Suncun Coal Mine Research Articles

Research on cooperative control method of comprehensive pressure relief and anchor grouting reinforcement in deep mining roadways

To address the surrounding rock control problems in high-stressed deep mining roadways, we used Suncun Coal Mine with maximum mining depth in China as the engineering background to analyze failure laws of surrounding rock of gob-side entry driving. Combined with field tests of anchor grouting parameters, we carried out numerical simulation with multi factors. The evolution of surrounding rock stress and displacement under different pressure relief parameters were clarified. On the basis, we proposed an integrated control method for the comprehensive pressure relief for coal and rock mass and anchor grouting reinforcement in deep mining roadway. We used geomechanical model test to compare gob-side entry driving method and this new method. The results showed that this new method can reduce average stress at the working face by 15.8% and peak stress of roadway shoulder by 12.5%. We applied this method in the field, which reduced roadway deformation by 535 mm.

Multi-Level Support Technology and Application of Deep Roadway Surrounding Rock in the Suncun Coal Mine, China

To solve these problems of poor supporting effect and serious deformation and failure of surrounding rock of mining roadway under deep mining stress, a FLAC-3D numerical calculation model is established with -800 m level no. 2424 upper roadway in the Suncun Coal Mine as the background to compare the stress, deformation, and failure law of surrounding rock of mining roadway under once support and multi-level support with the same support strength. It is found that the multi-level support technology has obvious advantages in the surrounding rock of the horizontal roadway on the 2424 working face. From this, the key parameters of multi-level support are determined, and the field industrial test is carried out. The results show that the overall deformation of the surrounding rock is obviously reduced after multi-level support. The displacement of the two sides is reduced by about 40%, the displacement of the roof and floor is reduced by about 30%, and the plastic zone of the roadway is reduced by about 75%. The peak value of concentrated stress decreases from 98.7 MPa to 95.8 MPa, which decreases slightly. The integrity and stability of the surrounding rock are excellent, and the support effect is satisfactory. The research can provide reference and technical support for surrounding rock control of deep high-stress mining roadways.

Mechanical Properties and Failure Mechanism of Anchored Bedding Rock Material under Impact Loading.

In view of the problem that anchored bedding rock material is prone to instability and failure under impact loading in the process of deep coal mining, and taking the lower roadway of a deep 2424 coal working face in the Suncun coal mine as the engineering background, a mechanical model of anchored bedding rock material was established, and the instability criterion of compression and shear failure of anchored bedding rock material was obtained. Then, the separated Hopkinson pressure bar was used to carry out an impact-loading test on the anchored bedding rock material, and the dynamic mechanical properties of the rock with different anchoring modes and bolt bedding angles were studied; the evolution law of the strain field of the anchored bedding rock material was also obtained. The results show the following: (1) The bolt support could effectively improve the dynamic load strength and dynamic elastic modulus of the rock material with anchorage bedding, the degree of improvement increased with the increase in the angle of the bolt bedding, and the full anchorage effect was much higher than the end anchorage effect was. (2) The bolt bedding angle and anchorage mode greatly influenced crack development and displacement characteristics. After an impact, the bedding rock material had obvious shear displacement along the bedding direction, and obvious macroscopic cracks were produced in the bedding plane. The research results offer theoretical guidance to and have reference significance for deep roadway anchorage support engineering.

Comparative study of model tests on automatically formed roadway and gob-side entry driving in deep coal mines

Automatically formed roadway (AFR) by roof cutting with bolt grouting (RCBG) is a new deep coal mining technology. By using this technology, the broken roadway roof is strengthened, and roof cutting is applied to cut off stress transfer between the roadway and gob to ensure the collapse of the overlying strata. The roadway is automatically formed owing to the broken expansion characteristics of the collapsed strata and mining pressure. Taking the Suncun Coal Mine as the engineering background, the control effect of this new technology on roadways was studied. To compare the law of stress evolution and the surrounding rock control mechanisms between AFR and traditional gob-side entry driving, a comparative study of geomechanical model tests on the above methods was carried out. The results showed that the new technology of AFR by RCBG effectively reduced the stress concentration of the roadway compared with gob-side entry driving. The side abutment pressure peak of the solid coal side was reduced by 24.3%, which showed an obvious pressure-releasing effect. Moreover, the position of the side abutment pressure peak was far from the solid coal side, making it more beneficial for roadway stability. The deformation of AFR surrounding rock was also smaller than the deformation of the gob-side entry driving by the overload test. The former was more beneficial for roadway stability than the latter under higher stress conditions. Field application tests showed that the new technology can effectively control roadway deformation. Moreover, the technology reduced roadway excavation and avoided resource waste caused by reserved coal pillars.

