Based on superelastic damping application in structural engineering, the damping characteristics of commercial Ti-50.8Ni(mole fraction, %) alloy have been systematically studied by adjusting frequency of mechanical sh...Based on superelastic damping application in structural engineering, the damping characteristics of commercial Ti-50.8Ni(mole fraction, %) alloy have been systematically studied by adjusting frequency of mechanical shock, temperature, stress, strain and number of cycling. The results show that at extremely low frequency mechanical shock at room temperature, the superelastic damping capacity increases with controlled strain, and such capacity of each cycle is greater than 50%. When the frequency of mechanical shock is 0.10.3 Hz, the superelastic damping capacity above room temperature is relatively large at high strain; when the temperature approaches to M_d, the damping begins at low stress. For specimen cycled under 0.5 Hz, above 6% strain mechanical shock at relatively high temperature, further large-strain cycling exhibits more than 35% damping capacity. The superelastic damping of trained specimen is relatively stable at 2050 ℃ and 0.10.5 Hz frequency mechanical shock.展开更多
A series of true triaxial unloading tests are conducted on sandstone specimens with a single structural plane to investigate their mechanical behaviors and failure characteristics under different in situ stress states...A series of true triaxial unloading tests are conducted on sandstone specimens with a single structural plane to investigate their mechanical behaviors and failure characteristics under different in situ stress states.The experimental results indicate that the dip angle of structural plane(θ)and the intermediate principal stress(σ2)have an important influence on the peak strength,cracking mode,and rockburst severity.The peak strength exhibits a first increase and then decrease as a function ofσ2 for a constantθ.However,whenσ2 is constant,the maximum peak strength is obtained atθof 90°,and the minimum peak strength is obtained atθof 30°or 45°.For the case of an inclined structural plane,the crack type at the tips of structural plane transforms from a mix of wing and anti-wing cracks to wing cracks with an increase inσ2,while the crack type around the tips of structural plane is always anti-wing cracks for the vertical structural plane,accompanied by a series of tensile cracks besides.The specimens with structural plane do not undergo slabbing failure regardless ofθ,and always exhibit composite tensile-shear failure whatever theσ2 value is.With an increase inσ2 andθ,the intensity of the rockburst is consistent with the tendency of the peak strength.By analyzing the relationship between the cohesion(c),internal friction angle(φ),andθin sandstone specimens,we incorporateθinto the true triaxial unloading strength criterion,and propose a modified linear Mogi-Coulomb criterion.Moreover,the crack propagation mechanism at the tips of structural plane,and closure degree of the structural plane under true triaxial unloading conditions are also discussed and summarized.This study provides theoretical guidance for stability assessment of surrounding rocks containing geological structures in deep complex stress environments.展开更多
Structural Health Monitoring(SHM)systems play a key role in managing buildings and infrastructure by delivering vital insights into their strength and structural integrity.There is a need for more efficient techniques...Structural Health Monitoring(SHM)systems play a key role in managing buildings and infrastructure by delivering vital insights into their strength and structural integrity.There is a need for more efficient techniques to detect defects,as traditional methods are often prone to human error,and this issue is also addressed through image processing(IP).In addition to IP,automated,accurate,and real-time detection of structural defects,such as cracks,corrosion,and material degradation that conventional inspection techniques may miss,is made possible by Artificial Intelligence(AI)technologies like Machine Learning(ML)and Deep Learning(DL).This review examines the integration of computer vision and AI techniques in Structural Health Monitoring(SHM),investigating their effectiveness in detecting various forms of structural deterioration.Also,it evaluates ML and DL models in SHM for their accuracy in identifying and assessing structural damage,ultimately enhancing safety,durability,and maintenance practices in the field.Key findings reveal that AI-powered approaches,especially those utilizing IP and DL models like CNNs,significantly improve detection efficiency and accuracy,with reported accuracies in various SHM tasks.However,significant research gaps remain,including challenges with the consistency,quality,and environmental resilience of image data,a notable lack of standardized models and datasets for training across diverse structures,and concerns regarding computational costs,model interpretability,and seamless integration with existing systems.Future work should focus on developing more robust models through data augmentation,transfer learning,and hybrid approaches,standardizing protocols,and fostering interdisciplinary collaboration to overcome these limitations and achieve more reliable,scalable,and affordable SHM systems.展开更多
The rise of deep learning has brought about transformative advancements in both scientific research and engineering applications.The 2024 Nobel Prizes,particularly in Physics and Chemistry,highlighted the revolutionar...The rise of deep learning has brought about transformative advancements in both scientific research and engineering applications.The 2024 Nobel Prizes,particularly in Physics and Chemistry,highlighted the revolutionary impact of deep learning,with AlphaFold’s breakthrough in protein structure prediction exemplifying its potential.This review explores the historical evolution of deep learning,from its foundational theories in neural networks and connectionism to its modern applications in various fields.Focus is given to its use in geotechnical engineering,particularly in geological disaster prediction,tunnel safety monitoring,and structural design optimization.The integration of deep learning models such as Convolutional Neural Networks(CNNs),Recurrent Neural Networks(RNNs),and Transformers has enabled significant progress in analyzing complex,unstructured data,offering innovative solutions to longstanding engineering challenges.The review also examines the opportunities and challenges faced by the field,advocating for interdisciplinary collaboration and open data sharing to further unlock deep learning’s potential in advancing both scientific and engineering disciplines.As deep learning continues to evolve,it promises to drive further innovation,shaping the future of engineering practices and scientific discovery.展开更多
Drains play an important role in seepage control in geotechnical engineering.The enormous number and one-dimensional(1D)geometry of drainage holes make their nature difficult to be accurately modeled in groundwater fl...Drains play an important role in seepage control in geotechnical engineering.The enormous number and one-dimensional(1D)geometry of drainage holes make their nature difficult to be accurately modeled in groundwater flow simulation.It has been well understood that drains function by presenting discharge boundaries,which can be characterized by water head,no-flux,unilateral or mixed water head-unilateral boundary condition.It has been found after years of practices that the flow simulation may become erroneous if the transitions among the drain boundary conditions are not properly considered.For this,a rigorous algorithm is proposed in this study to detect the onset of transitions among the water head,noflux and mixed water head-unilateral boundary conditions for downwards-drilled drainage holes,which theoretically completes the description of drain boundary conditions.After verification against a numerical example,the proposed algorithm is applied to numerical modeling of groundwater flow through a gravity dam foundation.The simulation shows that for hundreds of downwards-drilled drainage holes used to be prescribed with water head boundary condition,56%and 2%of them are transitioned to mixed water head-unilateral and no-flux boundary conditions,respectively.The phreatic surface around the drains will be overestimated by 25e33 m without the use of the mixed boundary condition.For the first time,this study underscores the importance of the mixed water head-unilateral boundary condition and the proposed transition algorithm in drain modeling,which may become more essential for simulation of transient flow because of groundwater dynamics.展开更多
