In the current practice of multi-axis machining of freeform surfaces, the interface surface between the roughing and finishing process is simply an offset surface of the nominal surface. While there have already been ...In the current practice of multi-axis machining of freeform surfaces, the interface surface between the roughing and finishing process is simply an offset surface of the nominal surface. While there have already been attempts at minimizing the machining time by considering the kinematic capacities of the machine tool and/or the physical constraints such as the cutting force, they all target independently at either the finishing or the roughing process alone and are based on the simple premise of an offset interface surface. Conceivably, since the total machining time should count that of both roughing and finishing process and both of them crucially depend on the interface surface, it is natural to ask if, under the same kinematic capacities and the same physical constraints, there is a nontrivial interface surface whose corresponding total machining time will be the minimum among all the possible（infinite） choices of interface surfaces, and this is the motivation behind the work of this paper. Specifically, with respect to the specific type of iso-planar milling for both roughing and finishing, we present a practical algorithm for determining such an optimal interface surface for an arbitrary freeform surface. While the algorithm is proposed for iso-planar milling, it can be easily adapted to other types of milling strategy such as contour milling. Both computer simulation and physical cutting experiments of the proposed method have convincingly demonstrated its advantages over the traditional simple offset method.展开更多
The surface texture of mineral flotation froth is well acknowledged as an important index of the flotation process.The surface texture feature closely relates to the flotation working conditions and hence can be used ...The surface texture of mineral flotation froth is well acknowledged as an important index of the flotation process.The surface texture feature closely relates to the flotation working conditions and hence can be used as a visual indicator for the zinc fast roughing working condition. A novel working condition identification method based on the dual-tree complex wavelet transform(DTCWT) is proposed for process monitoring of zinc fast roughing.Three-level DTCWT is implemented to decompose the froth image into different directions and resolutions in advance, and then the energy parameter of each sub-image is extracted as the froth texture feature. Then, an improved random forest integrated classification(i RFIC) with 10-fold cross-validation model is introduced as the classifier to identify the roughing working condition, which effectively improves the shortcomings of the single model and overcomes the characteristic redundancy but achieves higher generalization performance. Extensive experiments have verified the effectiveness of the proposed method.展开更多
Based on the characteristics of ferritic SUS430 heating and deformation,and combined with the features of the 1780 mm hot-rolling mill,a roughing model was introduced in two aspects:optimizing the rough rolling passes...Based on the characteristics of ferritic SUS430 heating and deformation,and combined with the features of the 1780 mm hot-rolling mill,a roughing model was introduced in two aspects:optimizing the rough rolling passes and improving the width control precision.Through reducing the rough rolling passes,the rough rolling time can be shortened,the precision rolling startup temperature can be raised and the yield of the hot-rolled products can be increased.Moreover,on the premise that the slab width fluctuation was great,the precision of the width control can be improved through optimizing the parameters of the hot-rolling width control model.The result shows that the optimization and perfection of the original rolling process of the stainless steel 430 series further improved its capacity and product quality.展开更多
Joint roughness coefficient(JRC)is the most commonly used parameter for quantifying surface roughness of rock discontinuities in practice.The system composed of multiple roughness statistical parameters to measure JRC...Joint roughness coefficient(JRC)is the most commonly used parameter for quantifying surface roughness of rock discontinuities in practice.The system composed of multiple roughness statistical parameters to measure JRC is a nonlinear system with a lot of overlapping information.In this paper,a dataset of eight roughness statistical parameters covering 112 digital joints is established.Then,the principal component analysis method is introduced to extract the significant information,which solves the information overlap problem of roughness characterization.Based on the two principal components of extracted features,the white shark optimizer algorithm was introduced to optimize the extreme gradient boosting model,and a new machine learning(ML)prediction model was established.The prediction accuracy of the new model and the other 17 models was measured using statistical metrics.The results show that the prediction result of the new model is more consistent with the real JRC value,with higher recognition accuracy and generalization ability.展开更多
The roughness of the fracture surface directly affects the strength,deformation,and permeability of the surrounding rock in deep underground engineering.Understanding the effect of high temperature and thermal cycle o...The roughness of the fracture surface directly affects the strength,deformation,and permeability of the surrounding rock in deep underground engineering.Understanding the effect of high temperature and thermal cycle on the fracture surface roughness plays an important role in estimating the damage degree and stability of deep rock mass.In this paper,the variations of fracture surface roughness of granite after different heating and thermal cycles were investigated using the joint roughness coefficient method(JRC),three-dimensional(3D)roughness parameters,and fractal dimension(D),and the mechanism of damage and deterioration of granite were revealed.The experimental results show an increase in the roughness of the granite fracture surface as temperature and cycle number were incremented.The variations of JRC,height parameter,inclination parameter and area parameter with the temperature conformed to the Boltzmann's functional distribution,while the D decreased linearly as the temperature increased.Besides,the anisotropy index(Ip)of the granite fracture surface increased as the temperature increased,and the larger parameter values of roughness characterization at different temperatures were attained mainly in directions of 20°–40°,60°–100°and 140°–160°.The fracture aperture of granite after fracture followed the Gauss distribution and the average aperture increased with increasing temperature,which increased from 0.665 mm at 25℃to 1.058 mm at 800℃.High temperature caused an uneven thermal expansion,water evaporation,and oxidation of minerals within the granite,which promoted the growth and expansion of microfractures,and reduced interparticle bonding strength.In particular,the damage was exacerbated by the expansion and cracking of the quartz phase transition after T>500℃.Thermal cycles contributed to the accumulation of this damage and further weakened the interparticle bonding forces,resulting in a significant increase in the roughness,anisotropy,and aperture of the fracture surface after five cycles.展开更多
