Nowadays, the main communication object of Internet is human-human. But it is foreseeable that in the near future any object will have a unique identification and can be addressed and con- nected. The Internet will ex...Nowadays, the main communication object of Internet is human-human. But it is foreseeable that in the near future any object will have a unique identification and can be addressed and con- nected. The Internet will expand to the Internet of Things. IPv6 is the cornerstone of the Internet of Things. In this paper, we investigate a fast active worm, referred to as topological worm, which can propagate twice to more than three times faster tl^an a traditional scan-based worm. Topological worm spreads over AS-level network topology, making traditional epidemic models invalid for modeling the propagation of it. For this reason, we study topological worm propagation relying on simulations. First, we propose a new complex weighted network mod- el, which represents the real IPv6 AS-level network topology. And then, a new worm propagation model based on the weighted network model is constructed, which descries the topological worm propagation over AS-level network topology. The simulation results verify the topological worm model and demonstrate the effect of parameters on the propagation.展开更多
Trivial elastic waveguides induced by line defects and nontrivial elastic waveguides protected by topological edge states have been extensively examined in planar waveguide systems.Despite these investigations,little ...Trivial elastic waveguides induced by line defects and nontrivial elastic waveguides protected by topological edge states have been extensively examined in planar waveguide systems.Despite these investigations,little is known about topologically protected bulk states and their resulting robust transmission properties,especially in nonplanar elastic waveguides with folded,curved,and twisted surfaces.Elastic Dirac waveguides with robust boundary-induced bulk states are presented.These states arise from the truncated boundaries of bulks with linear Dirac conical dispersions,differing from topologically protected edge states ensured by the bulk-edge correspondence.Experimental proof is provided,in which boundary-induced bulk states show robustly high-throughput transmissions along the waveguides,even with folded,curved,and twisted surfaces.These results not only open up new avenues for examining novel topological phenomena about bulk but also offer new platforms for developing topological devices with nonplanar surfaces.展开更多
This study investigates the relationship between atmospheric stratification (i.e., static stability given by N^(2)) and the vertical energy transfer of stationary planetary waves, and further illustrates the underlyin...This study investigates the relationship between atmospheric stratification (i.e., static stability given by N^(2)) and the vertical energy transfer of stationary planetary waves, and further illustrates the underlying physical mechanism. Specifically, for the simplified case of constant stratospheric N^(2), the refractive index square of planetary waves has a theoretical tendency to increase first and then decrease with an increased N^(2), whereas the group velocity weakens. Mechanistically, this behavior can be understood as an intensified suppression of vertical isentropic surface displacement caused by meridional heat transport of planetary waves under strong N^(2) conditions. Observational analysis corroborates this finding, demonstrating a reduction in the vertical-propagation velocity of waves with increased N^(2). A linear, quasi- geostrophic, mid-latitude beta-plane model with a constant background westerly wind and a prescribed N^(2) applicable to the stratosphere is used to obtain analytic solutions. In this model, the planetary waves are initiated by steady energy influx from the lower boundary. The analysis indicates that under strong N^(2) conditions, the amplitude of planetary waves can be sufficiently increased by the effective energy convergence due to the slowing vertical energy transfer, resulting in a streamfunction response in this model that contains more energy. For N^(2) with a quasi-linear vertical variation, the results bear a resemblance to the constant case, except that the wave amplitude and oscillating frequency show some vertical variations.展开更多
A number of porous models having the similar statistical characteristics of pores and physical properties with natural sandstones have been produced using reactive powder concrete(RPC) and polystyrenes.Spit-Hopkinson-...A number of porous models having the similar statistical characteristics of pores and physical properties with natural sandstones have been produced using reactive powder concrete(RPC) and polystyrenes.Spit-Hopkinson-Pressure-Bar tests and CT scans have been carried out on the models with the various porosities to probe the performance of wave propagations and the responses of pores and the matrix during wave propagations.It is shown that porosities significantly influence wave propagations.For an identical impact strain rate,the greater the porosity is,the larger the amplitude of the reflected wave appears,the more the peak in the reflected wave presents,and the smaller the amplitude of the trans-mitted wave turns out.A single peak emerges in the reflected wave when the porosity falls down to 5%.The larger the impact strain rate,the much remarkable the phenomena.The energy-dissipated ratio of porous models,i.e.,WJ /WI,linearly increases with the increment of porosities.The ratio is sensitive to the impact strain rate.Differences in the performance of wave propagations and energy dissipation result from the varied mechanisms that pores response to impacts.For the porosity less than 10%,the mechanism appears to be a process fracturing the matrix to generate new surfaces or pores.Energy has primarily been dissipated in creating new surfaces or pores.No apparent pore deformation takes place.The impact strain rate takes little effect on pore geometry.For the porosity of 15% or more,the mechanism works depending on the impact strain rate.When a low impact strain rate applies,the mechanism still appears to crack the matrix to generate surfaces or pores,but the amount is lower as compared to the case with a low porosity.If a large impact stain rate applies,the mechanism combines both fracturing the matrix and deforming the pores,with the deforming pores predominating.The vast majority of energy has been dissipated to deform pores.Only high porosity and impact strain rate can bring significant deformation to the pores.The proposed eccentricity of pores is capable of character-izing the geometry of pores and its change during wave propagations.展开更多
This paper deals with propagations of singularities in solutions to a parabolic system coupled with nonlocal nonlinear sources. The estimates for the four possible blow-up rates as well as the boundary layer profiles ...This paper deals with propagations of singularities in solutions to a parabolic system coupled with nonlocal nonlinear sources. The estimates for the four possible blow-up rates as well as the boundary layer profiles are established. The critical exponent of the system is determined also.展开更多