Cemented and mechanically clamped types of end fittings(fitting-C and fitting-M)are commonly used in transformer bushings.During the Luding Ms 6.8 earthquake that occurred in China on September 5,2022,all transformer ...Cemented and mechanically clamped types of end fittings(fitting-C and fitting-M)are commonly used in transformer bushings.During the Luding Ms 6.8 earthquake that occurred in China on September 5,2022,all transformer bushings with the two types of end fittings in a 500 kV substation were damaged.Post-earthquake field investigations were conducted,and the failures of the two types of bushings were compared.Two elementary simulation models of the transformer-bushing systems were developed to simulate the engineering failures,and further compute their seismic responses for comparison.The results indicate that the hitch lugs of the connection flange are structurally harmful to seismic resistance.Fitting-M can decrease the bending stiffness of the bushing due to the flexible sealing rubber gasket.Since it provides a more flexible connection that dissipates energy,the peak accelerations and relative displacements at the top of the bushing are significantly lower than those of the bushing with fitting-C.Compared with fitting-C,fitting-M transfers the high-stress areas from the connection flange to the root of the porcelain,so the latter becomes the most vulnerable component.Fitting-M increases the failure risk of the low-strength porcelain,indicating the unsuitability of applying it in high-intensity fortification regions.展开更多
In underground engineering,the detection of structural cracks on tunnel surfaces stands as a pivotal task in ensuring the health and reliability of tunnel structures.However,the dim and dusty environment inherent to u...In underground engineering,the detection of structural cracks on tunnel surfaces stands as a pivotal task in ensuring the health and reliability of tunnel structures.However,the dim and dusty environment inherent to under-ground engineering poses considerable challenges to crack segmentation.This paper proposes a crack segmentation algorithm termed as Focused Detection for Subsurface Cracks YOLOv8(FDSC-YOLOv8)specifically designed for underground engineering structural surfaces.Firstly,to improve the extraction of multi-layer convolutional features,the fixed convolutional module is replaced with a deformable convolutional module.Secondly,the model’s receptive field is enhanced by introducing a multi-branch convolutional module,improving the extraction of shallow features for small targets.Next,the Dynamic Snake Convolution module is incorporated to enhance the extraction capability for slender and weak cracks.Finally,the Convolutional Block Attention Module(CBAM)module is employed to achieve better target determination.The FDSC-YOLOv8s algorithm’s mAP50 and mAP50-95 reach 96.5%and 66.4%,according to the testing data.展开更多
A conceptual model of intermittent joints is introduced to the cyclic shear test in the laboratory to explore the effects of loading parameters on its shear behavior under cyclic shear loading.The results show that th...A conceptual model of intermittent joints is introduced to the cyclic shear test in the laboratory to explore the effects of loading parameters on its shear behavior under cyclic shear loading.The results show that the loading parameters(initial normal stress,normal stiffness,and shear velocity)determine propagation paths of the wing and secondary cracks in rock bridges during the initial shear cycle,creating different morphologies of macroscopic step-path rupture surfaces and asperities on them.The differences in stress state and rupture surface induce different cyclic shear responses.It shows that high initial normal stress accelerates asperity degradation,raises shear resistance,and promotes compression of intermittent joints.In addition,high normal stiffness provides higher normal stress and shear resistance during the initial cycles and inhibits the dilation and compression of intermittent joints.High shear velocity results in a higher shear resistance,greater dilation,and greater compression.Finally,shear strength is most sensitive to initial normal stress,followed by shear velocity and normal stiffness.Moreover,average dilation angle is most sensitive to initial normal stress,followed by normal stiffness and shear velocity.During the shear cycles,frictional coefficient is affected by asperity degradation,backfilling of rock debris,and frictional area,exhibiting a non-monotonic behavior.展开更多
A complex geological environment with faults can be encountered in the process of coal mining.Fault activation can cause instantaneous structure slipping,releasing a significant amount of elastic strain energy during ...A complex geological environment with faults can be encountered in the process of coal mining.Fault activation can cause instantaneous structure slipping,releasing a significant amount of elastic strain energy during underground coal mining.This would trigger strong rockburst disasters.To understand the occurrence of fault-slip induced rockbursts,we developed a physical model test system for fault-slip induced rockbursts in coal mine drifts.The boundary energy storage(BES)loading apparatus and bottom rapid retraction(BRR)apparatus are designed to realize energy compensation and continuous boundary stress transfer of the surrounding rocks for instantaneous fault slip,as well as to provide space for the potential fault slip.Taking the typical fault-slip induced rockburst in the Xinjulong Coal Mine,China,as the background,we conducted a model test using the test system.The deformation and stress in the rock surrounding the drift and the support unit force during fault slip are analyzed.The deformation and failure characteristics and dynamic responses of drifts under fault-slip induced rockbursts are obtained.The test results illustrate the rationality and effectiveness of the test system.Finally,corresponding recommendations and prospects are proposed based on our findings.展开更多
As coal mining depth increases,the combined effects of high stress,mining stress,and fault structures make dynamic impact hazards more frequent.The reproduction of dynamic impact phenomena is basis for studying their ...As coal mining depth increases,the combined effects of high stress,mining stress,and fault structures make dynamic impact hazards more frequent.The reproduction of dynamic impact phenomena is basis for studying their occurrence patterns and control mechanisms.Physical simulation test represents an efficacious methodology.However,there is currently a lack of simulation devices that can effectively simulate two types of dynamic impact phenomena,including high stress and fault slip dynamic impact.To solve aforementioned issues,the physical simulation test system for dynamic impact in deep roadways developed by authors is employed to carry out comparative tests of high stress and fault slip dynamic impact.The phenomena of high stress and fault slip dynamic impact are reproduced successfully.A comparative analysis is conducted on dynamic phenomena,stress evolution,roadway deformation,and support force.The high stress dynamic impact roadway instability mode,which is characterized by the release of high energy accompanied by symmetric damage,and the fault slip dynamic impact roadway instability mode,which is characterized by the propagation of unilateral stress waves accompanied by asymmetric damage,are clarified.On the basis,the differentiated control concepts for different types of dynamic impact in deep roadways are proposed.展开更多