Landslide susceptibility prediction(LSP)is significantly affected by the uncertainty issue of landslide related conditioning factor selection.However,most of literature only performs comparative studies on a certain c...Landslide susceptibility prediction(LSP)is significantly affected by the uncertainty issue of landslide related conditioning factor selection.However,most of literature only performs comparative studies on a certain conditioning factor selection method rather than systematically study this uncertainty issue.Targeted,this study aims to systematically explore the influence rules of various commonly used conditioning factor selection methods on LSP,and on this basis to innovatively propose a principle with universal application for optimal selection of conditioning factors.An'yuan County in southern China is taken as example considering 431 landslides and 29 types of conditioning factors.Five commonly used factor selection methods,namely,the correlation analysis(CA),linear regression(LR),principal component analysis(PCA),rough set(RS)and artificial neural network(ANN),are applied to select the optimal factor combinations from the original 29 conditioning factors.The factor selection results are then used as inputs of four types of common machine learning models to construct 20 types of combined models,such as CA-multilayer perceptron,CA-random forest.Additionally,multifactor-based multilayer perceptron random forest models that selecting conditioning factors based on the proposed principle of“accurate data,rich types,clear significance,feasible operation and avoiding duplication”are constructed for comparisons.Finally,the LSP uncertainties are evaluated by the accuracy,susceptibility index distribution,etc.Results show that:(1)multifactor-based models have generally higher LSP performance and lower uncertainties than those of factors selection-based models;(2)Influence degree of different machine learning on LSP accuracy is greater than that of different factor selection methods.Conclusively,the above commonly used conditioning factor selection methods are not ideal for improving LSP performance and may complicate the LSP processes.In contrast,a satisfied combination of conditioning factors can be constructed according to the proposed principle.展开更多
Two-terminal(2-T)perovskite(PVK)/CuIn(Ga)Se_(2)(CIGS)tandem solar cells(TSCs)have been considered as an ideal tandem cell because of their best bandgap matching regarding to Shockley–Queisser(S–Q)limits.However,the ...Two-terminal(2-T)perovskite(PVK)/CuIn(Ga)Se_(2)(CIGS)tandem solar cells(TSCs)have been considered as an ideal tandem cell because of their best bandgap matching regarding to Shockley–Queisser(S–Q)limits.However,the nature of the irregular rough morphology of commercial CIGS prevents people from improving tandem device performances.In this paper,D-homoserine lactone hydrochloride is proven to improve coverage of PVK materials on irregular rough CIGS surfaces and also passivate bulk defects by modulating the growth of PVK crystals.In addition,the minority carriers near the PVK/C60 interface and the incompletely passivated trap states caused interface recombination.A surface reconstruction with 2-thiopheneethylammonium iodide and N,N-dimethylformamide assisted passivates the defect sites located at the surface and grain boundaries.Meanwhile,LiF is used to create this field effect,repelling hole carriers away from the PVK and C60 interface and thus reducing recombination.As a result,a 2-T PVK/CIGS tandem yielded a power conversion efficiency of 24.6%(0.16 cm^(2)),one of the highest results for 2-T PVK/CIGS TSCs to our knowledge.This validation underscores the potential of our methodology in achieving superior performance in PVK/CIGS tandem solar cells.展开更多
LetΩbe homogeneous of degree zero,integrable on S^(d−1) and have vanishing moment of order one,a be a function on R^(d) such that ∇a∈L^(∞)(R^(d)).Let T*_(Ω,a) be the maximaloperator associated with the d-dimensional...LetΩbe homogeneous of degree zero,integrable on S^(d−1) and have vanishing moment of order one,a be a function on R^(d) such that ∇a∈L^(∞)(R^(d)).Let T*_(Ω,a) be the maximaloperator associated with the d-dimensional Calder´on commutator defined by T*_(Ωa)f(x):=sup_(ε>0)|∫_(|x-y|>ε)^Ω(x-y)/|x-y|^(d+1)(a(x)-a(y))f(y)dy.In this paper,the authors establish bilinear sparse domination for T*_(Ω,a) under the assumption Ω∈L∞(Sd−1).As applications,some quantitative weighted bounds for T*_(Ω,a) are obtained.展开更多
Let Ω be homogeneous of degree zero,integrable on S^(n−1) and have mean value zero,T_(Ω) be the homogeneous singular integral operator with kernel Ω(x)/|x|^(n) and[b,T_(Ω)]be the commutator of T_(Ω)with symbol b∈BMO(...Let Ω be homogeneous of degree zero,integrable on S^(n−1) and have mean value zero,T_(Ω) be the homogeneous singular integral operator with kernel Ω(x)/|x|^(n) and[b,T_(Ω)]be the commutator of T_(Ω)with symbol b∈BMO(R^(n)).In this paper,the authors prove that if sup ζ∈S^(n−1)∫Sn−1^(|Ω(θ)|log^(β)(1/|θ·ζ|)dθ<∞ with β>2,then[b,T_(Ω)]is bounded on Triebel–Lizorkin space F^(0,q)p(R^(n))provided that 1+1/β−1<p,q<β.展开更多
As a non-contact ultra-precision machining method,abrasive water jet polishing(AWJP)has signi-ficant application in optical elements processing due to its stable tool influence function(TIF),no subsurface damage and s...As a non-contact ultra-precision machining method,abrasive water jet polishing(AWJP)has signi-ficant application in optical elements processing due to its stable tool influence function(TIF),no subsurface damage and strong adaptability to workpiece shapes.In this study,the effects of jet pressure,nozzle diameter and impinging angle on the distribution of pressure,velocity and wall shear stress in the polishing flow field were systematically analyzed by computational fluid dynamics(CFD)simulation.Based on the Box-Behnken experimental design,a response surface regression model was constructed to investigate the influence mech-anism of process parameters on material removal rate(MRR)and surface roughness(Ra)of fused silica.And experimental results showed that increasing jet pressure and nozzle diameter significantly improved MRR,consistent with shear stress distribution revealed by CFD simulations.However,increasing jet pressure and impinging angle caused higher Ra values,which was unfavorable for surface quality improvement.Genetic algorithm(GA)was used for multi-objective optimization to establish Pareto solutions,achieving concurrent optimization of polishing efficiency and surface quality.A parameter combination of 2 MPa jet pressure,0.3 mm nozzle diameter,and 30°impinging angle achieved MRR of 169.05μm^(3)/s and Ra of 0.50 nm.Exper-imental verification showed prediction errors of 4.4%(MRR)and 3.8%(Ra),confirming the model’s reliabil-ity.This parameter optimization system provides theoretical basis and technical support for ultra-precision polishing of complex curved optical components.展开更多
As the dominant seepage channel in rock masses,it is of great significance to study the influence of fracture roughness distribution on seepage and heat transfer in rock masses.In this paper,the fracture roughness dis...As the dominant seepage channel in rock masses,it is of great significance to study the influence of fracture roughness distribution on seepage and heat transfer in rock masses.In this paper,the fracture roughness distribution functions of the Bakhtiary dam site and Oskarshamn/Forsmark mountain were fitted using statistical methods.The COMSOL Multiphysics finite element software was utilized to analyze the effects of fracture roughness distribution types and empirical formulas for fracture hydraulic aperture on the seepage field and temperature field of rock masses.The results show that:(1)The fracture roughness at the Bakhtiary dam site and Oskarshamn/Forsmark mountain follows lognormal and normal distributions,respectively;(2)For rock masses with the same expected value and standard deviation of fracture roughness,the outflow from rock masses with lognormal distribution of fracture roughness is significantly larger than that of rock masses with normal distribution of fracture roughness;(3)The fracture hydraulic aperture,outflow,and cold front distance of the Li and Jiang model are significantly larger than those of the Barton model;(4)The outflow,hydraulic pressure distribution,and temperature distribution of the Barton model are more sensitive to the fracture roughness distribution type than those of the Li and Jiang model.展开更多
