scholarly journals The Prediction Model of Super Large Subsidence in High Water Table Coal Mining Areas Covered with Thick Unconsolidated Layer

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Yueguan Yan ◽  
Weitao Yan ◽  
Jibo Liu ◽  
Junting Guo
Keyword(s):  
Coal Seam ◽  
Soft Rock ◽  
Simulation Software ◽  
Surface Subsidence ◽  
Thickness Ratio ◽  
Lagrangian Analysis ◽  
Ratio Increase ◽  
Rock Stratum ◽  
Maximum Surface ◽  
Subsidence Prediction

In mining engineering, after the extraction of underground resources, the maximum surface subsidence is usually less than the mining thickness of coal seam. However, under the condition of thick loose layer, some special phenomena appear in surface subsidence, for example, the maximum surface subsidence value is greater than the mining thickness of coal seam. This special phenomenon cannot be predicted by traditional subsidence prediction methods. To solve this problem, by using the numerical simulation software Fast Lagrangian analysis of continua (Flac), we study the changing rules of subsidence with different strata lithology and unconsolidated layer thickness and reveal the formation mechanism of this law. The results show that the effect of the thick unconsolidated layer on the hard rock is greater than that of the soft rock. When the rock is soft, the unconsolidated layer moves as a whole following the bedrock during the whole mining process. The surface subsidence decreases approximately linearly with the thickness ratio increase of the unconsolidated layer to bedrock. However, when the rock is hard or medium hard, there are supporting structures formed inside the rock stratum, which has supporting effect on the overlying strata. The surface subsidence undergoes three proportional sections, first increases, then decreases, and finally increases with the thickness ratio increase of the unconsolidated layer to bedrock. Combined with these laws, based on the theory that the rock strata space can be completely compressed gradually, we derive the calculation method of surface subsidence under the condition of thick unconsolidated layer and apply it to practice. The results show that the prediction results are consistent with the actual situation and meet the engineering requirements. The research results can provide a reference for the subsidence prediction of similar conditions.

scholarly journals Simulation Analysis of Influencing Factors of Subsidence Based on Mining under Huge Loose Strata: A Case Study of Heze Mining Area, China

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Xianxiang Zhu ◽  
Wenquan Zhang ◽  
Zaiyong Wang ◽  
Chenghao Wang ◽  
Wei Li ◽  
...  
Keyword(s):  
Coal Seam ◽  
Simulation Analysis ◽  
Soil Layer ◽  
Soft Rock ◽  
Mining Area ◽  
Simulation Software ◽  
Surface Subsidence ◽  
Ground Movement ◽  
Hard Soil ◽  
Seam Mining

Based on the coal seam mining under the condition of thick soil layer, the mechanical mining subsidence process under the condition of thick soil layer was analyzed. Combined with the results of core drilling and laboratory test in the mining area, the mechanical analysis of the special transition strata of “hard soil-soft rock” at the bottom of the soil layer was carried out. Additionally, the characteristics of the shallow buried soil layer were compared and analyzed. Furthermore, the significance of this transitional font to the surface subsidence law was proposed. By using the numerical simulation software of FLAC3D and choosing the thickness of “hard soil-soft rock” transitional font as the influencing factor, a model was established and the surface subsidence characteristics of different stratum combinations were numerically simulated. The research results show that the transitional font is the special strata indicating that the hard soil is transiting to the soft rock, having a significant effect on the ground movement and deformation induced by coal mining. It cannot be designated into the loose strata. Also, it cannot be regarded as the bed rock to study the influence of it on the surface subsidence. The “hard soil-soft rock” transitional font has the support effect on the overlying strata during coal seam mining, which can restrict the surface subsidence. Furthermore, the larger the thickness of the transitional font is, the more obvious the restricting effect of it on the surface subsidence is. Meantime, this restricting effect will not be changed with the variation of the proportion between the loss bed and the bed rock thickness. Only the restricting extent is a little different.

