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 CHEMICAL ENGINEERING TRANSACTIONS  
 

VOL. 59, 2017 

A publication of 

 

The Italian Association 
of Chemical Engineering 
Online at www.aidic.it/cet 

Guest Editors: Zhuo Yang, Junjie Ba, Jing Pan 
Copyright © 2017, AIDIC Servizi S.r.l. 
ISBN 978-88-95608- 49-5; ISSN 2283-9216 

Study on the Mechanical Properties and the Matching of Bolt 

Components 

Xiaowen Wang 

W eifang Science and Technology University, Shouguang 262700, China 

wangxiaowen@126.com 

The roadway has to adapt to the surrounding rock movement compensation tracking anchoring force changes, 

strong anchor bolt, lightweight and Recyclable reuse, the advantages of economy and environmental 

protection. Compared with the traditional bolt and rock is prone to lack of cohesion, not suitable for supporting 

or prone to large deformation of roadway in soft rock, the anchoring force of unstable phenomenon. Therefore, 

it is of great theoretical significance and practical value to study the bolt of roadway. This topic is based on the. 

In this paper, starting from the ground experimental roadway bolt, combined with elastic-plastic mechanics, 

rock mechanics theory, using finite element contact analysis of roadway bolt, provide a theoretical basis for 

the design and production of the bolt, and the simulation results with the theoretical and numerical results are 

verified by the numerical test on the ratio, improved model and lay the foundation for optimization of bolt 

structure. The mechanical properties and influencing factors of resin anchoring agent were studied. The 

results show that the bolt is in a normal state when the bolt is subjected to tension, bending, torsion, shear and 

its combination, and the 4 position of the rod is easy to break. The stress distribution of the surface and the 

near part of the thread is changed significantly, and the stress concentration is obvious at the bottom of the 

thread. 5 stages can be divided into arch plate deformation; arch height must meet in order to ensure sufficient 

bearing capacity to a certain value. The geometry, the parameters and the mechanical properties of the bolt 

end member should match each other, so that the anchor rod is in a good state of stress. The resin anchoring 

agent should be matched with the rod body and the hole to ensure the good bonding property between the 

anchor rod anchoring agent and the anchoring agent. The research results have been applied to many kinds 

of difficult roadway, which greatly reduced the damage of the bolt support and significantly improved the effect 

of roadway support. 

1. Introduction 

As the object of geotechnical engineering facing the complex geological body, in the long geological ages, due 

to experiencing tectonic movement, natural weathering erosion and human activity, resulting in large amounts 

such as bedding, fault, joint and weak interlayer, solution groove, solution groove etc. kinds of geological 

defects. Within a certain period of time and under certain conditions, they may be in a relatively stable state of 

equilibrium. If conditions change, the original balance state is likely to be destroyed, for example in the 

process of excavation in geotechnical engineering geologic body, the original balance is broken, the original 

stress field redistribution, which occurred in the rock and soil deformation, causing landslides, collapse and 

landslide, rock collapse, ground subsidence and other geological disasters. In order to prevent and control this 

kind of geological disaster, all kinds of support came into being. Bolt supporting is a tension member 

embedded in rock and soil, the structure and formation of chain tightly together, so that the surrounding rock 

from passive to active load bearing, arouse the rock and soil itself strength and stability. This is called the 

anchor rod (Kang et al., 2015). Therefore, the bolt has a good development prospect. Therefore, the research 

of this subject has important academic significance and engineering significance, at the same time, it has 

good economic and social benefits. In this paper, the influence of structural parameters on the performance of 

the flexible compression anchor is studied through three aspects: analytical analysis, numerical simulation and 

experiment. Nowadays, the bolt supporting technology has entered the stage of high strength pressurised 

anchor system. With the stress based bolting design method gradually mature, high strength and length of bolt 

                               
 
 

 

 
   

                                                  
DOI: 10.3303/CET1759014

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Please cite this article as: Xiaowen Wang, 2017, Study on the mechanical properties and the matching of bolt components, Chemical 
Engineering Transactions, 59, 79-84  DOI:10.3303/CET1759014   