Pavement condition monitoring and its timely maintenance is necessary to ensure the safety and quality of the roadway infrastructure. The International Roughness Index (IRI) is a commonly used measure to quantify road...Pavement condition monitoring and its timely maintenance is necessary to ensure the safety and quality of the roadway infrastructure. The International Roughness Index (IRI) is a commonly used measure to quantify road surface roughness and is a critical input to asset management. In Indiana, the IRI statistic contributes to roughly half of the pavement quality index computation used for asset management. Most agencies inventory IRI once a year, however, pavement conditions vary much more frequently. The objective of this paper is to develop a framework using crowdsourced connected vehicle data to identify and detect temporal changes in IRI. Over 3 billion connected vehicle records in Indiana were analyzed across 30 months between 2022 and 2024 to understand the spatiotemporal variations in roughness. Annual comparisons across all major interstates in Indiana showed the miles of interstates classified as “Good” decreased from 1896 to 1661 miles between 2022 and 2024. The miles of interstate classified as “Needs Maintenance” increased from 82 to 120 miles. A detailed case study showing monthly and daily changes of estimated IRI on I-65 are presented along with supporting dashcam images. Although the crowdsourced IRI estimates are not as robust as traditional specialized pavement profilers, they can be obtained on a monthly, weekly, or even daily basis. The paper concludes by suggesting a combination of frequent crowdsourced IRI and commercially available dashcam imagery of roadway can provide an agile and responsive mechanism for agencies to implement pavement asset management programs that can complement existing annual programs.展开更多
A two-step approach was employed to create a composite coating consisting of TiO_(2)nanoparticles and extremely elastic polydimethylsiloxane(PDMS).The TiO_(2)-PDMS composite coating demonstrates exceptional superhydro...A two-step approach was employed to create a composite coating consisting of TiO_(2)nanoparticles and extremely elastic polydimethylsiloxane(PDMS).The TiO_(2)-PDMS composite coating demonstrates exceptional superhydrophobicity and antifouling efficacy,as evidenced by the static contact angle,contact angle hysteresis,and antifouling tests.The electron microscopic analysis reveals that the composite coating consists of TiO_(2)particles and agglomerates,which forms a dual-level roughness structure at the nanometer and micron scales.This unique structure promotes the Cassie-Baxter state of the coating when in contact with the liquid,resulting in an increased static contact angle and a reduced contact angle hysteresis.The PDMS primer facilitates the attachment of TiO_(2)particles,resulting in a composite coating with excellent scratch-resistant characteristics.Additionally,the PDMS primer possesses the capacity to retain low surface energy modifiers.Simultaneously,the PDMS primer serves as a reservoir for a low surface energy modifier,enhancing the self-repairing properties of the TiO_(2)-PDMS composite coating.This composite coating exhibits effective self-cleaning capabilities against many forms of contaminants,including liquids,solids,and slurries.展开更多
Wire⁃Electrical Discharge Machining(WEDM)process can create any complex contour in any conducting material,regardless of its strength or hardness,with higher accuracy.Present experimental investigation aims to determi...Wire⁃Electrical Discharge Machining(WEDM)process can create any complex contour in any conducting material,regardless of its strength or hardness,with higher accuracy.Present experimental investigation aims to determine suitable input process/machining parameters,e.g.pulse on time(TON),peak current(IP),wire feed rate(WF),and pulse off time(TOFF),for optimizing the process performances,namely,cutting rate,kerf width,average roughness value of the machined surface,micro hardness,and surface crack density.Since four input parameters are considered in the present investigation,and each parameter is assumed to vary at three different levels(i.e.low,medium,high),the Taguchi L9 Orthogonal Array(OA)design approach has been used for the experimental purpose to enhance the process effiency.Similarly,a simple and popular multiresponse optimization approach,namely Grey Relational Analysis(GRA),is used to optimize five performance characteristics(output responses)simultaneously.The optimum process variables obtained are:TON of 110μs,TOFF of 40μs,IP of 10 A,and WF of 6 mm/min.These optimum process variables are validated with confirmatory experiment.The relative impact of input variables is determined using the Analysis of Variance(ANOVA)technique.Finally,correlations between individual outputs with different input parameters are established.This work will be helpful for industry personnel to use this machining process in a techno⁃economic way.展开更多
Control of the wetting properties of biomimetic functional surfaces is a desired functionality in many applications.In this paper,the photoresist SU-8 was used as fabrication material.A silicon wafer was used as a sub...Control of the wetting properties of biomimetic functional surfaces is a desired functionality in many applications.In this paper,the photoresist SU-8 was used as fabrication material.A silicon wafer was used as a substrate to prepare a biomimetic surface with different surface roughness and micro-pillars arranged in array morphology.The evaporation dynamics and interfacial heat transfer processes of deionised water droplets on the bioinspired microstructure surface were experimentally studied.The study not only proves the feasibility of preparing hydrophilic biomimetic functional surfaces directly through photoresist materials and photolithography technology but also shows that by adjusting the structural parameters and arrangement of the surface micro-pillar structure,the wettability of the biomimetic surface can be significantly linearly regulated,thereby effectively affecting the heat and mass transfer process at the droplet liquid-vapour interface.Analysis of the results shows that by controlling the biomimetic surface microstructure,the wettability can be enhanced by about 22%at most,the uniformity of the temperature distribution at the liquid-vapour interface can be improved by about 34%,and the average evaporation rate can be increased by about 28%.This study aims to provide some guidance for the research on bionic surface design based on photoresist materials.展开更多
The primary objective of this work is to improve our understanding of the mechanical involvements of two-order roughness in shear.First,wavelet analysis is used to separate the waviness(first-order)and unevenness(seco...The primary objective of this work is to improve our understanding of the mechanical involvements of two-order roughness in shear.First,wavelet analysis is used to separate the waviness(first-order)and unevenness(second-order)from four granite joint surfaces,with roughness characterized using Grasselli’s 3D morphology parameters.The results reveal that first-order roughness is more pronounced than second-order roughness,highlighting the dominant role of waviness in joint surface roughness.Additionally,the variation in first-order roughness with strike direction corresponds to the total roughness,while second-order roughness remains largely constant,indicating that roughness anisotropy is primarily driven by waviness.Then,direct shear tests on joint replicas are performed to investigate the contributions of both roughness orders to peak shear strength.The results show that the peak dilation angle is closely related to first-order roughness,while the shear component angle is closely associated with second-order roughness,both exhibiting a linear correlation.Based on these findings,relationships are established between the angles and their respective roughness orders.Finally,a joint shear strength criterion based on two-order roughness is proposed.A comparative analysis of prediction accuracy reveals that the average relative error for the proposed criterion is 13.79%,while the errors for Xia's,Yang's,and Ban's criteria are 15.19%,16.29%,and 13.87%,respectively.It demonstrates the proposed criterion can predict the peak shear strength of rock joints.展开更多
