Transmission towers,serving as the support structure of transmission lines,are significant for the functional-ity of an electric transmission system.Bolt joint loosening is one of the critical factors that can affect ...Transmission towers,serving as the support structure of transmission lines,are significant for the functional-ity of an electric transmission system.Bolt joint loosening is one of the critical factors that can affect the safety and stability of transmission towers.In this study,the effects of bolt joint loosening on the dynamic characteristics of a 220-kV angle steel transmission tower are the main topic of concern.First,the mechanical properties of typical joints subjected to different degrees of bolt loosening are studied by finite solid-element simulation,based on which a finite hybrid-element modeling method is developed for a tower structure suffering varying loose degrees in the joints.Taking a 220-kV angle steel transmission tower as the object,the influence of the position and degree of loosening on the tower’s natural frequencies and mode shapes are simulated and discussed.The results demonstrate that the main-member splice joint and the main diagonal-horizontal member gusset plate joint account for the dominant impact on the dynamic characteristics of the tower.In addition,the dominant joint shifts from the main-member splice joint to the main diagonal-horizontal member gusset plate joint as the considered modal order increases.In the case of double joints loosening simultaneously,the loosening of nondomi-nant joints has nonnegligible effects on the tower as well.展开更多
The shear performance of bolts plays a crucial role in controlling rock mass stability,and the roughness of the joint surface is one of the main factors affecting the mechanical properties of anchored joints.The 2nd g...The shear performance of bolts plays a crucial role in controlling rock mass stability,and the roughness of the joint surface is one of the main factors affecting the mechanical properties of anchored joints.The 2nd generation of negative Poisson ratio(2G-NPR)bolt is a new independently developed material characterized by high strength and toughness.However,the influence of joint surface roughness on its anchorage shear performance remains unexplored.This study involves preparing regular saw-tooth jointed rock masses and conducting laboratory shear comparison tests on unbolted samples,2G-NPR bolts,and Q235 steel anchors.A three-dimensional finite element method,developed by the author,was employed for numerical simulations to analyze the influence of saw-tooth angles on the shear resistance of anchored bolts.The findings show that the anchorage of bolts enhances the shear strength and deformation of saw-tooth rock joints.The 2G-NPR bolts demonstrate superior performance in shear strength and deformation enhancement compared to Q235 steel anchors,including improved toughening and crack-arresting effects.Furthermore,the improvement of the shear strength and displacement of the bolt decreases with the increase of the joint saw-tooth angle.These findings provide a valuable test basis for the engineering application of 2G-NPR bolts in rock mass stabilization.展开更多
In geotechnical engineering,rock bolts are commonly used for reinforcement,while the surrounding rock mass bears varying degrees of shear loads.The shear rate affects the stability of bolted rock joints,especially in ...In geotechnical engineering,rock bolts are commonly used for reinforcement,while the surrounding rock mass bears varying degrees of shear loads.The shear rate affects the stability of bolted rock joints,especially in projects susceptible to dynamic shear loads.In laboratory experiments,fully-grouted bolts and energy-absorbing bolts were used as research objects,and artificial rock specimens with rough joints were fabricated to analyze the shear characteristics and damage mechanisms of bolted rock joints under cyclic shear conditions and different shear velocities.The results showed that as the shear rate increased,the shear strength of bolted rock joint specimens decreased.Degradation of asperities resulted in no obvious peak shear stress in the specimens.Energy-absorbing bolts exhibited greater deformation capacity,with significant necking phenomena and the ability to withstand larger shear displacements.In contrast,fully-grouted bolts,which have threaded surfaces that provide higher bonding performance,exhibited a reduced capacity for plastic deformation and were prone to breaking under smaller shear displacements.Although the shear stiffness of specimens reinforced by energy-absorbing bolts was slightly lower than that of fully-grouted bolt specimens,they demonstrated greater stability under various shear rates.The absorbed shear energy showed that energy-absorbing bolts had superior coordinated deformation capabilities,thus exhibiting greater absorbed shear energy than fully-grouted bolts.Overall,fully-grouted bolts are more suitable for projects requiring higher rock shear strength and overall stiffness.In contrast,energy-absorbing bolts are more suitable for coping with dynamic or fluctuating load conditions to maintain the relative stability of jointed rock masses.展开更多
The excellent bonding performance between bolt and anchor materials is crucial for controlling the deformation of deep-buried surrounding rock and strengthening the rock and soil mass in the slope.This paper conducted...The excellent bonding performance between bolt and anchor materials is crucial for controlling the deformation of deep-buried surrounding rock and strengthening the rock and soil mass in the slope.This paper conducted an anchoring test and ABAQUS numerical simulation of an anchoring system comprising a micro-NPR(microscopic negative Poisson’s ratio)bolt and cement mortar as the anchoring material.The failure mode of this system and the distribution of average bonding strength,axial force,and shear stress along the anchoring depth were studied.We also evaluated the bonding properties at the micro-NPR(microscopic negative Poisson’s ratio)bolt-cement mortar interface.The findings indicate that the cement mortar is partially spalled from the micro-NPR bolt surface.The average bonding strength at the micro-NPR bolt-cement mortar interface is positively correlated with anchoring length and cement mortar strength.In contrast,it exhibits a negative correlation with bolt diameter.The axial force is generated at the starting point of the anchorage and decreases non-uniformly across the anchoring region.The axial force transfers or diffuses toward the deeper sections of the anchoring segment with increasing loads.The shear stress at the micro-NPR bolt-cement mortar interface exhibits a single-peak pattern,i.e.,it climbs to a peak value and decreases along the anchoring depth.The peak position varies with changes in bolt diameter and anchoring length.By comparison,it is independent of cement mortar strength.The simulated bonding properties of the micro-NPR bolt-cement mortar interface are consistent with experimental results.The findings can provide a reference for engineering applications and anchoring design of micro-NPR.展开更多
The M-shaped multi-row pile foundation retaining structure represents an enhanced version of conventional multi-row anti-sliding support systems.To date,the implementation of M-shaped pile configurations in foundation...The M-shaped multi-row pile foundation retaining structure represents an enhanced version of conventional multi-row anti-sliding support systems.To date,the implementation of M-shaped pile configurations in foundation pit excavations has not been extensively investigated,with particularly scant research focusing on their load-bearing mechanisms and stress redistribution characteristics.Furthermore,numerical modeling methodologies for such geometrically optimized pile networks remain underdeveloped compared to practical engineering applications,creating a notable research-practice gap in geotechnical engineering.A comparative finite element analysis was systematically conducted using ABAQUS software to establish three distinct excavation support configurations:single-row cantilever retaining structures,three-row cantilever configurations,and M-shaped multi-row pile foundation systems.Subsequent numerical simulations enabled quantitative comparisons of critical performance indicators,including pile stress distribution patterns,lateral displacement profiles,and bending moment diagrams across different structural typologies.The parametric investigation revealed characteristic mechanical responses associated with each configuration,establishing corresponding mechanical principles governing the interaction between pile topology and soil-structure behavior towers.The findings of this study provide critical references for the design optimization of M-shaped multi-row pile foundation retaining systems.展开更多