Overlying Strata Structure Evolution and Engineering Practice Based on the Mining of Lower Liberating Seam in Deep Bursting Coal Seam Group

Suncun coal mine in Xinwen mining area is a typical deep rockburst mine. And the main mining seams are the No.2 and No.4 coal seams. The No.2 coal seam is with the weak bursting liability, and its roof and floor with the strong bursting liability; the No.4 coal seam and its roof and floor are with the weak bursting liability. In order to ensure the safe production of mine, the No.4 coal seam should be chosen as the liberating seam and firstly mined. Therefore, first of all, the upward mining feasibility of coal seam group is studied by theoretical analysis method, and then the structural evolution, fracture development and stress distribution characteristics of overlying strata in stope after mining of No.4 coal seam are studied by numerical simulation method. The research results show that the mining of No.4 coal seam do not destroy the mining condition of No.2 coal seam, instead, it can effectively reduce or even eliminate the bursting risk in the process of No.2 coal seam mining. Based on the above research results, the No.4 coal seam was mined by the following prevention and control rockburst measures, namely: the large-diameter borehole for pressure relief of coal mass, and the drilling cutting method for effect test and evaluation. Besides, the borehole stress sensors are used to monitor and analyze the pressure relief effect of No.2 coal seam after mining of No.4 coal seam. The in-situ monitoring results show that the implementation of large-diameter pressure relief borehole in the front of working face can effectively ensure the safe production in coal seam with weak bursting liability; and the mining of liberating seam is an effective measure for safe production in coal seam with strong bursting liability.

Research on an automatic roadway formation method in deep mining areas by roof cutting with high-strength bolt-grouting

The excavation of deep mining roadways with traditional mining methods leads to various issues, such as the occurrence of large deformations, the waste of coal resources, complex conditions and the high cost of advanced support measures. In this study, we examined the roadway damage mechanism of the traditional gob-side entry driving method with coal pillars using the Suncun Coal Mine, the deepest mine in China, as an engineering case study. A method for the automatic formation of roadways in deep mining areas by roof cutting with high-strength bolt-grouting was proposed, and several quantitative evaluation indicators, namely, the roadway deformation control rate, anchor cable strength utilization ratio, and hydraulic prop strength utilization ratio, were established. The impacts of controlling the deformation of the surrounding rock were comparatively analysed in consideration of numerous factors, such as the mechanical parameters of the surrounding rock, roof cutting height, roof cutting angle, grouting anchor cable length, and hydraulic prop spacing. On this basis, the proposed method was applied in the field. The results showed that the automatically formed roadway cross-section exhibited decreased convergence deformation; moreover, the roof deformation was effectively controlled, and the passive hydraulic prop supports could be effectively replaced with the active support of grouting anchor cables, verifying the effect of the proposed method.

An innovative approach for gob‐side entry retaining in deep coal mines: A case study

AbstractDue to the complex geostress and mining conditions in the coal seam with depth of 800 m, stability of surrounding rock for gob‐side entry retaining is very difficult to achieve. In this paper, we firstly propose an innovative bolt‐grouting controlled roof‐cutting for gob‐side entry retaining (BCR‐GER) approach for deep coal mines. Secondly, a mechanical model of “surrounding rock‐supporting body” for BCR‐GER is constructed, which consists of coal wall, roadside props, and gangues in gob (the whole supporting body). Thirdly, the key parameters (ie, cutting height, cutting angle, grouting cable length, and row of roadside props) are designed. Finally, field practice was applied at the No. 31120 haulage roadway of the Suncun coal mine in China, and in situ investigations were conducted for verification. Field measurement results show that maximum convergences of roof‐to‐floor and side‐to‐side were 264 mm and 113 mm, respectively. What is more, the maximum support resistance of roadside props was reduced by approximately 58%. The deformation and failure of surrounding rock were effectively controlled, and the pressure on roadside props was greatly reduced. This research fully considers the bearing properties of gangues in gob, eliminates the secondary disasters caused by borehole blasting, and provides guidance and reference for deep surrounding rock control of the same or similar gob‐side entry.

