Study on stability of thick-hard key stratum based on numerical simulation in longwall mining

2014 ◽  
pp. 477-481
Author(s):  
Zhengxing Yu ◽  
Fuxing Jiang ◽  
Quanjie Zhu ◽  
Sitao Zhu
Keyword(s):  
Numerical Simulation ◽  
Longwall Mining ◽  
Key Stratum

scholarly journals Fracture Mechanism in Overlying Strata during Longwall Mining

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Zhengyi Ti ◽  
Jiazhen Li ◽  
Meng Wang ◽  
Kang Wang ◽  
Zhupeng Jin ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Fracture Mechanism ◽  
Longwall Mining ◽  
Flexural Rigidity ◽  
Central Area ◽  
Short Side ◽  
Wall Area ◽  
Key Stratum ◽  
Coal Wall ◽  
Overlying Strata

We used the key stratum theory to establish a more realistic thin-plate mechanical model of elastic foundation clamped boundary and study the fracture mechanism of overlying strata during longwall mining. We analyzed the fracture characteristics and factors affecting fracture of the key stratum combined with the Mohr–Coulomb yield criterion. Besides, we used numerical simulation methods to verify the evolution pattern of the overlying strata fracture. The results show that the fracture mechanisms of the elastic foundation clamped structure’s key stratum varied depending on the position under longwall mining. The advanced coal wall area of the upper surface is a compressive-shear fracture. The center area of the lower surface is a tensile fracture. With the increase of the excavation length and the load of the key stratum, the central area and the advanced coal wall area of the long side are fractured before the advanced coal wall area of the short side. With the increase of flexural rigidity of the key stratum, the advanced coal wall area of the long side fractures before the central area and the advanced coal wall area of the short side. With the increase of the foundation modulus and the advanced load of the key stratum, the central area fractures before the surrounding advanced coal wall area. The advanced influence distance was positively correlated with the key stratum’s flexural rigidity and advanced load and negatively correlated with the foundation modulus and excavation length. The advanced influence distance was not affected by the load of the key stratum. The numerical simulation results show that, with the increase of the mining area, the fracture trace of overlying strata in goaf extended to the coal wall’s interior. The fracture range of overlying strata is larger than that of the miningd: area. This study has a practical value for water disasters, gas outbursts, and rock strata control.

scholarly journals Control Technology of Surface Movement Scope with Directional Hydraulic Fracturing Technology in Longwall Mining: A Case Study

Energies ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 3480 ◽  
Author(s):  
Zhanjie Feng ◽  
Wenbing Guo ◽  
Feiya Xu ◽  
Daming Yang ◽  
Weiqiang Yang
Keyword(s):  
Numerical Simulation ◽  
Hydraulic Fracturing ◽  
Longwall Mining ◽  
Numerical Models ◽  
Surface Subsidence ◽  
The Sustainable Development ◽  
Surface Movement ◽  
Directional Hydraulic Fracturing ◽  
Simulation Results ◽  
Overlying Strata

Mining-induced surface subsidence causes a series of environmental hazards and social problems, including farmland destruction, waterlogging and building damage in the subsidence area. To reduce mining damages, an innovative method of controlling the surface movement scope via artificial weak planes generated by hydraulic fracturing technology was proposed in this paper. Numerical models were built to analyze the influence of weak planes with different heights and dips on the overlying strata movement. The numerical simulation results showed that the weak planes structure cut off the development of the overlying strata displacement to the surface and affected the surface movement scope. When the weak planes’ dips were bigger than the angle of critical deformation, with the increase of the weak planes’ heights (0–120 m) the advance angle of influence changed from 53.61° to 59.15°, and the advance distance of influence changed from 173.31 m to 140.27 m which decreased by 30.04 m. In applications at Sihe coal mine in China, directional hydraulic fracturing technology was used in panel 5304 to form artificial weak planes in overlying strata. The measured surface subsidence and deformation value met the numerical simulation results and the mining-induced surface movement scope reduced. Moreover, no damage occurred to the surface buildings which were predicted to be in the affected area after extraction. This technology provided a new method to protect the surface structures from damages and had great benefits for the sustainable development of coal mines.