A survey conducted on the premature bolting of Huarong large leaf mustard from 2018 to 2024 revealed that Huarong large leaf mustard sown in middle August was associated with a higher propensity for premature bolting....A survey conducted on the premature bolting of Huarong large leaf mustard from 2018 to 2024 revealed that Huarong large leaf mustard sown in middle August was associated with a higher propensity for premature bolting. Furthermore, it was observed that the earlier being sown, the greater the rate of premature bolting when being sown prior to middle August. The rate of premature bolting observed in seedlings sown on August 8 was recorded at 35.6%. It was noted that as the age of the seedlings increased, the rate of premature bolting correspondingly increased. There were notable differences in the tolerance of various cultivars to elevated temperatures and prolonged sunlight exposure. For instance, cultivars such as Zhangjie 1 and Sichuan Shaguodi, which exhibit greater heat resistance, did not demonstrate premature bolting when sown in early August. The prolonged exposure to elevated temperatures, drought conditions, and extended periods of sunlight during the seedling stage of Huarong large leaf mustard, coupled with delayed irrigation and transplantation, contributed to the occurrence of premature bolting. The Huarong large leaf mustard, when been sown from late August to early September and transplanted at the appropriate time, exhibited normal growth and development, with no instances of premature bolting observed. It is advisable to select heat-resistant varieties, such as Zhangjie 1, prior to middle August. Huarong large leaf mustard should be sown in early to middle September. Additionally, it is essential to ensure centralized production and timely release of seeds, prompt transplantation and harvesting, and enhance the management of pests and diseases.展开更多
Chive(Allium ascalonicum L.),a seeding-vernalization-type vegetable,is prone to bolting.To explore the physiological and molecular mechanisms of its bolting,bolting-prone(‘BA’)and bolting-resistant(‘WA’)chives wer...Chive(Allium ascalonicum L.),a seeding-vernalization-type vegetable,is prone to bolting.To explore the physiological and molecular mechanisms of its bolting,bolting-prone(‘BA’)and bolting-resistant(‘WA’)chives were sampled at the vegetative growth,floral bud differentiation,and bud emergence stages.No bolting was observed in bolting-resistant‘WA’on the 130th day after planting,whereas the bolting reached 39.22%in bolting-prone‘BA’,which was significantly higher than that of‘WA’.The contents of gibberellins,abscisic acid,and zeatin riboside after floral bud differentiation in‘WA’were significantly less than in‘BA’,whereas the indoleacetic acid content in‘WA’was significantly higher than that in‘BA’before and after floral bud differentiation.The soluble sugar content and nitrate reductase activity in‘BA’were significantly higher than those in‘WA’before and during floral bud differentiation periods.However,they were significantly lower in‘BA’compared with in‘WA’after bolting due to the nutrient consumption required by reproductive growth.A transcriptome analysis determined that the differentially expressed genes related to bolting tolerance were enriched in the terms‘photoperiodism,flowering’,‘auxin-activated signaling pathway’,‘gibberellic acid mediated signaling pathway’,and‘carbohydrate metabolic process’,and this was generally consistent with the physiological data.Additionally,12 key differentially expressed genes(including isoform_203018,isoform_481005,isoform_716975,and isoform_564877)related to bolting tolerance were investigated.This research provides new information for breeding bolting-tolerant chives.展开更多
The shear characteristics of bolted rock joints are crucial for the stability of tunneling and mining,particularly in deep underground engineering,where rock bolt materials are exposed to high stress,water pressure,an...The shear characteristics of bolted rock joints are crucial for the stability of tunneling and mining,particularly in deep underground engineering,where rock bolt materials are exposed to high stress,water pressure,and engineering disturbance.However,due to the complex interaction between bolted rock joints and various geological contexts,many challenges and unsolved problems arise.Therefore,more investigation is needed to understand the shear performance of bolted joints in the field of deep underground engineering.This study presents a comprehensive review of research findings on the responses of bolted joints subjected to shearing under different conditions.As is revealed,the average shear strength of bolted rock joints increases linearly with the normal stress and increases with the compressive strength of rock until it reaches a stable value.The joint roughness coefficient(JRC)affects the contact area,friction force,shear strength,bending angle,and axial force of bolted rock joints.A mathematical function is proposed to model the relationship between JRC,normal load,and shear strength.The normal stress level also influences the deformation model,load-carrying capacity,and energy absorption ratio of bolts within bolted rock joints,and can be effectively characterized by a two-phase exponential equation.Additionally,the angle of the bolts affects the ratio of tensile and shear strength of the bolts,as well as the mechanical behavior of both bolted rock joints and surrounding rock,which favors smaller angles.This comprehensive review of experimental data on the shear behavior of bolted rock joints offers valuable theoretical insights for the development of advanced shear devices and further pertinent investigations.展开更多
This study investigates the vibration characteristics of bolted-flange-joined conical-cylindrical shells(BFJCCSs)through both theoretical analysis and experimental testing.The proposed model incorporates the pressure ...This study investigates the vibration characteristics of bolted-flange-joined conical-cylindrical shells(BFJCCSs)through both theoretical analysis and experimental testing.The proposed model incorporates the pressure distribution within the bolted joint and accounts for the flange effect.The energy expressions for the conical and cylindrical shells are derived from Donnell's shell theory,while those for the flanges are obtained from the Euler-Bernoulli beam theory.The Lagrange equation is used to derive the dynamic equation,and the experimental studies on the BFJCCS are conducted to validate the accuracy of the model.Subsequently,the comprehensive effects of bolt loosening and bolt number on the frequency parameters are analyzed.Additionally,the effects of the flange dimensions and cone angle on the vibration behavior of the BFJCCS are discussed.In particular,the dynamic differences between the welded conical-cylindrical shell(WCCS)and BFJCCS are investigated.It is found that compared with the WCCS,the fundamental frequency of the BFJCCS is reduced by 7.6%,and the corresponding modal damping ratio is reduced by 21.0%.However,the high-order frequencies of the BFJCCS are higher than those of the WCCS,accompanied by a higher modal damping ratio.Compared with the bolt loosening degree,the bolt number has a more significant effect on frequencies.As the bolt number decreases,the impact of the bolt loosening degree diminishes gradually.展开更多
Understanding the mechanical properties of coal-rock-bolt(CRB)combinations at high strain rates and the anchoring mechanism of bolts is crucial for ensuring the safety of coal mining operations.However,the dynamic beh...Understanding the mechanical properties of coal-rock-bolt(CRB)combinations at high strain rates and the anchoring mechanism of bolts is crucial for ensuring the safety of coal mining operations.However,the dynamic behaviors of these combinations,especially the mechanism of action of prestressed bolts,still need to be further investigated.This study carried out split Hopkinson pressure bar(SHPB)tests on three sets of coal-rock(CR),CRB,and coal-rock-prestressed bolt(CRPB)combinations with different interface angles(β=15°,30°,45°,and 60°).The dynamic properties of the combinations were analyzed based on the stress-strain curve,energy dissipation,dynamic strength,fractal dimension of cracks,and failure mode of bolts.The test results show that a larger β will affect the stress transfer and anti-sliding ability of CR,resulting in a decrease in CR strength.The anchoring force of the bolt effectively suppresses the slip feature of CRB at the yield stage.As the strain rate increases,CRB shows a more pronounced'sudden increase'in strength,and the bolt significantly enhances its dynamic strength.The prestressed bolts enhance the dynamic strength of CRPB while weaken the effect of β.The fractal dimension of the macrocracks increases with strain rate,with smaller variations in CRB and CRPB,indicating that the bolt reduces the complexity degree of CRB and CRPB.The anchoring force of CRB depends on bolt strength,which reduces the slip along the interface.The anchoring force of CRPB balances the coal-rock slip and suppresses crack formation,resulting in a more cohesive response under dynamic load.展开更多
Recovery is a crucial supporting process for carrier aircraft,where a reasonable landing scheduling is expected to guide the fleet landing safely and quickly.Currently,there is little research on this topic,and most o...Recovery is a crucial supporting process for carrier aircraft,where a reasonable landing scheduling is expected to guide the fleet landing safely and quickly.Currently,there is little research on this topic,and most of it neglects potential influence factors,leaving the corresponding supporting efficiency questionable.In this paper,we study the landing scheduling problem for carrier aircraft considering the effects of bolting and aerial refueling.Based on the analysis of recovery mode involving the above factors,two types of primary constraints(i.e.,fuel constraint and wake interval constraint)are first described.Then,taking the landing sequencing as decision variables,a combinatorial optimization model with a compound objective function is formulated.Aiming at an efficient solution,an improved firefly algorithm is designed by integrating multiple evolutionary operators.In addition,a dynamic replanning mechanism is introduced to deal with special situations(i.e.,the occurrence of bolting and fuel shortage),where the high efficiency of the designed algorithm facilitates the online scheduling adjustment within seconds.Finally,numerical simulations with sufficient and insufficient fuel cases are both carried out,highlighting the necessity to consider bolting and aerial refueling during the planning procedure.Simulation results reveal that a higher bolting probability,as well as extra aerial refueling operations caused by fuel shortage,will lead to longer recovery complete time.Meanwhile,due to the strong optimum-seeking capability and solution efficiency of the improved algorithm,adaptive scheduling can be generated within milliseconds to deal with special situations,significantly improving the safety and efficiency of the recovery process.An animation is accessible at bilibili.com/video/BV1QprKY2EwD.展开更多