A cell-centered Lagrangian scheme is developed for the numerical simula-tion of wave propagations in one dimensional(1D)elastic-plasticflow.The classical elastic-plastic material model initially proposed by Wilkins is ...A cell-centered Lagrangian scheme is developed for the numerical simula-tion of wave propagations in one dimensional(1D)elastic-plasticflow.The classical elastic-plastic material model initially proposed by Wilkins is adopted.The linear elas-tic model(Hooke’s Law),perfectly plastic model and von Mises yield criterion are used to describe the constitutive relationship of elastic-plastic solid.The second-order ex-tension of this scheme is achieved by a linear reconstruction method.Various numer-ical tests are simulated to check the capability of this scheme in capturing nonlinear elastic-plastic waves.Compared with the well-developed operator splitting method used in simulating elastic-plasticflow,this scheme is more accurate due to the con-sideration of a list of 64 different types of the nonlinear elastic-plastic waves when constructing the elastic-perfectly plastic Riemann solver.The numerical simulations of typical examples show competitive results.展开更多
Using the software ANSYS-19.2/Explicit Dynamics,this study performedfinite-element modeling of the large-diameter steel pipeline cross-section for the Beineu-Bozoy-Shymkent gas pipeline with a non-through straight crac...Using the software ANSYS-19.2/Explicit Dynamics,this study performedfinite-element modeling of the large-diameter steel pipeline cross-section for the Beineu-Bozoy-Shymkent gas pipeline with a non-through straight crack,strengthened by steel wire wrapping.The effects of the thread tensile force of the steel winding in the form of single rings at the crack edges and the wires with different winding diameters and pitches were also studied.The results showed that the strengthening was preferably executed at a minimum value of the thread tensile force,which was 6.4%more effective than that at its maximum value.The analysis of the influence of the winding dia-meters showed that the equivalent stresses increased by 32%from the beginning of the crack growth until the wire broke.The increment in winding diameter decelerated the disclosure of the edge crack and reduced its length by 8.2%.The analysis of the influence of the winding pitch showed that decreasing the distance between the winding turns also led to a 33.6%reduction in the length of the straight crack and a 7.9%reduction in the maximum stres-ses on the strengthened pipeline cross-section.The analysis of the temperature effect on the pipeline material,within a range from-40℃to+50℃,resulted in a crack length change of up to 5.8%.As the temperature dropped,the crack length decreased.Within such a temperature range,the maximum stresses were observed along the cen-tral area of the crack,which were equal to 413 MPa at+50℃and 440 MPa at-40℃.The results also showed that the presence of the steel winding in the pipeline significantly reduced the length of crack propagation up to 8.4 times,depending on the temperature effect and design parameters of prestressing.This work integrated the existing methods for crack localization along steel gas pipelines.展开更多
Traffic engineering such as tunnels in various altitudinal gradient zone are at risk of accidental explosion,which can damage personnel and equipment.Accurate prediction of the distribution pattern of explosive loads ...Traffic engineering such as tunnels in various altitudinal gradient zone are at risk of accidental explosion,which can damage personnel and equipment.Accurate prediction of the distribution pattern of explosive loads and shock wave propagation process in semi-enclosed structures at various altitude environment is key research focus in the fields of explosion shock and fluid dynamics.The effect of altitude on the propagation of shock waves in tunnels was investigated by conducting explosion test and numerical simulation.Based on the experimental and numerical simulation results,a prediction model for the attenuation of the peak overpressure of tunnel shock waves at different altitudes was established.The results showed that the peak overpressure decreased at the same measurement points in the tunnel entrance under the high altitude condition.In contrast,an increase in altitude accelerated the propagation speed of the shock wave in the tunnel.The average error between the peak shock wave overpressure obtained using the overpressure prediction formula and the measured test data was less than15%,the average error between the propagation velocity of shock waves predicted values and the test data is less than 10%.The method can effectively predict the overpressure attenuation of blast wave in tunnel at various altitudes.展开更多
Supercritical CO_(2)(SC-CO_(2))fracturing stands out a promising waterless stimulation technique in the development of unconventional resources.While numerous studies have delved into the inducedfracture mechanism of ...Supercritical CO_(2)(SC-CO_(2))fracturing stands out a promising waterless stimulation technique in the development of unconventional resources.While numerous studies have delved into the inducedfracture mechanism of SC-CO_(2),the small scale of rock samples and synthetic materials used in many studies have limited a comprehensive understanding of fracture propagation in unconventional formations.In this study,cubic tight sandstone samples with dimensions of 300 mm were employed to conduct SC-CO_(2)fractu ring experiments under true-triaxial stre ss conditions.The spatial morphology and quantitative attributes of fracture induced by water and SC-CO_(2)fracturing were compared,while the impact of in-situ stress on fracture propagation was also investigated.The results indicate that the SCCO_(2)fracturing takes approximately ten times longer than water fracturing.Furthermore,under identical stress condition,the breakdown pressure(BP)for SC-CO_(2)fracturing is nearly 25%lower than that for water fracturing.A quantitative analysis of fracture morphology reveals that water fracturing typically produces relatively simple fracture pattern,with the primary fracture distribution predominantly controlled by bedding planes.In contrast,SC-CO_(2)fracturing results in a more complex fracture morphology.As the differential of horizontal principal stress increases,the BP for SC-CO_(2)fractured rock exhibits a downward trend,and the induced fracture morphology becomes more simplified.Moreover,the presence of abnormal in-situ stress leads to a further increase in the BP for SC-CO_(2)fracturing,simultaneously enhancing the development of a more conductive fracture network.These findings provide critical insights into the efficiency and behavior of SC-CO_(2)fracturing in comparison to traditional water-based fracturing,offering valuable implication for its potential applications in unconventional reservoirs.展开更多
Prepulse combined hydraulic fracturing facilitates the development of fracture networks by integrating prepulse hydraulic loading with conventional hydraulic fracturing.The formation mechanisms of fracture networks be...Prepulse combined hydraulic fracturing facilitates the development of fracture networks by integrating prepulse hydraulic loading with conventional hydraulic fracturing.The formation mechanisms of fracture networks between hydraulic and pre-existing fractures under different prepulse loading parameters remain unclear.This research investigates the impact of prepulse loading parameters,including the prepulse loading number ratio(C),prepulse loading stress ratio(S),and prepulse loading frequency(f),on the formation of fracture networks between hydraulic and pre-existing fractures,using both experimental and numerical methods.The results suggest that low prepulse loading stress ratios and high prepulse loading number ratios are advantageous loading modes.Multiple hydraulic fractures are generated in the specimen under the advantageous loading modes,facilitating the development of a complex fracture network.Fatigue damage occurs in the specimen at the prepulse loading stage.The high water pressure at the secondary conventional hydraulic fracturing promotes the growth of hydraulic fractures along the damage zones.This allows the hydraulic fractures to propagate deeply and interact with pre-existing fractures.Under advantageous loading conditions,multiple hydraulic fractures can extend to pre-existing fractures,and these hydraulic fractures penetrate or propagate along pre-existing fractures.Especially when the approach angle is large,the damage range in the specimen during the prepulse loading stage increases,resulting in the formation of more hydraulic fractures.展开更多