The recently developed SCCDS composite tube,a novel variant of the pipe-in-pipe(PIP)structure,demonstrates strong potential for subsea pipeline applications.However,theoretical research regarding its structural behavi...The recently developed SCCDS composite tube,a novel variant of the pipe-in-pipe(PIP)structure,demonstrates strong potential for subsea pipeline applications.However,theoretical research regarding its structural behavior under compression-torsion loading and bearing capacity calculations remains limited,particularly concerning the influence of dual hydraulic pressures during operation.This study examines the impact of dual hydraulic pressures on the compressive-torsional behavior of SCCDS composite tubes.A finite element(FE)model was developed and validated against experimental results,comparing failure modes,full-range loading curves,and bearing capacity to elucidate the working mechanism under dual pressures.A parametric study was then conducted to examine the effects of geometric-physical parameters.Results demonstrate that dual pressures substantially enhance the bearing capacity of sandwich concrete by increasing the normal contact stress at the interface.Increasing concrete strength(f_(c))provides minimal enhancement to torsional resistance compared to the yielding strengths of outer tube(f_(yo))and inner tube(f_(yi)).Higher diameter-to-thickness ratios of outer tube(D_(o)/t_(o))and inner tube(D_(i)/t_(i))significantly reduce torsional capacity.At 1000 m water depth,increasing the D_(o)/t_(o)ratio from 27.5 to 36.67,55,and 110 reduces bearing capacity by 11.17%,23.08%,and 36.14%respectively.Strict measures should be implemented to prevent substantial reductions in strength and ductility for SCCDS composite tubes with large hollow ratios(e.g.,χ=0.849)or high axial compression ratios(e.g.,n=0.8).The study proposes a modified calculation method for determining N-T curves that incorporates dual hydraulic pressure effects,providing guidance for performance evaluation of novel SCCDS composite tubes in deep-sea engineering.展开更多
Grouting has been the most effective approach to mitigate water inrush disasters in underground engineering due to its ability to plug groundwater and enhance rock strength.Nevertheless,there is a lack of potent numer...Grouting has been the most effective approach to mitigate water inrush disasters in underground engineering due to its ability to plug groundwater and enhance rock strength.Nevertheless,there is a lack of potent numerical tools for assessing the grouting effectiveness in water-rich fractured strata.In this study,the hydro-mechanical coupled discontinuous deformation analysis(HM-DDA)is inaugurally extended to simulate the grouting process in a water-rich discrete fracture network(DFN),including the slurry migration,fracture dilation,water plugging in a seepage field,and joint reinforcement after coagulation.To validate the capabilities of the developed method,several numerical examples are conducted incorporating the Newtonian fluid and Bingham slurry.The simulation results closely align with the analytical solutions.Additionally,a set of compression tests is conducted on the fresh and grouted rock specimens to verify the reinforcement method and calibrate the rational properties of reinforced joints.An engineering-scale model based on a real water inrush case of the Yonglian tunnel in a water-rich fractured zone has been established.The model demonstrates the effectiveness of grouting reinforcement in mitigating water inrush disaster.The results indicate that increased grouting pressure greatly affects the regulation of water outflow from the tunnel face and the prevention of rock detachment face after excavation.展开更多
During normal de-ballasting operations for floating docks,each ballast pump independently manages a specific group of ballast tanks.However,when a pump malfunctions,a connection valve between the two groups of ballast...During normal de-ballasting operations for floating docks,each ballast pump independently manages a specific group of ballast tanks.However,when a pump malfunctions,a connection valve between the two groups of ballast water systems is opened.This allows the adjacent pump to serve as a helper pump,simultaneously controlling two groups of ballast water systems.This study explores a full-scale floating dock’s dynamic behaviours during the de-ballasting operations under this situation through a numerical model.In the developed numerical model,the dock is described as a six-degree-of-freedom rigid body which is subjected to hydrostatic,hydrodynamic,and mooring loads.A hydraulic model of the piping network of the malfunctioning pump and the helper pump is proposed.A modified P-controller regulates opening angles of all tank valves for minimal pitch and roll.Two configurations of the floating dock,i.e.,a single floating dock and a floating dock with an onboard vessel,are considered.The numerical results show that the optimal helper pumps can be identified regarding the pumps’total de-ballasting capacity and the dock’s stability.The most severe scenarios can be determined in term of the dock’s maximum draught differences caused by its roll and pitch.The observed maximum draught differences remain small relative to the dock’s width,indicating the effectiveness of employing helper pumps and the proposed automatic ballast control strategy for one-pump malfunction scenarios.展开更多
The evaluation of rock mass quality and its mechanical properties is crucial for tunnel construction.The basic quality(BQ)method is the national standard for rock mass classification in China,with the BQ value determi...The evaluation of rock mass quality and its mechanical properties is crucial for tunnel construction.The basic quality(BQ)method is the national standard for rock mass classification in China,with the BQ value determined by the uniaxial compressive strength(UCS)and the integrity index(Kv).However,traditional rock mechanics testing methods have inherent limitations,which complicate the rapid evaluation of rock mass quality at tunnel sites.Digital drilling process monitoring(DPM)offers a novel approach for evaluating rock mass quality and its mechanical properties.A hydraulic rotary drilling rig,equipped with the DPM system,was used to conduct digital drilling tests at the tunnel face.The DPM data for the net drilling process and each sub-process were then analyzed.The correlations between DPM parameter indices and rock mechanical parameters were investigated.Finally,the rock mass quality and its mechanical properties along three boreholes were evaluated.The results indicate that drilling speed in the linear zone(V_(DPM))is quantitatively correlated with rock UCS.Higher UCS values of the drilled rocks correspond to lower V_(DPM) values of the drilling rig.The variability in specific energy is associated with structural disturbances within the rock mass.There is an approximately linear relationship between the standard deviation of normalized specific energy and rock mass K_(v) across the three boreholes.The rock mass quality along drilling depth generally ranges from good(Ⅰ-Ⅱ)to poor(Ⅲ-Ⅴ).This digitalization method provides more detailed information for tunnel stability analysis and design optimization than geological survey data.展开更多
During the development blasting of circular tunnels, the detonation of multiple blastholes arranged onconcentric circles induces a complex dynamic response in the surrounding rocks. This process involvesmultiple blast...During the development blasting of circular tunnels, the detonation of multiple blastholes arranged onconcentric circles induces a complex dynamic response in the surrounding rocks. This process involvesmultiple blast loadings, static stress unloadings, and stress redistributions. In this study, the dynamicstresses of the surrounding rocks during development blasting, considering multiple blasting-unloadingstages with exponential paths and triangular paths (linear simplified paths of exponential paths), aresolved based on the dynamic theory and the Fourier transform method. Then, a corresponding discreteelement model is established using particle flow code (PFC). The multiple-stage dynamic stress andfracture distribution under different in situ stress levels and lateral coefficients are investigated. Theoreticalresults indicate that the peak compressive stresses in the surrounding rocks induced by bothtriangular and exponential paths are equal, while the triangular path generates greater additional dynamictensile stresses, particularly in the circumferential direction, compared to the exponential path.Numerical results show that the exponential path causes less dynamic circumferential tensile damageand forms fewer radial fractures than the triangular path in the first few blast stages;conversely, itexacerbates the damage and instability in the final blasting-unloading stage and forms more circumferentialfractures. Furthermore, the in situ stress determines which of the two opposite effects isdominant. Therefore, when using overly simplified triangular paths to evaluate the stability of surroundingrocks, potential overestimation or underestimation caused by different failure mechanismsshould be considered. Specifically, under high horizontal and vertical stresses, the static stress redistributionwith layer-by-layer blasting suppresses dynamic circumferential tensile and radial compressivedamage. The damage evolution of surrounding rocks in multi-stage blasting under different in situstresses is summarized and classified according to the damage mechanism and characteristics, which canguide blasting and support design.展开更多