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supporting system has been widely used in engineering construction, and has become the symbol of this 

stage, at the same time in order to realize the detection of rock dynamic, developing instrument of roof 

separation and force anchor rod and other equipment, to realize the objective to provide technical support 

means. It is considered that the function of the bolt support is to hang the roof of the tunnel to the upper stable 

rock layer, although the theory is easy to understand, there are many defects. Usually when calculating the 

anchoring force of anchor bolt that is equal to the lower suspension rock weight, but this phenomenon exists 

only in loose rock or unstable strata completely out of the stable rock, which is rare (Kan and Qian, 2016). 

Although the suspension theory can explain the bolt in hard rock exists in the anchorage area in the case of 

the supporting role, but in the soft rock roadway in soft rock roadway, especially when the span is large, the 

rock high natural arch will generally be greater than the length of the anchor, in this case, the success of rock 

bolt support and reinforcement, reasonable explanation of the suspension theory. In conclusion, suspension 

theory only take into account the effect of bolt tensile, shear capacity for rock bolt reinforcement, improving the 

overall strength of the rock bolt is not involved, so the load calculated with actual numerical difference, 

suspension function diagram as shown in Figure 1, on the one hand the layers are squeezed two contact 

surface pressure makes the friction between the two layers increased, the frictional resistance and the 

positioning bolt can prevent the anchorage system in rock sliding along the level, thereby avoiding the 

phenomenon of layered rock; on the other hand, the multilayer rock bolt as a whole, so that the shear stiffness 

increase in order to prevent the generation of surrounding rock, strata horizontal dislocation. At the same tim e, 

the stress and deflection of each layer are greatly reduced under the overburden rock, so the bending strength 

of the composite beam is increased. The bolt embedded in rock and soil depth, the equivalent of the simple 

superposition of several layers of beam into composite beam, composite beam inside the thicker the, 

maximum stress, strain and deflection is small, and the bearing capacity of beams is bigger. The greater the 

anchoring force of the anchor, the greater the friction resistance between the rock layers, the higher the 

degree of integration of the composite beam, the greater the intensity of the composite beam schematic 

diagram shown in Figure 2. 

The maximum horizontal stress is considered that the deformation of the surrounding rock is caused by the 

maximum horizontal stress and the shear resistance of the rock, which results in the dislocation or looseness 

of the rock. And the bolt in the surrounding rock is to limit the limit of the roof and floor rock due to the 

expansion of the axial movement and the shear stress due to the axial and vertical dislocation. So the bolt 

material must be selected with high shear resistance, high rigidity and high strength, the only way to play the 

role of constraints of surrounding rock deformation (Li et al., 2015). 

 

 

Figure 1: Schematic diagram of suspension effect    Figure 2: Schematic diagram of composite beam 

2. Down whole test and finite element contact analysis of anchor member 

2.1 Introduction to underground test of anchor member 

The bolt ends are respectively arranged in the hole of rock (coal hole) and simulated pipe, placed tight, there 

is no exposed part, and then to anchor the cavity filling air or hydraulic pressure, tensile test of drawing bolt 

Jack power. The hollow jack loading equipment, drawing stroke range for 0~30t, 0~50mm, used as indicator 

measuring equipment, pressure gauge range for 0~16MPa.  

At the end of filling pressure, anchor cavity pressure stability, the flexible pressurized anchor pull-out force 

applied, anti-drawing performance of ground test, by pressing the drawing jack handle, the top rod, bolt 

tension began, over a period of time to check and record Jack external pressure gauge and dial indicator 

measuring numerical tensile length to anchor, until the bolt failure or slippage. In order to investigate the 

influence of internal pressure on the allowable drawing load of bolt, the pressure value of internal pressure can 

be recorded at the time of injection. When the anchor shear performance of the ground test, by pressing the 

jack handle, the jack bolt rod, slow shear, over a period of time to check and record the pressure gauge and 