scholarly journals A Method of Backfill Mining Crossing the Interchange Bridge and Application of a Ground Subsidence Prediction Model

Minerals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 945
Author(s):  
Shuaigang Liu ◽  
Jianbiao Bai ◽  
Gongyuan Wang ◽  
Xiangyu Wang ◽  
Bowen Wu
Keyword(s):  
Prediction Model ◽  
Dynamic Change ◽  
Simulation Software ◽  
Surface Subsidence ◽  
Ground Subsidence ◽  
Mining Method ◽  
Subsidence Prediction ◽  
Probability Integral Method ◽  
Backfill Mining ◽  
Step Distance

The traditional backfill mining method is a technology developed by the general trend of green coal mining, but with a high cost and an impact on production efficiency. This paper proposes a structured backfill mining method with high-water materials and pillars. The evolution of roof pressure appearance is assessed through the sensor and monitoring system in the hydraulic support. The main roof fracture step distance is determined based on the roof structure characteristics of backfill mining, and the backfill step distance of underground structural backfill is 22.7 m considering the safety factor. Through the simulation results of Abaqus commercial simulation software, the roof subsidence evolution of different backfill schemes under temporary load and permanent load is compared, and the rationality of the backfill step distance is verified. Based on the probability integral method, the surface subsidence prediction model is proposed, then the final value and the maximum dynamic change value of the surface subsidence at the north and south ends of the interchange bridge by traditional mining and backfill mining are analyzed, which verifies the rationality of the structural backfill mining method.

Time-dependent squeezing deformation mechanism of tunnels in layered soft-rock stratum under high geo-stress

2021 ◽  
Vol 18 (5) ◽  
pp. 1371-1390
Author(s):  
Zi-quan Chen ◽  
Chuan He ◽  
Jun Wang ◽  
Chun-chi Ma
Keyword(s):  
Deformation Mechanism ◽  
Soft Rock ◽  
Time Dependent ◽  
Rock Stratum

scholarly journals A numerical simulation of realistic top coal caving intervals under different top coal thicknesses in longwall top coal caving working face

2021 ◽  
Author(s):  
Chuang Liu ◽  
Huamin Li
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Distinct Element ◽  
Simulation Models ◽  
Simulation Software ◽  
Thick Coal Seam ◽  
Coal Recovery ◽  
Working Face ◽  
Longwall Top Coal Caving ◽  
Selection Of

Abstract In the process of longwall top coal caving, the selection of the top coal caving interval along the advancing direction of the working face has an important effect on the top coal recovery. To explore a realistic top coal caving interval of the longwall top coal caving working face, longwall top coal caving panel 8202 in the Tongxin Coal Mine is used as an example, and 30 numerical simulation models are established by using Continuum-based Distinct Element Method (CDEM) simulation software to study the top coal recovery with 4.0 m, 8.0 m, 12.0 m, 16.0 m, 20.0 m and 24.0 m top coal thicknesses and 0.8 m, 1.0 m, 1.2 m, 1.6 m and 2.4 m top coal caving intervals. The results show that with an increase in the top coal caving interval, the single top coal caving amount increases. The top coal recovery is the highest with a 0.8 m top coal caving interval when the thickness of the top coal is less than 4.0 m, and it is the highest with a 1.2 m top coal caving interval when the coal seam thickness is greater than 4.0 m. These results provide a reference for the selection of a realistic top coal caving interval in thick coal seam caving mining.

scholarly journals Calculation Method of Overburden Damage Height Based on Fracture Mechanics Analysis of Soft and Hard Rock Layers

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Liang Chen ◽  
Shaowu Fan ◽  
Can Zhao ◽  
Lang Zhang ◽  
Zhiheng Cheng
Keyword(s):  
Fracture Mechanics ◽  
Coal Seam ◽  
Calculation Method ◽  
Hard Rock ◽  
Soft Rock ◽  
Mining Area ◽  
Overburden Rock ◽  
Rock Interaction ◽  
Mechanics Analysis ◽  
Seam Mining