The real-time monitoring of fracture propagation during hydraulic fracturing is crucial for obtaining a deeper understanding of fracture morphology and optimizing hydraulic fracture designs.Accurate measurements of ke...The real-time monitoring of fracture propagation during hydraulic fracturing is crucial for obtaining a deeper understanding of fracture morphology and optimizing hydraulic fracture designs.Accurate measurements of key fracture parameters,such as the fracture height and width,are particularly important to ensure efficient oilfield development and precise fracture diagnosis.This study utilized the optical frequency domain reflectometer(OFDR)technique in physical simulation experiments to monitor fractures during indoor true triaxial hydraulic fracturing experiments.The results indicate that the distributed fiber optic strain monitoring technology can efficiently capture the initiation and expansion of fractures.In horizontal well monitoring,the fiber strain waterfall plot can be used to interpret the fracture width,initiation location,and expansion speed.The fiber response can be divided into three stages:strain contraction convergence,strain band formation,and postshutdown strain rate reversal.When the fracture does not contact the fiber,a dual peak strain phenomenon occurs in the fiber and gradually converges as the fracture approaches.During vertical well monitoring in adjacent wells,within the effective monitoring range of the fiber,the axial strain produced by the fiber can represent the fracture height with an accuracy of 95.6%relative to the actual fracture height.This study provides a new perspective on real-time fracture monitoring.The response patterns of fiber-induced strain due to fractures can help us better understand and assess the dynamic fracture behavior,offering significant value for the optimization of oilfield development and fracture diagnostic techniques.展开更多
This study primarily investigates the rock fracture mechanism of bottom cushion layer blasting and explores the effects of the bottom cushion layer on rock fragmentation.It involves analyses of the evolution patterns ...This study primarily investigates the rock fracture mechanism of bottom cushion layer blasting and explores the effects of the bottom cushion layer on rock fragmentation.It involves analyses of the evolution patterns of blasting stress,characteristics of crack distribution,and rock fracture features in the specimens.First,blasting model experiments were carried out using the dynamic caustics principle to investigate the influence of bottom cushion layers and initiation methods on the integrity of the bottom rock mass.The experimental results indicate that the combined use of bottom cushion layers and inverse initiation effectively protects the integrity of the bottom rock mass.Subsequently,the process of stress wave propagation and dynamic crack propagation in rocks was simulated using the continuum-discontinuum element method(CDEM)and the Landau explosion source model,with varying thicknesses of bottom cushion layers.The numerical simulation results indicate that with increasing cushion thickness,the absorption of energy generated by the explosion becomes more pronounced,resulting in fewer cracks in the bottom rock mass.This illustrates the positive role of the cushion layer in protecting the integrity of the bottom rock mass.展开更多
Ice load on underwater vehicles breaking through ice covers from underneath is a significant concern for researchers in polar exploration,and the research on this problem is still in its early stages.Both mechanical e...Ice load on underwater vehicles breaking through ice covers from underneath is a significant concern for researchers in polar exploration,and the research on this problem is still in its early stages.Both mechanical experimental measurement and numerical simulation pose research challenges.This study focuses on the ice load of a cylinder structure breaking upward through the ice sheet form underneath in the Small Ice Model Basin of China Ship Scientific Research Center(CSSRC SIMB).A high-speed camera system was employed to observe the ice sheet failure during the tests,in which,with the loading position as center,local radial cracks and circumferential cracks were generated.A load sensor was used to measure the overall ice load during this process.Meanwhile,a numerical model was developed using LS-DYNA for validation and comparison.With this model,numerical simulation was conducted under various ice thicknesses and upgoing speeds to analyze the instantaneous curves of ice load.The calculation results were statistically analyzed under different working conditions to determine the influence of the factors on the ice load of the cylinder.The study explores the measurement method about ice load of objects vertically breaking through model ice sheet and is expected to provide some fundamental insights into the safety design of underwater structures operating in ice waters.展开更多
The crack initiation and early propagation are of great significance to the overall fatigue life of material.In order to investigate the anisotropic fracture behavior of laser metal deposited Ti-6Al-4V alloy(LMD Ti64)...The crack initiation and early propagation are of great significance to the overall fatigue life of material.In order to investigate the anisotropic fracture behavior of laser metal deposited Ti-6Al-4V alloy(LMD Ti64)during the early stage,the fourpoint bending fatigue test was carried out on specimens of three different directions,as well as the forged specimens.The results indicate the anisotropic crack initiation and early propagation of LMD Ti64.The direction perpendicular to the deposition direction exhibits a better fatigue resistance than the other two.The crack initiation position and propagation path are dominated by the microstructure in the vicinity of U-notch.LMD Ti64 has a typical small crack effect,and the early crack propagation velocities in three directions are similar.Affected by the slip system of LMD Ti64,secondary cracks frequently occur,which are often found to have an angle of 60°to the main crack.The electron backscatter diffraction analysis indicates that LMD Ti64 has preferred orientations,i.e.,strong 0001//Z texture and 001//Z texture.Their crystallographic orientation will change as the direction of columnarβgrains turns over,resulting in the fatigue anisotropy of LMD Ti64 in crack initiation and early crack propagation process.展开更多
Multi-stage and multi-cluster fracturing(MMF)is a crucial technology in unconventional oil and gas development,aiming to enhance production by creating extensive fracture networks.However,achieving uniform expansion o...Multi-stage and multi-cluster fracturing(MMF)is a crucial technology in unconventional oil and gas development,aiming to enhance production by creating extensive fracture networks.However,achieving uniform expansion of multi-cluster hydraulic fractures(HFs)in MMF remains a significant challenge.Field practice has shown that the use of temporary plugging and diversion fracturing(TPDF)can promote the balanced expansion of multi-cluster HFs.This study conducted TPDF experiments using a true triaxial fracturing simulation system setting a horizontal well completion with multi-cluster jetting perforations to investigate the equilibrium initiation and extension of multi-cluster fractures.The influence of key parameters,including cluster spacing,fracturing fluid viscosity,differential stress,and fracturing fluid injection rate,on fracture initiation and propagation was systematically examined.The results indicate that while close-spaced multi-cluster fracturing significantly increases the number of HFs,it also leads to uneven extension of HFs in their propagation.In contrast,TPDF demonstrates effectiveness in mitigating uneven HF extension,increasing the number of HFs,and creating a larger stimulated reservoir volume,ultimately leading to improved oil and gas well productivity.Moreover,under conditions of high differential stress,the differential stress within the formation exerts a stronger guiding effect in HFs,which are more closely aligned with the minimum principal stress.Low-viscosity fluids facilitate rapid and extensive fracture propagation within the rock formation.High-volume fluid injection,on the other hand,more comprehensively fills the formation.Therefore,employing lowviscosity and high-volume fracturing is advantageous for the initiation and extension of multi-cluster HFs.展开更多