Glass,with its valuable properties,finds extensive use in aerospace,optics,and biomedical fields.Owing to its low fracture toughness,glass typically fractures in a brittle manner during machining,resulting in poor sur...Glass,with its valuable properties,finds extensive use in aerospace,optics,and biomedical fields.Owing to its low fracture toughness,glass typically fractures in a brittle manner during machining,resulting in poor surface quality.This paper presents an experimental investigation of vibration-assisted machining(VAM)techniques to enhance the machining of glass materials.A novel high-frequency two-dimensional VAM system specifically designed for glass is introduced,and slot milling experiments are conducted using ultrasonic high-frequency vibrations.A low-frequency nonresonant VAM system is also employed for comparison purposes.A comprehensive examination is made of the effects of various machining parameters,such as feed rate,cutting speeds,and vibration parameters,including vibration modes and amplitudes,on the machining performance of glass.Surface roughness,edge chipping generation,and tool wear are thoroughly characterized using scanning electron microscopy.The findings demonstrate that under specific machining and vibration parameters,the proposed ultrasonic vibration-assisted micro-milling(UVAMM)system can achieve a nanometric surface roughness Ra for glass.The UVAMM system offers enhanced surface quality,improved edge quality,and reduced tool wear compared with conventional machining techniques.This study provides valuable insights and directions for the application of 2D VAM systems in achieving superior machining results for glass components at small scales with nanometric surface finishes.展开更多
The mineralogy and texture of granite have been found to have a pronounced effect on its mechanical behavior.However,the precise manner in which the texture of granite affects the shear behavior of fractures remains e...The mineralogy and texture of granite have been found to have a pronounced effect on its mechanical behavior.However,the precise manner in which the texture of granite affects the shear behavior of fractures remains enigmatic.In this study,fine-grained granite(FG)and coarse-grained granite(CG)were used to create tensile fractures with surface roughness(i.e.joint roughness coefficient(JRC))within the range of 5.48-8.34 and 12.68-16.5,respectively.The pre-fractured specimens were then subjected to direct shear tests under normal stresses of 1-30 MPa.The results reveal that shear strengths are smaller and stick-slip behaviors are more intense for FG fractures than for CG fractures,which is attributed to the different conditions of the shear surface constrained by the grain size.The smaller grain size in FG contributes to the smoother fracture surface and lower shear strength.The negative friction rate parameter a-b for both CG and FG fractures and the larger shear stiffness for FG than for CG fractures can account for the more intense stick-slip behaviors in FG fractures.The relative crack density for the post-shear CG fractures is greater than that of the FG fractures under the same normal stress,both of which decrease with the distance away from the shear surface following the power law.Moreover,the damage of CG fracture extends to a larger extent beneath the surface compared with the FG fracture.Our findings demonstrate that the grain size of the host rock exerts a significant influence on the fracture roughness,and thus should be incorporated into the assessment of fault slip behavior to better understand the role of mineralogy and texture in seismic activities.展开更多
The fracture surfaces of coal-rock masses formed under mining-induced stress generally exhibit complex geometries, and the fracture geometry is one of the primary factors affecting the seepage characteristics of coal-...The fracture surfaces of coal-rock masses formed under mining-induced stress generally exhibit complex geometries, and the fracture geometry is one of the primary factors affecting the seepage characteristics of coal-rock penetrating fracture. This paper investigates the seepage characteristics of 5 groups of coal penetrating fracture(CPF) with different joint roughness coefficients(JRCs). Based on 3D morphology scanner tests and hydraulic coupling tests, a characterization method of effective geometric parameters in fracture surfaces under various confining pressures was improved, and a relationship between effective geometric parameters and the confining pressure is established. The results indicate that the nonlinear flow behavior in a CPF primarily includes three types: non-Newtonian fluid seepage under high confining pressure and low JRC, non-Darcy seepage under low confining pressure and high JRC, and the whole process of seepage characteristics between these two conditions. Among them, nonNewtonian fluid seepage is caused by significant fracture expansion, while non-Darcy seepage can be attributed to turbulence effects. During the seepage process, the geometric parameters with different JRC fracture samples all exhibit exponential changes with the increase of confining pressure. In addition,under high confining pressure, the effective contact ratio, effective fracture aperture, and void deviation ratio with high JRC fracture samples under high confining pressure increase by 93.5%, 67.4%, and 24.9%,respectively, compared with those of low JRC fracture samples. According to the variation of geometric parameters in a CPF with external stress, a seepage model considering geometric parameters in a CPF is proposed. By introducing the root mean square error(RMSE) and coefficient of determination(R2) to evaluate the error and goodness of fit between model curves and experimental data, it is found that the theoretical curves of model in this paper have the best matching with the experimental data. The average values of RMSE and R2for model in this paper are 0.002 and 0.70, respectively, which are better than models in the existing literature.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
文摘In the current practice of multi-axis machining of freeform surfaces, the interface surface between the roughing and finishing process is simply an offset surface of the nominal surface. While there have already been attempts at minimizing the machining time by considering the kinematic capacities of the machine tool and/or the physical constraints such as the cutting force, they all target independently at either the finishing or the roughing process alone and are based on the simple premise of an offset interface surface. Conceivably, since the total machining time should count that of both roughing and finishing process and both of them crucially depend on the interface surface, it is natural to ask if, under the same kinematic capacities and the same physical constraints, there is a nontrivial interface surface whose corresponding total machining time will be the minimum among all the possible（infinite） choices of interface surfaces, and this is the motivation behind the work of this paper. Specifically, with respect to the specific type of iso-planar milling for both roughing and finishing, we present a practical algorithm for determining such an optimal interface surface for an arbitrary freeform surface. While the algorithm is proposed for iso-planar milling, it can be easily adapted to other types of milling strategy such as contour milling. Both computer simulation and physical cutting experiments of the proposed method have convincingly demonstrated its advantages over the traditional simple offset method.
