scholarly journals Study on Overburden Stability and Development Height of Water Flowing Fractured Zone in Roadway Mining with Cemented Backfill

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Yu Dong ◽  
Yucheng Huang ◽  
Jifang Du ◽  
Fei Zhao
Keyword(s):  
Empirical Formula ◽  
Mechanical Model ◽  
Fractured Rock ◽  
Coal Pillar ◽  
Main Roof ◽  
Mechanical Analysis ◽  
Overburden Rock ◽  
Fractured Zone ◽  
The Stability ◽  
Rock Beam

In order to explore the stability of overburden rock and the development height of water flowing fractured zone in roadway filling mining, based on the movement and deformation mechanism of overburden rock, the mechanical analysis of overburden stability and failure was carried out, and the mechanical model of main roof rock beam was established, and the ultimate span and limit deflection of rock beam fracture were deduced. Combined with the mechanical model of the main roof fractured rock, the basis for the judgment of overburden failure developing to fractured zone is given in this paper. Taking a coal mine roadway backfill under water-bearing stratum as an example, based on the equivalent mining height, the theoretical calculation and analysis are carried out on the stability of overburden rock and the height of water flowing fractured zone. The reliability of the theoretical analysis is verified compared with the empirical formula and the numerical simulation results. The results showed that the water flowing fractured zone developed to the bottom of no. 7 glutenite, with a height of 32.5 m, slightly less than the calculation result of the empirical formula. The thickness of the waterproof coal pillar was 39.8 m, which was much less than the distance from the aquifer to the coal seam and can be mined safely.

scholarly journals Accident Analysis in Relation to Main Roof Structure When Longwall Face Advances toward a Roadway: A Case Study

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Chang Liu ◽  
Zengqiang Yang ◽  
Peilin Gong ◽  
Kai Wang ◽  
Xiaoqiang Zhang ◽  
...  
Keyword(s):  
Sharp Increase ◽  
Coal Pillar ◽  
Main Roof ◽  
Mechanical Analysis ◽  
Longwall Face ◽  
Good Effect ◽  
Key Factors ◽  
Roof Structure ◽  
Similar Simulation Experiment ◽  
The Stability

Practices show that hydraulic supports crushing accidents or roadway supports failure often take place when a longwall face advances toward an abandoned roadway or a predriven equipment recovery room. Therefore, a 2D similar simulation experiment is conducted to reveal the loading mechanism. The result shows that when the workface advances close to roadways, the main roof breaks ahead of the workface and leads to instability of higher strata. These two changes induce a sharp increase of the load on supports and lead to an accident. Thus, more attention should be paid to the advanced fracture. Therefore, mechanical analysis is used to explain the advanced fracture. Results show that the failure of coal pillar being excavated induces a sharp increase in the main roof’s hanging length. Once the hanging length reaches the limit, the advanced fracture takes place. Therefore, the stability of the coal pillar and the hanging length of roof strata are two key factors that may induce an accident. To prevent the a similar supports crushing accident, the partial backfilled technology which partly backfills the abandoned roadway in height and length to maintain the stability of the coal pillar is put forward and put into practice. The field test shows a good effect.

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 Mechanical Modeling of Roof Fracture Instability Mechanism and Its Control in Top-Coal Caving Mining under Thin Topsoil of Shallow Coal Seam

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Peilin Gong ◽  
Tong Zhao ◽  
Kaan Yetilmezsoy ◽  
Kang Yi
Keyword(s):  
Coal Seam ◽  
Mechanical Model ◽  
Main Roof ◽  
Stability Control ◽  
Hydraulic Support ◽  
Rock Stability ◽  
Shallow Coal Seam ◽  
Minimum Height ◽  
The Stability ◽  
Working Resistance

This study aimed to explore the safe and efficient top-coal caving mining under thin topsoil of shallow coal seam (SCS) and realize the optimization of hydraulic support. Numerical simulation and theoretical analysis were used to reveal the stress distribution of the topsoil, the structure characteristics of the main roof blocks, and the development of the roof subsidence convergence. Step subsidence of the initial fractured main roof after sliding destabilization frequently existed, which seriously threatened the safety of the hydraulic supports. Hence, a mechanical model of the main roof blocks, where the topsoil thickness was less than the minimum height of the unloading arch, was established, and the mechanical criterion of the stability was achieved. The working resistance of the hydraulic support was calculated, and the reasonable type was optimized so as to avoid crushing accident. Findings of the present analysis indicated that the hydraulic support optimization was mainly affected by fractured main roof blocks during the first weighting. According to the block stability mechanical model based on Mohr–Coulomb criterion, the required working resistance and the supporting intensity were determined as 4899 kN and 0.58 MPa, respectively. The ZZF5200/19/32S low-position top-coal caving hydraulic support was selected for the studied mine and support-surrounding rock stability control of thin-topsoil SCS could be achieved without crushing accident.

scholarly journals Stability Analysis of the Entry in a New Mining Approach Influenced by Roof Fracture Position