The acoustic wave propagation in gas-saturated double-porosity materials composed of a microporous matrix and mesopores with arrays of plate-type resonators is investigated.A macroscopic description,established with t...The acoustic wave propagation in gas-saturated double-porosity materials composed of a microporous matrix and mesopores with arrays of plate-type resonators is investigated.A macroscopic description,established with the two-scale asymptotic homogenization method,evidences the combined effect of inner resonances on the acoustic properties of the respective effective visco-thermal fluid.One type of resonance originates from strong pore-scale fluid-structure interaction,while the other one arises from pressure diffusion.These phenomena respectively cause weakly and highly damped resonances,which are activated by internal momentum or mass sources,and can largely influence,depending on the material's morphology,either the effective fluid's dynamic density,compressibility,or both.We introduce semi-analytical models to illustrate the key effective properties of the studied multiscale metamaterials.The results provide insights for the bottom-up design of multiscale acoustic metamaterials with exotic behaviors,such as the negative,very slow,or supersonic phase velocity,as well as sub-wavelength bandgaps.展开更多
The approximately 3000 km long Tan-Lu fault zone(TLFZ)in East Asia is the longest continental strike-slip fault zone in the world and exemplifies how such a fault zone forms and propagates on a continental scale.Struc...The approximately 3000 km long Tan-Lu fault zone(TLFZ)in East Asia is the longest continental strike-slip fault zone in the world and exemplifies how such a fault zone forms and propagates on a continental scale.Structural and geochronological data from the TLFZ and surrounding regions indicate that the fault zone originated as NE/SW-striking sinistral ductile shear zones along an oblique continental convergence margin during the Triassic indentation collision between the North China Craton and the Yangtze Block.The Triassic fault zone,with a total length of about 720 km between the Dabie and Sulu orogens,exhibited an apparent sinistral offset of approximately 300 km along the TLFZ.The second stage of sinistral movement occurred in the earliest Late Jurassic,reactivating the pre-existing southern segment and propagating northwards to the southern coastline of present-day Bohai Bay,as well as forming a significant portion of the Dunhua-Mishan fault zone.The third stage of sinistral movement,in the earliest Early Cretaceous,was the most intense strike-slip movement of the Mesozoic,leading to the complete linkage of the TLFZ.This stage included further northward propagation of the southern-middle segment,both southward and northward propagation of the Dunhua-Mishan fault zone,as well as the formation of the entire Yilan-Yitong fault zone.The fourth stage,in the earliest Late Cretaceous,involved the reactivation of the entire TLFZ.Following its Triassic origin due to the indentation collision,the subduction of the Paleo-Pacific Plate and the subduction and closure of the Mongol-Okhotsk Ocean were responsible for the multi-stage sinistral movements from the Late Jurassic to the Cretaceous.The evolution of the TLFZ demonstrates that a continental-scale strike-slip fault zone(>1000 km long)forms through multiple stages of propagation and linkage in dynamic settings of plate convergence.展开更多
The southern part of East Siberia(SES)is highly vulnerable to flooding caused by the extreme precipitation events(EPEs)during summer.Building on previously detected EPEs in SES and Mongolia,we examined wave propagatio...The southern part of East Siberia(SES)is highly vulnerable to flooding caused by the extreme precipitation events(EPEs)during summer.Building on previously detected EPEs in SES and Mongolia,we examined wave propagation patterns for two periods:1982-98 and 1999-2019.Our analysis revealed distinct wave train configurations and geopotential anomalies preceding EPEs,with an increase in wave activity flux across the Northern Hemisphere,followed by a subsequent decrease during EPEs.Consequently,Eastern Siberia has experienced a significant rise in wave activity.Based on geopotential anomalies over Central Siberia accompanying EPEs,we identified two main types.The first,the ridge type,is predominant during the first period and features a meridional contrast with a positive geopotential(and temperature)anomaly over Central Siberia and a negative anomaly over the subtropical regions along the same longitude.The second type,termed the trough type,is more typical for the second period.It involves either a negative geopotential anomaly or the zonal proximity of positive and negative geopotential anomalies over Central Siberia.The trough type,marked by zonally oriented anomalies in geopotential and temperature,results in a more pronounced temperature decrease before EPEs and significant zonal temperature contrasts.Further,it is related to more stationary waves over Northern Eurasia,with persistent positive geopotential anomalies over Europe linked to quasi-stationary troughs over Central Siberia and positive anomalies east of Lake Baikal.Our findings align with shifts in boreal summer teleconnection patterns,reflecting significant changes in wave propagation patterns that have occurred since the late 1990s.展开更多
The mainstream method for extracting shale gas involves hydraulic fracturing to create fracture networks.However,as extraction depth increases,notable issues such as rapid production decline,low recovery rates,high wa...The mainstream method for extracting shale gas involves hydraulic fracturing to create fracture networks.However,as extraction depth increases,notable issues such as rapid production decline,low recovery rates,high water consumption,and resource waste become apparent.Identifying new and efficient auxiliary rock-breaking technologies is crucial for overcoming these challenges.The laser,successfully utilized in industrial production,medical treatment,and technological research,offers unique features such as good directionality,coherence,and high energy density,providing novel possibilities for addressing the limitations of existing deep reservoir transformation.This research focuses on a novel laser-assisted rock-breaking technology,with shale featuring different bedding angles as the subject of investigation.The investigation methodically explored how shale responded to thermal fracture at high temperatures when exposed to laser irradiation with different spot diameter.It investigates the spatiotemporal evolution characteristics of the shale temperature field under laser irradiation,the propagation features of cracks on shale surface,and the physicochemical fracture mechanisms.The research yields the following results:(1)The region of thermal influence of the irradiation surface can be divided into three regions based on the change of rise curve of temperature in the shale surface.(2)Based on the scanning electron microscopy(SEM)testing,combined with the macroscopic and microscopic morphological characteristics of shale fracture surfaces,it reveals significantly distinct zoning characteristics in the roughness of the rock sample’s fracture surfaces after laser irradiation.(3)The thermal fracturing process of shale under laser irradiation involves chemical reactions of constituent minerals and stress generated by the thermal expansion of shale oil in the reservoir.(4)The damage and fracture of shale under the irradiation of laser show significant bedding effect,and there are three modes of rock sample failure:Pattern T(thermal failure),Pattern T-B(thermal and bedding synergistic failure),and Pattern B(bedding failure).The research findings presented in this article serve as a foundation and reference for the theory and technology of laser-assisted shale gas extraction.展开更多
