scholarly journals Bearing Characteristics of Surrounding Rock of Deep Mining Roadway with Full and End Bolt Anchorages: A Comparative Numerical and Experimental Study

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Wenbao Shi ◽  
Yan Li ◽  
Wanfeng Li ◽  
Shihui Li
Keyword(s):  
Stress Distribution ◽  
Axial Force ◽  
Axial Stress ◽  
Field Tests ◽  
Surrounding Rock ◽  
Deep Mining ◽  
Pull Out ◽  
Laboratory Test Results ◽  
Full Anchorage ◽  
Bolt Support

The support strength of surrounding rock in deep mining roadways can be significantly improved by replacing the end bolt anchorage with a full one. The support effects of both types of anchorage and the axial stress distribution characteristics in anchored bolt bodies were assessed via the indoor pull-out test, simulated via the FLAC3D software, and verified by field measurements. The stability and variation patterns of the axial force, as well as the evolution law of bearing characteristics of surrounding rock, were analyzed. The results indicate that the polymorphic deformations of deep mining roadway surrounding rock and the bolt support body interact synchronously. The axial force evolution trend in bolt bodies with end anchorage revealed by field tests was consistent with the laboratory test results, in contrast to that of full anchorage. Although stress distribution laws in both sides of the mining roadway were the same for both types of anchorage, the vertical stress peak and damage range of full-anchored surrounding rock slightly exceeded those of the end-anchored one. The anchored area bearing a higher load alleviated the stress concentration of the surrounding rock. Since the deformations in fully and end anchored surrounding rocks increased gradually and sharply, respectively, the full anchorage is more conducive to deformation moving control of deep mining roadway surrounding rock. The research results can provide theoretical guidance for the design and construction of deep mining roadway bolt support.

Stress Distributions During Fiber Pull-Out

1996 ◽  
Vol 63 (2) ◽  
pp. 301-306 ◽  
Author(s):  
R. Krishna Kumar ◽  
J. N. Reddy
Keyword(s):  
Stress Distribution ◽  
Axial Stress ◽  
Friction Stress ◽  
Stress Distributions ◽  
Pull Out ◽  
Reinforced Composite ◽  
First Case ◽  
The Matrix ◽  
Axial Stress Distribution ◽  
Perturbed Lagrangian

Fiber pull-out resistance is an important mechanism of energy absorption during the failure of fiber-reinforced composite materials. This paper deals with axial stress distribution in the fiber during a pull-out. The frictional constraint between the fiber and the matrix is modeled with a perturbed Lagrangian approach and Coulomb’s law of friction. Stress distribution has been determined for three cases, using the finite element method. The first case deals with the pull out of a fully embedded fiber. The second determines the stress distribution during fiber pull-out in the presence of a broken-embedded fiber. The third model attempts to solve the pull out of a coated fiber. The results for the first case compares favorably with those in existing literature. A local “pinching” effect, due to the matrix collapse behind the pulled fiber, is brought out clearly by this model. The second study indicates that the “plug” effect may not be significant in affecting the stress distribution. Lastly, the effects of coating stiffness and thickness are investigated.

scholarly journals Experimental Study of the Failure Mechanism of the Anchorage Interface under Different Surrounding Rock Strengths and Ambient Temperatures

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Xiaohu Liu ◽  
Zhishu Yao ◽  
Weipei Xue ◽  
Xuesong Wang ◽  
Xianwen Huang
Keyword(s):  
Energy Consumption ◽  
Failure Mechanism ◽  
Failure Modes ◽  
Rock Strength ◽  
Axial Stress ◽  
Surrounding Rock ◽  
Slip Mode ◽  
Pull Out ◽  
Axial Forces ◽  
Consumption Value