scholarly journals The Study of Key Stratum Location and Characteristics on the Mining of Extremely Thick Coal Seam under Goaf

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Gaochuan Guo ◽  
Yongkang Yang
Keyword(s):  
Coal Seam ◽  
Longwall Mining ◽  
Maximum Principal Stress ◽  
Engineering Practice ◽  
Coal Seams ◽  
Thick Coal Seam ◽  
Key Strata ◽  
Key Stratum ◽  
Arch Structure ◽  
Overlying Strata

The basis of traditional ground pressure and strata control techniques is the key strata theory, wherein the position of the key stratum can easily be determined for coal seams with regular thickness and without goaf. However, in the case of mining ultrathick coal seams underneath goaf, the traditional methods used for the calculation of key stratum position need to be improved in order to account for the additional coal seam thickness and the presence of an upper goaf. This study analyzed the failure height and collapse characteristics of overlying strata during excavation for determining the structure of the failed overlying strata. The results indicate that the intercalation and overlying strata gradually evolve into a large “arch structure” and a small “arch structure” during longwall mining, respectively. A mechanical model of the bearing characteristics of the interlayer key strata structure was established according to the structure of the intercalation rock layer, which is a hinged block structure. The results of the model indicate that the maximum principal stress occurs when the key strata portion of the arch structure bears the overlying load. Consequently, the movement and position of the interlayer key strata can be evaluated throughout the mining process of the ultrathick coal seams underneath goaf. This method was used to determine the position of interlayer key stratum of overlying strata in Xiegou coal mine. And the results agree with that of the engineering practice. The results are significant to determine the key strata position during ultrathick coal seam underneath goaf longwall mining.

Grouting of bed separation spaces to control sliding of the high-located main key stratum during longwall mining

2020 ◽  
Vol 53 (4) ◽  
pp. 569-578
Author(s):  
Xiang-yu Wang ◽  
Wen-da Wu ◽  
Bo-wen Wu
Keyword(s):  
Coal Mine ◽  
Longwall Mining ◽  
Mine Safety ◽  
New Technique ◽  
High Water Content ◽  
Beam Model ◽  
Key Stratum ◽  
Geological Conditions ◽  
Bed Separation ◽  
A New Technique

The gob-side entry 150–180 m behind the 14201 working face at Majialiang coal mine is severely deformed. We developed a new technique to control the behaviour of the high-located main key stratum (HMKS) to improve mine safety. The failure type and breaking span of the HMKS were determined based on key stratum theory and the voussoir beam model. By monitoring the deformation of the entry and surface subsidence, we found that the main cause of the large deformation of the gob-side entry was sliding of the HMKS. A new technique is proposed to add grout between the separated beds during mining. Physical simulations indicated that this technique is efficient in controlling sliding of the HMKS and avoiding strong dynamic loading, with the peak abutment stress reduced by 59%. Grouting stations were set up at a spacing of 150 m behind the advancing work face based on the principles and key parameters of the technique and the geological conditions at Majialiang coal mine. Before the HMKS began to slide, we injected high-water content materials with a water to cement ratio of 1.5:1 into the bed separation space to prevent breaking of the key strata.

scholarly journals Controlling the Deformation of a Small Coal Pillar Retaining Roadway by Non-Penetrating Directional Pre-Splitting Blasting with a Deep Hole: A Case Study in Wangzhuang Coal Mine

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3084
Author(s):  
Shixing Cheng ◽  
Zhanguo Ma ◽  
Peng Gong ◽  
Kelong Li ◽  
Ning Li ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Coal Mine ◽  
High Efficiency ◽  
Longwall Mining ◽  
Coal Pillar ◽  
Field Application ◽  
Vertical Stress ◽  
Mine Pressure ◽  
Deep Hole ◽  
Fracture Length