During fully mechanized caving mining of thick coal seams,a large amount of strain energy accumulates in the roof,especially when the roof is thick and hard,making it difficultfor the roof to collapse naturally.When t...During fully mechanized caving mining of thick coal seams,a large amount of strain energy accumulates in the roof,especially when the roof is thick and hard,making it difficultfor the roof to collapse naturally.When the roof eventually collapses,the accumulated energy is released instantaneously,exerting a strong impact on the roadway.To address this issue,we proposed the synergistic control method of directional comprehensive pressure relief and energy-absorbing support(PREA)for roadways with hard roofs.In this study,we developed a three-dimensional physical model test apparatus for roof cutting and pressure relief.The 122108 ventilation roadway at the Caojiatan Coal Mine,which has a thick and hard roof,was taken as the engineering example.We analyzed the evolution patterns of stress and displacement in both the stope and the roadway surrounding rocks under different schemes.The PREA reinforcement mechanism for the roadway was investigated through comparative model tests between the new and original methods.The results showed that,compared to the original method,the new method reduced surrounding rock stress by up to 60.4%,and the roadway convergence decreased by up to 52.1%.Based on these results,we proposed corresponding engineering recommendations,which can guide fieldreinforcement design and application.The results demonstrate that the PREA method effectively reduces stress and ensures the safety and stability of the roadway.展开更多
Understanding the anchorage performance of en-echelon joints under cyclic shear loading is crucial for optimizing support strategies in jointed rock masses.This study examines the anchorage effects on enechelon joints...Understanding the anchorage performance of en-echelon joints under cyclic shear loading is crucial for optimizing support strategies in jointed rock masses.This study examines the anchorage effects on enechelon joints with various orientations using laboratory cyclic shear tests.By comparing unbolted and bolted en-echelon joints,we analyze shear zone damage,shear properties,dilatancy,energy absorption,and acoustic emission characteristics to evaluate anchoring effects across shear cycles and joint orientations.Results reveal that bolted en-echelon joints experience more severe shear zone damage after cycles,with bolt deformation correlating to shear zone width.Bolted en-echelon joints exhibit faster shear strength deterioration and higher cumulative strength loss compared to unbolted ones,with losses ranging from 20.04%to 72.76%.The compressibility of en-echelon joints reduces the anchoring effect during shear cycles,leading to lower shear strength of bolted en-echelon joints in later stages of shear cycles compared to unbolted ones.Bolts reinforce en-echelon joints more effectively at non-positive angles,with the best performance observed at 0°and-60°.Anchorage accelerates the transition from rolling friction to sliding friction in the shear zone,enhancing energy absorption,which is crucial for rock projects under dynamic shear loading.Additionally,rock bolts expedite the transition of the cumulative AE hits and cumulative AE energy curves from rapid to steady growth,indicating that strong bolt-rock interactions accelerate crack initiation,propagation,and energy release.展开更多
Blast-loaded reinforced concrete(RC)slabs should fail under a ductile bending mechanism enabling high energy absorption capacity.Hence,brittle shear failure must be avoided.However,due to the uncertainties related to ...Blast-loaded reinforced concrete(RC)slabs should fail under a ductile bending mechanism enabling high energy absorption capacity.Hence,brittle shear failure must be avoided.However,due to the uncertainties related to the materials,geometry,and resistance models,it may be difficult to predict which failure mode will prevail.This study analytically estimated the probability of premature flexural shear failure of slender RC one-way slabs subjected to blast loading considering such uncertainties and using the Monte Carlo(MC)method.The resistance models in Eurocode 2 were adopted.Specimens with and without shear reinforcement were analyzed.Bending failure was shown to be the most likely failure mode in the studied slabs.However,the probability of shear failure developing before bending failure was still relatively high,particularly for slabs without stirrups.To increase the confidence level concerning the preferred failure mechanism,the article proposes an overstrength factor to magnify the shear demand of the blast-loaded RC slab.Values of the overstrength factor for different target reliability levels were calculated.The study also found that the probability of premature shear failure increased with increasing amount of longitudinal reinforcement and decreasing slenderness.Likewise,greater impulse was found to enhance the risk for shear failure.展开更多
This study aims to understand the effect of injection rate on injection-induced fracture activation in granite.We performed water injection-induced slip tests on samples containing either a smooth or a rough fracture ...This study aims to understand the effect of injection rate on injection-induced fracture activation in granite.We performed water injection-induced slip tests on samples containing either a smooth or a rough fracture at four different injection rates under undrained conditions and monitored the acoustic emission(AE)signals during the tests.Experimental results reveal that the critical activation fluid pressure is related to the injection rate,pressure diffusion rate,stress state,and fracture roughness.For the smooth fracture,as the injection rate increases,the critical activation fluid pressure increases significantly,while the injection rate has little effect on the critical activation fluid pressure of the rough fracture.The quasi-static slip distance of fractures decreases as the injection rate increases,with rough fractures exhibiting a greater overall slip distance compared to smooth fractures.The number of AE events per unit sliding distance increases with the injection rate,while the global b value decreases.These results indicate that higher injection rates produce more large-magnitude AE events and more severe slip instability and asperity damage.We established a linkage between fluid injection volume,injection rate,and AE events using the seismogenic index(Σ).The smooth fracture exhibits a steadily increasingΣwith the elapse of injection time,and the rate of increase is higher at higher injection rates;while the rough fracture is featured by a fluctuatingΣ,signifying the intermittent occurrence of large-magnitude AE events associated with the damage of larger fracture asperities.Our results highlight the importance of fracture surface heterogeneity on injection-induced fracture activation and slip.展开更多
文摘Based on superelastic damping application in structural engineering, the damping characteristics of commercial Ti-50.8Ni(mole fraction, %) alloy have been systematically studied by adjusting frequency of mechanical shock, temperature, stress, strain and number of cycling. The results show that at extremely low frequency mechanical shock at room temperature, the superelastic damping capacity increases with controlled strain, and such capacity of each cycle is greater than 50%. When the frequency of mechanical shock is 0.10.3 Hz, the superelastic damping capacity above room temperature is relatively large at high strain; when the temperature approaches to M_d, the damping begins at low stress. For specimen cycled under 0.5 Hz, above 6% strain mechanical shock at relatively high temperature, further large-strain cycling exhibits more than 35% damping capacity. The superelastic damping of trained specimen is relatively stable at 2050 ℃ and 0.10.5 Hz frequency mechanical shock.