In order to study the anchoring instability mechanism of surrounding rock in deep roadway, the failure mechanism of the bolt-anchoring agent interface was studied by simulating different strength rock mass and ground temperature environment, using C20, C40, and C60 strength concrete and steel pipe to simulate different surrounding rock strength environments. Indoor pull-out tests were carried out to study the pull-out load displacement relationship, ultimate pull-out force, residual anchoring force, the distribution law of axial stress and tangential stress along the bar, and the energy consumption value of drawing failure at 20, 50, and 70°C. The test results show that, with the decrease of surrounding rock strength or the increase of ambient temperature, the pull-out force, residual anchoring force, and energy consumption value of anchorage interface gradually decrease; under different axial forces, the axial force distribution of the rod body decreases exponentially from the anchoring end to the opposite end; and the shear stress transfers to the deep part of the anchor body with the increase of the load. According to the failure phenomenon of the specimen, the failure modes of the bolt bolt-anchorage agent interface can be divided into shear slip mode and shear expansion slip mode. The shear expansion slip formula of anchorage interface is derived. Using high-strength and temperature-resistant resin anchoring agent for comparative test, the rationality of the mechanism analysis is proved, which provides more clear guidance for the construction of anchor support.

scholarly journals Monitoring and Analysis of Stress Distribution of the Interaction between Rock and Backfill and the Influence of Geometric Features of the Backfill Boundary

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Rong Lu ◽  
Fengshan Ma ◽  
Jie Zhao ◽  
Jianbo Wang ◽  
Guilin Li ◽  
...  
Keyword(s):  
Stress Distribution ◽  
Contact Zone ◽  
Local Stability ◽  
Horizontal Stress ◽  
Field Investigation ◽  
Surrounding Rock ◽  
Geometric Features ◽  
Deep Mining ◽  
Boundary Part ◽  
Distribution Of Stress

Backfill mining methods are widely used in metal mines. The boundary part of the backfill has a direct effect on the local stability in mining engineering. The distribution of stress on the boundary part of the backfill and surrounding rock had their own features. To study the characteristics of stress distribution of backfill and surrounding rock on the boundary part, we conducted a field investigation, field monitoring, and numerical simulation. According to the underground monitoring, the overall characteristics of the boundary part of the backfill were that the accumulated horizontal stress was larger than the accumulated vertical stress on the deep sublevel and the accumulated horizontal stress was smaller on the shallow sublevel. On the contact zone (i.e., the boundary part), the stress of the surrounding rock was larger than the stress of the backfill. Combined with the numerical model analysis, we determined that the geometric features of the backfill boundary had an influence on the stress distribution of stress. The multistep boundary helped the integrity of the contact zone and local stability in deep mining.

scholarly journals Cooperative Control Mechanism of Long Flexible Bolts and Blasting Pressure Relief in Hard Roof Roadways of Extra-Thick Coal Seams: A Case Study

2021 ◽  
Vol 11 (9) ◽  
pp. 4125
Author(s):  
Zhe Xiang ◽  
Nong Zhang ◽  
Zhengzheng Xie ◽  
Feng Guo ◽  
Chenghao Zhang
Keyword(s):  
Coal Seam ◽  
Cooperative Control ◽  
Field Tests ◽  
Surrounding Rock ◽  
Deep Hole ◽  
Coal Seams ◽  
Thick Coal Seam ◽  
Structure Damage ◽  
Hard Roof

The higher strength of a hard roof leads to higher coal pressure during coal mining, especially under extra-thick coal seam conditions. This study addresses the hard roof control problem for extra-thick coal seams using the air return roadway 4106 (AR 4106) of the Wenjiapo Coal Mine as a case study. A new surrounding rock control strategy is proposed, which mainly includes 44 m deep-hole pre-splitting blasting for stress releasing and flexible 4-m-long bolt for roof supporting. Based on the new support scheme, field tests were performed. The results show that roadway support failure in traditional scenarios is caused by insufficient bolt length and extensive rotary subsidence of the long cantilever beam of the hard roof. In the new proposed scheme, flexible 4-m-long bolts are shown to effectively restrain the initial expansion deformation of the top coal. The deflection of the rock beam anchored by the roof foundation are improved. Deep-hole pre-splitting blasting effectively reduces the cantilever distance of the “block B” of the voussoir beam structure. The stress environment of the roadway surrounding rock is optimized and anchorage structure damage is inhibited. The results provide insights regarding the safe control of roadway roofs under extra-thick coal seam conditions.

scholarly journals Experimental Investigation of Steel Plate Shear Walls under Shear-Compression Interaction

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Yang Lv ◽  
Ling Li ◽  
Di Wu ◽  
Bo Zhong ◽  
Yu Chen ◽  
...  
Keyword(s):  
Stress Distribution ◽  
Steel Plate ◽  
Axial Stress ◽  
Shear Walls ◽  
Shear Capacity ◽  
Steel Plate Shear Walls ◽  
Steel Plate Shear Wall ◽  
Gravity Load ◽  
Moment Resisting ◽  
Axial Stress Distribution