In the civil and mining industries,bolts are critical components of support systems,playing a vital role in ensuring their stability.Glass fibre reinforced polymer(GFRP)bolts are widely used because they are corrosion...In the civil and mining industries,bolts are critical components of support systems,playing a vital role in ensuring their stability.Glass fibre reinforced polymer(GFRP)bolts are widely used because they are corrosion-resistant and cost-effective.However,the damage mechanisms of GFRP bolts under blasting dynamic loads are still unclear,especially compared to metal bolts.This study investigates the cumulative damage of fully grouted GFRP bolts under blasting dynamic loads.The maximum axial stress at the tails of the bolts is defined as the damage variable,based on the failure characteristics of GFRP bolts.By combining this with Miner's cumulative damage theory,a comprehensive theoretical and numerical model is established to calculate cumulative damage.Field data collected from the Jinchuan No.3 Mining Area,including GFRP bolts parameters and blasting vibration data are used for further analysis of cumulative damage in fully grouted GFRP bolts.Results indicate that with an increasing number of blasts,axial stress increases in all parts of GFRP bolts.The tail exhibits the most significant rise,with stress extending deeper into the anchorage zone.Cumulative damage follows an exponential trend with the number of blasts,although the incremental damage per blast decelerates over time.Higher dynamic load intensities accelerate damage accumulation,leading to an exponential decline in the maximum loading cycles before failure.Additionally,stronger surrounding rock and grout mitigate damage accumulation,with the effect of surrounding rock strength being more pronounced than that of grout.In contrast,the maximum axial stress of metal bolts increases quickly to a certain point and then stabilizes.This shows a clear difference between GFRP and metal bolts.This study presents a new cumulative damage theory that underpins the design of GFRP bolt support systems under blasting conditions,identifies key damage factors,and suggests mitigation measures to enhance system stability.展开更多
The influence of rockbolt pretension on bolting has not been well addressed,despite its critical importance in drift support systems.In this study,laboratory and numerical simulations of gravel bolting are conducted t...The influence of rockbolt pretension on bolting has not been well addressed,despite its critical importance in drift support systems.In this study,laboratory and numerical simulations of gravel bolting are conducted to investigate the effects of varying rockbolt pretensions.The simulations are developed using the particle flow code(PFC3D),enabling detailed analysis of contact forces between gravel particles under low and high rockbolt pretensions.The results indicate that bolted gravel can maintain stability even without pretension,though bearing capacity is significantly enhanced under high pretension.Two distinct bolting behaviors are identified:a pressure arch structure is formed under low pretension,while high pretension creates a compression zone characterized by intensified particle interlocking and superior load-bearing capacity.Based on these findings,a concept for drift support is proposed,integrating rockbolts and cables to stabilize both shallow and deep rocks.This study advances our understanding of bolting behaviors and provides theoretical guidance for designing effective drift support systems in practical applications.展开更多
The wet-assembly hybrid bonded/bolted(WHBB)joint is increasingly employed in aircraft fuel tank structures owing to its advantageous mechanical strength and sealing performance.However,the integral tank is susceptible...The wet-assembly hybrid bonded/bolted(WHBB)joint is increasingly employed in aircraft fuel tank structures owing to its advantageous mechanical strength and sealing performance.However,the integral tank is susceptible to leakage during service,particularly at the joint,which seriously endangers the flight safety of the aircraft.In this paper,a leakage prediction method of WHBB joint based on porous media theory is proposed,in which the shape and characteristic length of the sealant layer are taken into consideration.The model parameters are determined by the analysis and treatment of the defect state of the WHBB joint section.The prediction results agree well with the experimental data,which were acquired by self-designed sealing leakage rate measurement system,and the deviation between the predicted results and the average value of the experimental data is less than 20%.Furthermore,in order to verify the environmental adaptability,the prediction results based on 2D cutting sections of the joints and experimental results under three different loading conditions are compared.The comparison results not only prove the accuracy of the prediction model,but also reveal the important influence of tensile fatigue load on the sealing performance of the structure.The tensile fatigue loads lead to two orders of magnitude increase in leakage rate,and the reason is that the repeated stretching and compression process lead to an increase in interfacial cracks between the adhesive layer and the hole wall,thereby accentuating the defects within the adhesive layer.展开更多
A series of laboratory pull-out tests was conducted to study the effects of temperature on the performance and behaviours of fully grouted rock bolt specimens cured within a specific temperature range,as well as for d...A series of laboratory pull-out tests was conducted to study the effects of temperature on the performance and behaviours of fully grouted rock bolt specimens cured within a specific temperature range,as well as for different durations.Each specimen consisted of a 20M rebar bolt at 1300 mm embedment length grouted inside a Schedule 80 steel pipe using Portland cement grout at a 0.4 water-to-cement ratio.Two temperatures(20℃and 45℃)were explored to investigate the effects of geothermally active temperature conditions on fully grouted rock bolts.Distributed fiber optic sensors were employed to provide continuous strain profiles along the entire embedment length to observe micro-mechanisms and monitor internal specimen temperature change during testing.The specimens cured at 45℃generally resulted in higher grout UCS(in certain cases 25%e50%higher)compared to those at 20℃;the ultimate capacity was not significantly impacted as the specimens'embedment length allowed full development of the rock bolt's capacity.The resulting strain profile trends showed generally higher strains experienced by the shorter(i.e.3-d)curing duration specimens under both curing temperatures compared to long-term curing.The 45℃specimens generally experienced lower strains and faster strain profile attenuation compared to specimens cured at 20℃.Understanding these effects and further analysis of FGRB specimen behaviours over time provide insights for mobilized and critical embedment lengths,capacity development,and support system stabilization.This paper highlights the results of this study and aims to bridge selected gaps in existing literature with a view to aid practitioners.展开更多
In addition to blade-to-casing rubbing,drum-to-labyrinth rubbing is another common interaction in aero-engines.In this study,the labyrinth seal is simplified and modeled as an inner ring.First,considering the flexibil...In addition to blade-to-casing rubbing,drum-to-labyrinth rubbing is another common interaction in aero-engines.In this study,the labyrinth seal is simplified and modeled as an inner ring.First,considering the flexibility of both the drum and inner ring,a novel rubbing force model applicable to drum-inner ring rubbing is proposed,and this model is partially validated with the measured vibration responses.Incorporating both drum-inner ring rubbing faults and bolt joint effects,a dynamic model of the shaft-diskdrum-inner ring-vane-casing system(SDDIRVCS)is established with beam-shell hybrid elements to investigate the nonlinear dynamic responses induced by rubbing at various rotational speeds.The established dynamic model of the SDDIRVCS is validated by the comparison of its modal characteristics with those obtained from the ANSYS simulations.The results indicate that the rotor spectrum is dominated by odd-multiple harmonics,while the stator spectrum exhibits prominent even-multiple harmonics.Moreover,the rubbing location between the drum and the inner ring varies with the dynamic behavior of the rotor system.展开更多