基金supports from the National Natural Science Foundation of China (Grant Nos.52004143 and 52374095)the open fund for the Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines (Grant No.SKLMRDPC21KF06).
文摘A series of true triaxial unloading tests are conducted on sandstone specimens with a single structural plane to investigate their mechanical behaviors and failure characteristics under different in situ stress states.The experimental results indicate that the dip angle of structural plane(θ)and the intermediate principal stress(σ2)have an important influence on the peak strength,cracking mode,and rockburst severity.The peak strength exhibits a first increase and then decrease as a function ofσ2 for a constantθ.However,whenσ2 is constant,the maximum peak strength is obtained atθof 90°,and the minimum peak strength is obtained atθof 30°or 45°.For the case of an inclined structural plane,the crack type at the tips of structural plane transforms from a mix of wing and anti-wing cracks to wing cracks with an increase inσ2,while the crack type around the tips of structural plane is always anti-wing cracks for the vertical structural plane,accompanied by a series of tensile cracks besides.The specimens with structural plane do not undergo slabbing failure regardless ofθ,and always exhibit composite tensile-shear failure whatever theσ2 value is.With an increase inσ2 andθ,the intensity of the rockburst is consistent with the tendency of the peak strength.By analyzing the relationship between the cohesion(c),internal friction angle(φ),andθin sandstone specimens,we incorporateθinto the true triaxial unloading strength criterion,and propose a modified linear Mogi-Coulomb criterion.Moreover,the crack propagation mechanism at the tips of structural plane,and closure degree of the structural plane under true triaxial unloading conditions are also discussed and summarized.This study provides theoretical guidance for stability assessment of surrounding rocks containing geological structures in deep complex stress environments.
文摘Structural Health Monitoring(SHM)systems play a key role in managing buildings and infrastructure by delivering vital insights into their strength and structural integrity.There is a need for more efficient techniques to detect defects,as traditional methods are often prone to human error,and this issue is also addressed through image processing(IP).In addition to IP,automated,accurate,and real-time detection of structural defects,such as cracks,corrosion,and material degradation that conventional inspection techniques may miss,is made possible by Artificial Intelligence(AI)technologies like Machine Learning(ML)and Deep Learning(DL).This review examines the integration of computer vision and AI techniques in Structural Health Monitoring(SHM),investigating their effectiveness in detecting various forms of structural deterioration.Also,it evaluates ML and DL models in SHM for their accuracy in identifying and assessing structural damage,ultimately enhancing safety,durability,and maintenance practices in the field.Key findings reveal that AI-powered approaches,especially those utilizing IP and DL models like CNNs,significantly improve detection efficiency and accuracy,with reported accuracies in various SHM tasks.However,significant research gaps remain,including challenges with the consistency,quality,and environmental resilience of image data,a notable lack of standardized models and datasets for training across diverse structures,and concerns regarding computational costs,model interpretability,and seamless integration with existing systems.Future work should focus on developing more robust models through data augmentation,transfer learning,and hybrid approaches,standardizing protocols,and fostering interdisciplinary collaboration to overcome these limitations and achieve more reliable,scalable,and affordable SHM systems.
基金support provided by the Hebei Province Full-Time Recruitment of National High-Level Innovative Talents Research Project(Grant No.2023HBQZYCSB004).
文摘The rise of deep learning has brought about transformative advancements in both scientific research and engineering applications.The 2024 Nobel Prizes,particularly in Physics and Chemistry,highlighted the revolutionary impact of deep learning,with AlphaFold’s breakthrough in protein structure prediction exemplifying its potential.This review explores the historical evolution of deep learning,from its foundational theories in neural networks and connectionism to its modern applications in various fields.Focus is given to its use in geotechnical engineering,particularly in geological disaster prediction,tunnel safety monitoring,and structural design optimization.The integration of deep learning models such as Convolutional Neural Networks(CNNs),Recurrent Neural Networks(RNNs),and Transformers has enabled significant progress in analyzing complex,unstructured data,offering innovative solutions to longstanding engineering challenges.The review also examines the opportunities and challenges faced by the field,advocating for interdisciplinary collaboration and open data sharing to further unlock deep learning’s potential in advancing both scientific and engineering disciplines.As deep learning continues to evolve,it promises to drive further innovation,shaping the future of engineering practices and scientific discovery.
基金Financial support from the National Natural Science Foundation of China(Grant Nos.51925906 and U2340228)the Natural Science Foundation of Hubei Province(Grant No.2022CFA028)is acknowledged.
文摘Drains play an important role in seepage control in geotechnical engineering.The enormous number and one-dimensional(1D)geometry of drainage holes make their nature difficult to be accurately modeled in groundwater flow simulation.It has been well understood that drains function by presenting discharge boundaries,which can be characterized by water head,no-flux,unilateral or mixed water head-unilateral boundary condition.It has been found after years of practices that the flow simulation may become erroneous if the transitions among the drain boundary conditions are not properly considered.For this,a rigorous algorithm is proposed in this study to detect the onset of transitions among the water head,noflux and mixed water head-unilateral boundary conditions for downwards-drilled drainage holes,which theoretically completes the description of drain boundary conditions.After verification against a numerical example,the proposed algorithm is applied to numerical modeling of groundwater flow through a gravity dam foundation.The simulation shows that for hundreds of downwards-drilled drainage holes used to be prescribed with water head boundary condition,56%and 2%of them are transitioned to mixed water head-unilateral and no-flux boundary conditions,respectively.The phreatic surface around the drains will be overestimated by 25e33 m without the use of the mixed boundary condition.For the first time,this study underscores the importance of the mixed water head-unilateral boundary condition and the proposed transition algorithm in drain modeling,which may become more essential for simulation of transient flow because of groundwater dynamics.