Under the geological condition of soft and hard rock interaction stratum, the overburden damage height can provide a quantitative support for the design of the locations of gas drainage boreholes in the roof mining fracture zone and the determination of the hydraulic fracture zone in coal seam mining. The interbedded structure of overlying mud rock and sandstone in the Lu’an mining area in Shanxi is a typical soft and hard rock interaction stratum. In view of the lack of soft rock fracture mechanics analysis and the improper calculation of the damage height of overburden rock caused by constant rock residual bulking coefficient to be used regularly in the analysis, in this paper, we constructed a fracture model of soft and hard strata by giving a quantitative classification criterion of soft and hard rocks and introducing a fracture failure criterion of soft rock strata and the space constraint condition of broken-expansion rock formation. Aiming at improving the calculation precision of overburden damage height, we presented a calculation method based on fracture mechanics analysis of soft and hard strata, which could delineate the extent of intact rock in overlying strata from bottom to top to determine the damage height of overburden rock. This research took Yuwu coal mine in Lu’an mining area as an example. Results showed that (1) by the calculation method, the overburden damage height of the N1102 fully mechanized caving face in Yuwu coal mine was 51.44 m, which was less than the value obtained by an actual borehole TV method as well as the numerical simulation result of 53.46 m, with a calculation accuracy about 96.22%, which is quite high for both. The calculation accuracy of the proposed method was higher than that of the three conventional theoretical methods, and it effectively solved the limitation of the fracture analysis method without the inclusion of the soft rock layer in design and the distortion problem due to the residual bulking coefficient to be improperly used in simulation. (2) There was no noticeable fractures in the broken soft rock zone, and the whole fractures were mainly low-angle rupture; the fractures in hard rock layer had obvious ruptures and multiangle cracks, and the average fracture width of soft rock was 2.8 mm smaller than that of hard rock. The fracture modes of soft rock and hard rock were mainly tensile failure and tensile shear failure, which verified the correctness of the fracture mechanics model of soft and hard rock layers constructed in this paper. (3) It is noticed that the tensile strength of rock in this method needs to be obtained through rock mechanics experiment on overlying strata in the study area, and our proposed method was applicable to the mining conditions of near horizontal coal seam. The calculation accuracy of this method meets the engineering error requirements and can be applied to the prediction of overburden damage height in near horizontal coal seam mining.

scholarly journals Surface Subsidence Prediction Method for Coal Mines with Ultrathick and Hard Stratum

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Hongkai Han ◽  
Jialin Xu ◽  
Xiaozhen Wang ◽  
Jianlin Xie ◽  
Yantuan Xing
Keyword(s):  
Coal Mining ◽  
Coal Mine ◽  
Prediction Method ◽  
Prediction Equation ◽  
Arbitrary Cross Section ◽  
Surface Subsidence ◽  
Strong Impact ◽  
Subsidence Prediction ◽  
Movement Characteristics ◽  
Mining Condition

Overburden conditions consisting of ultrathick and hard stratum (UTHS) are widespread in China and other countries, but existing surface subsidence prediction methods ignore the strong impact of UTHS on surface subsidence. They are thus not applicable for surface subsidence prediction for coal mining with the presence of UTHS. We conducted actual measurements of surface and UTHS subsidence in the Tingnan Coal Mine. The results showed that under the UTHS mining condition, the required gob dimension is much larger than the empirical value when the surface reaches sufficient mining and that the actual measured maximum value of surface subsidence is much smaller than the empirical value. The UTHS subsidence is approximately equal to the surface subsidence. The movement of UTHS has a strong impact on surface subsidence and has a controlling function for it. It was proposed that surface subsidence could be approximately predicted by calculating the UTHS subsidence. The UTHS movement characteristics were studied using Winkler’s theory of beams on an elastic foundation, the subsidence prediction equation of the main sections in the strike and dip directions was obtained under different mining dimensions, and the subsidence prediction equation of any arbitrary cross section parallel to the two main sections was established. Then, the surface subsidence prediction method for coal mining with the presence of UTHS was developed, and the influences of UTHS thickness, strength, and layer position on the surface subsidence were discussed. The Tingnan Coal Mine was taken as an example, and the subsidence curves of the strike and dip main sections were calculated using different mining dimensions. Subsequently, the surface subsidence after the mining of working faces 204, 205, 206, and 207, respectively, was predicted, and the prediction method was verified by comparing the results with the measured surface subsidence results of working faces 204, 205, and 206.