文摘The surface texture of mineral flotation froth is well acknowledged as an important index of the flotation process.The surface texture feature closely relates to the flotation working conditions and hence can be used as a visual indicator for the zinc fast roughing working condition. A novel working condition identification method based on the dual-tree complex wavelet transform(DTCWT) is proposed for process monitoring of zinc fast roughing.Three-level DTCWT is implemented to decompose the froth image into different directions and resolutions in advance, and then the energy parameter of each sub-image is extracted as the froth texture feature. Then, an improved random forest integrated classification(i RFIC) with 10-fold cross-validation model is introduced as the classifier to identify the roughing working condition, which effectively improves the shortcomings of the single model and overcomes the characteristic redundancy but achieves higher generalization performance. Extensive experiments have verified the effectiveness of the proposed method.
文摘Based on the characteristics of ferritic SUS430 heating and deformation,and combined with the features of the 1780 mm hot-rolling mill,a roughing model was introduced in two aspects:optimizing the rough rolling passes and improving the width control precision.Through reducing the rough rolling passes,the rough rolling time can be shortened,the precision rolling startup temperature can be raised and the yield of the hot-rolled products can be increased.Moreover,on the premise that the slab width fluctuation was great,the precision of the width control can be improved through optimizing the parameters of the hot-rolling width control model.The result shows that the optimization and perfection of the original rolling process of the stainless steel 430 series further improved its capacity and product quality.
基金funding from the National Natural Science Foundation of China (Grant No.42277175)the pilot project of cooperation between the Ministry of Natural Resources and Hunan Province“Research and demonstration of key technologies for comprehensive remote sensing identification of geological hazards in typical regions of Hunan Province” (Grant No.2023ZRBSHZ056)the National Key Research and Development Program of China-2023 Key Special Project (Grant No.2023YFC2907400).
文摘Joint roughness coefficient(JRC)is the most commonly used parameter for quantifying surface roughness of rock discontinuities in practice.The system composed of multiple roughness statistical parameters to measure JRC is a nonlinear system with a lot of overlapping information.In this paper,a dataset of eight roughness statistical parameters covering 112 digital joints is established.Then,the principal component analysis method is introduced to extract the significant information,which solves the information overlap problem of roughness characterization.Based on the two principal components of extracted features,the white shark optimizer algorithm was introduced to optimize the extreme gradient boosting model,and a new machine learning(ML)prediction model was established.The prediction accuracy of the new model and the other 17 models was measured using statistical metrics.The results show that the prediction result of the new model is more consistent with the real JRC value,with higher recognition accuracy and generalization ability.
基金funding support from the National Natural Science Foundation of China(Grant No.52274082)the Program of Qingjiang Excellent Young Talents,Jiangxi University of Science and Technology(Grant No.JXUSTQJBJ2020003)the Innovation Fund Designated for Graduate Students of Jiangxi Province(Grant No.YC2023-B215).
文摘The roughness of the fracture surface directly affects the strength,deformation,and permeability of the surrounding rock in deep underground engineering.Understanding the effect of high temperature and thermal cycle on the fracture surface roughness plays an important role in estimating the damage degree and stability of deep rock mass.In this paper,the variations of fracture surface roughness of granite after different heating and thermal cycles were investigated using the joint roughness coefficient method(JRC),three-dimensional(3D)roughness parameters,and fractal dimension(D),and the mechanism of damage and deterioration of granite were revealed.The experimental results show an increase in the roughness of the granite fracture surface as temperature and cycle number were incremented.The variations of JRC,height parameter,inclination parameter and area parameter with the temperature conformed to the Boltzmann's functional distribution,while the D decreased linearly as the temperature increased.Besides,the anisotropy index(Ip)of the granite fracture surface increased as the temperature increased,and the larger parameter values of roughness characterization at different temperatures were attained mainly in directions of 20°–40°,60°–100°and 140°–160°.The fracture aperture of granite after fracture followed the Gauss distribution and the average aperture increased with increasing temperature,which increased from 0.665 mm at 25℃to 1.058 mm at 800℃.High temperature caused an uneven thermal expansion,water evaporation,and oxidation of minerals within the granite,which promoted the growth and expansion of microfractures,and reduced interparticle bonding strength.In particular,the damage was exacerbated by the expansion and cracking of the quartz phase transition after T>500℃.Thermal cycles contributed to the accumulation of this damage and further weakened the interparticle bonding forces,resulting in a significant increase in the roughness,anisotropy,and aperture of the fracture surface after five cycles.