Research on the required width of a fault waterproof coal pillar based on underground pressure control theory

Based on underground pressure control theory, this paper expounds the distribution characteristics of abutment stress and the resulting damage to a coal seam in front of a working face. In addition, the distribution and propagation features of vertical underground pressure in floor strata is characterized by simulation results obtained from 2D-σ finite element analysis software. Numerical simulation reveals that the peak stress line of the vertical underground pressure is inclined toward the coal mining direction of the working face. Based on the establishment of a mechanics model for water inrush from floor aquifer through a fault in a stope, a formula for calculating the distance between the bottom of the coal seam and the intersection point of the peak stress line with the fault is derived. The condition allowing water inrush from a floor aquifer through a fault is described as follows: the destroyed floor depth caused by underground pressure is not less than the distance between the bottom of the coal seam and the intersection point of the peak stress line with the fault. The water inrush pathway is composed of the fault and the floor strata destroyed by underground pressure. Based on gray multivariate nonlinear regression analysis, the formula for calculating the destroyed floor depth with four main factors is deduced: these factors are the mining depth, dip angle of the coal seam, inclination width of the working face, and Platts’ coefficient of the floor strata. According to the mechanics model for water inrush from a floor, the formula for a fault waterproof coal pillar in a stope is presented, and the rationality of the model and formula has been verified by cases of water inrush from floor aquifers in the Suncun Coal Mine and the Xiaoyun Coal Mine, China.

Roof Cutting Parameters Design for Gob-Side Entry in Deep Coal Mine: A Case Study

Roof cutting is an effective technique for controlling the deformation and failure of the surrounding rock in deep gob-side entry. The determination of the roof cutting parameters has become a popular research subject. Initially, two mechanical models are established for the non-roof-cutting and roof-cutting of gob-side entry in deep mining conditions. On this basis, the necessity and significance of roof cutting is revealed by analysing the stress and displacement of roadside prop. The Universal Distinct Element Code numerical simulation model is established to determine the key roof-cutting parameters (cutting angle and cutting height) according to the on-site situation of No. 2415 headentry of the Suncun coal mine, China. The numerical simulation results show that with the cutting angle and height increase, the vertical stress and horizontal displacement of the coal wall first increase and then decrease, as in the case of the vertical stress and displacement of roadside prop. Therefore, the optimum roof cutting parameters are determined as a cutting angle of 70° and cutting height of 8 m. Finally, a field application was performed at the No. 2415 headentry of the Suncun coal mine. In situ investigations show that after 10 m lagged the working face, the stress and displacement of roadside prop are obviously reduced with the hanging roof smoothly cut down, and they are stable at 19 MPa and 145 mm at 32 m behind the working face, respectively. This indicates that the stability of the surrounding rock was effectively controlled. This research demonstrates that the key parameters determined through a numerical simulation satisfactorily meet the production requirements and provide a reference for ensuring safe production in deep mining conditions.

Multiparameter Monitoring and Prevention of Fault-Slip Rock Burst

Fault-slip rock burst is one type of the tectonic rock burst during mining. A detailed understanding of the precursory information of fault-slip rock burst and implementation of monitoring and early warning systems, as well as pressure relief measures, are essential to safety production in deep mines. This paper first establishes a mechanical model of stick-slip instability in fault-slip rock bursts and then reveals the failure characteristics of the instability. Then, change rule of mining-induced stress and microseismic signals before the occurrence of fault-slip rock burst are proposed, and multiparameter integrated early warning methods including mining-induced stress and energy are established. Finally, pressure relief methods targeting large-diameter boreholes and coal seam infusion are presented in accordance with the occurrence mechanism of fault-slip rock burst. The research results have been successfully applied in working faces 2310 of the Suncun Coal Mine, and the safety of the mine has been enhanced. These research results improve the theory of fault-slip rock burst mechanisms and provide the basis for prediction and forecasting, as well as pressure relief, of fault-slip rock bursts.

Study on the Relationship between the Depth of Coal Seam and the Quantity of CH<sub>4</sub> Produced

Based on the geological and the experimental data of the 13#coal seam of Sun-Cun Coal Mine, the relationship curve between the depth of coal seam and the amount of CH4 produced has been fit out. According this and the laboratory experiments, the relational expression between the quantity of CH4 and the period of spontaneous combustion has been obtained. The research results show that the relationship curve between the period of spontaneous combustion in coal sample and the quantity of CH4 fit exponential expression. Especially when the quantity of CH4 produced exceeds 5 mol / (Kg min), the period of spontaneous combustion in this experiment is almost unchanged. This law should be paid more attention to.