scholarly journals Study on the Rheological Failure Mechanism of Weakly Cemented Soft Rock Roadway during the Mining of Close-Distance Coal Seams: A Case Study

2020 ◽  
Vol 2020 ◽  
pp. 1-20
Author(s):  
Wenkai Ru ◽  
Shanchao Hu ◽  
Jianguo Ning ◽  
Jun Wang ◽  
Qingheng Gu ◽  
...  
Keyword(s):  
Coal Seam ◽  
Failure Mechanism ◽  
Coal Pillar ◽  
Soft Rock ◽  
Western China ◽  
Creep Failure ◽  
Mining Areas ◽  
Geological Conditions ◽  
Residual Coal ◽  
Close Distance

During the mining of the shallow-buried and close-distance multiple coal seam, the rheological failure of the surrounding weakly cemented soft rock of the roadway in the lower coal seam under the concentrated stress is very rare. However, the stress on the roof of the upper coal seam is transmitted down through the residual pillar, resulting in this situation. Taking the Gaojialiang coal mine which is located in the mining areas of western China as the research object, the failure mechanism of the roadway roof under the residual coal pillar in the shallow-buried and close-distance multiple seam is studied in combination with field monitoring and numerical simulation. Furthermore, suggestions on the roadway support under such geological conditions are proposed. The results show that the residual coal pillar in the working face of the lower coal seam gradually collapses during the mining of the shallow-buried and close-distance multiple coal seam. The concentrated stress transferred by the coal pillar increases further, which makes the roof stress of the lower coal seam roadway to increase continuously. In addition, the stress of the roadway roof also increases further due to the rotation of the broken rock above the goaf, and the peek region of stress moves to the nongoaf area. Combining the heavy concentrated stress and weakly cemented property, the shallow-buried surrounding rock shows rheological behavior and failure. Therefore, we must pay more attention on the creep failure of the roadway roof under the action of the residual coal pillar even in the shallow-buried coal seam.

Research on Mining Technological Parameters of 7# Thin Coal Seam in Liuquan Mine

2012 ◽  
Vol 629 ◽  
pp. 937-942
Author(s):  
Dong Sheng Zhang ◽  
Xu Feng Wang ◽  
Yang Zhang ◽  
Jin Liang Wang
Keyword(s):  
Coal Seam ◽  
Distinct Element ◽  
Horizontal Displacement ◽  
Simulation Software ◽  
Surrounding Rock ◽  
Technological Parameters ◽  
Thin Coal Seam ◽  
Geological Conditions ◽  
Universal Distinct Element Code ◽  
Distinct Element Code

Aimed at the specific geological conditions of 7# thin coal seam in Liuquan Mine, this paper used the methods of numerical calculation and theoretical analysis to determine the reasonable technological parameters of high-grade conventional mining face. The numerical simulation software of UDEC (Universal Distinct Element Code) was used to contrast and analyse the characteristics of surrounding rock stress distribution and overlying rock horizontal displacement under the condition of different length of coalface, then it was indicated that the surrounding rock deformation was less when length of coalface was 110 m which was advantageous for roof control; according to the conditions of roof and floor, the roof support strength was being calculated systematically to determine the row space of props being 700×1200 mm; the main equipments of coalface was assorted, and reasonable work manner in coalface and gob processing measure was put forward, which provided guidance for efficient mining in thin coal seam.

Sign in / Sign up

Export Citation Format

Share Document