Purpose–This study aims to investigate the fatigue behavior and failure modes of bolted lap joints using Modified Tensile Specimens(MTS)under various cyclic load conditions.Emphasis is placed on identifying the relat...Purpose–This study aims to investigate the fatigue behavior and failure modes of bolted lap joints using Modified Tensile Specimens(MTS)under various cyclic load conditions.Emphasis is placed on identifying the relationship between load amplitude,fatigue life,and damage progression in low-carbon steel assemblies.Design/methodology/approach–An experimental approach was adopted using MTS specimens fabricated from St 1203 cold-rolled steel,joined with Grade 8.8 M4 bolts.Cyclic fatigue tests were conducted under zerobased loading at seven distinct force levels.Fracture surfaces were visually analyzed to identify dominant failure mechanisms.Findings–The results revealed a strong inverse correlation between applied cyclic load and fatigue life.Three distinct failure modes were identified:bolt shear at high loads(5.4 kN),interface cracking and slippage at moderate loads(4.9–5.1 kN),and plate tearing or stable fatigue behavior at lower loads(54.1 kN).The results highlight a progressive transition in failure mechanisms,from bolt shear at high loads to plate tearing and interface cracking at lower loads,providing essential insights for fatigue-resistant bolted joint design.Originality/value–This study offers original insights into the fatigue behavior of bolted lap joints using MTS,a relatively underexplored configuration in fatigue assessment.By experimentally evaluating failure modes under varied cyclic load levels,the authors uncover critical transitions in damage mechanisms—from bolt shear to interface cracking and plate tearing—depending on the applied load.Unlike many existing studies focused on numerical modeling or bonded joints alone,this work provides empirical data rooted in real-world fastening conditions using cold-rolled low-carbon steel.展开更多
The grouted bolt,combining rock bolting with grouting techniques,provides an effective solution for controlling the surrounding rock in deep soft rock and fractured roadways.It has been extensively applied in numerous...The grouted bolt,combining rock bolting with grouting techniques,provides an effective solution for controlling the surrounding rock in deep soft rock and fractured roadways.It has been extensively applied in numerous deep mining areas characterized by soft rock roadways,where it has demonstrated remarkable control results.This article systematically explores the evolution of grouted bolting,covering its theoretical foundations,design methods,materials,construction processes,monitoring measures,and methods for assessing its effectiveness.The overview encompassed several key elements,delving into anchoring theory and grouting reinforcement theory.The new principle of high pretensioned high-pressure splitting grouted bolting collaborative active control is introduced.A fresh method for dynamic information design is also highlighted.The discussion touches on both conventional grouting rock bolts and cable bolts,as well as innovative grouted rock bolts and cables characterized by their high pretension,strength,and sealing hole pressure.An examination of the merits and demerits of standard inorganic and organic grouting materials versus the new inorganic–organic composite materials,including their specific application conditions,was conducted.Additionally,the article presents various methods and instruments to assess the support effect of grouting rock bolts,cable bolts,and grouting reinforcement.Furthermore,it provides a foundation for understanding the factors influencing decisions on grouted bolting timing,the sequence of grouting,the pressure applied,the volume of grout used,and the strategic arrangement of grouted rock bolts and cable bolts.The application of the high pretensioned high-pressure splitting grouted bolting collaborative control technology in a typical kilometer-deep soft rock mine in China—the soft coal seam and soft rock roadway in the Kouzidong coal mine,Huainan coal mining area,was introduced.Finally,the existing problems in grouted bolting control technology for deep soft rock roadways are analyzed,and the future development trend of grouted bolting control technology is anticipated.展开更多
Rock bolts are extensively utilized in underground engineering as a means of offering support and stability to rock masses in tunnels,mines,and other underground structures.In environments of high ground stress,faults...Rock bolts are extensively utilized in underground engineering as a means of offering support and stability to rock masses in tunnels,mines,and other underground structures.In environments of high ground stress,faults or weak zones can frequently arise in rock formations,presenting a significant challenge for engineering and potentially leading to underground engineering collapse.Rock bolts serve as a crucial structural element for the transmission of tensile stress and are capable of withstanding shear loads to prevent sliding of weak zones within rock mass.Therefore,a complete understanding of the behavior of rock bolts subjected to shear loads is essential.This paper presents a state-of-the-art review of the research progress of rock bolts subjected to shear load in three categories:experiment,numerical simulation,and analytical model.The review focuses on the research studies and developments in this area since the 1970s,providing a comprehensive overview of numerous factors that influence the anchorage performance of rock bolts.These factors include the diameter and angle of the rock bolt installation,rock strength,grouting material,bolt material,borehole diameter,rock bolt preload,normal stress,joint surface roughness and joint expansion angle.The paper reviews the improvement of mechanical parameter setting in numerical simulation of rock bolt shear.Furthermore,it delves into the optimization of the analytical model concerning rock bolt shear theory,approached from the perspectives of both Elastic foundation beam theory coupled with Elastoplasticity theory and Structural mechanic methods.The significance of this review lies in its ability to provide insights into the mechanical behavior of rock bolts.The paper also highlights the limitations of current research and guidelines for further research of rock bolts.展开更多
The mechanical properties of bolts are important factors affecting the shear behavior of bolted joints.In this study,tensile and pure shear tests were conducted on five kinds of bolts made from different materials to ...The mechanical properties of bolts are important factors affecting the shear behavior of bolted joints.In this study,tensile and pure shear tests were conducted on five kinds of bolts made from different materials to measure their tensile and shear parameters.Direct shear tests were conducted to analyze the effects of tensile and shear strength parameters on the shear behavior of bolted joints.The test results showed that the mechanical properties of bolts made from different materials were clearly different and that these differences mainly affected the plastic deformation stage of the bolted joints.The larger the bolt elongation was,the larger the joint shear displacement at bolt failure.The tensile and shear strengths of the bolts were positively correlated with the shear strength of the bolted joints.According to the standard regression analysis,the bolt shear strength had a greater influence than the bolt tensile strength on the bolt contributions when the bolts were perpendicular to the joint surface.Based on the empirical equation for the bolt contribution proposed by Spang,the maximum shear loads in the pure shear test were introduced,and a new equation was established to predict the contributions of bolts.The prediction results obtained using the modified equation were in good agreement with the experimental results.展开更多
基金The Youth Foundation Project of Jiangsu Province(No.BK20230337)the Natural Science Research of Jiangsu Higher Education Institutions of China(No.22KJB560004)the National Natu-ral Science Foundation of China(No.52278523)。
文摘Transmission towers,serving as the support structure of transmission lines,are significant for the functional-ity of an electric transmission system.Bolt joint loosening is one of the critical factors that can affect the safety and stability of transmission towers.In this study,the effects of bolt joint loosening on the dynamic characteristics of a 220-kV angle steel transmission tower are the main topic of concern.First,the mechanical properties of typical joints subjected to different degrees of bolt loosening are studied by finite solid-element simulation,based on which a finite hybrid-element modeling method is developed for a tower structure suffering varying loose degrees in the joints.Taking a 220-kV angle steel transmission tower as the object,the influence of the position and degree of loosening on the tower’s natural frequencies and mode shapes are simulated and discussed.The results demonstrate that the main-member splice joint and the main diagonal-horizontal member gusset plate joint account for the dominant impact on the dynamic characteristics of the tower.In addition,the dominant joint shifts from the main-member splice joint to the main diagonal-horizontal member gusset plate joint as the considered modal order increases.In the case of double joints loosening simultaneously,the loosening of nondomi-nant joints has nonnegligible effects on the tower as well.
