scholarly journals Dome Roof Fall Geohazards of Full-Seam Chamber with Ultra-Large Section in Coal Mine

2019 ◽  
Vol 9 (18) ◽  
pp. 3891 ◽  
Author(s):  
Rui Gao ◽  
Hongchun Xia ◽  
Kun Fang ◽  
Chunwang Zhang
Keyword(s):  
Shear Strength ◽  
Coal Mine ◽  
Shear Failure ◽  
High Strength ◽  
Surrounding Rock ◽  
Mine Pressure ◽  
Mechanical Equipment ◽  
Large Section ◽  
Crack Penetration ◽  
Roof Fall

The roof fall hazard is more likely to take place within chamber with ultra-large section, which would not only damage mechanical equipment, but also cause casualties. In this paper, the strap joint chamber of the Tashan coal mine is studied, and finite and discrete element method (FDEM) is used to establish the numerical model of the roof fall of the chamber dome. The simulation results show that the chamber dome mainly undergoes shear failure and forms a large number of cracks. With further development and penetration of cracks, a distinct roof separation is found in the chamber dome. When the crack develops to the dome surface of the chamber, under the effect of the mine pressure, the coal body is separated from the surface of the chamber and the roof fall hazard occurs. Based on the mechanism of roof fall hazard of the chamber dome, it is concluded that improving the shear strength of the surrounding rock and reducing the crack penetration are the main ways to control the roof fall. Therefore, the high-strength anchor bolt and cable support is adopted to fill the cracks and improve the shear strength of the surrounding rock. The result showed that the roof separation of the chamber dome in the field is confined to 0.012 m. The surrounding rock is well controlled and no roof fall occurs.

scholarly journals Study on Surrounding Rock Deformation Mechanism and Control of Roadway with Large Section and Extra-Thick Top Coal

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Yuliang Yang ◽  
Xiaobin Li ◽  
Pengfei Li
Keyword(s):  
Support System ◽  
Deformation Mechanism ◽  
Shear Failure ◽  
High Strength ◽  
Surrounding Rock ◽  
Shanxi Province ◽  
Large Section ◽  
Anchor Cable ◽  
Geological Conditions ◽  
And Control

In order to solve the problem of safe and rapid excavation and support of roadway with large section and extra-thick top coal under complex geological conditions, the deformation mechanism and control of roadway are analyzed by means of field investigation, numerical simulation, theoretical analysis, and field practice, taking the 2203 transportation roadway of a mine in Shanxi Province as the engineering background. The results show the following: (1) the concentration of normal tensile stress in the middle of large-span roadway roof and end shear stress is significant, which may easily lead to the separation of roof and the extrusion deformation of surrounding rock; (2) the surface shear failure depth of the roadway side is large, and the insufficient length of the bolt, the small density of the protective side, and the insufficient support strength are easy to cause the bulge and splitting of the coal wall; (3) roof joints and fractures are developed, and the dirt band of different thickness occurs, so it is easy for the roof separation and the anchor solids to cut down along the weak surface of the dirt band; (4) the geological structure produces horizontal movement of surrounding rock, which easily leads to poor supporting effect of roadway roof and material deformation and failure. Finally, a safe and economic comprehensive support system of “high-strength, high-resistance, and high-prestressed anchor cable support system + high-strength support of the two sides roadway + U-shaped anchor cable combined truss” is proposed, and the control mechanism is explained and applied successfully in the field.

Sensitivity of shear strength to fracture energy of high-strength concrete slabs

1998 ◽  
Vol 25 (1) ◽  
pp. 40-50 ◽  
Author(s):  
H Marzouk ◽  
M Emam ◽  
M S Hilal
Keyword(s):  
Compressive Strength ◽  
Shear Strength ◽  
High Strength Concrete ◽  
Shear Failure ◽  
High Strength ◽  
Tensile Fracture ◽  
Concrete Slabs ◽  
Square Root ◽  
Fracture Properties ◽  
Strength Concrete