基金supported by the Ministry of Education Research Project for Returned Talents after Studying Abroadthe Ministry of Education Project of Science and Technology Basic Resource Data Platform(No.507001)+1 种基金International Scientific and Technological Cooperation Program(S2010GR0902)Chinese Universities Scientific Fund(2009RC0502)
文摘Nowadays, the main communication object of Internet is human-human. But it is foreseeable that in the near future any object will have a unique identification and can be addressed and con- nected. The Internet will expand to the Internet of Things. IPv6 is the cornerstone of the Internet of Things. In this paper, we investigate a fast active worm, referred to as topological worm, which can propagate twice to more than three times faster tl^an a traditional scan-based worm. Topological worm spreads over AS-level network topology, making traditional epidemic models invalid for modeling the propagation of it. For this reason, we study topological worm propagation relying on simulations. First, we propose a new complex weighted network mod- el, which represents the real IPv6 AS-level network topology. And then, a new worm propagation model based on the weighted network model is constructed, which descries the topological worm propagation over AS-level network topology. The simulation results verify the topological worm model and demonstrate the effect of parameters on the propagation.
基金supported by the National Natural Science Foundation of China(Grant No.12072108)the Natural Science Foundation of Hunan Province for Distinguished Young Scholars(Grant No.2022JJ10003)。
文摘Trivial elastic waveguides induced by line defects and nontrivial elastic waveguides protected by topological edge states have been extensively examined in planar waveguide systems.Despite these investigations,little is known about topologically protected bulk states and their resulting robust transmission properties,especially in nonplanar elastic waveguides with folded,curved,and twisted surfaces.Elastic Dirac waveguides with robust boundary-induced bulk states are presented.These states arise from the truncated boundaries of bulks with linear Dirac conical dispersions,differing from topologically protected edge states ensured by the bulk-edge correspondence.Experimental proof is provided,in which boundary-induced bulk states show robustly high-throughput transmissions along the waveguides,even with folded,curved,and twisted surfaces.These results not only open up new avenues for examining novel topological phenomena about bulk but also offer new platforms for developing topological devices with nonplanar surfaces.
基金supported by the National Natural Science Foundation of China(Grant No.42261134532,42405059,and U2342212)。
文摘This study investigates the relationship between atmospheric stratification (i.e., static stability given by N^(2)) and the vertical energy transfer of stationary planetary waves, and further illustrates the underlying physical mechanism. Specifically, for the simplified case of constant stratospheric N^(2), the refractive index square of planetary waves has a theoretical tendency to increase first and then decrease with an increased N^(2), whereas the group velocity weakens. Mechanistically, this behavior can be understood as an intensified suppression of vertical isentropic surface displacement caused by meridional heat transport of planetary waves under strong N^(2) conditions. Observational analysis corroborates this finding, demonstrating a reduction in the vertical-propagation velocity of waves with increased N^(2). A linear, quasi- geostrophic, mid-latitude beta-plane model with a constant background westerly wind and a prescribed N^(2) applicable to the stratosphere is used to obtain analytic solutions. In this model, the planetary waves are initiated by steady energy influx from the lower boundary. The analysis indicates that under strong N^(2) conditions, the amplitude of planetary waves can be sufficiently increased by the effective energy convergence due to the slowing vertical energy transfer, resulting in a streamfunction response in this model that contains more energy. For N^(2) with a quasi-linear vertical variation, the results bear a resemblance to the constant case, except that the wave amplitude and oscillating frequency show some vertical variations.
基金Supported by the Natural Sciences & Engineering Research Council of Canada (PGS-D2-2006)the National Basic Research Program of China ("973" Project) (Grant No. 2002CB412705)the New Century Excellent Talents Program of the Ministry of Education of China (NCET-05-0215)
文摘A number of porous models having the similar statistical characteristics of pores and physical properties with natural sandstones have been produced using reactive powder concrete(RPC) and polystyrenes.Spit-Hopkinson-Pressure-Bar tests and CT scans have been carried out on the models with the various porosities to probe the performance of wave propagations and the responses of pores and the matrix during wave propagations.It is shown that porosities significantly influence wave propagations.For an identical impact strain rate,the greater the porosity is,the larger the amplitude of the reflected wave appears,the more the peak in the reflected wave presents,and the smaller the amplitude of the trans-mitted wave turns out.A single peak emerges in the reflected wave when the porosity falls down to 5%.The larger the impact strain rate,the much remarkable the phenomena.The energy-dissipated ratio of porous models,i.e.,WJ /WI,linearly increases with the increment of porosities.The ratio is sensitive to the impact strain rate.Differences in the performance of wave propagations and energy dissipation result from the varied mechanisms that pores response to impacts.For the porosity less than 10%,the mechanism appears to be a process fracturing the matrix to generate new surfaces or pores.Energy has primarily been dissipated in creating new surfaces or pores.No apparent pore deformation takes place.The impact strain rate takes little effect on pore geometry.For the porosity of 15% or more,the mechanism works depending on the impact strain rate.When a low impact strain rate applies,the mechanism still appears to crack the matrix to generate surfaces or pores,but the amount is lower as compared to the case with a low porosity.If a large impact stain rate applies,the mechanism combines both fracturing the matrix and deforming the pores,with the deforming pores predominating.The vast majority of energy has been dissipated to deform pores.Only high porosity and impact strain rate can bring significant deformation to the pores.The proposed eccentricity of pores is capable of character-izing the geometry of pores and its change during wave propagations.