基金National Natural Science Foundation of China under Grant No.51878508。
文摘Cemented and mechanically clamped types of end fittings(fitting-C and fitting-M)are commonly used in transformer bushings.During the Luding Ms 6.8 earthquake that occurred in China on September 5,2022,all transformer bushings with the two types of end fittings in a 500 kV substation were damaged.Post-earthquake field investigations were conducted,and the failures of the two types of bushings were compared.Two elementary simulation models of the transformer-bushing systems were developed to simulate the engineering failures,and further compute their seismic responses for comparison.The results indicate that the hitch lugs of the connection flange are structurally harmful to seismic resistance.Fitting-M can decrease the bending stiffness of the bushing due to the flexible sealing rubber gasket.Since it provides a more flexible connection that dissipates energy,the peak accelerations and relative displacements at the top of the bushing are significantly lower than those of the bushing with fitting-C.Compared with fitting-C,fitting-M transfers the high-stress areas from the connection flange to the root of the porcelain,so the latter becomes the most vulnerable component.Fitting-M increases the failure risk of the low-strength porcelain,indicating the unsuitability of applying it in high-intensity fortification regions.
基金This research was funded by the National Key R&D Program of China(Project:Key Technologies and Equipment for Multi-View Stereoscopic Disaster Detection and Emergency Response to Derived Disasters in Underground Spaces,2022YFC3005600)the National Natural Science Foundation of China(52378402)+2 种基金Shandong Provincial Natural Science Foundation Youth Project(ZR2022QE021 and ZR202211100077)Shandong Province Higher Education Young Innovative Team Project(2022KJ037)State Key Laboratory of Precision Blasting and Hubei Key Laboratory of Blasting Engineering,Jianghan University(PBSKL2022C03),funding from Shandong Railway Investment Holding Group Co.,Ltd.(“Key Technologies for Rapid and Intelligent Construction of Large Section High-Speed Railway Tunnels in Low Mountain and Hilly Areas”and“Intelligent Construction Trolley Equipment and Key Technologies for the Lining of Ultra-Long Open Tunnel Sections”).
文摘In underground engineering,the detection of structural cracks on tunnel surfaces stands as a pivotal task in ensuring the health and reliability of tunnel structures.However,the dim and dusty environment inherent to under-ground engineering poses considerable challenges to crack segmentation.This paper proposes a crack segmentation algorithm termed as Focused Detection for Subsurface Cracks YOLOv8(FDSC-YOLOv8)specifically designed for underground engineering structural surfaces.Firstly,to improve the extraction of multi-layer convolutional features,the fixed convolutional module is replaced with a deformable convolutional module.Secondly,the model’s receptive field is enhanced by introducing a multi-branch convolutional module,improving the extraction of shallow features for small targets.Next,the Dynamic Snake Convolution module is incorporated to enhance the extraction capability for slender and weak cracks.Finally,the Convolutional Block Attention Module(CBAM)module is employed to achieve better target determination.The FDSC-YOLOv8s algorithm’s mAP50 and mAP50-95 reach 96.5%and 66.4%,according to the testing data.
基金financially supported by the National Natural Science Foundation of China(Grant No.42172292)Taishan Scholars Project Special Funding,and Shandong Energy Group(Grant No.SNKJ 2022A01-R26).
文摘A conceptual model of intermittent joints is introduced to the cyclic shear test in the laboratory to explore the effects of loading parameters on its shear behavior under cyclic shear loading.The results show that the loading parameters(initial normal stress,normal stiffness,and shear velocity)determine propagation paths of the wing and secondary cracks in rock bridges during the initial shear cycle,creating different morphologies of macroscopic step-path rupture surfaces and asperities on them.The differences in stress state and rupture surface induce different cyclic shear responses.It shows that high initial normal stress accelerates asperity degradation,raises shear resistance,and promotes compression of intermittent joints.In addition,high normal stiffness provides higher normal stress and shear resistance during the initial cycles and inhibits the dilation and compression of intermittent joints.High shear velocity results in a higher shear resistance,greater dilation,and greater compression.Finally,shear strength is most sensitive to initial normal stress,followed by shear velocity and normal stiffness.Moreover,average dilation angle is most sensitive to initial normal stress,followed by normal stiffness and shear velocity.During the shear cycles,frictional coefficient is affected by asperity degradation,backfilling of rock debris,and frictional area,exhibiting a non-monotonic behavior.
基金support from the National Natural Science Foundation of China (Grant Nos.51927807,42077267 and 42277174).
文摘A complex geological environment with faults can be encountered in the process of coal mining.Fault activation can cause instantaneous structure slipping,releasing a significant amount of elastic strain energy during underground coal mining.This would trigger strong rockburst disasters.To understand the occurrence of fault-slip induced rockbursts,we developed a physical model test system for fault-slip induced rockbursts in coal mine drifts.The boundary energy storage(BES)loading apparatus and bottom rapid retraction(BRR)apparatus are designed to realize energy compensation and continuous boundary stress transfer of the surrounding rocks for instantaneous fault slip,as well as to provide space for the potential fault slip.Taking the typical fault-slip induced rockburst in the Xinjulong Coal Mine,China,as the background,we conducted a model test using the test system.The deformation and stress in the rock surrounding the drift and the support unit force during fault slip are analyzed.The deformation and failure characteristics and dynamic responses of drifts under fault-slip induced rockbursts are obtained.The test results illustrate the rationality and effectiveness of the test system.Finally,corresponding recommendations and prospects are proposed based on our findings.
基金supported by the National Natural Science Foundation of China(Nos.U24A2088,42177130,42277174,and 42477166).
文摘As coal mining depth increases,the combined effects of high stress,mining stress,and fault structures make dynamic impact hazards more frequent.The reproduction of dynamic impact phenomena is basis for studying their occurrence patterns and control mechanisms.Physical simulation test represents an efficacious methodology.However,there is currently a lack of simulation devices that can effectively simulate two types of dynamic impact phenomena,including high stress and fault slip dynamic impact.To solve aforementioned issues,the physical simulation test system for dynamic impact in deep roadways developed by authors is employed to carry out comparative tests of high stress and fault slip dynamic impact.The phenomena of high stress and fault slip dynamic impact are reproduced successfully.A comparative analysis is conducted on dynamic phenomena,stress evolution,roadway deformation,and support force.The high stress dynamic impact roadway instability mode,which is characterized by the release of high energy accompanied by symmetric damage,and the fault slip dynamic impact roadway instability mode,which is characterized by the propagation of unilateral stress waves accompanied by asymmetric damage,are clarified.On the basis,the differentiated control concepts for different types of dynamic impact in deep roadways are proposed.
基金supported by the High-level Talent Research Startup Fund(Grant No.1608722024)of Xi’an University of Archit-ectureTechnology and the Shaanxi Province High-level Youth Talents Program(Grant No.Z20240589).