Four scaled one-storey single-bay steel plate shear wall (SPSW) specimens with unstiffened panels were tested to determine their behaviour under cyclic loadings. The shear walls had moment-resisting beam-to-column connections. Four different vertical loads, i.e., 300 kN, 600 kN, 900 kN, and 1200 kN, representing the gravity load of the upper storeys were applied at the top of the boundary columns through a force distribution beam. A horizontal cyclic load was then applied at the top of the specimens. The specimen behaviour, envelope curves, axial stress distribution of the infill steel plate, and shear capacity were analyzed. The axial stress distribution and envelope curves were compared with the values predicted using an analytical model available in the literature.

Reasonable Entry Layout of Lower Seam in Multi-Seam Mining Based on Numerical Simulation

2013 ◽  
Vol 295-298 ◽  
pp. 2980-2984
Author(s):  
Xiang Qian Wang ◽  
Da Fa Yin ◽  
Zhao Ning Gao ◽  
Qi Feng Zhao
Keyword(s):  
Numerical Simulation ◽  
Stress Distribution ◽  
Coal Seam ◽  
Coal Mine ◽  
Abutment Pressure ◽  
Surrounding Rock ◽  
Geological Conditions ◽  
Seam Mining

Based on the geological conditions of 6# coal seam and 8# coal seam in Xieqiao Coal Mine, to determine reasonable entry layout of lower seam in multi-seam mining, alternate internal entry layout, alternate exterior entry layout and overlapping entry layout were put forward and simulated by FLAC3D. Then stress distribution and displacement characteristics of surrounding rock were analyzed in the three ways of entry layout, leading to the conclusion that alternate internal entry layout is a better choice for multi-seam mining, for which makes the entry located in stress reduce zone and reduces the influence of abutment pressure of upper coal seam mining to a certain extent,. And the mining practice of Xieqiao Coal Mine tested the results, which will offer a beneficial reference for entry layout with similar geological conditions in multi-seam mining.

Strength Assessments of Concrete-Filled Steel Tubular Support of Soft Rock Roadway

2013 ◽  
Vol 838-841 ◽  
pp. 1884-1890 ◽  
Author(s):  
Guang Long Qu ◽  
Yan Fa Gao ◽  
Liu Yang ◽  
Bin Jing Xu ◽  
Guo Lei Liu ◽  
...  
Keyword(s):  
Bearing Capacity ◽  
Coal Mine ◽  
Soft Rock ◽  
Surrounding Rock ◽  
Flexural Performance ◽  
Laboratory Test Results ◽  
Different Types ◽  
Soft Rock Roadway ◽  
Core Concrete ◽  
Rock Roadway

Compared with I-shaped and U-shaped supports in soft rock roadway, concrete-filled steel tubular (CFST) support, as a new supporting form, has stronger bearing capacity with reasonable price. So it is becoming more and more popular in roadway supporting of coal mine in China. In this article, the surrounding rock in soft rock roadway was classified into three different types: hard rock in deep coal mine, soft surrounding rock, extremely soft surrounding rock. And, according to the characteristics of deformation failure of the CFST support and the surrounding rock in the industrial tests, three different strength assessments, including assessment of axial compressive strength, assessment of lateral flexural performance, assessment of hardening rate of core concrete, were proposed through mechanical analysis and laboratory tests for the three different types of the surrounding rock, respectively. Moreover, aimed to insufficient flexural strength of the support or low hardening rate of the core concrete in some of the roadway supporting, strengthening lateral flexural performance or making early strength concrete was necessary for the above unfavorable situations. The laboratory test results showed that the ultimate bearing capacity for the CFST support with φ194*8mm of steel tube reinforced by φ38mm round steel was 31% greater than that of the unreinforced one, 177% greater than that of the U-shaped one with equivalent weight per unit length.

scholarly journals The Influence of Pile-Driving Vibration on the Soil Nailing Support of a Silty Soil Foundation Pit