2019 ◽  
Vol 11 (22) ◽  
pp. 6349
Author(s):  
Jun Yang ◽  
Hongyu Wang ◽  
Yajun Wang ◽  
Binhui Liu ◽  
Shilin Hou ◽  
...  
Keyword(s):  
Coal Pillar ◽  
Main Roof ◽  
Surrounding Rock ◽  
Fracture Position ◽  
Solid Coal ◽  
Rock Structure ◽  
Temporary Support ◽  
Coal Wall ◽  
Pillar Mining ◽  
The Stability

Non-coal pillar mining with roadway formed automatically (RFANM) is a new mining approach, which demonstrates revolutionary significance because it does not require making roadway before mining and coal pillar retaining. In order to explore the stability of the surrounding rock structure in RFANM, the deformation of the surrounding rock was theoretically analyzed and simulated based on three different fracture positions of the main roof. It was concluded that reasonable control of temporary support strength in roadway is of great importance to control the deformation of the entry. The deformation process of surrounding rock under different fracture positions in RFANM was simulated by using the Universal Discrete Element Code (UDEC). The results of the numerical simulation showed that the main roof was fractured at the solid coal side or gob side; the deformation of the roadway was small. The fracture condition of the main roof at the gob side required a higher effect of roof slitting or temporary support from the roadway. Through drilling and peeping at the retained roadway, it was judged that the main roof was broken inside the coal wall. Field monitoring results revealed that the deformation of the roadway can be effectively controlled.

scholarly journals Stability of Coal Pillar and Roof Movement Characteristics in Roadway Backfill Mining

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Hai Lin ◽  
Renshu Yang ◽  
Yongliang Li ◽  
Shizheng Fang
Keyword(s):  
Mechanical Model ◽  
Maximum Stress ◽  
Coal Pillar ◽  
Engineering Practice ◽  
Alternate Bearing ◽  
Local Pressure ◽  
Immediate Roof ◽  
Backfill Mining ◽  
Coal Pillars ◽  
The Stability

In order to explore the stability of coal pillar and the characteristics of roof movement during the process of roadway backfill mining (RBM), the 301 backfilling test working face of Ordos Chahasu coal mine is taken as the background. Based on the expansive pressure arch theory, the evolution process of the stope expansive pressure arch in RBM is studied; by establishing a mechanical model for the stability of coal pillars, the interactions between the height, width, and the maximum number of branches are obtained. When the width and height of the branch are both 5 m, the optimal number of the branches is obtained. Then, by establishing a mechanical model for the subsidence of the immediate roof, the process of the immediate roof subsidence is divided into three stages, namely, the formation stage of the local pressure arch, the merge stage of the pressure arch, and the expansion stage of the pressure arch. In addition, using the numerical method, the alternate bearing process of coal pillars and filling bodies and the change of the maximum supporting stress are studied, and the evolution of the pressure arch bearing structure above the stope and the staged subsidence characteristics of the roof are analyzed. The on-site test showed that the coal pillar has a good stability during the mining process. The maximum stress of the coal pillar is 16.5 MPa, and the maximum stress of the filling body is 9 MPa. The maximum settlement of the immediate roof is 102 mm, indicating that the roof control effect is good. This research will play an important role on engineering practice.

scholarly journals Research on the Mechanism of Main Roof Advanced Breaking and Supporting Technology When Long-wall Face Passing Through Abandoned Roadways

2021 ◽  
Author(s):  
Pan Weidong ◽  
Deng Cang ◽  
Li Boyang ◽  
Zhang Kunming ◽  
Gao Shan
Keyword(s):  
Underground Mining ◽  
Coal Pillar ◽  
Main Roof ◽  
Simulation Method ◽  
Critical Value ◽  
Ground Pressure ◽  
Restricted Problems ◽  
Mining Condition ◽  
Support Force ◽  
The Stability

Abstract Unlike general long-wall mining, the roof activity is more intense when long-wall face passes through the abandoned roadway. Technically, the coal pillar between the abandoned roadway and the long-wall face will suddenly fail with a certain critical value of its width, leading to the roof breaks in advance and other production-restricted problems because of the support loss, which will be a great threat to underground mining activities. In order to guarantee a safe mining condition, therefore, it is greatly necessary to uncover how the roof breaks in advance and how to cope with it. From the stability maintaining of the key block perspective, this paper took for research that the 12404-1 long-wall face of Wulanmulun coal mine, China. The critical value of the coal pillar’s width was determined to be about 5m by theoretical analysis, likely, the appropriate support force of the abandoned roadway’s roof is about 4020KN per meter. Meanwhile, a numerical simulation method was adopted to study the ground pressure when the long-wall face passing through the abandoned roadway. Correspondingly, a compound supporting technology involving the roof presplit technique, anchor cable supporting and pumping pillar supporting were proposed for the roof of the abandoned roadway, and it practically worked well.

