Investigating the Influence of Embedment Length on the Anchorage Force of Rock Bolts with Modified Pile Elements

Chen, Jianhang; Wang, Shiji; Sun, Guoxin; Zhang, Han; Skrzypkowski, Krzysztof; Zagórski, Krzysztof; Zagórska, Anna

doi:10.3390/app13010052

Cited by 3 publications

(1 citation statement)

References 26 publications

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“…Due to the advantages of easy disassembly and reliable connection, bolts are usually used in vehicles, ships, and various important equipment. Extensive research on bolts has been carried out in recent years, such as dynamic analysis, finite element modeling, effects of environmental and material parameters, and optimal design of structures [1][2][3][4]. Among these bolted connection applications, flanges have attracted much attention since the complex contact surfaces and a large number of bolts have brought challenges to research [5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Bolt looseness localization with connection-stiffness-varying flange

Huang,

2024

Smart Mater. Struct.

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Electromechanical impedance analysis is a traditional method to identify the occurrence of bolt looseness, but accurate localization of blot looseness is hard to realize on the flange. In this study, a flange model with bolt connection stiffness varying with position is proposed. The location of bolt looseness can be then determined from the impedance spectrum of the model since the uniformity and symmetry of the flange are broken. The analytic model is established to reveal the distinguishability of the eigenfrequency shifting characteristics when the connection stiffness at different positions changes. The frequency shifting sequence is extracted from the coupling impedance spectrum as a feature, and the correlation between the sequences corresponding to bolt looseness at different positions is low. The relationship between the sequence and the degree of looseness is highly related so that the unknown degree of looseness can be matched with the calibrated sequence to realize the localization of the looseness. Based on the distinguishability of the frequency shifting sequence, the connection-stiffness-varying model shows great potential in the field of flanges or other connecting structures for structural health monitoring and damage localization.

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Section: Introductionmentioning

confidence: 99%

Bolt looseness localization with connection-stiffness-varying flange

Huang,

2024

Smart Mater. Struct.

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Numerical study of the interaction of rock bolts with the block-structured rock mass

Krukovskyi,

Krukovska,

Demin

et al. 2024

Geoteh. meh.

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In order to ground parameters of rock bolting for mine workings, it is necessary to study the stressedly-deformed state of the host rock and the elements of rock bolting. Under certain mining and geological conditions, the rock mass is broken by cracks and divided into blocks. Methods designed for modelling solid environments are not sufficient for the study of a block-structured rocks. In this regard, the purpose of this work was to develop a method of studying the state of block-structured rock mass around the mine working with rock bolting and to ground the possibility of preventing the rock blocks from sliding with the help of rock bolting structure. As a result of the work, a numerical model of a block-structured rock mass with a mine working supported with rock bolts, which were modeled using two-node rod finite elements, was developed. Cracks were simulated using a four-node contact finite element, which has zero thickness, and the initial coordinates of the nodes of its opposite sides coincide. The generation and growth of a crack can occur in the form of its opening or displacement along its surface. A method was developed, which, due to the introduction of special contact elements into the finite-element scheme, allows simulating the stressedly-deformed state of rocks with cracks. The use of the proposed method of studying the block-structured rock mass makes it possible to check the efficiency of the rock bolting elements during the development of the supporting scheme. Using the developed method, the relative displacement of the block formed in the mine roof was investigated in four cases: when the mine working is not supported, the mine working is supported with the use of simple, reinforced and powerful rock bolting structures. It was shown that in the cracked rocks divided into blocks, the displacement of the rock block reaches a maximum in the unsupported mine roof. The simple rock bolting structure almost does not prevent the rock block from shifting into the mine working space, together with a row of rock bolts installed vertically. The inclination of the rock bolts by 70° to the mine face in the reinforced rock bolting structure significantly improves the condition of the mine roof; its displacement is reduced by 87%. And the use of the powerful rock bolting structure blocks the movement of the rock-bolts block almost completely, by 93%. Therefore, the reinforced and powerful rock bolting structures allows you to keep the cracked rock mass divided into blocks in a stable condition. Keywords: block-structured rocks, mine working, rock deformation, rock bolting structure, numerical simulation.

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Mechanical Properties of Fully-Grouted Bolts Support Based on Compression Tests of Anchored Rock Mass

Han,

Jin,

et al. 2024

Applied Sciences

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The mechanical properties of fully-grouted bolt support are critical for the safety of support engineering works. To study the influences of factors including the bolt length and diameter, strength of the rock, and fracture angle on the mechanical properties of fully-grouted bolt support, compression tests were conducted on an anchored rock mass, considering the shortcomings of pullout tests on bolts. The discrete element software PFC2D (4.0) was adopted for numerical simulation and analysis from two aspects, namely, the stress distribution and anchorage force supplied by such bolts. The research found that by increasing the bolt diameter and length as well as the strength of the rock, the maximum anchorage force of bolts increases. Whereas the stress distribution of all bolts increases at first and then decreases along the bolts, and there is only one peak on the stress distribution curves, which also gradually shifts to a greater depth. In a fractured rock mass, the maximum anchorage force of bolts decreases, then increases (and is minimized at a fracture angle of 45°) with the decrease in fracture angle. The influence of fractures with different angles on the stress distribution of bolts is mainly reflected in the fracture zone. The bolt stress decreases abruptly in the zone with a fracture angle of 90°, forming a valley. The bolt stress increases suddenly in the zones with fracture angles of 60° and 45°, thus forming peaks. The bolt stress does not increase or decrease suddenly in the zone with a fracture angle of 30°. Therefore, it necessitates consideration of the influences of fractures on the anchorage force and the selection of bolts of appropriate size during anchorage design. After installation, the bolt stress should be monitored for stability and early warning of anchored rock mass according to changes in the stress provided.

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Investigating the Influence of Embedment Length on the Anchorage Force of Rock Bolts with Modified Pile Elements

Cited by 3 publications

References 26 publications

Bolt looseness localization with connection-stiffness-varying flange

Bolt looseness localization with connection-stiffness-varying flange

Numerical study of the interaction of rock bolts with the block-structured rock mass

Mechanical Properties of Fully-Grouted Bolts Support Based on Compression Tests of Anchored Rock Mass

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