基金funded by the Natural Science Foundation of China(Grant Nos.42377164 and 41972280)the Badong National Observation and Research Station of Geohazards(Grant No.BNORSG-202305).
文摘Landslide susceptibility prediction(LSP)is significantly affected by the uncertainty issue of landslide related conditioning factor selection.However,most of literature only performs comparative studies on a certain conditioning factor selection method rather than systematically study this uncertainty issue.Targeted,this study aims to systematically explore the influence rules of various commonly used conditioning factor selection methods on LSP,and on this basis to innovatively propose a principle with universal application for optimal selection of conditioning factors.An'yuan County in southern China is taken as example considering 431 landslides and 29 types of conditioning factors.Five commonly used factor selection methods,namely,the correlation analysis(CA),linear regression(LR),principal component analysis(PCA),rough set(RS)and artificial neural network(ANN),are applied to select the optimal factor combinations from the original 29 conditioning factors.The factor selection results are then used as inputs of four types of common machine learning models to construct 20 types of combined models,such as CA-multilayer perceptron,CA-random forest.Additionally,multifactor-based multilayer perceptron random forest models that selecting conditioning factors based on the proposed principle of“accurate data,rich types,clear significance,feasible operation and avoiding duplication”are constructed for comparisons.Finally,the LSP uncertainties are evaluated by the accuracy,susceptibility index distribution,etc.Results show that:(1)multifactor-based models have generally higher LSP performance and lower uncertainties than those of factors selection-based models;(2)Influence degree of different machine learning on LSP accuracy is greater than that of different factor selection methods.Conclusively,the above commonly used conditioning factor selection methods are not ideal for improving LSP performance and may complicate the LSP processes.In contrast,a satisfied combination of conditioning factors can be constructed according to the proposed principle.
基金supported by“National Natural Science Foundation of China(U21A20171,U20A20245)”“Hubei Provincial Natural Science Foundation of China(2023AFA010)”+1 种基金“Independent Innovation Projects of the Hubei Longzhong Laboratory(2022ZZ-09)”“Social Public Welfare and Basic Research Special Project of Zhongshan(2020B2015).”。
文摘Two-terminal(2-T)perovskite(PVK)/CuIn(Ga)Se_(2)(CIGS)tandem solar cells(TSCs)have been considered as an ideal tandem cell because of their best bandgap matching regarding to Shockley–Queisser(S–Q)limits.However,the nature of the irregular rough morphology of commercial CIGS prevents people from improving tandem device performances.In this paper,D-homoserine lactone hydrochloride is proven to improve coverage of PVK materials on irregular rough CIGS surfaces and also passivate bulk defects by modulating the growth of PVK crystals.In addition,the minority carriers near the PVK/C60 interface and the incompletely passivated trap states caused interface recombination.A surface reconstruction with 2-thiopheneethylammonium iodide and N,N-dimethylformamide assisted passivates the defect sites located at the surface and grain boundaries.Meanwhile,LiF is used to create this field effect,repelling hole carriers away from the PVK and C60 interface and thus reducing recombination.As a result,a 2-T PVK/CIGS tandem yielded a power conversion efficiency of 24.6%(0.16 cm^(2)),one of the highest results for 2-T PVK/CIGS TSCs to our knowledge.This validation underscores the potential of our methodology in achieving superior performance in PVK/CIGS tandem solar cells.
文摘LetΩbe homogeneous of degree zero,integrable on S^(d−1) and have vanishing moment of order one,a be a function on R^(d) such that ∇a∈L^(∞)(R^(d)).Let T*_(Ω,a) be the maximaloperator associated with the d-dimensional Calder´on commutator defined by T*_(Ωa)f(x):=sup_(ε>0)|∫_(|x-y|>ε)^Ω(x-y)/|x-y|^(d+1)(a(x)-a(y))f(y)dy.In this paper,the authors establish bilinear sparse domination for T*_(Ω,a) under the assumption Ω∈L∞(Sd−1).As applications,some quantitative weighted bounds for T*_(Ω,a) are obtained.
基金Supported by NSFC(No.11971295)Guangdong Higher Education Teaching Reform Project(No.2023307)。
文摘Let Ω be homogeneous of degree zero,integrable on S^(n−1) and have mean value zero,T_(Ω) be the homogeneous singular integral operator with kernel Ω(x)/|x|^(n) and[b,T_(Ω)]be the commutator of T_(Ω)with symbol b∈BMO(R^(n)).In this paper,the authors prove that if sup ζ∈S^(n−1)∫Sn−1^(|Ω(θ)|log^(β)(1/|θ·ζ|)dθ<∞ with β>2,then[b,T_(Ω)]is bounded on Triebel–Lizorkin space F^(0,q)p(R^(n))provided that 1+1/β−1<p,q<β.
文摘As a non-contact ultra-precision machining method,abrasive water jet polishing(AWJP)has signi-ficant application in optical elements processing due to its stable tool influence function(TIF),no subsurface damage and strong adaptability to workpiece shapes.In this study,the effects of jet pressure,nozzle diameter and impinging angle on the distribution of pressure,velocity and wall shear stress in the polishing flow field were systematically analyzed by computational fluid dynamics(CFD)simulation.Based on the Box-Behnken experimental design,a response surface regression model was constructed to investigate the influence mech-anism of process parameters on material removal rate(MRR)and surface roughness(Ra)of fused silica.And experimental results showed that increasing jet pressure and nozzle diameter significantly improved MRR,consistent with shear stress distribution revealed by CFD simulations.However,increasing jet pressure and impinging angle caused higher Ra values,which was unfavorable for surface quality improvement.Genetic algorithm(GA)was used for multi-objective optimization to establish Pareto solutions,achieving concurrent optimization of polishing efficiency and surface quality.A parameter combination of 2 MPa jet pressure,0.3 mm nozzle diameter,and 30°impinging angle achieved MRR of 169.05μm^(3)/s and Ra of 0.50 nm.Exper-imental verification showed prediction errors of 4.4%(MRR)and 3.8%(Ra),confirming the model’s reliabil-ity.This parameter optimization system provides theoretical basis and technical support for ultra-precision polishing of complex curved optical components.