Study on the Relationship of the Quantity of CO<sub>2</sub> Produced and the Wind Speed

Based on the geological and the experimental data of the13#coal seam of Sun-Cun Coal Mine, the relationship curve between the geothermal heat in Sun-Cun coal mine and experimental wind speed has been fit out.According this and the laboratory experiments,the relational expression between the quantity of CO2 produced in the period of spontaneous combustion and the wind speed in the coal mine has been developed. The research results show that when the wind speed exceeds 2m/s,the quantity of CO2 produced has a sharp rising tendency.

Study on the Relation between the Deep and the Spontaneous Combustion of Coal Seam

Based on the data and laboratory analysis of Sun-Cun Coal Mine, the relationship between the geothermal gradient and the depth of mine in Suncun Coal Mine has been developed. According to this and the laboratory experiments, the relationship between spontaneous combustion period of coal seam and the depth of the mine has been obtained in this article. The results show that the law of coal seam spontaneous combustion period and the mine depth in accordance with the relationship of the gauss curve expression and when the coal mine depth is around 1000 m, the coal seam spontaneous combustion period shortened dramatically. This law should be pay more attention to.

The Relationship between the Period of Spontaneous Combustion and the Wind Speed

Based on the geological and the experimental data of the 13# coal seam of Sun-Cun Coal Mine, the relationship curve between the geothermal heat in Sun-Cun coal mine and experimental wind speed has been fit out. According this and the laboratory experiments, the relational expression between the period of spontaneous combustion in coal sample and the wind speed has been developed. The research results show that the curve of wind speed and the spontaneous combustion period fitted quadratic polynomial forms.

Paste-like self-flowing transportation backfilling technology based on coal gangue

A paste-like self-flowing pipeline transportation backfilling technology with coal gangue as aggregate is proposed to remove the potential damage caused by coal gangue piles. As well, the difficult problems of recovering high quality safety coal pillars and deep mining of the Suncun Coal Mine (SCM), Xinwen Coal Group, Shandong are resolved. The physical-chemical properties of coal gangue, optimized proportion of materials, backfilling system and craft in the SCM were studied in the laboratory and then an industrial test was carried out on high quality coal pillars under a town. The results show that finely crushed kaolinized and fresh gangue with granularity less than 5 mm can be used as aggregate with fly ash to replace part of the cement and a composite water reducer as an additive, accounting for 1.0%–1.5% of the total amount of cement and fly ash. The recommended proportion is 1(cement):4(fly ash):15(coal gangue), with a mass fraction of 72%–75%, rheological paste-like properties and a strength of more than 0.7 MPa at 7 d. The sequence of adding cement, fly ash, water reducer and then coal gangue ensures that the suspended state of the slurry, reducing the wear and jam of pipelines. The working face is advancing continuously by the alternating craft of building block walls with coal gangue and backfilling mined-out gobs with paste-like slurry. The recovery rate is as high as 90% with a backfilling cost of 36.9 Yuan/t, good utilization of coal gangue and no subsidence on the surface. This technology provides a good theoretical basis and application experience for coal mines, cement backfilling with paste-like slurry.

Hydraulic calculation of gravity transportation pipeline system for backfill slurry

Taking cemented coal gangue pipeline transportation system in Suncun Coal Mine, Xinwen Mining Group, Shandong Province, China, as an example, the hydraulic calculation approaches and process about gravity pipeline transportation of backfill slurry were investigated. The results show that the backfill capability of the backfill system should be higher than 74.4 m3/h according to the mining production and backfill times in the mine; the minimum velocity (critical velocity) and practical working velocity of the backfill slurry are 1.44 and 3.82 m/s, respectively. Various formulae give the maximum ratio of total length to vertical height of pipeline (L/H ratio) of the backfill system of 5.4, and then the reliability and capability of the system can be evaluated.

Performance of cemented coal gangue backfill

Possibility of cemented gangue backfill was studied with gangue of Suncun Coal Mine, Xinwen Coal Group, Shandong, and fly ash of nearby thermal power plant, in order to treat enormous coal gangue on a large scale and to recovery safety coal pillars. The results indicate that coal gangue is not an ideal aggregate for pipeline gravity flow backfill, but such disadvantages of gangue as bad fluidity and serious pipe wear can be overcome by addition of fly ash. It is approved that quality indexes such as strength and dewatering ratio and piping feature of slurry can satisfy requirement of cemented backfill if mass ratio of cement to fly ash to gangue is 1:4:15 and mass fraction of solid materials reaches 72%–75%. Harden mechanism suggests that the cemented gangue fill has a higher middle and long term comprehensive strength.