scholarly journals Study on Control Technology for Working Faces Passing through Long-Span Abandoned Roadways

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Zhenghe Liu ◽  
Hailong Ye ◽  
Lusheng Yang ◽  
Shaohua Wang ◽  
Junwen Zhang ◽  
...  
Keyword(s):  
Plastic Zone ◽  
Impact Load ◽  
Great Influence ◽  
Coal Pillar ◽  
Field Testing ◽  
Engineering Practice ◽  
Hydraulic Support ◽  
Long Span ◽  
Working Face ◽  
Working Resistance

The width of an abandoned roadway has a great influence on the roof stability of the working face. According to the coal seam conditions of the 30106 working face in the Sanyuan Shiku mine, the advance of a working face through an abandoned roadway was studied by using theoretical analysis, similar material simulation, numerical simulation, and field testing to determine the law of stope roof fracture migration, the stress distribution characteristics, and the variation in support resistance. Several conclusions are drawn: (1) The roof of the overlying strata is fractured at the edge of the abandoned roadway in front of the coal pillar and rotates downward due to the run-through of the plastic zone between the working face and abandoned roadway. (2) The hydraulic support working resistance gradually increases with decreasing coal pillar width between the working face and abandoned roadway, and the working resistance of the support tends to peak when the plastic zone extends to the coal, resulting in 3~4 times the normal recovery. Leakage occurred in front of the support in the caving zone. (3) The analysis of the relationship between the support and surrounding rock with the mechanical model for calculating the support load allows the derivation of the support working resistance formula for a working face passing through an abandoned roadway. (4) When the working face is excavated to expose the abandoned roadway, the shrinkage of the front column of the hydraulic support is significantly greater than that of the back column, and the stability is greatly reduced. This problem can be effectively solved when the uniaxial compressive strength of the backfill ≥2 MPa. (5) The engineering practice showed that the danger of leakage and roof fracture impact load was eliminated with the mining pressure reduction after reinforcement measures were taken in the abandoned roadway. The working face passed the abandoned roadway safely, providing the theoretical basis and guidance for coal remining under similar conditions.

scholarly journals Research on the Influence of Slurry Filling on the Stability of Floor Coal Pillars during Mining above the Room-and-Pillar Goaf: A Case Study

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-21
Author(s):  
Zhu Li ◽  
Guorui Feng ◽  
Jiaqing Cui
Keyword(s):  
Plastic Zone ◽  
Coal Mine ◽  
Body Height ◽  
Coal Pillar ◽  
Northwest China ◽  
Engineering Practice ◽  
Working Face ◽  
The Stability ◽  
Safe Mining ◽  
Upward Mining

Room-and-pillar mining is a commonly used mining method in previous practice in northwest China mining area. Due to priority selection of high-quality resources, coal mines in northwest China generally have to face upward mining above goaf. Thus, the stability of a floor coal pillar influenced by mining activities plays an essential role in upward mining above goaf. The results indicated that a floor coal pillar kept stable before coal excavation in the no. 6107 working face in the Yuanbaowan coal mine; however, the plastic zone in the floor coal pillar expanded sharply and the elastic core zone reduced suddenly on the influence of abutment pressure. Finally, the floor coal pillar supported failure. Accordingly, the paper proposed a floor coal pillar reinforcing technique through a grout injection filling goaf area. As physically limited by a different-height filling body on the double sides, the plastic zone scope and horizontal displacement and loading capacity of the floor coal pillar were studied, working out that the critical height of the filling body should be about 6 m which can ensure safe mining when upward mining above goaf. Case practice indicated that the fractures induced by mining in the floor coal pillar, filling body, and floor can be restrained effectively when the filling body height is 6 m, which can ensure floor coal pillar stability and safe mining of the no. 6107 working face in the Yuanbaowan coal mine. The research can provide theoretical and technical guidance for upward mining above goaf and have a critical engineering practice value.

scholarly journals Study on the Fracture Law of Inclined Hard Roof and Surrounding Rock Control of Mining Roadway in Longwall Mining Face

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5344
Author(s):  
Feng Cui ◽  
Shuai Dong ◽  
Xingping Lai ◽  
Jianqiang Chen ◽  
Chong Jia ◽  
...  
Keyword(s):  
Energy Release ◽  
Longwall Mining ◽  
Coal Pillar ◽  
High Energy ◽  
Mechanical Analysis ◽  
Engineering Practice ◽  
Analysis Model ◽  
Hard Roof ◽  
Working Face ◽  
The Stability

