The coal pillar design method for a deep mining roadway based on the shape of the plastic zone in surrounding rocks

2020 ◽  
Vol 13 (12) ◽  
Author(s):  
Ji Li
Keyword(s):  
Plastic Zone ◽  
Design Method ◽  
Coal Pillar ◽  
Pillar Design ◽  
Deep Mining

scholarly journals Research on Evaluation Index and Application of Rockburst Risk in Deep Strip Mining

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Bangyou Jiang ◽  
Hongguang Ji ◽  
Long Fu ◽  
Shitan Gu ◽  
Tong Zou ◽  
...  
Keyword(s):  
Plastic Zone ◽  
Coal Mine ◽  
Coal Pillar ◽  
Width Ratio ◽  
Strip Mining ◽  
Index Method ◽  
Research On Evaluation ◽  
Mechanics Model ◽  
Evolution Characteristics ◽  
Comprehensive Index Method

The practice shows that deep strip mining induces rockburst disaster easily. Accurately evaluating rockburst risk of the strip coal pillar is of great significance for ensuring the safety of deep strip mining. In this paper, the catastrophe mechanics model was used to analyze the abrupt instability condition of strip coal pillar. And the three indicators that are the medium stiffness ratio (k) of the elastic and plastic zone in the coal pillar, the plastic zone width ratio (aY), and the elastic deformation index (Uq) of core zone were put forward with considering the geometry size of coal pillar. Based on the 3202 panel of Gucheng Coal Mine, the evolution characteristics of rockburst risk of coal pillar under different mining widths and coal pillar widths were studied by numerical simulation. The evaluation result shows that the strip coal pillar of the 3202 panel is in danger of strong rockburst, which is more in line with the actual situation than the results of the traditional rockburst tendency identification test and comprehensive index method. These three indicators can be regarded as important indicators to evaluate the rockburst risk in the strip mining engineering field. Based on that, the design principle of strip mining in Gucheng Coal Mine was put forward, which is considered an important reference for similar cases.

scholarly journals Study on Protective Coal Pillar Size Design for Ultra High Voltage Line Tower Mining in Mountain Areas

Designs ◽  
2019 ◽  
Vol 3 (2) ◽  
pp. 20
Author(s):  
Feiya Xu ◽  
Wenbing Guo ◽  
Jianli Li
Keyword(s):  
Coal Mining ◽  
High Voltage ◽  
Coal Pillar ◽  
Vertical Line ◽  
Mountain Areas ◽  
Pillar Design ◽  
Critical Deformation ◽  
Line Method ◽  
Coal Pillars ◽  
Ultra High Voltage

High voltage line towers in mining areas are sensitive to surface deformation caused by mining. Protective coal pillar design for high voltage towers is one of the commonly-used technical measures. Aiming to solve the coal mining safety problem under the Ultra High Voltage transmission line in Sihe Coal Mine of Shanxi Province, the angle and size of protective coal pillars with the vertical line method were analyzed in this paper. The effect of additional displacement caused by landslide or slippage mining in mountain areas and repeated mining was considered. Based on the principle of the vertical line method, the protective coal pillar range and size were calculated. The amount of coal deposited in coal pillars for high voltage line towers was compared and analyzed between the vertical line method and the linear structure method. The results showed that the angle of critical deformation decreased by 2~10° caused by slippage due to mining in a mountainous area, and the angle in the uphill direction of building decreased more than that in the downhill direction; when multi-seams were mined repeatedly, the angle of critical deformation in the lower seam coal mining was reduced by 5~10° compared with that of the upper seam. The protective coal pillar design with the vertical line method can protect the high voltage line towers more effectively, and the amount of protective coal pillars with the vertical line method was 5.8 million tons less, which avoided the waste of coal resources.

scholarly journals Roadway Surrounding Rock under Multi-Coal-Seam Mining: Deviatoric Stress Evolution and Control Technology

2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Dongdong Chen ◽  
En Wang ◽  
Shengrong Xie ◽  
Fulian He ◽  
Long Wang ◽  
...  
Keyword(s):  
Plastic Zone ◽  
Coal Seam ◽  
Coal Pillar ◽  
Surrounding Rock ◽  
Deviatoric Stress ◽  
Mine Pressure ◽  
Coal Face ◽  
Surrounding Rock Control ◽  
Seam Mining ◽  
Peak Value

Multi-coal-seam mining creates surrounding rock control difficulties, because the mining of a coal face in one seam can affect coal faces in another. We examine the effects of multi-coal-seam mining on the evolution of the deviatoric stress distribution and plastic zone in the roadway surrounding rock. In particular, we use numerical simulation, theoretical calculation, drilling detection, and mine pressure observation to study the distribution and evolution characteristics of deviatoric stress on Tailgate 8709 in No. 11 coal seam in Jinhuagong mine when the N8707 and N8709 coal faces in No. 7-4 coal seam and the N8707 and N8709 coal faces in No. 11 coal seam are mined. The evolution laws of deviatoric stress and the plastic zone of roadway surrounding rock in the advance and behind sections of the coal face are studied, and a corresponding control technology is proposed. The results show that the peak value of deviatoric stress increases with the advance of the coal face, and the positions of the peak value of deviatoric stress and the plastic zone become deeper. The deflection angle of the peak stress after mining at each coal face and the characteristics of the peak zone of deviatoric stress and the plastic zone of the roadway surrounding rock under the disturbance of multi-coal-seam mining are determined. In conclusion, the damage range in the roadway roof in the solid-coal side and coal pillar is large and must be controlled. A combined support technology based on high-strength and high pretension anchor cables and truss anchor cables is proposed; long anchor cables are used to strengthen the support of the roadway roof in the solid-coal side and coal pillar. The accuracy of the calculated plastic zone range and the reliability of the combined support technology are verified through drilling detection and mine pressure observation on site. This research can provide a point of reference for roadway surrounding rock control 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.