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Yuancheng Guo ◽  
Hao Wu ◽  
Chenglin Li
Keyword(s):  
Axial Force ◽  
Soil Strength ◽  
Interface Strength ◽  
Pile Driving ◽  
Vibration Exciter ◽  
Foundation Pit ◽  
Soil Nail ◽  
Pull Out ◽  
Working Length ◽  
Soil Interface

The ground vibration induced by pile driving affects the safety of the adjacent foundation pit. In this paper, the influence of pile-driving vibration on the soil strength and the nail-soil interface strength was studied, and the variation in the axial force and displacement of the soil nail under vibration was analyzed. The paper studied the effects under different vibration parameters on the soil strength and the nail-soil interface strength by using a vibration exciter and a nail pull-out model box. The results showed that the stronger the excitation force was and the higher the frequency was, the greater the attenuation of the soil strength and nail-soil interface strength was. On the contrary, the change of the internal friction angle of the soil was not obvious under the vibration. The nail-soil interface strength recovered when the vibration terminated. Decreases in c and τp led to an increase in the working length of the soil nail, a redistribution of the axial force, and an augmentation in the soil nail displacement.

scholarly journals Stress Distribution Around Mechanized Longwall Face at Deep Mining in Quang Ninh Underground Coal Mine

2021 ◽  
Vol 1 (2) ◽  
Author(s):  
Manh Tung BUI ◽  
Tien Dung LE ◽  
Trong Hung VO
Keyword(s):  
Stress Distribution ◽  
Sea Level ◽  
Coal Mine ◽  
Coal Mines ◽  
Longwall Face ◽  
Geological Condition ◽  
Deep Mining ◽  
Roof Fall ◽  
The Impact ◽  
Quang Ninh

Quang Ninh underground coal mines are currently in the phase of finishing up the mineralreserves located near the surface. Also, in this phase, a number of coal mines have opened and preparednew mine sites for the extraction of the reserves at greater depth. Several mines have mined at -350 mdepth and are driving opening excavations at -500 m depth below sea level. The mining at greater depthfaces many difficulties, such as a significant increase in support and excavation pressures. The longwallface pressure is mostly manifested in great magnitude that causes support overloaded and jumped andface spall/roof fall. This paper, based on the geological condition of the Seam 11 Ha Lam coal mine,uses the numerical program UDEC for studying the impact of mining depth on stress distribution aroundthe longwall face. The results show that the deeper the mining is, the greater the plastic deformationzone is. The peak front abutment stress moves closer to the coal wall, mainly concentrating on theimmediate roof and top coal. The top coal is greatly broken, and its bearing capacity is decreased. Somesolutions to the stability of roof strata are proposed, and a proper working resistance of support isdetermined. Additionally, the paper suggests that the starting depth for deep mining in Quang Ninhunderground coal mines should be -350 m below sea level.

scholarly journals Mechanical Characteristics of Fully Grouted and Antiseismic Bolts considering Transverse Deformation in Underground Caverns

2019 ◽  
Vol 2019 ◽  
pp. 1-15
Author(s):  
Buyun Yang ◽  
Ming Xiao ◽  
Guoqing Liu ◽  
Juntao Chen
Keyword(s):  
Axial Stress ◽  
Time History ◽  
Beam Theory ◽  
Support Effect ◽  
Transverse Force ◽  
Surrounding Rock ◽  
Axial Deformation ◽  
Transverse Deformation ◽  
Rock Interaction ◽  
Underground Caverns

The load transfer control equations under bolt-surrounding rock interaction are established on the basis of classical beam theory and the trilinear shear slip model. The axial stress and transverse shear force distributions of the anchorage body are obtained by solving the equations. The equivalent forces obtained by the transverse force and axial shear stress of the bolts are applied to rock mass elements to simulate the support effect. A new dynamic algorithm for bolts is proposed in considering of the axial and transverse deformation of the anchorage body. The rationality of the algorithm is verified by comparing with laboratory pullout and shear tests of bolts. A dynamic time-history case study of underground caverns is conducted using this algorithm. Results indicate that (1) the algorithm may reflect the stress and deformation characteristics of bolts during an earthquake; (2) for the antiseismic support effect of the surrounding rock at fault, the bolt algorithm in this study is more valid than the algorithm that considered only the axial deformation of bolts; (3) in the support force of the bolt to the surrounding rock, transverse force is the key to limit fault dislocation and reduce the dynamic damage of the rock at fault.

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