The test results of an earlier experimental investigation conducted at Memorial University of Newfoundland on high-strength concrete slabs indicated that as the concrete slab strength increased from 35 to 75 MPa the shear strength increased by 7-20%, depending on the case of loading, i.e., concentric or eccentric loads. The increasing ratio of shear strength is less than half that prescribed in the Canadian code CSA-A23.3 (1994) or the ACI-318 code (1995). Hence, the significant difference between the experimental results and the predicted strength by existing North American codes tacitly means that the proportionality between the shear strength and the square root of the compressive strength is not accurate enough to predict the shear strength of high-strength concrete slabs. In the present investigation, a fracture mechanics model suitable for concrete was proposed. It was also suggested that this model might be an advantageous aid in the analysis of the shear failure of reinforced concrete slabs. In this research investigation the fracture mechanics approach utilizing finite element aided computer analysis of several reinforced slabs is briefly described, and calculated shear failure loads are given. The recommended model proves that it is necessary to consider not only the tensile strength of concrete, instead of the square root of the compressive strength, but also the tensile fracture properties of high-strength concrete. The tensile fracture properties of concrete are characterized by the parameter called characteristic length and the brittleness of concrete. The brittleness ratio of concrete slabs must be considered in any rational shear design expression to reflect the size effect factor and the aggregate type.Key words: fracture energy, uniaxial direct tension, shear strength, high-strength concrete, punching shear, slab, size effect, finite element analysis.

scholarly journals Occurrence Mechanism of Roof-Fall Accidents in Large-Section Coal Seam Roadways and Related Support Design for Bayangaole Coal Mine, China

2018 ◽  
Vol 2018 ◽  
pp. 1-17 ◽  
Author(s):  
Shitan Gu ◽  
Bangyou Jiang ◽  
Gensheng Wang ◽  
Huabin Dai ◽  
Mingpeng Zhang
Keyword(s):  
Coal Seam ◽  
Coal Mine ◽  
Large Scale ◽  
Control Method ◽  
Tensile Failure ◽  
Large Section ◽  
Support Design ◽  
Roof Fall ◽  
Occurrence Mechanism ◽  
Fall Accidents

This study focused on large-scale roof-fall accidents occurred in large-section coal seam roadways of Bayangaole Coal Mine, Inner Mongolia, China, and investigated the occurrence mechanism of roof-fall and the related supporting control method in detail. Firstly, the fracture characteristics of the surrounding rocks on the roadway roof were measured using a stratum detector. The results showed that the roadway roof underwent the most severe failure with a maximum deformation of 3.53 m; the bedding separation and fracture zones were distributed at irregular intervals. Accordingly, the entire stratum was separated into several thin sublayers, significantly reducing the stability of roof. In addition, the roof medium grained sandstone of roadway is water-rich strata, and water aggravates the damage of roof. Next, the mechanism of the occurrence of roof-fall accidents in the roadway was elucidated in detail. The following three reasons are mainly attributed to the occurrence of roof-fall accidents: (i) effects of mining-induced stress and tectonic stress, (ii) existence of equipment cavern on the side of roadway, and (iii) unreasonable support parameters. On that basis, a new supporting design is proposed, including a more reasonable arrangement of anchor cables and bolts, bolts with full-length anchorage which are applicable in cracked and water-rich roadway, high-strength anchor cables, and crisscrossed steel bands. Moreover, high pretightening force was applied. Finally, a field test was performed, and the mining-induced roof displacement and stress on anchor cable (bolt) were monitored in the test section. The maximum roof displacements at the two monitoring sections were 143 mm and 204 mm, respectively, far smaller than the roadway’s allowable deformation. Moreover, the stress on roof anchor cables (bolts) was normal, and no anchorage-dragging and tensile failure phenomena were observed. The monitoring data indicated that the new supporting design was remarkable on the control of large-section coal seam roadway roof deformation.

scholarly journals Research and Application of Directional Roof Cutting and Pressure Releasing Technology for Retracement Channel of 3314 Working Face in Hexi Coal Mine

2021 ◽  
Author(s):  
Jindong Cao ◽  
Xiaojie Yang ◽  
Ruifeng Huang ◽  
Qiang Fu ◽  
Yubing Gao
Keyword(s):  
Coal Mine ◽  
High Stress ◽  
Surrounding Rock ◽  
Engineering Practice ◽  
Mine Pressure ◽  
Working Face ◽  
Geological Conditions ◽  
Cutting Effect ◽  
The Stability ◽  
Two Sides