The Choice of Basic Pillar Design Theory for Locked Sand Condition

2012 ◽  
Vol 256-259 ◽  
pp. 354-357
Author(s):  
Zi Wei Ding ◽  
Amirhossein Bagherieh ◽  
Rui Min Feng ◽  
Xing Xing Wen
Keyword(s):  
Design Theory ◽  
Design Method ◽  
Friction Angle ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Pillar Design ◽  
Design Theories ◽  
Locked Sand ◽  
Unconfined Strength ◽  
Very High

Because of unique properties of locked sand (very high friction angle and very low cohesion), a new pillar design method based on present basic pillar design theories must be developed. Wilson theory puts its focus on confining pressure, which is related to friction angle and cohesion. Triaxial tests results show that locked sand at Pattison mine has an average friction angle of 57°, which means the strength of the material increases rapidly with the confining pressure, and average cohesion of 2.6 MPa. Results show that choosing Wilson theory as basic pillar design theory not only considers the high friction angle of locked sand, but also minimizes the effects of Wilson’s hypothesis of neglecting the unconfined strength.

scholarly journals Numerical Study on Soft Coal Pillar Stability in an Island Longwall Panel

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Qingyun Xu ◽  
Jian-Biao Bai ◽  
Shuai Yan ◽  
Rui Wang ◽  
Shaoxu Wu
Keyword(s):  
Plastic Zone ◽  
Numerical Study ◽  
Deformation Characteristic ◽  
Coal Pillar ◽  
Surrounding Rock ◽  
Pillar Width ◽  
Soft Coal ◽  
Geological Conditions ◽  
Longwall Panel ◽  
Coal Pillars

Roadway support and management of longwall panels in an island soft coal panel are always difficult work. In a test mine, stress distribution, deformation characteristic, and plastic zone distribution around the roadway and coal pillars in the development and mining periods were investigated with respect to the widths of different coal pillars using theoretical and simulation methods. The most reasonable width of coal pillars was comprehensively determined, and the field test was conducted successfully. The results show that a reasonable width of coal pillars is 7.0–8.2 m using the analytical method. The distribution of vertical stress in the coal pillars showed an asymmetric “double-hump” shape, in which the range of abutment pressure was about 26.0–43.0 m, and the roadway should be laid away from stress concentration. When the coal pillar width is 5.0–7.0 m, deformation of the roadway is half that with 8.0–10.0 m coal pillar in the development and mining period. The plastic zone in the surrounding rock firstly decreases and increases with increasing coal pillar width; the smallest range occurs with a coal pillar width of 5.0 m. Finally, a reasonable width for coal pillars in an island panel was determined to be 5.0 m. Industrial practice indicated that a coal pillar width of 5.0 m efficiently controlled deformation of the surrounding rock, which was an important basis for choosing the width of coal pillars around gob-side entries in island longwall panels with similar geological conditions.

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 Dynamic Evolution Law and Width Determination of Section Coal Pillars in Deep Mining Height Working Face

2021 ◽  
Author(s):  
Lei Zhaoyuan ◽  
Cui Feng ◽  
Liu Jianwei ◽  
Lai Xingping ◽  
Yi Ruiqiang
Keyword(s):  
Dynamic Instability ◽  
Coal Pillar ◽  
Field Measurements ◽  
Deep Mining ◽  
Evolution Law ◽  
Working Face ◽  
Large Mining Height ◽  
Coal Pillars ◽  
Lower Corner ◽  
Mining Height

Abstract The coal column undergoes three types of force evolution from the formation to the end of mining. This paper takes large mining height working face at No.2 Coal Mine as example to study the ways to avoid dynamic instability of the coal column triggered by the deep mining. By means of geological survey, theoretical analysis, numerical calculation and field verification, the load processes under the three stress stage are proposed, and the evolution law of the coal column is analyzed. The study shows that the depth, large mining height working face, coal pillar force and size altogether determine the damage characteristics of the coal pillar. With the combination of Flac3D and 3DEC, it can be analyzed that the plastic failure and displacement characteristics of the 35m coal column under the action of secondary dynamic load coincide. The perturbation stress distribution is stable, which finally determines the reasonable width of the 35m coal column. Field measurements show that the top and gang of the 35m coal column undergo three kinds of displacement characteristics. The lower part is more stable. The top plate of the upper and lower corner completely collapsed in the emptying area, which can play a good supporting role.

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