In the inclination direction, the fracture law of a longwall face roof is very important for roadway control. Based on the W1123 working face mining of Kuangou coal mine, the roof structure, stress and energy characteristics of W1123 were studied by using mechanical analysis, model testing and engineering practice. The results show that when the width of W1123 is less than 162 m, the roof forms a rock beam structure in the inclined direction, the floor pressure is lower, the energy and frequency of microseismic (MS) events are at a low level, and the stability of the section coal pillar is better. When the width of W1123 increases to 172 m, the roof breaks along the inclined direction, forming a double-hinged structure, the floor pressure is increased, and the frequency and energy of MS events also increases. The roof gathers elastic energy release, and combined with the MS energy release speed it can be considered that the stability of the section coal pillar is better. As the width of W1123 increases to 184 m, the roof in the inclined direction breaks again, forming a multi-hinged stress arch structure, and the floor pressure increases again. MS high-energy events occur frequently, and are not conducive to the stability of the section coal pillar. Finally, through engineering practice we verified the stability of the section coal pillar when the width of W1123 was 172 m, which provides a basis for determining the width of the working face and section coal pillar under similar conditions.

scholarly journals Deviatoric Stress Evolution Laws and Control in Surrounding Rock of Soft Coal and Soft Roof Roadway under Intense Mining Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Dongdong Chen ◽  
Chunwei Ji ◽  
Shengrong Xie ◽  
En Wang ◽  
Fulian He ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Plastic Zone ◽  
Theoretical Calculations ◽  
Coal Pillar ◽  
Surrounding Rock ◽  
Deviatoric Stress ◽  
Anchor Cable ◽  
Soft Coal ◽  
Working Face ◽  
Failure Line

Aiming at the problem of large deformation and instability failure and its control of soft coal and soft roof roadway under intense mining, laboratory experiments, theoretical calculations, Flac3D numerical simulation, borehole peeping, and pressure observation were used to study the deflection characteristics of the deviatoric stress of the gas tailgate and the distribution and failure characteristics of the plastic zone in the mining face considering the strain softening characteristics of the roof and coal of roadway, and then the truss anchor cable-control technology is proposed. The results show the following: (1) The intense mining influence on the working face will deflect the peak deviatoric stress zone (PDSZ) of the surrounding rock of the gas tailgate. The influence distance of PDSZ is about 20 m in advance and 60 m in lag; the PDSZ at the gob side of the roadway is located in the range of 3–5.5 m from the surface of the coal pillar, while the coal wall side is mainly located in the range of 3–4.5 m at the shoulder corner and bottom corner of the solid coal. (2) The intense mining in the working face caused the nonuniform expansion of the surrounding rock plastic area of the gas tailgate. The two shoulder angles of the roadway and the bottom of the coal pillar have the largest damage range, and the maximum damage location is the side angle of the coal pillar (5 m). Angle and bottom angle of coal pillar are the key points of support control. (3) The plastic failure line of the surrounding rock of the gas tailgate is always between the inner and outer contours of the PDSZ, and the rock mass in the PDSZ is in a stable and unstable transition state, so the range of anchor cable support should be cross plastic failure line. (4) The theoretical calculations and numerical simulation results agree well with the drilling peep results. Based on the deflection law of the PDSZ and the expansion characteristics of the plastic zone, a truss anchor cable supporting system with integrated locking and large-scale support function is proposed to jointly control the roof and the two sides, which effectively solves the problem of weak surrounding rock roadway under severe mining deformation control problems realizing safety and efficient production in coal mines under intense mining.

Study on the Terminal Line Reasonable Position of Two Coal Seam under the Down-Protective Layer Pressure-Relieved Mining

2013 ◽  
Vol 295-298 ◽  
pp. 2913-2917
Author(s):  
Xiang Yang Zhang ◽  
Min Tu
Keyword(s):  
Coal Seam ◽  
Coal Pillar ◽  
Protective Layer ◽  
Simulation Software ◽  
Surrounding Rock ◽  
Rock Properties ◽  
Engineering Practice ◽  
Working Face ◽  
Roadway Deformation ◽  
The Impact

In order to study the stress distribution and its dynamic influence law while the protective layer mining, based on the transfer law of mining-induced stress in the coal seam floor and in front of the working face, using numerical simulation software to simulate the surrounding rock stress under the different pillar width mining conditions, and carried through the roadway deformation engineering practice observations. It is shown that reserved 110m coal pillar could weaken the impact on the front of the floor tunnel under the protective layer mining process. When the top liberated layer mining to reduce the impact of mining stress superposition, it should avoid the terminal lines on the two coal seams at the same location and may be staggered at least about 30m ~ 50m. And it obtained that the roadway deformation not only by mining impact, but also considering the geological environment surrounding rock conditions, tunnel position in which layers of rock, rock properties and other factors. The research guided the engineering practice successfully.

scholarly journals Study on temporary support of continuous girder bridge in construction

2017 ◽  
Vol 6 (1) ◽  
pp. 8
Author(s):  
Chun Ming Xu
Keyword(s):  
Great Influence ◽  
Engineering Practice ◽  
Rigid Support ◽  
Structural System ◽  
Fixed Bearing ◽  
Long Span ◽  
Temporary Support ◽  
Continuous Girder Bridge ◽  
Girder Bridge ◽  
Supporting Force