基金Project(GZB202405561)supported by the Postdoctoral Fellowship Program of China Postdoctoral Science FoundationProject(42377154)supported by the National Natural Science Foundation of China。
文摘The shear performance of bolts plays a crucial role in controlling rock mass stability,and the roughness of the joint surface is one of the main factors affecting the mechanical properties of anchored joints.The 2nd generation of negative Poisson ratio(2G-NPR)bolt is a new independently developed material characterized by high strength and toughness.However,the influence of joint surface roughness on its anchorage shear performance remains unexplored.This study involves preparing regular saw-tooth jointed rock masses and conducting laboratory shear comparison tests on unbolted samples,2G-NPR bolts,and Q235 steel anchors.A three-dimensional finite element method,developed by the author,was employed for numerical simulations to analyze the influence of saw-tooth angles on the shear resistance of anchored bolts.The findings show that the anchorage of bolts enhances the shear strength and deformation of saw-tooth rock joints.The 2G-NPR bolts demonstrate superior performance in shear strength and deformation enhancement compared to Q235 steel anchors,including improved toughening and crack-arresting effects.Furthermore,the improvement of the shear strength and displacement of the bolt decreases with the increase of the joint saw-tooth angle.These findings provide a valuable test basis for the engineering application of 2G-NPR bolts in rock mass stabilization.
基金partially funded by the National Natural Science Foundation of China(Grant Nos.52179098 and 41907251)the State Scholarship Fund of China(Grant No.202306650001).
文摘In geotechnical engineering,rock bolts are commonly used for reinforcement,while the surrounding rock mass bears varying degrees of shear loads.The shear rate affects the stability of bolted rock joints,especially in projects susceptible to dynamic shear loads.In laboratory experiments,fully-grouted bolts and energy-absorbing bolts were used as research objects,and artificial rock specimens with rough joints were fabricated to analyze the shear characteristics and damage mechanisms of bolted rock joints under cyclic shear conditions and different shear velocities.The results showed that as the shear rate increased,the shear strength of bolted rock joint specimens decreased.Degradation of asperities resulted in no obvious peak shear stress in the specimens.Energy-absorbing bolts exhibited greater deformation capacity,with significant necking phenomena and the ability to withstand larger shear displacements.In contrast,fully-grouted bolts,which have threaded surfaces that provide higher bonding performance,exhibited a reduced capacity for plastic deformation and were prone to breaking under smaller shear displacements.Although the shear stiffness of specimens reinforced by energy-absorbing bolts was slightly lower than that of fully-grouted bolt specimens,they demonstrated greater stability under various shear rates.The absorbed shear energy showed that energy-absorbing bolts had superior coordinated deformation capabilities,thus exhibiting greater absorbed shear energy than fully-grouted bolts.Overall,fully-grouted bolts are more suitable for projects requiring higher rock shear strength and overall stiffness.In contrast,energy-absorbing bolts are more suitable for coping with dynamic or fluctuating load conditions to maintain the relative stability of jointed rock masses.
基金supported by the National Natural Science Foundation of China(Grant No.42377154)Henan Provincial Department of Science and Technology(Grant No.232102321009).
文摘The excellent bonding performance between bolt and anchor materials is crucial for controlling the deformation of deep-buried surrounding rock and strengthening the rock and soil mass in the slope.This paper conducted an anchoring test and ABAQUS numerical simulation of an anchoring system comprising a micro-NPR(microscopic negative Poisson’s ratio)bolt and cement mortar as the anchoring material.The failure mode of this system and the distribution of average bonding strength,axial force,and shear stress along the anchoring depth were studied.We also evaluated the bonding properties at the micro-NPR(microscopic negative Poisson’s ratio)bolt-cement mortar interface.The findings indicate that the cement mortar is partially spalled from the micro-NPR bolt surface.The average bonding strength at the micro-NPR bolt-cement mortar interface is positively correlated with anchoring length and cement mortar strength.In contrast,it exhibits a negative correlation with bolt diameter.The axial force is generated at the starting point of the anchorage and decreases non-uniformly across the anchoring region.The axial force transfers or diffuses toward the deeper sections of the anchoring segment with increasing loads.The shear stress at the micro-NPR bolt-cement mortar interface exhibits a single-peak pattern,i.e.,it climbs to a peak value and decreases along the anchoring depth.The peak position varies with changes in bolt diameter and anchoring length.By comparison,it is independent of cement mortar strength.The simulated bonding properties of the micro-NPR bolt-cement mortar interface are consistent with experimental results.The findings can provide a reference for engineering applications and anchoring design of micro-NPR.
文摘The M-shaped multi-row pile foundation retaining structure represents an enhanced version of conventional multi-row anti-sliding support systems.To date,the implementation of M-shaped pile configurations in foundation pit excavations has not been extensively investigated,with particularly scant research focusing on their load-bearing mechanisms and stress redistribution characteristics.Furthermore,numerical modeling methodologies for such geometrically optimized pile networks remain underdeveloped compared to practical engineering applications,creating a notable research-practice gap in geotechnical engineering.A comparative finite element analysis was systematically conducted using ABAQUS software to establish three distinct excavation support configurations:single-row cantilever retaining structures,three-row cantilever configurations,and M-shaped multi-row pile foundation systems.Subsequent numerical simulations enabled quantitative comparisons of critical performance indicators,including pile stress distribution patterns,lateral displacement profiles,and bending moment diagrams across different structural typologies.The parametric investigation revealed characteristic mechanical responses associated with each configuration,establishing corresponding mechanical principles governing the interaction between pile topology and soil-structure behavior towers.The findings of this study provide critical references for the design optimization of M-shaped multi-row pile foundation retaining systems.
基金Supported by Key R&D Projects of Hunan Provincial Department of Science and Technology"Study on Key Modern Processing Techniques and Product Development of Huarong Mustard"(2023NK2039).