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Jack external value by the dial indicator to get the shear displacement of anchor, anchor until failure or 

slippage. According to the experimental results of the tensile force of the anchor bolt, the tensile force of the 

bolt is approximately linear with the injection pressure in the anchor bolt (Chou and Zhao, 2015). Through the 

test of bolt tensile force and the shear stress of the anti-load performance can satisfy the need of engineering 

anchor; flexible tensile load injection bolt and shear load will increase with the injection pressure increasing, 

however, the change of internal pressure, tensile anchor rod the sensitivity values change greatly and the 

shear resistance of relatively small changes in a short time; for the underground work, the anchor bolt sealing 

performance and the long-term capacity to meet the basic engineering needs. The anchor rod selection of 

materials with flame retardancy, antistatic properties, aging resistance, in order to meet the underground 

safety performance requirements, the cost of resin bolt with same specifications and the length of plastic 

anchor roughly (Gao and Li, 2016; Su, 2016). Figure 3 shows schematic diagram of down whole test results. 

 

 

Figure 3: Schematic diagram of down whole test results. 

2.2 The establishment of the mathematical model of bolt anchorage system 

Under the ideal working condition, the axial tensile stress of the bolt body is equal to the longitudinal tensile 

stress of the bolt. So we can ignore the secondary factors that of longitudinal stress has little influence, such 

as radial constraint on bolt and rock wall friction (the friction is part of the dangerous section to the anchor 

head end part of the surrounding rock and bolt body no sliding or sliding trend), gas or liquid on the inner wall 

of the radial pressure. At this time the anchor forces balance. Therefore P and by drawing load injection in the 

internal pressure of P produced in the dangerous section and equal to the longitudinal reinforced polymer 

material with high strength steel wire and anchor rod body layer of tension and, in short, the total force shared 

by high strength steel wire and polymer materials. The longitudinal reinforcement layer of steel material, main 

bearing drawing force to the longitudinal (or axial) enhanced transverse on the polymer rod body and rock 

anchor hole (or radial) extrusion effect negligible; sealing layer is made of rubber materials for injection 

pressure, and the pressure to the contact surface to the ring; the fixed length enhancement layer material for 

fiber (such as nylon, nylon), to limit the effect of bolt diameter, only when the bolt reaches the limit when the 

size of the ring to be fixed layer, wear-resistant bearing layer materials for rubber, mainly used to bear the 

pressure of bolt hole wall between the wall and the anchor, and provide enough friction for the anchorage 

system. The anchor wall as internal boundary under uniform internal pressure injection effect of p; as the 

anchor wall mechanics model of the outer boundary, only consider the surrounding rock anchor hole wall is far 

away from the rigid body and the distance of rock hole wall stress is zero this two typical situations. The 

following two cases were solved (Wang, 2016). The anchor body under shear stress refers to shear between 

the steel wire and rod polymer materials stress, because the analysis is complicated to calculate the shear 

stress, so the engineering calculation assumptions. In order to simulate the stress and working state of the 

bolt in rock mass more accurately, the 3D modelling is chosen. The structure of the flexible grouting anchor 

rod is shown in figure 4. In order to solve the load increment and gradually increasing load but, unfortunately, 

this method will be the inevitable error of each step with the cumulative increase, and the final results and for 

far, unable to achieve the balance (Luo et al., 2015). 

 

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Figure 4: Schematic diagram of the structure of flexible grouting anchor rod. 

2.3 Basic theory of contact analysis 

 

Figure 5: Schematic diagram of the bearing force of bolt and surrounding rock. 

ANSYS nonlinear solution can be divided into three levels: load step, sub step and equilibrium iteration. In 

order to obtain the convergence of the solution procedure not sub steps will conduct a series of equilibrium 

iteration, in each step, the control program execution sub step (or time step) complete step-by-step loading; 

the top level refers to those in a "time" within the defined load step, can assume these loads in the load step is 

linear change. Because the surrounding rock the gravel rock anchor rod for polymer materials, so the contact 

problem of flexible pressurized anchor and surrounding rock is assumed to be flexible contact type flexible 

body, more in line with the actual situation. According to the mechanical model of the anchorage system, it 