文摘The recently developed SCCDS composite tube,a novel variant of the pipe-in-pipe(PIP)structure,demonstrates strong potential for subsea pipeline applications.However,theoretical research regarding its structural behavior under compression-torsion loading and bearing capacity calculations remains limited,particularly concerning the influence of dual hydraulic pressures during operation.This study examines the impact of dual hydraulic pressures on the compressive-torsional behavior of SCCDS composite tubes.A finite element(FE)model was developed and validated against experimental results,comparing failure modes,full-range loading curves,and bearing capacity to elucidate the working mechanism under dual pressures.A parametric study was then conducted to examine the effects of geometric-physical parameters.Results demonstrate that dual pressures substantially enhance the bearing capacity of sandwich concrete by increasing the normal contact stress at the interface.Increasing concrete strength(f_(c))provides minimal enhancement to torsional resistance compared to the yielding strengths of outer tube(f_(yo))and inner tube(f_(yi)).Higher diameter-to-thickness ratios of outer tube(D_(o)/t_(o))and inner tube(D_(i)/t_(i))significantly reduce torsional capacity.At 1000 m water depth,increasing the D_(o)/t_(o)ratio from 27.5 to 36.67,55,and 110 reduces bearing capacity by 11.17%,23.08%,and 36.14%respectively.Strict measures should be implemented to prevent substantial reductions in strength and ductility for SCCDS composite tubes with large hollow ratios(e.g.,χ=0.849)or high axial compression ratios(e.g.,n=0.8).The study proposes a modified calculation method for determining N-T curves that incorporates dual hydraulic pressure effects,providing guidance for performance evaluation of novel SCCDS composite tubes in deep-sea engineering.
基金supported by the China Scholarship Council(CSC,Grant No.202108050072)JSPS KAKENHI(Grant No.JP19KK0121)。
文摘Grouting has been the most effective approach to mitigate water inrush disasters in underground engineering due to its ability to plug groundwater and enhance rock strength.Nevertheless,there is a lack of potent numerical tools for assessing the grouting effectiveness in water-rich fractured strata.In this study,the hydro-mechanical coupled discontinuous deformation analysis(HM-DDA)is inaugurally extended to simulate the grouting process in a water-rich discrete fracture network(DFN),including the slurry migration,fracture dilation,water plugging in a seepage field,and joint reinforcement after coagulation.To validate the capabilities of the developed method,several numerical examples are conducted incorporating the Newtonian fluid and Bingham slurry.The simulation results closely align with the analytical solutions.Additionally,a set of compression tests is conducted on the fresh and grouted rock specimens to verify the reinforcement method and calibrate the rational properties of reinforced joints.An engineering-scale model based on a real water inrush case of the Yonglian tunnel in a water-rich fractured zone has been established.The model demonstrates the effectiveness of grouting reinforcement in mitigating water inrush disaster.The results indicate that increased grouting pressure greatly affects the regulation of water outflow from the tunnel face and the prevention of rock detachment face after excavation.
基金The article is a result of joined research performed during the project:“A Floating Dock Digital Twin towards Efficient,Safer and Autonomous Docking Operations”-NOR/POLNOR/DigiFloDock/0009/2019-00 which is cofinanced by the programme“Applied research”under the Norwegian Financial Mechanisms 2014-2021 POLNOR 2019-Digital and Industry.
文摘During normal de-ballasting operations for floating docks,each ballast pump independently manages a specific group of ballast tanks.However,when a pump malfunctions,a connection valve between the two groups of ballast water systems is opened.This allows the adjacent pump to serve as a helper pump,simultaneously controlling two groups of ballast water systems.This study explores a full-scale floating dock’s dynamic behaviours during the de-ballasting operations under this situation through a numerical model.In the developed numerical model,the dock is described as a six-degree-of-freedom rigid body which is subjected to hydrostatic,hydrodynamic,and mooring loads.A hydraulic model of the piping network of the malfunctioning pump and the helper pump is proposed.A modified P-controller regulates opening angles of all tank valves for minimal pitch and roll.Two configurations of the floating dock,i.e.,a single floating dock and a floating dock with an onboard vessel,are considered.The numerical results show that the optimal helper pumps can be identified regarding the pumps’total de-ballasting capacity and the dock’s stability.The most severe scenarios can be determined in term of the dock’s maximum draught differences caused by its roll and pitch.The observed maximum draught differences remain small relative to the dock’s width,indicating the effectiveness of employing helper pumps and the proposed automatic ballast control strategy for one-pump malfunction scenarios.
基金The support provided by the National Natural Science Foundation of China(Grant No.42277160)the Natural Science Foundation of Hubei Province(Grant No.2021CFA081)the Fundamental Research Funds for the Central Universities(Grant No.2042023kf0210)is gratefully acknowledged.
文摘The evaluation of rock mass quality and its mechanical properties is crucial for tunnel construction.The basic quality(BQ)method is the national standard for rock mass classification in China,with the BQ value determined by the uniaxial compressive strength(UCS)and the integrity index(Kv).However,traditional rock mechanics testing methods have inherent limitations,which complicate the rapid evaluation of rock mass quality at tunnel sites.Digital drilling process monitoring(DPM)offers a novel approach for evaluating rock mass quality and its mechanical properties.A hydraulic rotary drilling rig,equipped with the DPM system,was used to conduct digital drilling tests at the tunnel face.The DPM data for the net drilling process and each sub-process were then analyzed.The correlations between DPM parameter indices and rock mechanical parameters were investigated.Finally,the rock mass quality and its mechanical properties along three boreholes were evaluated.The results indicate that drilling speed in the linear zone(V_(DPM))is quantitatively correlated with rock UCS.Higher UCS values of the drilled rocks correspond to lower V_(DPM) values of the drilling rig.The variability in specific energy is associated with structural disturbances within the rock mass.There is an approximately linear relationship between the standard deviation of normalized specific energy and rock mass K_(v) across the three boreholes.The rock mass quality along drilling depth generally ranges from good(Ⅰ-Ⅱ)to poor(Ⅲ-Ⅴ).This digitalization method provides more detailed information for tunnel stability analysis and design optimization than geological survey data.
基金supported by the National Natural Science Foundation of China(Grant Nos.51927808 and 41630642)the Postgraduate Innovation Fund Project of Hunan Province(Grant No.CX20200242).