The reasonable design of the temporary support of the continuous girder bridge is a safe guarantee for the smooth closing. According to the characteristics of temporary support of the closed section, the corresponding calculation method is put forward, and then several kinds of temporary support locking devices colmmonly used in engineering practice are discussed. Based on the engineering example, the paper discusses the selection and design of the temporary support form of the construction of the continuous girder bridge. The results show that the transition of the structural system has great influence on the temporary supporting force, and it is feasible to use the external rigid support when the long - span continuous girder bridge decouples the temporary fixed bearing restraint.

Study on Rational Width of Entry Protection Coal-Pillar in Large Mining Height Working Face

2011 ◽  
Vol 413 ◽  
pp. 404-409
Author(s):  
Xu Feng Wang ◽  
Dong Sheng Zhang ◽  
Ting Feng Cui ◽  
Jin Liang Wang ◽  
Wei Zhang
Keyword(s):  
Numerical Simulation ◽  
Theoretical Calculation ◽  
Coal Pillar ◽  
Engineering Practice ◽  
Pillar Width ◽  
Pillar Design ◽  
Working Face ◽  
Large Mining Height ◽  
Mining Height

This paper demonstrates the attempt to identify a reasonable chain pillar width in the condition of large mining height, along with a case study at the gateway of No.1103 panel with large mining height in Suancigou Mine. Theoretical calculation and numerical simulation were employed as the main approaches during the research to figure out the rational width of entry protection coal-pillar, which was then proved to be capable for engineering practice. The results that derived from our research can offer technical support for spot production, and serve as references for future investigation upon chain pillar design under large mining height.

scholarly journals Surrounding Rock Control Technology When the Longwall Face Crosses Abandoned Roadways: A Case Study

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Zhenpeng Jiang ◽  
Fangtian Wang ◽  
Kaijun Miao ◽  
Qinghua Cao
Keyword(s):  
Plastic Zone ◽  
Rock Fracture ◽  
Coal Pillar ◽  
Numerical Comparison ◽  
Reinforcement Scheme ◽  
Working Face ◽  
Roof Fall ◽  
Support Resistance ◽  
Key Block ◽  
Surrounding Rock Control

When a working face is crossing the abandoned roadways, problems such as roof subsidence, rock fracture, and instability will occur, resulting in widespread roof fall and rib spalling, which seriously affect safe and efficient mining on the working face. In this paper, the no. 23 coal pillar working face of Juji coal mine is taken as the engineering background, a mechanical model of crossing the abandoned roadways is constructed aimed at the problem of the working face crossing the abandoned roadway group, the collapse of the abandoned roadway roof is analyzed, a scheme of crossing the abandoned roadways is designed, and the development law of the stress and plastic zone after the reinforcement scheme is stimulated and analyzed. The results show that when the working face advances to the abandoned roadway, key block B crosses the abandoned roadway and the solid coal to form a “cross-roadway long key block.” It is calculated that the minimum support resistance required for the abandoned roadway is 6700 kN. Based on the results of numerical comparison, it is concluded that filling wood pile when the working face passes through the roof abandoned roadway and adding anchor cables for reinforcement support when the working face crosses the coal seam abandoned roadway effectively reduce the stress concentration of surrounding rocks, decrease the development of the plastic zone, and achieve safe and efficient mining when the working face crosses the abandoned roadways.

scholarly journals Study on Pressure Relief Technology of High-Pressure Water Jet of Residual Coal Pillar in Overlying Goaf in Close Seam Mining

2022 ◽  
Vol 2022 ◽  
pp. 1-19
Author(s):  
Shang Yang ◽  
Xuehui Li ◽  
Jun Wang ◽  
Shuhao Yang ◽  
Zhen Shen ◽  
...  
Keyword(s):  
High Pressure ◽  
Coal Seam ◽  
Coal Pillar ◽  
Water Jet ◽  
Hydraulic Support ◽  
Working Face ◽  
Pressure Water ◽  
High Pressure Water Jet ◽  
Residual Coal ◽  
Close Distance