基金College Students Innovation and Entrepreneurship Project of Guangzhou Railway Polytechnic(2025CXCY015)。
文摘As the dominant seepage channel in rock masses,it is of great significance to study the influence of fracture roughness distribution on seepage and heat transfer in rock masses.In this paper,the fracture roughness distribution functions of the Bakhtiary dam site and Oskarshamn/Forsmark mountain were fitted using statistical methods.The COMSOL Multiphysics finite element software was utilized to analyze the effects of fracture roughness distribution types and empirical formulas for fracture hydraulic aperture on the seepage field and temperature field of rock masses.The results show that:(1)The fracture roughness at the Bakhtiary dam site and Oskarshamn/Forsmark mountain follows lognormal and normal distributions,respectively;(2)For rock masses with the same expected value and standard deviation of fracture roughness,the outflow from rock masses with lognormal distribution of fracture roughness is significantly larger than that of rock masses with normal distribution of fracture roughness;(3)The fracture hydraulic aperture,outflow,and cold front distance of the Li and Jiang model are significantly larger than those of the Barton model;(4)The outflow,hydraulic pressure distribution,and temperature distribution of the Barton model are more sensitive to the fracture roughness distribution type than those of the Li and Jiang model.
文摘Pavement condition monitoring and its timely maintenance is necessary to ensure the safety and quality of the roadway infrastructure. The International Roughness Index (IRI) is a commonly used measure to quantify road surface roughness and is a critical input to asset management. In Indiana, the IRI statistic contributes to roughly half of the pavement quality index computation used for asset management. Most agencies inventory IRI once a year, however, pavement conditions vary much more frequently. The objective of this paper is to develop a framework using crowdsourced connected vehicle data to identify and detect temporal changes in IRI. Over 3 billion connected vehicle records in Indiana were analyzed across 30 months between 2022 and 2024 to understand the spatiotemporal variations in roughness. Annual comparisons across all major interstates in Indiana showed the miles of interstates classified as “Good” decreased from 1896 to 1661 miles between 2022 and 2024. The miles of interstate classified as “Needs Maintenance” increased from 82 to 120 miles. A detailed case study showing monthly and daily changes of estimated IRI on I-65 are presented along with supporting dashcam images. Although the crowdsourced IRI estimates are not as robust as traditional specialized pavement profilers, they can be obtained on a monthly, weekly, or even daily basis. The paper concludes by suggesting a combination of frequent crowdsourced IRI and commercially available dashcam imagery of roadway can provide an agile and responsive mechanism for agencies to implement pavement asset management programs that can complement existing annual programs.
基金Funded by the National Science and Technology Major Project(No.J2019-VII-0015-0155)the National Natural Science Foundation of China(No.51705533)。
文摘A two-step approach was employed to create a composite coating consisting of TiO_(2)nanoparticles and extremely elastic polydimethylsiloxane(PDMS).The TiO_(2)-PDMS composite coating demonstrates exceptional superhydrophobicity and antifouling efficacy,as evidenced by the static contact angle,contact angle hysteresis,and antifouling tests.The electron microscopic analysis reveals that the composite coating consists of TiO_(2)particles and agglomerates,which forms a dual-level roughness structure at the nanometer and micron scales.This unique structure promotes the Cassie-Baxter state of the coating when in contact with the liquid,resulting in an increased static contact angle and a reduced contact angle hysteresis.The PDMS primer facilitates the attachment of TiO_(2)particles,resulting in a composite coating with excellent scratch-resistant characteristics.Additionally,the PDMS primer possesses the capacity to retain low surface energy modifiers.Simultaneously,the PDMS primer serves as a reservoir for a low surface energy modifier,enhancing the self-repairing properties of the TiO_(2)-PDMS composite coating.This composite coating exhibits effective self-cleaning capabilities against many forms of contaminants,including liquids,solids,and slurries.
文摘Wire⁃Electrical Discharge Machining(WEDM)process can create any complex contour in any conducting material,regardless of its strength or hardness,with higher accuracy.Present experimental investigation aims to determine suitable input process/machining parameters,e.g.pulse on time(TON),peak current(IP),wire feed rate(WF),and pulse off time(TOFF),for optimizing the process performances,namely,cutting rate,kerf width,average roughness value of the machined surface,micro hardness,and surface crack density.Since four input parameters are considered in the present investigation,and each parameter is assumed to vary at three different levels(i.e.low,medium,high),the Taguchi L9 Orthogonal Array(OA)design approach has been used for the experimental purpose to enhance the process effiency.Similarly,a simple and popular multiresponse optimization approach,namely Grey Relational Analysis(GRA),is used to optimize five performance characteristics(output responses)simultaneously.The optimum process variables obtained are:TON of 110μs,TOFF of 40μs,IP of 10 A,and WF of 6 mm/min.These optimum process variables are validated with confirmatory experiment.The relative impact of input variables is determined using the Analysis of Variance(ANOVA)technique.Finally,correlations between individual outputs with different input parameters are established.This work will be helpful for industry personnel to use this machining process in a techno⁃economic way.
基金supported by H2020-MSCA-RISE-778104–ThermaSMART,Royal Society(IEC\NSFC\211210)doctoral degree scholarship of China Scholarship Council(CSC).
文摘Control of the wetting properties of biomimetic functional surfaces is a desired functionality in many applications.In this paper,the photoresist SU-8 was used as fabrication material.A silicon wafer was used as a substrate to prepare a biomimetic surface with different surface roughness and micro-pillars arranged in array morphology.The evaporation dynamics and interfacial heat transfer processes of deionised water droplets on the bioinspired microstructure surface were experimentally studied.The study not only proves the feasibility of preparing hydrophilic biomimetic functional surfaces directly through photoresist materials and photolithography technology but also shows that by adjusting the structural parameters and arrangement of the surface micro-pillar structure,the wettability of the biomimetic surface can be significantly linearly regulated,thereby effectively affecting the heat and mass transfer process at the droplet liquid-vapour interface.Analysis of the results shows that by controlling the biomimetic surface microstructure,the wettability can be enhanced by about 22%at most,the uniformity of the temperature distribution at the liquid-vapour interface can be improved by about 34%,and the average evaporation rate can be increased by about 28%.This study aims to provide some guidance for the research on bionic surface design based on photoresist materials.