基金supported by the National Natural Science Foundation of China (Grant No. 10771024)
文摘This paper deals with propagations of singularities in solutions to a parabolic system coupled with nonlocal nonlinear sources. The estimates for the four possible blow-up rates as well as the boundary layer profiles are established. The critical exponent of the system is determined also.
基金The author would like to thank the referees for the helpful suggestions.This work is supported by National Science Foundation of China(Grants Nos.12002062,91852207,11801036,12002063 and 11972093)NSFC-NSAF Joint Fund(Grants No.U1730118)+1 种基金President Foundation of CAEP(Grant No.YZJJLX2018012)National Key Project(Grant No.GJXM92579).
文摘A cell-centered Lagrangian scheme is developed for the numerical simula-tion of wave propagations in one dimensional(1D)elastic-plasticflow.The classical elastic-plastic material model initially proposed by Wilkins is adopted.The linear elas-tic model(Hooke’s Law),perfectly plastic model and von Mises yield criterion are used to describe the constitutive relationship of elastic-plastic solid.The second-order ex-tension of this scheme is achieved by a linear reconstruction method.Various numer-ical tests are simulated to check the capability of this scheme in capturing nonlinear elastic-plastic waves.Compared with the well-developed operator splitting method used in simulating elastic-plasticflow,this scheme is more accurate due to the con-sideration of a list of 64 different types of the nonlinear elastic-plastic waves when constructing the elastic-perfectly plastic Riemann solver.The numerical simulations of typical examples show competitive results.
基金funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan(Grant No.AP19680589).
文摘Using the software ANSYS-19.2/Explicit Dynamics,this study performedfinite-element modeling of the large-diameter steel pipeline cross-section for the Beineu-Bozoy-Shymkent gas pipeline with a non-through straight crack,strengthened by steel wire wrapping.The effects of the thread tensile force of the steel winding in the form of single rings at the crack edges and the wires with different winding diameters and pitches were also studied.The results showed that the strengthening was preferably executed at a minimum value of the thread tensile force,which was 6.4%more effective than that at its maximum value.The analysis of the influence of the winding dia-meters showed that the equivalent stresses increased by 32%from the beginning of the crack growth until the wire broke.The increment in winding diameter decelerated the disclosure of the edge crack and reduced its length by 8.2%.The analysis of the influence of the winding pitch showed that decreasing the distance between the winding turns also led to a 33.6%reduction in the length of the straight crack and a 7.9%reduction in the maximum stres-ses on the strengthened pipeline cross-section.The analysis of the temperature effect on the pipeline material,within a range from-40℃to+50℃,resulted in a crack length change of up to 5.8%.As the temperature dropped,the crack length decreased.Within such a temperature range,the maximum stresses were observed along the cen-tral area of the crack,which were equal to 413 MPa at+50℃and 440 MPa at-40℃.The results also showed that the presence of the steel winding in the pipeline significantly reduced the length of crack propagation up to 8.4 times,depending on the temperature effect and design parameters of prestressing.This work integrated the existing methods for crack localization along steel gas pipelines.
基金financially supported by National Natural Science Foundation of China(Grant Nos.52378401,52278504)the Fundamental Research Funds for the Central Universities(Grant No.30922010918)。
文摘Traffic engineering such as tunnels in various altitudinal gradient zone are at risk of accidental explosion,which can damage personnel and equipment.Accurate prediction of the distribution pattern of explosive loads and shock wave propagation process in semi-enclosed structures at various altitude environment is key research focus in the fields of explosion shock and fluid dynamics.The effect of altitude on the propagation of shock waves in tunnels was investigated by conducting explosion test and numerical simulation.Based on the experimental and numerical simulation results,a prediction model for the attenuation of the peak overpressure of tunnel shock waves at different altitudes was established.The results showed that the peak overpressure decreased at the same measurement points in the tunnel entrance under the high altitude condition.In contrast,an increase in altitude accelerated the propagation speed of the shock wave in the tunnel.The average error between the peak shock wave overpressure obtained using the overpressure prediction formula and the measured test data was less than15%,the average error between the propagation velocity of shock waves predicted values and the test data is less than 10%.The method can effectively predict the overpressure attenuation of blast wave in tunnel at various altitudes.
基金funded by the National Natural Scientific Foundation of China(Nos.52304008,52404038,52474043)the China Postdoctoral Science Foundation(No.2023MD734223)+1 种基金the Key Laboratory of Well Stability and Fluid&Rock Mechanics in Oil and Gas Reservoir of Shaanxi Province(No.23JS047)the Youth Talent Lifting Program of Xi'an Science and Technology Association(No.959202413078)。
文摘Supercritical CO_(2)(SC-CO_(2))fracturing stands out a promising waterless stimulation technique in the development of unconventional resources.While numerous studies have delved into the inducedfracture mechanism of SC-CO_(2),the small scale of rock samples and synthetic materials used in many studies have limited a comprehensive understanding of fracture propagation in unconventional formations.In this study,cubic tight sandstone samples with dimensions of 300 mm were employed to conduct SC-CO_(2)fractu ring experiments under true-triaxial stre ss conditions.The spatial morphology and quantitative attributes of fracture induced by water and SC-CO_(2)fracturing were compared,while the impact of in-situ stress on fracture propagation was also investigated.The results indicate that the SCCO_(2)fracturing takes approximately ten times longer than water fracturing.Furthermore,under identical stress condition,the breakdown pressure(BP)for SC-CO_(2)fracturing is nearly 25%lower than that for water fracturing.A quantitative analysis of fracture morphology reveals that water fracturing typically produces relatively simple fracture pattern,with the primary fracture distribution predominantly controlled by bedding planes.In contrast,SC-CO_(2)fracturing results in a more complex fracture morphology.As the differential of horizontal principal stress increases,the BP for SC-CO_(2)fractured rock exhibits a downward trend,and the induced fracture morphology becomes more simplified.Moreover,the presence of abnormal in-situ stress leads to a further increase in the BP for SC-CO_(2)fracturing,simultaneously enhancing the development of a more conductive fracture network.These findings provide critical insights into the efficiency and behavior of SC-CO_(2)fracturing in comparison to traditional water-based fracturing,offering valuable implication for its potential applications in unconventional reservoirs.