文摘A survey conducted on the premature bolting of Huarong large leaf mustard from 2018 to 2024 revealed that Huarong large leaf mustard sown in middle August was associated with a higher propensity for premature bolting. Furthermore, it was observed that the earlier being sown, the greater the rate of premature bolting when being sown prior to middle August. The rate of premature bolting observed in seedlings sown on August 8 was recorded at 35.6%. It was noted that as the age of the seedlings increased, the rate of premature bolting correspondingly increased. There were notable differences in the tolerance of various cultivars to elevated temperatures and prolonged sunlight exposure. For instance, cultivars such as Zhangjie 1 and Sichuan Shaguodi, which exhibit greater heat resistance, did not demonstrate premature bolting when sown in early August. The prolonged exposure to elevated temperatures, drought conditions, and extended periods of sunlight during the seedling stage of Huarong large leaf mustard, coupled with delayed irrigation and transplantation, contributed to the occurrence of premature bolting. The Huarong large leaf mustard, when been sown from late August to early September and transplanted at the appropriate time, exhibited normal growth and development, with no instances of premature bolting observed. It is advisable to select heat-resistant varieties, such as Zhangjie 1, prior to middle August. Huarong large leaf mustard should be sown in early to middle September. Additionally, it is essential to ensure centralized production and timely release of seeds, prompt transplantation and harvesting, and enhance the management of pests and diseases.
基金funded by the‘National Key R&D Program Subject of China’(No.2021YFD1100301)the post subsidy project of National Key R&D Program,and the Guizhou Modern Agriculture Research System(GZMARS)-Plateau characteristic vegetable industry.
文摘Chive(Allium ascalonicum L.),a seeding-vernalization-type vegetable,is prone to bolting.To explore the physiological and molecular mechanisms of its bolting,bolting-prone(‘BA’)and bolting-resistant(‘WA’)chives were sampled at the vegetative growth,floral bud differentiation,and bud emergence stages.No bolting was observed in bolting-resistant‘WA’on the 130th day after planting,whereas the bolting reached 39.22%in bolting-prone‘BA’,which was significantly higher than that of‘WA’.The contents of gibberellins,abscisic acid,and zeatin riboside after floral bud differentiation in‘WA’were significantly less than in‘BA’,whereas the indoleacetic acid content in‘WA’was significantly higher than that in‘BA’before and after floral bud differentiation.The soluble sugar content and nitrate reductase activity in‘BA’were significantly higher than those in‘WA’before and during floral bud differentiation periods.However,they were significantly lower in‘BA’compared with in‘WA’after bolting due to the nutrient consumption required by reproductive growth.A transcriptome analysis determined that the differentially expressed genes related to bolting tolerance were enriched in the terms‘photoperiodism,flowering’,‘auxin-activated signaling pathway’,‘gibberellic acid mediated signaling pathway’,and‘carbohydrate metabolic process’,and this was generally consistent with the physiological data.Additionally,12 key differentially expressed genes(including isoform_203018,isoform_481005,isoform_716975,and isoform_564877)related to bolting tolerance were investigated.This research provides new information for breeding bolting-tolerant chives.
基金Open Fund of Badong National Observation and Research Station of Geohazards,Grant/Award Number:BNORSG202315Key R&D Program of Xinjiang Uygur Autonomous Region,Grant/Award Number:2021B03004-3+1 种基金National Natural Science Foundation of China,Grant/Award Numbers:42207169,U22A20569Natural Science Foundation of Jiangsu Province,Grant/Award Number:BK20221126。
文摘The shear characteristics of bolted rock joints are crucial for the stability of tunneling and mining,particularly in deep underground engineering,where rock bolt materials are exposed to high stress,water pressure,and engineering disturbance.However,due to the complex interaction between bolted rock joints and various geological contexts,many challenges and unsolved problems arise.Therefore,more investigation is needed to understand the shear performance of bolted joints in the field of deep underground engineering.This study presents a comprehensive review of research findings on the responses of bolted joints subjected to shearing under different conditions.As is revealed,the average shear strength of bolted rock joints increases linearly with the normal stress and increases with the compressive strength of rock until it reaches a stable value.The joint roughness coefficient(JRC)affects the contact area,friction force,shear strength,bending angle,and axial force of bolted rock joints.A mathematical function is proposed to model the relationship between JRC,normal load,and shear strength.The normal stress level also influences the deformation model,load-carrying capacity,and energy absorption ratio of bolts within bolted rock joints,and can be effectively characterized by a two-phase exponential equation.Additionally,the angle of the bolts affects the ratio of tensile and shear strength of the bolts,as well as the mechanical behavior of both bolted rock joints and surrounding rock,which favors smaller angles.This comprehensive review of experimental data on the shear behavior of bolted rock joints offers valuable theoretical insights for the development of advanced shear devices and further pertinent investigations.
基金supported by the National Natural Science Foundation of China(No.12272088)the Out-standing Youth Science Foundation of Liaoning Province of China(No.2024JH3/50100013)。
文摘This study investigates the vibration characteristics of bolted-flange-joined conical-cylindrical shells(BFJCCSs)through both theoretical analysis and experimental testing.The proposed model incorporates the pressure distribution within the bolted joint and accounts for the flange effect.The energy expressions for the conical and cylindrical shells are derived from Donnell's shell theory,while those for the flanges are obtained from the Euler-Bernoulli beam theory.The Lagrange equation is used to derive the dynamic equation,and the experimental studies on the BFJCCS are conducted to validate the accuracy of the model.Subsequently,the comprehensive effects of bolt loosening and bolt number on the frequency parameters are analyzed.Additionally,the effects of the flange dimensions and cone angle on the vibration behavior of the BFJCCS are discussed.In particular,the dynamic differences between the welded conical-cylindrical shell(WCCS)and BFJCCS are investigated.It is found that compared with the WCCS,the fundamental frequency of the BFJCCS is reduced by 7.6%,and the corresponding modal damping ratio is reduced by 21.0%.However,the high-order frequencies of the BFJCCS are higher than those of the WCCS,accompanied by a higher modal damping ratio.Compared with the bolt loosening degree,the bolt number has a more significant effect on frequencies.As the bolt number decreases,the impact of the bolt loosening degree diminishes gradually.
基金Financial support from the National Natural Science Foundation of China(Grant No.52374119)the Province Education Department of Liaoning(Grant No.LJ212410146068)the opening fund of State Key Laboratory of Performance Monitoring and Protecting of Rail Transit Infrastructure,East China Jiaotong University(Grant No.HJGZ2023103).
文摘Understanding the mechanical properties of coal-rock-bolt(CRB)combinations at high strain rates and the anchoring mechanism of bolts is crucial for ensuring the safety of coal mining operations.However,the dynamic behaviors of these combinations,especially the mechanism of action of prestressed bolts,still need to be further investigated.This study carried out split Hopkinson pressure bar(SHPB)tests on three sets of coal-rock(CR),CRB,and coal-rock-prestressed bolt(CRPB)combinations with different interface angles(β=15°,30°,45°,and 60°).The dynamic properties of the combinations were analyzed based on the stress-strain curve,energy dissipation,dynamic strength,fractal dimension of cracks,and failure mode of bolts.The test results show that a larger β will affect the stress transfer and anti-sliding ability of CR,resulting in a decrease in CR strength.The anchoring force of the bolt effectively suppresses the slip feature of CRB at the yield stage.As the strain rate increases,CRB shows a more pronounced'sudden increase'in strength,and the bolt significantly enhances its dynamic strength.The prestressed bolts enhance the dynamic strength of CRPB while weaken the effect of β.The fractal dimension of the macrocracks increases with strain rate,with smaller variations in CRB and CRPB,indicating that the bolt reduces the complexity degree of CRB and CRPB.The anchoring force of CRB depends on bolt strength,which reduces the slip along the interface.The anchoring force of CRPB balances the coal-rock slip and suppresses crack formation,resulting in a more cohesive response under dynamic load.