基金funded by the National Natural Science Foundation of China (Grant nos. 42272333 and 42377154)the China Association for Science and Technology Youth Talent Support Program for PhD Students.
文摘The primary objective of this work is to improve our understanding of the mechanical involvements of two-order roughness in shear.First,wavelet analysis is used to separate the waviness(first-order)and unevenness(second-order)from four granite joint surfaces,with roughness characterized using Grasselli’s 3D morphology parameters.The results reveal that first-order roughness is more pronounced than second-order roughness,highlighting the dominant role of waviness in joint surface roughness.Additionally,the variation in first-order roughness with strike direction corresponds to the total roughness,while second-order roughness remains largely constant,indicating that roughness anisotropy is primarily driven by waviness.Then,direct shear tests on joint replicas are performed to investigate the contributions of both roughness orders to peak shear strength.The results show that the peak dilation angle is closely related to first-order roughness,while the shear component angle is closely associated with second-order roughness,both exhibiting a linear correlation.Based on these findings,relationships are established between the angles and their respective roughness orders.Finally,a joint shear strength criterion based on two-order roughness is proposed.A comparative analysis of prediction accuracy reveals that the average relative error for the proposed criterion is 13.79%,while the errors for Xia's,Yang's,and Ban's criteria are 15.19%,16.29%,and 13.87%,respectively.It demonstrates the proposed criterion can predict the peak shear strength of rock joints.
文摘Glass,with its valuable properties,finds extensive use in aerospace,optics,and biomedical fields.Owing to its low fracture toughness,glass typically fractures in a brittle manner during machining,resulting in poor surface quality.This paper presents an experimental investigation of vibration-assisted machining(VAM)techniques to enhance the machining of glass materials.A novel high-frequency two-dimensional VAM system specifically designed for glass is introduced,and slot milling experiments are conducted using ultrasonic high-frequency vibrations.A low-frequency nonresonant VAM system is also employed for comparison purposes.A comprehensive examination is made of the effects of various machining parameters,such as feed rate,cutting speeds,and vibration parameters,including vibration modes and amplitudes,on the machining performance of glass.Surface roughness,edge chipping generation,and tool wear are thoroughly characterized using scanning electron microscopy.The findings demonstrate that under specific machining and vibration parameters,the proposed ultrasonic vibration-assisted micro-milling(UVAMM)system can achieve a nanometric surface roughness Ra for glass.The UVAMM system offers enhanced surface quality,improved edge quality,and reduced tool wear compared with conventional machining techniques.This study provides valuable insights and directions for the application of 2D VAM systems in achieving superior machining results for glass components at small scales with nanometric surface finishes.
基金the National Natural Science Foundation of China(Grant No.52309130)the Natural Science Foundation of Shandong Province(Grant No.ZR2022QD004).
文摘The mineralogy and texture of granite have been found to have a pronounced effect on its mechanical behavior.However,the precise manner in which the texture of granite affects the shear behavior of fractures remains enigmatic.In this study,fine-grained granite(FG)and coarse-grained granite(CG)were used to create tensile fractures with surface roughness(i.e.joint roughness coefficient(JRC))within the range of 5.48-8.34 and 12.68-16.5,respectively.The pre-fractured specimens were then subjected to direct shear tests under normal stresses of 1-30 MPa.The results reveal that shear strengths are smaller and stick-slip behaviors are more intense for FG fractures than for CG fractures,which is attributed to the different conditions of the shear surface constrained by the grain size.The smaller grain size in FG contributes to the smoother fracture surface and lower shear strength.The negative friction rate parameter a-b for both CG and FG fractures and the larger shear stiffness for FG than for CG fractures can account for the more intense stick-slip behaviors in FG fractures.The relative crack density for the post-shear CG fractures is greater than that of the FG fractures under the same normal stress,both of which decrease with the distance away from the shear surface following the power law.Moreover,the damage of CG fracture extends to a larger extent beneath the surface compared with the FG fracture.Our findings demonstrate that the grain size of the host rock exerts a significant influence on the fracture roughness,and thus should be incorporated into the assessment of fault slip behavior to better understand the role of mineralogy and texture in seismic activities.
基金supported by the National Natural Science Foundation of China (Nos. 52474161, and 52404093)Fundamental Research Program of Shanxi Province (Nos. 202303021222168 and 202203021221143)+1 种基金Taiyuan University of Science and Technology Scientific Research Initial Funding (No. 20242103)the Postdoctoral Research Foundation of China(No. 2023M733778)。
文摘The fracture surfaces of coal-rock masses formed under mining-induced stress generally exhibit complex geometries, and the fracture geometry is one of the primary factors affecting the seepage characteristics of coal-rock penetrating fracture. This paper investigates the seepage characteristics of 5 groups of coal penetrating fracture(CPF) with different joint roughness coefficients(JRCs). Based on 3D morphology scanner tests and hydraulic coupling tests, a characterization method of effective geometric parameters in fracture surfaces under various confining pressures was improved, and a relationship between effective geometric parameters and the confining pressure is established. The results indicate that the nonlinear flow behavior in a CPF primarily includes three types: non-Newtonian fluid seepage under high confining pressure and low JRC, non-Darcy seepage under low confining pressure and high JRC, and the whole process of seepage characteristics between these two conditions. Among them, nonNewtonian fluid seepage is caused by significant fracture expansion, while non-Darcy seepage can be attributed to turbulence effects. During the seepage process, the geometric parameters with different JRC fracture samples all exhibit exponential changes with the increase of confining pressure. In addition,under high confining pressure, the effective contact ratio, effective fracture aperture, and void deviation ratio with high JRC fracture samples under high confining pressure increase by 93.5%, 67.4%, and 24.9%,respectively, compared with those of low JRC fracture samples. According to the variation of geometric parameters in a CPF with external stress, a seepage model considering geometric parameters in a CPF is proposed. By introducing the root mean square error(RMSE) and coefficient of determination(R2) to evaluate the error and goodness of fit between model curves and experimental data, it is found that the theoretical curves of model in this paper have the best matching with the experimental data. The average values of RMSE and R2for model in this paper are 0.002 and 0.70, respectively, which are better than models in the existing literature.
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.