In longwall mining of coal mines, the large deformation of small pillar retaining roadways creates difficulties for the safe and efficient retreating of the mining panel. Based on the engineering background of a small coal pillar retaining roadway in Wangzhuang coal mine, pressure relief technology for non-penetrating directional pre-splitting blasting with a deep hole ahead was proposed. The influence of the non-penetrating fracture length on the pre-splitting effect was studied by numerical simulation. The results showed that the vertical stress in the coal pillar center, the small pillar retaining roadway deformation, and the energy accumulation on the pillar decreased with an increase in the non-penetrating fracture length. The vertical stress at the working face end increased with an increase in the non-penetrating fracture length. The field application and monitoring results indicated that non-penetrating directional pre-splitting blasting could effectively control the deformation of small pillar retaining roadways. The roof-to-floor and rib-to-rib maximum convergences of the 6208 tail entry were reduced by 53.66% and 52.62%, respectively, compared to the results with no blasting. The roadway section met the demands of mining panel high-efficiency retreating, thereby demonstrating the rationality of the technical and numerical simulation results. The research results shed light on the improvement of small coal pillar retaining roadway maintenance theory and technology.

Buckling and Post-Buckling Behavior for Roof Strata in Longwall Mining

2012 ◽  
Vol 170-173 ◽  
pp. 751-754
Author(s):  
Qun Song ◽  
Zhi Lin Yang
Keyword(s):  
Longwall Mining ◽  
Main Roof ◽  
Equilibrium Path ◽  
Fracture Characteristics ◽  
Key Stratum ◽  
Buckling Behavior ◽  
Roof Stratum ◽  
Post Buckling ◽  
The Stability ◽  
Roof Strata

In accordance with the occurrence behavior of roof strata and the fracture characteristics of key stratum in shallow seam longwall mining, this paper studied the post-buckling behaviors of key roof stratum in the process of mining by using initial post-buckling theory, which derived a critical load and a breaking span of the main roof during the first weighting, determined the final subsidence for broken key stratum, and presented an application with the example of Daliuta 1203 face. The results indicate that the rock blocks a in are state of non-equilibrium after main roof breaking, the equilibrium path of main roof is unstable from breaking to final subsidence; thick unconsolidated layers above roof have effect on post-buckling behaviors of key stratum; the stability for bifurcation point equilibrium configuration and post-buckling equilibrium path of roof strata could be revealed and an effective method for determining displacement field of imperfection structure could be provided by using initial post -buckling theory.

Application of Cusp Catastrophe Model to Predicting of Water Inrush from Mine Floor

2012 ◽  
Vol 446-449 ◽  
pp. 1546-1550
Author(s):  
Chun Lei Zhang ◽  
Guo Sheng Zhong
Keyword(s):  
Numerical Simulation ◽  
Catastrophe Theory ◽  
Mechanical Model ◽  
Water Inrush ◽  
Cusp Catastrophe ◽  
Theory Analysis ◽  
Catastrophe Model ◽  
Key Stratum ◽  
Cusp Catastrophe Model ◽  
Mine Floor

Based on cusp catastrophe characteristics of water inrush from floor, a cusp catastrophic mechanical model of a key stratum of floor is established by catastrophe theory. By the model, the paper analyzes mechanical mechanism of water inrush from key stratum of floor with the cusp catastrophic theory. Using an engineering example, the numerical simulation proves that this method of the theory analysis is practical.

Analysis of Numerical Simulation on Breaking Law of the Composite Key Stratum Affected by Coal Mining

2012 ◽  
Vol 616-618 ◽  
pp. 350-355
Author(s):  
Hai Feng Ren ◽  
Shu Gang Li ◽  
Hong Yu Pan
Keyword(s):  
Numerical Simulation ◽  
Coal Mining ◽  
Simulation Software ◽  
Composite Effect ◽  
Key Stratum ◽  
The Law

Using FLCA3Dnumerical simulation software, analyzed the different models of different extraction from the composite key layer of breaking the law, respectively to the Composite Key Stratum and non-Composite Key Stratum .The results show that Composite Key Stratum breaking interval was significantly greater than The non-Composite Key Stratum, showing a more obvious composite effect, provides a more adequate proof to the Composite Key Stratum theory.

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