基金the financial support of the National Natural Science Foundation of China(12102077,12161076)the Natural Science and Technology Program of Liaoning Province(2023-BS-061).
文摘Recovery is a crucial supporting process for carrier aircraft,where a reasonable landing scheduling is expected to guide the fleet landing safely and quickly.Currently,there is little research on this topic,and most of it neglects potential influence factors,leaving the corresponding supporting efficiency questionable.In this paper,we study the landing scheduling problem for carrier aircraft considering the effects of bolting and aerial refueling.Based on the analysis of recovery mode involving the above factors,two types of primary constraints(i.e.,fuel constraint and wake interval constraint)are first described.Then,taking the landing sequencing as decision variables,a combinatorial optimization model with a compound objective function is formulated.Aiming at an efficient solution,an improved firefly algorithm is designed by integrating multiple evolutionary operators.In addition,a dynamic replanning mechanism is introduced to deal with special situations(i.e.,the occurrence of bolting and fuel shortage),where the high efficiency of the designed algorithm facilitates the online scheduling adjustment within seconds.Finally,numerical simulations with sufficient and insufficient fuel cases are both carried out,highlighting the necessity to consider bolting and aerial refueling during the planning procedure.Simulation results reveal that a higher bolting probability,as well as extra aerial refueling operations caused by fuel shortage,will lead to longer recovery complete time.Meanwhile,due to the strong optimum-seeking capability and solution efficiency of the improved algorithm,adaptive scheduling can be generated within milliseconds to deal with special situations,significantly improving the safety and efficiency of the recovery process.An animation is accessible at bilibili.com/video/BV1QprKY2EwD.
基金funded by the National Natural Science Foundation of China(No.51974206)the Hubei Province Safety Production Special Fund Science and Technology Project(No.KJZX202007007).
文摘In the civil and mining industries,bolts are critical components of support systems,playing a vital role in ensuring their stability.Glass fibre reinforced polymer(GFRP)bolts are widely used because they are corrosion-resistant and cost-effective.However,the damage mechanisms of GFRP bolts under blasting dynamic loads are still unclear,especially compared to metal bolts.This study investigates the cumulative damage of fully grouted GFRP bolts under blasting dynamic loads.The maximum axial stress at the tails of the bolts is defined as the damage variable,based on the failure characteristics of GFRP bolts.By combining this with Miner's cumulative damage theory,a comprehensive theoretical and numerical model is established to calculate cumulative damage.Field data collected from the Jinchuan No.3 Mining Area,including GFRP bolts parameters and blasting vibration data are used for further analysis of cumulative damage in fully grouted GFRP bolts.Results indicate that with an increasing number of blasts,axial stress increases in all parts of GFRP bolts.The tail exhibits the most significant rise,with stress extending deeper into the anchorage zone.Cumulative damage follows an exponential trend with the number of blasts,although the incremental damage per blast decelerates over time.Higher dynamic load intensities accelerate damage accumulation,leading to an exponential decline in the maximum loading cycles before failure.Additionally,stronger surrounding rock and grout mitigate damage accumulation,with the effect of surrounding rock strength being more pronounced than that of grout.In contrast,the maximum axial stress of metal bolts increases quickly to a certain point and then stabilizes.This shows a clear difference between GFRP and metal bolts.This study presents a new cumulative damage theory that underpins the design of GFRP bolt support systems under blasting conditions,identifies key damage factors,and suggests mitigation measures to enhance system stability.
基金supported by the National Natural Science Foundation of China(Grant Nos.52274124,52274123)funding of the Coal Mining and Designing Department,Tiandi Science&Technology Co.,Ltd.(Grant No.2022-2-TD-QN008).
文摘The influence of rockbolt pretension on bolting has not been well addressed,despite its critical importance in drift support systems.In this study,laboratory and numerical simulations of gravel bolting are conducted to investigate the effects of varying rockbolt pretensions.The simulations are developed using the particle flow code(PFC3D),enabling detailed analysis of contact forces between gravel particles under low and high rockbolt pretensions.The results indicate that bolted gravel can maintain stability even without pretension,though bearing capacity is significantly enhanced under high pretension.Two distinct bolting behaviors are identified:a pressure arch structure is formed under low pretension,while high pretension creates a compression zone characterized by intensified particle interlocking and superior load-bearing capacity.Based on these findings,a concept for drift support is proposed,integrating rockbolts and cables to stabilize both shallow and deep rocks.This study advances our understanding of bolting behaviors and provides theoretical guidance for designing effective drift support systems in practical applications.
基金co-supported by the National Natural Science Foundation of China(NSFC)(No.52035011)the Fundamental Research Funds for the Central Universities,and the Research Project of the Ministry of Industry and Information Technology,China(No.MJZ4-4N22)。
文摘The wet-assembly hybrid bonded/bolted(WHBB)joint is increasingly employed in aircraft fuel tank structures owing to its advantageous mechanical strength and sealing performance.However,the integral tank is susceptible to leakage during service,particularly at the joint,which seriously endangers the flight safety of the aircraft.In this paper,a leakage prediction method of WHBB joint based on porous media theory is proposed,in which the shape and characteristic length of the sealant layer are taken into consideration.The model parameters are determined by the analysis and treatment of the defect state of the WHBB joint section.The prediction results agree well with the experimental data,which were acquired by self-designed sealing leakage rate measurement system,and the deviation between the predicted results and the average value of the experimental data is less than 20%.Furthermore,in order to verify the environmental adaptability,the prediction results based on 2D cutting sections of the joints and experimental results under three different loading conditions are compared.The comparison results not only prove the accuracy of the prediction model,but also reveal the important influence of tensile fatigue load on the sealing performance of the structure.The tensile fatigue loads lead to two orders of magnitude increase in leakage rate,and the reason is that the repeated stretching and compression process lead to an increase in interfacial cracks between the adhesive layer and the hole wall,thereby accentuating the defects within the adhesive layer.
基金funded by the Canadian Department of National Defence(DND),the RMC Green Team Military GeoWorks Lab,and the National Sciences and Engineering Research Council(NSERC)of Canada.
文摘A series of laboratory pull-out tests was conducted to study the effects of temperature on the performance and behaviours of fully grouted rock bolt specimens cured within a specific temperature range,as well as for different durations.Each specimen consisted of a 20M rebar bolt at 1300 mm embedment length grouted inside a Schedule 80 steel pipe using Portland cement grout at a 0.4 water-to-cement ratio.Two temperatures(20℃and 45℃)were explored to investigate the effects of geothermally active temperature conditions on fully grouted rock bolts.Distributed fiber optic sensors were employed to provide continuous strain profiles along the entire embedment length to observe micro-mechanisms and monitor internal specimen temperature change during testing.The specimens cured at 45℃generally resulted in higher grout UCS(in certain cases 25%e50%higher)compared to those at 20℃;the ultimate capacity was not significantly impacted as the specimens'embedment length allowed full development of the rock bolt's capacity.The resulting strain profile trends showed generally higher strains experienced by the shorter(i.e.3-d)curing duration specimens under both curing temperatures compared to long-term curing.The 45℃specimens generally experienced lower strains and faster strain profile attenuation compared to specimens cured at 20℃.Understanding these effects and further analysis of FGRB specimen behaviours over time provide insights for mobilized and critical embedment lengths,capacity development,and support system stabilization.This paper highlights the results of this study and aims to bridge selected gaps in existing literature with a view to aid practitioners.