can be seen that the deformation of the surrounding rock mass and the bolt body will be affected by the 

pressure and the surrounding rock pressure (Gong et al., 2016). Therefore, we need to discuss the distribution 

of the contact stress, the stress of the bolt and surrounding rock, and the distribution of the displacement of 

the anchor. As shown in Figure 5, the bolt body, the contact edge of polymer material and steel wire on the 

maximum equivalent stress, equivalent stress is 7.862MPa; the minimum occurs at the edge of polymer 

materials and close to the anchor hole in between two steel, 0.173MPa. The reason for the maximum stress is 

due to the sudden change of the material on the contact edge of the steel wire and the polymer material. It can 

be seen that the stress of the polymer material near the wire is worse than that of the steel wire, and the 

stress value of the polymer material near the wire is much higher than that of the steel wire. Correspondingly, 

the stress on the inner wall of the anchor body is much higher than that of the outer wall. Therefore, the 

equivalent stress of the bolt body is related to the diameter of the steel wire and the quantity of the steel wire. 

In order to study the influence of various structural parameters on the anchoring system, only one set of 

parameters is chosen to study the data. Keeping the other parameters unchanged, the data are classified 

according to the type of the parameters, and the influence of the parameters on the anchoring system is 

obtained. No matter the anchor of the longitudinal reinforcement layer select wire strengthened with increasing 

the elastic modulus of polymer materials, the surrounding rock and the maximum equivalent stress of bolt 

anchorage system, maximum contact stress is reduced, but the bolt body decreases the maximum equivalent 

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stress amplitude is not obvious. Therefore, in order to play a good anchorage effect of the surrounding rock 

should be in the material to meet the strength requirements of the premise of the selection of small elastic 

modulus of the material to make the body. As the injection pressure increases, the three group of anchor rod 

the maximum equivalent stress of surrounding rock, the maximum equivalent should be the same trends and 

anchorage system of the maximum contact stress, increases, and a linear increase, but the increasing rate is 

different, the maximum equivalent stress of anchor bolt internal pressure changes were more sensitive 

therefore, in order to enhance the anchoring effect and increase in injection pressure should pay special 

attention to strength bolt body. 

3. Influence of structural parameters of bolt member on allowable drawing load 

When the anchor bolt is installed, in order to prevent the anchor bolt from being pulled out of the anchor hole, 

the surrounding rock at the end of the anchor bolt must be provided with enough pulling force. Therefore, it is 

necessary to get the allowable drawing load of the anchor bolt, so that the pulling force of the anchor bolt is 

under the secondary strength, so as to ensure the normal operation of the anchor rod. Considering the 

physical structure is more complex, the difficulty in modelling the finite element simulation and the local 

material and shape change of the paper is not affected, so the bolt is simplified as a polymer material with 

steel wire reinforced body cavity. According to symmetry, select anchor section 1/4 finite element model is 

established, and according to the characteristics of plane strain and need the three-dimensional display, select 

the middle part of the bolt body is smaller than the original length as the research object, the model shown in 

Figure 6 the simplified. After the physical model is built, the SOLID186 with the intermediate node is chosen 

as the unit type of the model. When the mesh is divided, the nodes on the contact surface of different 

materials are taken into account, so the finite element method is used to divide the mesh, so as to ensure the 

smooth calculation. Due to the overall size of the longitudinal reinforcement layer is less than the surrounding 

rock, the number of qualified units should be increased. Because of the nonlinear problem, the mesh can be 

guaranteed to be accurate enough. The Hex/Wedge method is used to divide the grid into Sweep, because 

the grid is divided into cuboid and mesh, which is easy to calculate. Taking into account the working state of 

the anchor bolt, the analysis of the allowable drawing load of the bolt is also taken by the method of contact 

analysis. Firstly, the contact pair is defined. Because the flexible work pressure injection through bolt, injection 

pressure, rod radial expansion to the direction of extrusion of rock, rock bolt, so the wall and the anchor hole 

wall extrusion contact, therefore, set the anchor wall and anchor hole wall of contact. Because of the anchor 