Abstract The high stress of the surrounding rock of Hexi Coal Mine easily leads to severe deformation of the retracement channel and the appearance of the mine pressure during the retreat severely affects the stability of the roadway. In order to solve the above problems, a roadway surrounding rock control technology is proposed and tested. The bidirectional energy-concentrated tensile blasting technology is used to perform directional cutting to cut off the stress propagation path. Firstly, the deformation mechanism of the roof is analyzed by establishing the deformation mechanical model of the roof of the retracement channel. Then, according to the geological conditions of working face 3314 and theoretical calculation, the key parameters of roof cutting and pressure releasing of retracement channel are determined, and through the numerical analysis of its cutting effect, the length of cutting seam is 11.5m, and the cutting angle is 10°. Finally, a field test is carried out on the retracement channel of 3314 working face to verify the effect of roof cutting. The results show that the deformation of the retracement channel and the main roadway is very small. In the process of connecting the working face and the retracement channel, the maximum roof to floor convergence is 141mm, and the two sides convergence is 79mm. After the hydraulic support was retracted, the maximum roof to floor convergence of the surrounding rock is 37 mm, and the two sides convergence is 33mm. The roof cutting and pressure releasing of the retracement channel ensures the safe evacuation of the equipment and the stability of the main roadway. The cutting effect is obvious for the release of pressure, which is of great significance to engineering practice.

Study on Mine Pressure Behavior of Roadway in Highly Irregular Working Face in Daizhuang Coal Mine

2012 ◽  
Vol 256-259 ◽  
pp. 1443-1446
Author(s):  
Xing Lin Wen ◽  
Lin Hai Gao ◽  
Chuan Lei Li ◽  
Meng Meng Dong
Keyword(s):  
Coal Mine ◽  
Surrounding Rock ◽  
Mine Pressure ◽  
Mining Engineering ◽  
Deformation Characteristics ◽  
Working Face ◽  
Production Safety ◽  
Support Force ◽  
Mining Face ◽  
Important Significance

The irregular face mechanized mining is one of the difficult problems in the field of mining engineering. In this thesis, the roadways of 4324 extremely irregular face in DaiZhuang Mine were taken as research object. Through on-site mine pressure observation, the deformation characteristics of the surrounding rock and support force was analyzed. Next the mine pressure appeared rule of the roadways was study. This study benefited that the production of 4324 mining face went on wheels, at the same time, it had important significance to production safety of irregular working face with similar conditions.

A case study on control technology of surrounding rock of a large section chamber under a 1200-m deep goaf in Xingdong coal mine, China

2019 ◽  
Vol 104 ◽  
pp. 112-125 ◽  
Author(s):  
Shengrong Xie ◽  
Hao Pan ◽  
Junchao Zeng ◽  
En Wang ◽  
Dongdong Chen ◽  
...  
Keyword(s):  
Coal Mine ◽  
Surrounding Rock ◽  
Control Technology ◽  
Large Section

Deformation Failure Analysis and Stability Control Technology of Large Section Soft Rock Chamber in Deep Coal Mine

2013 ◽  
Vol 353-356 ◽  
pp. 1035-1039
Author(s):  
Chang Hui An ◽  
Gui Bin Zhang ◽  
Zhi Da Liu ◽  
Kai Zhao ◽  
Wei Guo ◽  
...  
Keyword(s):  
Coal Mine ◽  
Soft Rock ◽  
Stability Control ◽  
Surrounding Rock ◽  
Mine Safety ◽  
Large Section ◽  
Deformation And Failure ◽  
Deep Coal Mine ◽  
Ground Pressure ◽  
The Impact

The chambers of certain coal mine in Shandong such as central substation situate in soft rock which consists of mudstone and fine sandstone, etc. Obvious ground pressure behaviors, large deformation and failure of surrounding rock have serious effect on mine safety production, with the impact of various complicated deep large ground pressure. This paper presents a rational scheme to control the surrounding rock steadily, based on analysis of deformation and failure on large section soft rock chamber, combined with the concept of the" combined supporting technology of long and short anchors" and "the combined supporting technology of three anchors".

scholarly journals Numerical investigation of failure evolution for the surrounding rock of a super‐large section chamber group in a deep coal mine