To solve the problem of strong ground pressure behaviour under a residual coal pillar in the overlying goaf of a close-distance coal seam, this paper proposes the technology of weakening and relieving the residual coal pillar in the overlying goaf by a high-pressure water jet. Based on the geological occurrence of the No. 3 coal seam and mountain No. 4 coal seam in the Yanzishan coal mine, the high-pressure water jet pressure relief technology of residual coal pillars in the overlying goaf of close-distance coal seams was studied by theoretical analysis and field industrial tests. First, the elastic-plastic zone of the residual coal pillar and the stress distribution law of the floor are obtained by theoretical analysis, and the influence degree of the residual coal pillar on the support of the lower coal seam working face is revealed. Then, a high-pressure water jet combined with mine pressure is proposed to weaken the residual coal pillar. Finally, through the residual coal pillar hydraulic cutting mechanical model and “double-drilling double-slot” model, the high-pressure water jet drilling layout parameters are determined, and an industrial field test is carried out. The single knife cutting coal output and 38216 working face hydraulic support monitoring data show that high-pressure hydraulic slotting can weaken the strength of the coal body to a certain extent, destroy the integrity of the residual coal pillar, cut off the load transmission path of the overlying strata, and reduce the working resistance of the hydraulic support under the residual coal pillar to a certain extent, which is beneficial to the safe mining of the working face.

scholarly journals Gob-Side Entry Retained with Soft Roof, Floor, and Seam in Thin Coal Seams: A Case Study

2020 ◽  
Vol 12 (3) ◽  
pp. 1197 ◽  
Author(s):  
Zhijun Tian ◽  
Zizheng Zhang ◽  
Min Deng ◽  
Shuai Yan ◽  
Jianbiao Bai
Keyword(s):  
Mining Industry ◽  
Coal Pillar ◽  
Surrounding Rock ◽  
Engineering Practice ◽  
Mine Pressure ◽  
Coal Seams ◽  
Rock Stability ◽  
Working Face ◽  
Geological Conditions ◽  
Surrounding Rock Control

Gob-side entry retained technology is of great significance to develop coal mining industry sustainably, which can improve the coal recovery rate by mining without the coal pillar. However, scholars and researchers pay little attention to the gob-side entry retained with soft roof, floor, and seam in thin coal seams. In this study, the difficulties and key points of surrounding rock control for gob-side entry retained with soft roof, floor, and seam in thin coal seams were firstly proposed. Secondly, the mechanical model of the interaction between the roadside backfill body and the roof for gob-side entry retained with soft roof, floor, and seam in thin coal seams was established, and the relevant parameters were designed. Finally, the above results were verified by the engineering practice of gob-side entry retained technology and the monitoring of mine pressure on the 1103 working face of the Heilong Coal Mine. Moreover, the effect factors of surrounding rock stability for gob-side entry retained with soft roof, floor, and seam in thin coal seams were discussed using the discrete element method. The results could provide guidance for gob-side entry retained with soft roof, floor, and seam in thin coal seams under similar geological conditions.

scholarly journals Study on the Characteristics of Top-Coal Caving and Optimization of Recovery Ratio in Steeply Inclined Residual High Sectional Coal Pillar

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Wenhua Yang ◽  
Xingping Lai ◽  
Pengfei Shan ◽  
Feng Cui ◽  
Yiran Yang
Keyword(s):  
Bulk Density ◽  
Coal Pillar ◽  
Engineering Practice ◽  
Recovery Ratio ◽  
Coal Seams ◽  
Balance System ◽  
Coal Recovery ◽  
Working Face ◽  
Coal Rock ◽  
Arch Structure

This paper is aimed at solving the technical problems such as low recovery ratio and frequent disasters in steeply inclined and extrathick coal seams at residual high sectional coal pillar. It takes the Wudong Coal Mine as an engineering background, a typical mine of steeply inclined and extrathick coal seams; the structural features of the top-coal caving at the steeply inclined residual high sectional coal pillar were analyzed using methods such as field monitoring and numerical simulation; a mechanical model of the top-coal arch structure was constructed, and the calculation method of top-coal caving height and related influencing factors was obtained. The results showed that the top-coal caving in the steeply inclined residual high sectional coal pillar was characterized as arch. Due to the existence of arch structure, the smooth caving of the top coal was hindered, resulting in a low top-coal recovery ratio, low support pressure at the working face, and differences detected by borehole television on the distribution of the top-coal cracks. With the advancement of the working face, the top-coal arch structure was in the process of dynamic evolution, as the old arch balance system was continuously replaced by the new arch balance system, and it continuously moved towards the upper top coal. The top-coal caving height was affected by factors such as length of the working face, bulk density of overlying coal rock, and cohesion of the top coal. The top-coal caving height increased with the length of the working face and the bulk density of the overlying coal rock mass but was inversely proportional to the cohesion of the top coal. Under the current mining conditions, the top-coal caving height was 39.8 m, which was much lower than the residual high sectional coal pillar height (71 m); the top coal cannot collapse completely. Based on the characteristics of the top-coal caving structure, the technology of sublevel advanced presplitting blasting was adopted to weaken the top coal in engineering practice, so that the top-coal caving structure moved up naturally. The daily coal production in the working face has increased by an average of 2419.6 tons, which has significantly improved the top-coal recovery ratio and production efficiency. The result provided a theoretical basis and application reference for similar residual high sectional coal pillar recovery.

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