the maximum tensile-stress criterion modified by T-stress, this study probed into the crack propagation behavior of two collinear mode Ⅰ cracks extending opposite to each other by using Abaqus and Hypermesh.The numerical results indicated that model size(ratio of model width to height: W/H ), crack length(ratio of initial crack length to circular hole radius: a/r)and pressure distribution of explosive gas on crack surface have a significant effect on crack growth behavior.Deflection occurs during the propagation of mode I crack, which makes the crack propagation path presents hooked loops.The explosive gas on the crack surface reduces the degree of deflection in mode I crack propagation, and makes it more difficult for the crack growth path to show "hooking" phenomenon The crack propagation path is simulated by the method of incremental crack propagation and the results show that the crack propagation path of mode I crack does present hooked loops.The phenomenon of "hooking" of crack propagation path is related to the interaction between the cracks, which can be represented by the crack growth angle θ.

The influence of complex topography on the stress of underlying coal strata

Zhang Daming, Fu Song, Li Gang

2023, 8(4): 548-559. doi: 10.19606/j.cnki.jmst.2023.04.011

Abstract(97) HTML (26) PDF(10)

Abstract:
To master the influence law of complex landform such as the surface mountain and the valley area between the mountains on the underlying coal rock stress, this study constructed a calculation model of the vertical stress of the coal strata under the mountain through theoretical analysis.Taking the 50205 working face of Hecaogou coal mine as example for analysis, This paper studied the complex landform on the underlying coal rock load characteristics and stress transfer law.Results show that: mountain load has significant stress effect on shallow coal seam.In the horizontal direction, the influence range is negatively correlated with the mountain slope, and the coefficient of influence range is positively related to the mountain slope.The effect of mountain on the vertical stress of the underlying coal seam can be divided into three stages: initial effect, intense growth effect and slow growth effect.The vertical stress superposition value of the underlying coal strata in the gully region firstly increases and then decreases with the change of depth.Moreover, when the distance between two adjacent mountains increases to more than.1.25 times of the width of the mountain bottom, the effect of stress superposition is very small and can be ignored.As the distance between adjacent mountains gradually increases, an inverted triangle area with insignificant stress superposition is formed in the coal strata under the gully area.

Formation mechanism of non-ideal posture of hydraulic support at setting stage in the soft rock condition

Hu Xiangpeng, Ma Bin

2023, 8(4): 560-568. doi: 10.19606/j.cnki.jmst.2023.04.012

Abstract(98) HTML (26) PDF(10)

Abstract:
This paper proposed the kinematic model and load-bearing mechanics model of the four-leg support based on the plane bar system to tackle the unclear formation mechanism of the non-ideal posture of the hydraulic support in the setting stage under the condition of soft surrounding rock.Then, this study obtained the velocity relationship between the front and rear leg when the canopy moving in a fixed posture at the setting stage, as well as the variation characteristics of the resultant force and resultant force positions of the canopy and the base.The results of theoretical analysis and numerical calculation show that only the setting stage is the best time to adjust the posture of the support.When the canopy rises in a horizontal or head-up posture compared with the base, the velocity ratio of the front and rear leg is a cubic function.When the canopy rises in a head-down posture compared with the base, the velocity ratio of the front and the rear leg shows a five-order function relationship.The change of the resultant force positions of the canopy and the base depends on the posture of the canopy contact to the roof, which tends to change fast at first and then slow.The increase of the resultant force of the canopy and the base is slow at first and then rapid.The research results can offer reference for the design of support structure and posture controller, as well as field operation.

Multi-scale joint characterization of coal seam pore structure and its influence on movable fluid

Li Tian, Ren Dazhong, Ning Bo, Li Qihui, Zhang Hanpeng, Zhou Junli, Zhang Zhifeng

2023, 8(4): 569-582. doi: 10.19606/j.cnki.jmst.2023.04.013

Abstract(159) HTML (71) PDF(21)

Abstract:
Micro-pore structure affects the fluid storage and seepage in coal seams.In this paper, six samples from the Jurassic Yan'an Formation coal seam in the Shenmu area of the Ordos Basin were taken as the object of study.The pore distribution characteristics of coal seams were jointly characterized by NMR, CO₂ adsorption and N₂ adsorption at multiple scales, and the connectivity and homogeneity of microscopic pores were investigated by combining multi-scale joint characiterization with CT scanning.Results show that the micro-pores of coal are the main contributors to the specific surface area and pore volume, followed by meso-pores.There is a good uniformity in the pore size distribution of the micro-pores and meso-pores by combing NMR and adsorption, while considerable differences are found in the macro-pores.Displacement NMR and CT excel in reflecting the degree of connectivity, both of which are consistent in the characterization of connectivity.Parameters such as coordination number and seepage pore ratio can effectively reflect the degree of connectivity of the sample, whose patterns of connectivity is M6>M2>M12>M15>M10>M4.The saturation of bound water shows a satisfactory positive correlation with pore-throat ratio of coal samples.It can be seen that the pore structure has a great influence on the degree of fluid migration, which is the basis for studying and evaluating gas occurrence and seepage.

The application of grouting reinforcement to the broken surrounding rock of 1366 stoping roadway

Zhang Lixin, Wei Xiujie, Liu Guangchao

2023, 8(4): 583-592. doi: 10.19606/j.cnki.jmst.2023.04.014

Abstract(115) HTML (81) PDF(30)

Abstract:
This study proposes a fractional grouting reinforcement scheme of the roadway with full section to tackle surrounding rock breakage in the stoping roadway of 1366 working face and roadway deformation, floor heave and support failure.The infiltration grouting process is adopted to determine reasonable grouting pressure and grout diffusion radius for full section reinforcement.The stress, plastic zone distribution and surface displacement of surrounding rock before and after grouting are forecast through numerical simulation.Field application and monitoring show that: after the full section fractional grouting scheme is used to reinforce the mining roadway, the roadway deformation is considerably reduced, the roadway force is balanced, and the stress concentration is alleviated, which is basically consistent with the numerical simulation results.The grouting reinforcement scheme works to strengthen the surrounding rock of 1366 mining roadway, maintain the stability of surrounding rock of roadway, and provided references for the control of surrounding rock of roadway under similar conditions.

2023 Vol. 8, No. 4