基金supported by the Fundamental Research Funds for the Central Universities(No.N25BSS052)the National Science and Technology Major Project(No.J2022-IV-0005-0022)+2 种基金the Aero Science Foundation of China(No.20230015050001)the Shenyang Science and Technology Plan Project of China(No.24-202-6-01)the Independent Research Project of the National Key Laboratory of Strength and Structural Integrity(No.BYST-QZSYS-24-072-8)。
文摘In addition to blade-to-casing rubbing,drum-to-labyrinth rubbing is another common interaction in aero-engines.In this study,the labyrinth seal is simplified and modeled as an inner ring.First,considering the flexibility of both the drum and inner ring,a novel rubbing force model applicable to drum-inner ring rubbing is proposed,and this model is partially validated with the measured vibration responses.Incorporating both drum-inner ring rubbing faults and bolt joint effects,a dynamic model of the shaft-diskdrum-inner ring-vane-casing system(SDDIRVCS)is established with beam-shell hybrid elements to investigate the nonlinear dynamic responses induced by rubbing at various rotational speeds.The established dynamic model of the SDDIRVCS is validated by the comparison of its modal characteristics with those obtained from the ANSYS simulations.The results indicate that the rotor spectrum is dominated by odd-multiple harmonics,while the stator spectrum exhibits prominent even-multiple harmonics.Moreover,the rubbing location between the drum and the inner ring varies with the dynamic behavior of the rotor system.
文摘Purpose–This study aims to investigate the fatigue behavior and failure modes of bolted lap joints using Modified Tensile Specimens(MTS)under various cyclic load conditions.Emphasis is placed on identifying the relationship between load amplitude,fatigue life,and damage progression in low-carbon steel assemblies.Design/methodology/approach–An experimental approach was adopted using MTS specimens fabricated from St 1203 cold-rolled steel,joined with Grade 8.8 M4 bolts.Cyclic fatigue tests were conducted under zerobased loading at seven distinct force levels.Fracture surfaces were visually analyzed to identify dominant failure mechanisms.Findings–The results revealed a strong inverse correlation between applied cyclic load and fatigue life.Three distinct failure modes were identified:bolt shear at high loads(5.4 kN),interface cracking and slippage at moderate loads(4.9–5.1 kN),and plate tearing or stable fatigue behavior at lower loads(54.1 kN).The results highlight a progressive transition in failure mechanisms,from bolt shear at high loads to plate tearing and interface cracking at lower loads,providing essential insights for fatigue-resistant bolted joint design.Originality/value–This study offers original insights into the fatigue behavior of bolted lap joints using MTS,a relatively underexplored configuration in fatigue assessment.By experimentally evaluating failure modes under varied cyclic load levels,the authors uncover critical transitions in damage mechanisms—from bolt shear to interface cracking and plate tearing—depending on the applied load.Unlike many existing studies focused on numerical modeling or bonded joints alone,this work provides empirical data rooted in real-world fastening conditions using cold-rolled low-carbon steel.
基金the National Natural Science Foundation of China(Nos.52304141 and 52074154)。
文摘The grouted bolt,combining rock bolting with grouting techniques,provides an effective solution for controlling the surrounding rock in deep soft rock and fractured roadways.It has been extensively applied in numerous deep mining areas characterized by soft rock roadways,where it has demonstrated remarkable control results.This article systematically explores the evolution of grouted bolting,covering its theoretical foundations,design methods,materials,construction processes,monitoring measures,and methods for assessing its effectiveness.The overview encompassed several key elements,delving into anchoring theory and grouting reinforcement theory.The new principle of high pretensioned high-pressure splitting grouted bolting collaborative active control is introduced.A fresh method for dynamic information design is also highlighted.The discussion touches on both conventional grouting rock bolts and cable bolts,as well as innovative grouted rock bolts and cables characterized by their high pretension,strength,and sealing hole pressure.An examination of the merits and demerits of standard inorganic and organic grouting materials versus the new inorganic–organic composite materials,including their specific application conditions,was conducted.Additionally,the article presents various methods and instruments to assess the support effect of grouting rock bolts,cable bolts,and grouting reinforcement.Furthermore,it provides a foundation for understanding the factors influencing decisions on grouted bolting timing,the sequence of grouting,the pressure applied,the volume of grout used,and the strategic arrangement of grouted rock bolts and cable bolts.The application of the high pretensioned high-pressure splitting grouted bolting collaborative control technology in a typical kilometer-deep soft rock mine in China—the soft coal seam and soft rock roadway in the Kouzidong coal mine,Huainan coal mining area,was introduced.Finally,the existing problems in grouted bolting control technology for deep soft rock roadways are analyzed,and the future development trend of grouted bolting control technology is anticipated.
基金The Project(52174101)supported by the National Natural Science Foundation of ChinaThe Project(2023A1515011634)supported by Guangdong Basic and Applied Basic Research Foundation.
文摘Rock bolts are extensively utilized in underground engineering as a means of offering support and stability to rock masses in tunnels,mines,and other underground structures.In environments of high ground stress,faults or weak zones can frequently arise in rock formations,presenting a significant challenge for engineering and potentially leading to underground engineering collapse.Rock bolts serve as a crucial structural element for the transmission of tensile stress and are capable of withstanding shear loads to prevent sliding of weak zones within rock mass.Therefore,a complete understanding of the behavior of rock bolts subjected to shear loads is essential.This paper presents a state-of-the-art review of the research progress of rock bolts subjected to shear load in three categories:experiment,numerical simulation,and analytical model.The review focuses on the research studies and developments in this area since the 1970s,providing a comprehensive overview of numerous factors that influence the anchorage performance of rock bolts.These factors include the diameter and angle of the rock bolt installation,rock strength,grouting material,bolt material,borehole diameter,rock bolt preload,normal stress,joint surface roughness and joint expansion angle.The paper reviews the improvement of mechanical parameter setting in numerical simulation of rock bolt shear.Furthermore,it delves into the optimization of the analytical model concerning rock bolt shear theory,approached from the perspectives of both Elastic foundation beam theory coupled with Elastoplasticity theory and Structural mechanic methods.The significance of this review lies in its ability to provide insights into the mechanical behavior of rock bolts.The paper also highlights the limitations of current research and guidelines for further research of rock bolts.
基金funded by the National Natural Science Foundation of China(Nos.41931295,41877258)the China Postdoctoral Science Foundation(No.2022M712953)+1 种基金the Open foundation of State Key Laboratory of Geohazard Prevention and Geoenvironment Protection(No.SKLGP2022K001)the China Three Gorges Corporation(No.2019073)。
文摘The mechanical properties of bolts are important factors affecting the shear behavior of bolted joints.In this study,tensile and pure shear tests were conducted on five kinds of bolts made from different materials to measure their tensile and shear parameters.Direct shear tests were conducted to analyze the effects of tensile and shear strength parameters on the shear behavior of bolted joints.The test results showed that the mechanical properties of bolts made from different materials were clearly different and that these differences mainly affected the plastic deformation stage of the bolted joints.The larger the bolt elongation was,the larger the joint shear displacement at bolt failure.The tensile and shear strengths of the bolts were positively correlated with the shear strength of the bolted joints.According to the standard regression analysis,the bolt shear strength had a greater influence than the bolt tensile strength on the bolt contributions when the bolts were perpendicular to the joint surface.Based on the empirical equation for the bolt contribution proposed by Spang,the maximum shear loads in the pure shear test were introduced,and a new equation was established to predict the contributions of bolts.The prediction results obtained using the modified equation were in good agreement with the experimental results.