rod body compression expansion, active extrusion wall, so the selected anchor whole wall for the target 

surface, the outer wall of the bolt body as the contact surface (Meng et al., 2015). Considering the anchor wall 

as the polymer material, the anchor whole wall is uneven, so the friction coefficient of anchor wall and anchor 

whole wall can select a larger value. The anchor whole surface is defined as the target surface, and the outer 

surface of the anchor bolt is the contact surface, and the outer surface of the outer surface of the outer surface 

of the bolt is the external normal of the surface element. The external normal of the target surface points to the 

contact surface, and the normal surface of the contact surface points to the target surface. At the same time, it 

gives a certain amount of displacement of the left end of the rod, and carries out second load steps. By 

changing the amount of displacement, the steel wire and the polymer material can meet the allowable stress. 

At the same time, the original 1/4 model is extended to the whole bolt body and surrounding rock mass model 

and the constraint force acting on the right end face of the anchor bolt is taken as the allowable drawing load 

of the flexible compression anchor bolt. When the elastic modulus is less than 90MPa, the Poisson ratio of 

polymer materials, the allowable anchor pull-out load increases, and when the elastic modulus is greater than 

90MPa, small material Poisson's ratio but can get large allowable pull-out load, but the growth trend slowed 

down. Therefore, when the elastic modulus of polymer material is greater than 90MPa, it is not ideal to 

improve the drawing load by changing the material properties. Besides the position of the inner wall close to 

the anchor bolt, the allowable drawing load increases with the increase of the distance between the center of 

steel wire and the inner wall. But from the numerical point of view, the increase is not large, so in the process 

of the anchor, the steel wire can be inclined to the outer wall, in order to increase the allowable drawing load. 

In the finite element analysis, the elastic modulus of the polymer materials for 70MPa, bolt diameter 13mm, 

diameter 26mm, elastic modulus of rock material is 800MPa, Poisson ratio is 0.32, the Poisson's ratio of 0.45 

bolt material, anchor hole diameter 28mm, the bolt filling pressure is 3~ and 8MPa respectively, the stress 

through the comparison of the axial and radial bolt outer ring, the influence of internal pressure on flexible 

pressurized anchor. With the increase of internal pressure, bolt allowable pull-out load change increases, but 

looked from the value increase is not obvious, while the anchor ring increase of stress and radial stress with 

internal pressure increases, the pressure increases, the force of bolt is worse, but the strong performance of 

anchorage. With the increase of the diameter of steel wire, the drawing load of anchor bolt increases, and is 

almost linear. And when the diameter is small equal to 2.5mm, the deviation is small, but when the diameter is 

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greater than 3mm, the deviation increases, that is, the proportion of the two are different. 

 

Figure 6: Schematic diagram of the system login interface. 

4. Conclusion 

In this paper, the history of the development of anchor and its theory are summarized and analysed. On this 

basis, a new type of bolt and anchor member is studied. By destroying the summary on force of bolt, the 

classification of the anchoring force and the bolt anchoring force mathematical model of various components. 

At the same time, through the experiment, discuss the internal pressure of anchor bolt component allowable 

pull-out load and shear capacity influence, according to the work characteristics of bolt, finite element model is 

established, and the model of contact analysis, discuss the design parameters of bolt anchoring system and 

bolt allowable pull-out load effect, and compared the results with the mathematical model, test, mutual 

authentication. Based on the mechanics model, gives the anchor stress field, including wire tensile stress 

calculation formula of longitudinal bolt body polymer material stress, radial stress, circumferential stress and 

shearing wire between the polymer and the stress calculation formula. This is a new type of anchor bolt 

anchor component calculation, structure design, size parameter selection, the anchoring effect and failure 

analysis provides a theoretical basis for it. 

Acknowledgments 

The authors acknowledge the 2016 Study Subject on the Education and Teaching of Young Teachers in 

Shandong Province, Subject name: Study on Physics Inquiry-based Teaching Design and Practice in Higher 

Vocational Colleges, Subject number: 16SDJ086. 

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