文摘During the development blasting of circular tunnels, the detonation of multiple blastholes arranged onconcentric circles induces a complex dynamic response in the surrounding rocks. This process involvesmultiple blast loadings, static stress unloadings, and stress redistributions. In this study, the dynamicstresses of the surrounding rocks during development blasting, considering multiple blasting-unloadingstages with exponential paths and triangular paths (linear simplified paths of exponential paths), aresolved based on the dynamic theory and the Fourier transform method. Then, a corresponding discreteelement model is established using particle flow code (PFC). The multiple-stage dynamic stress andfracture distribution under different in situ stress levels and lateral coefficients are investigated. Theoreticalresults indicate that the peak compressive stresses in the surrounding rocks induced by bothtriangular and exponential paths are equal, while the triangular path generates greater additional dynamictensile stresses, particularly in the circumferential direction, compared to the exponential path.Numerical results show that the exponential path causes less dynamic circumferential tensile damageand forms fewer radial fractures than the triangular path in the first few blast stages;conversely, itexacerbates the damage and instability in the final blasting-unloading stage and forms more circumferentialfractures. Furthermore, the in situ stress determines which of the two opposite effects isdominant. Therefore, when using overly simplified triangular paths to evaluate the stability of surroundingrocks, potential overestimation or underestimation caused by different failure mechanismsshould be considered. Specifically, under high horizontal and vertical stresses, the static stress redistributionwith layer-by-layer blasting suppresses dynamic circumferential tensile and radial compressivedamage. The damage evolution of surrounding rocks in multi-stage blasting under different in situstresses is summarized and classified according to the damage mechanism and characteristics, which canguide blasting and support design.
基金supported by the National Natural Science Foundation of China(Grant Nos.U24A2088 and 42277174)the Fundamental Research Funds for the Central Universities,China(Grant No.2024JCCXSB01).
文摘During fully mechanized caving mining of thick coal seams,a large amount of strain energy accumulates in the roof,especially when the roof is thick and hard,making it difficultfor the roof to collapse naturally.When the roof eventually collapses,the accumulated energy is released instantaneously,exerting a strong impact on the roadway.To address this issue,we proposed the synergistic control method of directional comprehensive pressure relief and energy-absorbing support(PREA)for roadways with hard roofs.In this study,we developed a three-dimensional physical model test apparatus for roof cutting and pressure relief.The 122108 ventilation roadway at the Caojiatan Coal Mine,which has a thick and hard roof,was taken as the engineering example.We analyzed the evolution patterns of stress and displacement in both the stope and the roadway surrounding rocks under different schemes.The PREA reinforcement mechanism for the roadway was investigated through comparative model tests between the new and original methods.The results showed that,compared to the original method,the new method reduced surrounding rock stress by up to 60.4%,and the roadway convergence decreased by up to 52.1%.Based on these results,we proposed corresponding engineering recommendations,which can guide fieldreinforcement design and application.The results demonstrate that the PREA method effectively reduces stress and ensures the safety and stability of the roadway.
基金financially supported by the National Natural Science Foundation of China (No.42172292)Taishan Scholars Project Special Funding,and Shandong Energy Group (No.SNKJ2022A01-R26)funded by the China Scholarship Council (CSC No.202006220274)。
文摘Understanding the anchorage performance of en-echelon joints under cyclic shear loading is crucial for optimizing support strategies in jointed rock masses.This study examines the anchorage effects on enechelon joints with various orientations using laboratory cyclic shear tests.By comparing unbolted and bolted en-echelon joints,we analyze shear zone damage,shear properties,dilatancy,energy absorption,and acoustic emission characteristics to evaluate anchoring effects across shear cycles and joint orientations.Results reveal that bolted en-echelon joints experience more severe shear zone damage after cycles,with bolt deformation correlating to shear zone width.Bolted en-echelon joints exhibit faster shear strength deterioration and higher cumulative strength loss compared to unbolted ones,with losses ranging from 20.04%to 72.76%.The compressibility of en-echelon joints reduces the anchoring effect during shear cycles,leading to lower shear strength of bolted en-echelon joints in later stages of shear cycles compared to unbolted ones.Bolts reinforce en-echelon joints more effectively at non-positive angles,with the best performance observed at 0°and-60°.Anchorage accelerates the transition from rolling friction to sliding friction in the shear zone,enhancing energy absorption,which is crucial for rock projects under dynamic shear loading.Additionally,rock bolts expedite the transition of the cumulative AE hits and cumulative AE energy curves from rapid to steady growth,indicating that strong bolt-rock interactions accelerate crack initiation,propagation,and energy release.
基金supported by Trafikverket(Swedish Transport Administration)Fortifikationsverket(Swedish Fortifications Agency)Myndigheten för samhällsskydd och beredskap(Swedish Civil Contingencies Agency).
文摘Blast-loaded reinforced concrete(RC)slabs should fail under a ductile bending mechanism enabling high energy absorption capacity.Hence,brittle shear failure must be avoided.However,due to the uncertainties related to the materials,geometry,and resistance models,it may be difficult to predict which failure mode will prevail.This study analytically estimated the probability of premature flexural shear failure of slender RC one-way slabs subjected to blast loading considering such uncertainties and using the Monte Carlo(MC)method.The resistance models in Eurocode 2 were adopted.Specimens with and without shear reinforcement were analyzed.Bending failure was shown to be the most likely failure mode in the studied slabs.However,the probability of shear failure developing before bending failure was still relatively high,particularly for slabs without stirrups.To increase the confidence level concerning the preferred failure mechanism,the article proposes an overstrength factor to magnify the shear demand of the blast-loaded RC slab.Values of the overstrength factor for different target reliability levels were calculated.The study also found that the probability of premature shear failure increased with increasing amount of longitudinal reinforcement and decreasing slenderness.Likewise,greater impulse was found to enhance the risk for shear failure.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFB2390300)the National Natural Science Foundation of China(Grant No.42172292)Yinlin Ji is grateful for the support by the Helmholtz Association's Initiative and Networking Fund for the Helmholtz Young Investigator Group ARES(Contract No.VH-NG-1516).
文摘This study aims to understand the effect of injection rate on injection-induced fracture activation in granite.We performed water injection-induced slip tests on samples containing either a smooth or a rough fracture at four different injection rates under undrained conditions and monitored the acoustic emission(AE)signals during the tests.Experimental results reveal that the critical activation fluid pressure is related to the injection rate,pressure diffusion rate,stress state,and fracture roughness.For the smooth fracture,as the injection rate increases,the critical activation fluid pressure increases significantly,while the injection rate has little effect on the critical activation fluid pressure of the rough fracture.The quasi-static slip distance of fractures decreases as the injection rate increases,with rough fractures exhibiting a greater overall slip distance compared to smooth fractures.The number of AE events per unit sliding distance increases with the injection rate,while the global b value decreases.These results indicate that higher injection rates produce more large-magnitude AE events and more severe slip instability and asperity damage.We established a linkage between fluid injection volume,injection rate,and AE events using the seismogenic index(Σ).The smooth fracture exhibits a steadily increasingΣwith the elapse of injection time,and the rate of increase is higher at higher injection rates;while the rough fracture is featured by a fluctuatingΣ,signifying the intermittent occurrence of large-magnitude AE events associated with the damage of larger fracture asperities.Our results highlight the importance of fracture surface heterogeneity on injection-induced fracture activation and slip.