2019 ◽  
Vol 7 (6) ◽  
pp. 3124-3146 ◽  
Author(s):  
Yunliang Tan ◽  
Deyuan Fan ◽  
Xuesheng Liu ◽  
Shilin Song ◽  
Xianfeng Li ◽  
...  
Keyword(s):  
Numerical Investigation ◽  
Coal Mine ◽  
Surrounding Rock ◽  
Large Section ◽  
Deep Coal Mine ◽  
Failure Evolution

scholarly journals Failure Mechanism and Control Technology for a Large-Section Roadway under Weakly Cemented Formation Condition

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Jiadi Yin ◽  
Baojie Fu ◽  
Hualei Zhang
Keyword(s):  
Numerical Simulation ◽  
Large Scale ◽  
Formation Condition ◽  
Mechanical Equipment ◽  
Analysis Model ◽  
Large Section ◽  
Crack Penetration ◽  
Roof Caving ◽  
Upper Aquifer ◽  
Rock Strata

The roof of a large-section roadway will usually undergo progressive deformation and failure under the action of deep surrounding rock stress. The large-section rectangular roadway is more prone to sudden roof caving accident under the weakly cemented formation condition, which poses great threats to operating personnel and mechanical equipment and brings about considerable difficulties to roof monitoring and evaluation. A large-scale caving accident that occurred on a large-section rectangular roadway in Bojianghaizi Mine in Inner Mongolia was taken as the study object. The factors that triggered the roadway roof caving were analyzed by investigating the roof caving mechanism of weakly cemented overlying strata, and an effective roof supporting method was proposed. A numerical mechanical analysis model was established for surrounding rocks of the roadway by using the discrete element method, and numerical simulation results showed that obvious vertical cracks would be generated at two ends of the roof under the action of shearing stress. With upward crack propagation and transverse crack penetration at the roof separation, a dangerous caving zone penetrated by cracks formed inside the roof. The permeation of the upper aquifer would reduce the rock strata strength at the roof and further aggravate the risk of roadway caving. In accordance with the numerical simulation and comprehensive analysis of field exploration data, the main reasons for the roadway caving accident were concluded as follows: (1) low rock strata strength at the roof and the influence of tectonic stress in deep surrounding rocks, (2) unreasonable original support pattern, and (3) permeation of the upper aquifer. On this basis, an improved support scheme was proposed, and field monitoring data showed that the maximum separation amount of the roof was controlled at 14 mm, and the roof deformation was well controlled, thus meeting the safety production requirements. The proposed method can provide a reference for the control of weak roadway roof and its support scheme design.

scholarly journals Fracturing of the Soft Rock Surrounding a Roadway Subjected to Mining at Kouzidong Coal Mine

2020 ◽  
Vol 2020 ◽  
pp. 1-17 ◽  
Author(s):  
Zhili Su ◽  
Wenbing Xie ◽  
Shengguo Jing ◽  
Xingkai Wang ◽  
Qingteng Tang
Keyword(s):  
Failure Mechanism ◽  
Coal Mine ◽  
Shear Failure ◽  
Soft Rock ◽  
Surrounding Rock ◽  
Asymmetric Distribution ◽  
Rock Layer ◽  
Imaging Results ◽  
Fracture Development ◽  
Borehole Imaging

The fracture development and distribution around the deep soft rock roadway are pivotal to any underground design. In this paper, both field investigation and numerical simulation were taken to study the fracture evolution and rock deformation of a coal mine roadway at Kouzidong mine, Fuyang, Anhui Province, China. Based on the borehole imaging technique, we found an asymmetric distribution of the fracture zone in the surrounding rock of the roadway. By analyzing the C value of the fractures in the borehole images,we found that the fracture interval distribution of the surrounding rock of the tunnel, the number of fractures will fluctuate decrease with the increase of the depth. To effectively study the fracture propagation and distribution of the roadway under longwall retreatment and roadway excavation, the global-local numerical technique was applied via FLAC3D and PFC2D. In the roadway excavation process, fractures were first formed in the shallow section of the roadway and progressively propagated toward the deeper soft rock layer; the main failure mechanism was a tensile failure. During longwall retreatment, fractures continuously developed toward the deeper soft rock layer. However, the failure mechanism transformed to shear failure. From numerical results, it can be seen that the stress concentration at the ribs was released, which led to shear failure at the roof and floor. Due to the extensive tensile cracks in the shallow section, the surrounding rock experienced expansion and fracture. The deep shear failure also induced the formation of the nonadjacent crushing zone and elastic zone, which is in line with the borehole imaging results.

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