基金financially supported by,the Fundamental Research Funds for the Central Universities(Grant No.2023QN1064)the China Postdoctoral Science Foundation(Grant No.2023M733772)Jiangsu Funding Program for Excellent Postdoctoral Talent(Grant No.2023ZB847)。
文摘Prepulse combined hydraulic fracturing facilitates the development of fracture networks by integrating prepulse hydraulic loading with conventional hydraulic fracturing.The formation mechanisms of fracture networks between hydraulic and pre-existing fractures under different prepulse loading parameters remain unclear.This research investigates the impact of prepulse loading parameters,including the prepulse loading number ratio(C),prepulse loading stress ratio(S),and prepulse loading frequency(f),on the formation of fracture networks between hydraulic and pre-existing fractures,using both experimental and numerical methods.The results suggest that low prepulse loading stress ratios and high prepulse loading number ratios are advantageous loading modes.Multiple hydraulic fractures are generated in the specimen under the advantageous loading modes,facilitating the development of a complex fracture network.Fatigue damage occurs in the specimen at the prepulse loading stage.The high water pressure at the secondary conventional hydraulic fracturing promotes the growth of hydraulic fractures along the damage zones.This allows the hydraulic fractures to propagate deeply and interact with pre-existing fractures.Under advantageous loading conditions,multiple hydraulic fractures can extend to pre-existing fractures,and these hydraulic fractures penetrate or propagate along pre-existing fractures.Especially when the approach angle is large,the damage range in the specimen during the prepulse loading stage increases,resulting in the formation of more hydraulic fractures.
基金supported by the National Natural Science Foundation of China(Grant No.52104060)the Natural Science Foundation of Shandong Province,China(Grant No.ZR2021QE015).
文摘The real-time monitoring of fracture propagation during hydraulic fracturing is crucial for obtaining a deeper understanding of fracture morphology and optimizing hydraulic fracture designs.Accurate measurements of key fracture parameters,such as the fracture height and width,are particularly important to ensure efficient oilfield development and precise fracture diagnosis.This study utilized the optical frequency domain reflectometer(OFDR)technique in physical simulation experiments to monitor fractures during indoor true triaxial hydraulic fracturing experiments.The results indicate that the distributed fiber optic strain monitoring technology can efficiently capture the initiation and expansion of fractures.In horizontal well monitoring,the fiber strain waterfall plot can be used to interpret the fracture width,initiation location,and expansion speed.The fiber response can be divided into three stages:strain contraction convergence,strain band formation,and postshutdown strain rate reversal.When the fracture does not contact the fiber,a dual peak strain phenomenon occurs in the fiber and gradually converges as the fracture approaches.During vertical well monitoring in adjacent wells,within the effective monitoring range of the fiber,the axial strain produced by the fiber can represent the fracture height with an accuracy of 95.6%relative to the actual fracture height.This study provides a new perspective on real-time fracture monitoring.The response patterns of fiber-induced strain due to fractures can help us better understand and assess the dynamic fracture behavior,offering significant value for the optimization of oilfield development and fracture diagnostic techniques.
基金financially supported by the National Natural Science Foundation of China(Nos.52204085 and 52104074)the Youth Science and Technology Foundation Key Laboratory for Mechanics in Fluid Solid Coupling System,Institute of Mechanics(No.E0XM040401)。
文摘This study primarily investigates the rock fracture mechanism of bottom cushion layer blasting and explores the effects of the bottom cushion layer on rock fragmentation.It involves analyses of the evolution patterns of blasting stress,characteristics of crack distribution,and rock fracture features in the specimens.First,blasting model experiments were carried out using the dynamic caustics principle to investigate the influence of bottom cushion layers and initiation methods on the integrity of the bottom rock mass.The experimental results indicate that the combined use of bottom cushion layers and inverse initiation effectively protects the integrity of the bottom rock mass.Subsequently,the process of stress wave propagation and dynamic crack propagation in rocks was simulated using the continuum-discontinuum element method(CDEM)and the Landau explosion source model,with varying thicknesses of bottom cushion layers.The numerical simulation results indicate that with increasing cushion thickness,the absorption of energy generated by the explosion becomes more pronounced,resulting in fewer cracks in the bottom rock mass.This illustrates the positive role of the cushion layer in protecting the integrity of the bottom rock mass.
文摘Ice load on underwater vehicles breaking through ice covers from underneath is a significant concern for researchers in polar exploration,and the research on this problem is still in its early stages.Both mechanical experimental measurement and numerical simulation pose research challenges.This study focuses on the ice load of a cylinder structure breaking upward through the ice sheet form underneath in the Small Ice Model Basin of China Ship Scientific Research Center(CSSRC SIMB).A high-speed camera system was employed to observe the ice sheet failure during the tests,in which,with the loading position as center,local radial cracks and circumferential cracks were generated.A load sensor was used to measure the overall ice load during this process.Meanwhile,a numerical model was developed using LS-DYNA for validation and comparison.With this model,numerical simulation was conducted under various ice thicknesses and upgoing speeds to analyze the instantaneous curves of ice load.The calculation results were statistically analyzed under different working conditions to determine the influence of the factors on the ice load of the cylinder.The study explores the measurement method about ice load of objects vertically breaking through model ice sheet and is expected to provide some fundamental insights into the safety design of underwater structures operating in ice waters.
基金National Natural Science Foundation of China(12172292,12072287)。
文摘The crack initiation and early propagation are of great significance to the overall fatigue life of material.In order to investigate the anisotropic fracture behavior of laser metal deposited Ti-6Al-4V alloy(LMD Ti64)during the early stage,the fourpoint bending fatigue test was carried out on specimens of three different directions,as well as the forged specimens.The results indicate the anisotropic crack initiation and early propagation of LMD Ti64.The direction perpendicular to the deposition direction exhibits a better fatigue resistance than the other two.The crack initiation position and propagation path are dominated by the microstructure in the vicinity of U-notch.LMD Ti64 has a typical small crack effect,and the early crack propagation velocities in three directions are similar.Affected by the slip system of LMD Ti64,secondary cracks frequently occur,which are often found to have an angle of 60°to the main crack.The electron backscatter diffraction analysis indicates that LMD Ti64 has preferred orientations,i.e.,strong 0001//Z texture and 001//Z texture.Their crystallographic orientation will change as the direction of columnarβgrains turns over,resulting in the fatigue anisotropy of LMD Ti64 in crack initiation and early crack propagation process.