Study of a High Slope Stability Considering the Stochastic Distribution of Rock Joint Set

2011 ◽  
Vol 90-93 ◽  
pp. 786-790 ◽  
Author(s):  
Yun Hua Guo ◽  
Wei Shen Zhu ◽  
Da Jun Yu ◽  
Xin Ping Li
Keyword(s):  
Numerical Model ◽  
Fractured Rock ◽  
Rock Joint ◽  
Back Analysis ◽  
Fracture Network ◽  
Jointed Rock ◽  
Mechanical Analysis ◽  
Site Monitoring ◽  
Dadu River ◽  
The Stability

A hydropower station is located in the middle reach of the Dadu River in southwest China. The natural slope angles at the project site are generally 40~65 and the relative elevation drop is more than 600m. Complex different fractures such as faults, dykes and dense fracture zones due to unloading are developed. The stability of these steep and high slopes during construction and operation period plays an important role for the safe construction and operation of the project. According to the statistical distribution of joints at the construction site, the slope is divided into a number of engineering geological zones. For each zone, a stochastic fracture network and a numerical model are established by the Monte-Carlo method. The mechanical characters of fractured rock with different sizes are studied using FLAC3D. The REV characteristic scale is identified for rock masses. Numerical simulation is performed to obtain the mechanical parameters and the strength of the jointed rock. With the numerical model and the site monitoring data, a self-developed stochastic mechanical analysis software is applied for back analysis and stability assessment.

scholarly journals Automatic Roadway Backfilling of Caving Gangue for Cutting Roofs by Combined Support on Gob-Side Entry Retaining with No-Pillars: A Case Study

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Shengrong Xie ◽  
Xiaoyu Wu ◽  
Dongdong Chen ◽  
Yaohui Sun ◽  
Junchao Zeng ◽  
...  
Keyword(s):  
Longwall Mining ◽  
Control Process ◽  
Coal Pillar ◽  
Main Roof ◽  
Control Effect ◽  
Mining Technology ◽  
Thick Coal Seam ◽  
Immediate Roof ◽  
Seam Mining ◽  
And Control

Automatic roadways on gob-side entry retaining with no-pillars are used for longwall mining technology. The mining technology with no-pillars can recover coal pillar resources and reduce the amount and cost of roadway excavations. Automatic roadway technology for cutting roofs by combined support on gob-side entry retaining with no-pillars is adopted for the condition of thick immediate roof and medium-thick coal seam mining, cutting off the immediate roof and the main roof on the gob by combined support. The fractured roof forms gangue blocks to fill the gob and loads the overlying strata. The gangue control system is placed on the roadside, which controls the caving gangue to form a gangue rib. In this paper, the viewpoints and key technologies (the roof-cutting technology, the reinforcement and support technology, the gangue rib control technology, and the auxiliary support technology) of automatic roadway technology for cutting roofs by combined support on the gob-side entry retaining with no-pillars are introduced. Furthermore, the formation and control process are explained. The numerical simulation is used to simulate and analyze the roof hanging and the roof cutting structures. In addition, a field engineering test is performed. The field test shows that automatic roadway technology for cutting roofs by combined support on gob-side entry retaining with no-pillars is feasible. This process uses construction techniques and technologies to meet on-site production needs. The combined support has high resistance strength and is shrinkable. In engineering applications, the combined support has a low damage rate. The deformation of the automatic roadway with gob-side entry retaining is small, and the control effect is significant.

scholarly journals Mechanisms behind strong strata behaviour in high longwall mining face-ends under shallow covers

2019 ◽  
Vol 16 (3) ◽  
pp. 559-570 ◽  
Author(s):  
Weibing Zhu ◽  
Xiangrui Qi ◽  
Jinfeng Ju ◽  
Jingmin Xu
Keyword(s):  
Longwall Mining ◽  
Coal Pillar ◽  
Field Measurements ◽  
Main Roof ◽  
Longwall Face ◽  
Effective Control ◽  
Coal Seams ◽  
Roof Collapse ◽  
Coal Pillars ◽  
Roadway Deformation

Abstract Safe and efficient mining of shallow coal seams relies on the understanding and effective control of strata behaviour. Field measurements, theoretical analysis and numerical simulations are presented in this study to investigate the mechanism behind abnormal strata behaviour, such as roof collapse and severe roadway deformation, that occurs in high longwall face-ends under shallow cover. We observed that coal pillars with two sides being mined out become unstable when the cover depth exceeds a certain value. The instability of the coal pillar can alter the fracture line of the overlying strata, triggering a reversed rotation of the ‘curved triangle blocks’ that form after the breakage of the overlying main roof. The revolving blocks apply stress on the roof strata directly above the longwall face-end, resulting in roof collapse. The collapse of both the coal pillars and the roof also leads to the advancement and increase of the overlying abutment pressure, which further causes severe roadway deformation in front of the working face. The strong strata behaviour that occurs in high longwall face-ends with shallow cover is presented in this study and countermeasures are proposed, such as widening or strengthening the coal pillar, or implementing destress blasting. The countermeasures we proposed and the results of our analyses may facilitate the safe mining of shallow coal seams with similar problems in the future, and may improve the safety and efficient working of coal mines.

Sign in / Sign up

Export Citation Format

Share Document