基金funded by the National Natural Science Foundation of China(52104046).
文摘Multi-stage and multi-cluster fracturing(MMF)is a crucial technology in unconventional oil and gas development,aiming to enhance production by creating extensive fracture networks.However,achieving uniform expansion of multi-cluster hydraulic fractures(HFs)in MMF remains a significant challenge.Field practice has shown that the use of temporary plugging and diversion fracturing(TPDF)can promote the balanced expansion of multi-cluster HFs.This study conducted TPDF experiments using a true triaxial fracturing simulation system setting a horizontal well completion with multi-cluster jetting perforations to investigate the equilibrium initiation and extension of multi-cluster fractures.The influence of key parameters,including cluster spacing,fracturing fluid viscosity,differential stress,and fracturing fluid injection rate,on fracture initiation and propagation was systematically examined.The results indicate that while close-spaced multi-cluster fracturing significantly increases the number of HFs,it also leads to uneven extension of HFs in their propagation.In contrast,TPDF demonstrates effectiveness in mitigating uneven HF extension,increasing the number of HFs,and creating a larger stimulated reservoir volume,ultimately leading to improved oil and gas well productivity.Moreover,under conditions of high differential stress,the differential stress within the formation exerts a stronger guiding effect in HFs,which are more closely aligned with the minimum principal stress.Low-viscosity fluids facilitate rapid and extensive fracture propagation within the rock formation.High-volume fluid injection,on the other hand,more comprehensively fills the formation.Therefore,employing lowviscosity and high-volume fracturing is advantageous for the initiation and extension of multi-cluster HFs.
基金Project supported by the Chilean National Agency for Research and Development(ANID)through Grants ANID FONDECYT Regular(Nos.1211310 and 1250496)ANID Anillo de Tecnologia(No.ACT240015)the Polish National Science Centre(NCN)through Grant Agreement(No.2021/41/B/ST8/04492)。
文摘The acoustic wave propagation in gas-saturated double-porosity materials composed of a microporous matrix and mesopores with arrays of plate-type resonators is investigated.A macroscopic description,established with the two-scale asymptotic homogenization method,evidences the combined effect of inner resonances on the acoustic properties of the respective effective visco-thermal fluid.One type of resonance originates from strong pore-scale fluid-structure interaction,while the other one arises from pressure diffusion.These phenomena respectively cause weakly and highly damped resonances,which are activated by internal momentum or mass sources,and can largely influence,depending on the material's morphology,either the effective fluid's dynamic density,compressibility,or both.We introduce semi-analytical models to illustrate the key effective properties of the studied multiscale metamaterials.The results provide insights for the bottom-up design of multiscale acoustic metamaterials with exotic behaviors,such as the negative,very slow,or supersonic phase velocity,as well as sub-wavelength bandgaps.
基金funded by the Ministry of Science and Technology of the People's Republic of China(Grant 2024ZD1001301)the National Natural Science Foundation of China(Grants 42272241,42102254 and 41830213)the Fundamental Research Funds for the Central Universities(Grant JZ2023HGTB0238).
文摘The approximately 3000 km long Tan-Lu fault zone(TLFZ)in East Asia is the longest continental strike-slip fault zone in the world and exemplifies how such a fault zone forms and propagates on a continental scale.Structural and geochronological data from the TLFZ and surrounding regions indicate that the fault zone originated as NE/SW-striking sinistral ductile shear zones along an oblique continental convergence margin during the Triassic indentation collision between the North China Craton and the Yangtze Block.The Triassic fault zone,with a total length of about 720 km between the Dabie and Sulu orogens,exhibited an apparent sinistral offset of approximately 300 km along the TLFZ.The second stage of sinistral movement occurred in the earliest Late Jurassic,reactivating the pre-existing southern segment and propagating northwards to the southern coastline of present-day Bohai Bay,as well as forming a significant portion of the Dunhua-Mishan fault zone.The third stage of sinistral movement,in the earliest Early Cretaceous,was the most intense strike-slip movement of the Mesozoic,leading to the complete linkage of the TLFZ.This stage included further northward propagation of the southern-middle segment,both southward and northward propagation of the Dunhua-Mishan fault zone,as well as the formation of the entire Yilan-Yitong fault zone.The fourth stage,in the earliest Late Cretaceous,involved the reactivation of the entire TLFZ.Following its Triassic origin due to the indentation collision,the subduction of the Paleo-Pacific Plate and the subduction and closure of the Mongol-Okhotsk Ocean were responsible for the multi-stage sinistral movements from the Late Jurassic to the Cretaceous.The evolution of the TLFZ demonstrates that a continental-scale strike-slip fault zone(>1000 km long)forms through multiple stages of propagation and linkage in dynamic settings of plate convergence.
文摘The southern part of East Siberia(SES)is highly vulnerable to flooding caused by the extreme precipitation events(EPEs)during summer.Building on previously detected EPEs in SES and Mongolia,we examined wave propagation patterns for two periods:1982-98 and 1999-2019.Our analysis revealed distinct wave train configurations and geopotential anomalies preceding EPEs,with an increase in wave activity flux across the Northern Hemisphere,followed by a subsequent decrease during EPEs.Consequently,Eastern Siberia has experienced a significant rise in wave activity.Based on geopotential anomalies over Central Siberia accompanying EPEs,we identified two main types.The first,the ridge type,is predominant during the first period and features a meridional contrast with a positive geopotential(and temperature)anomaly over Central Siberia and a negative anomaly over the subtropical regions along the same longitude.The second type,termed the trough type,is more typical for the second period.It involves either a negative geopotential anomaly or the zonal proximity of positive and negative geopotential anomalies over Central Siberia.The trough type,marked by zonally oriented anomalies in geopotential and temperature,results in a more pronounced temperature decrease before EPEs and significant zonal temperature contrasts.Further,it is related to more stationary waves over Northern Eurasia,with persistent positive geopotential anomalies over Europe linked to quasi-stationary troughs over Central Siberia and positive anomalies east of Lake Baikal.Our findings align with shifts in boreal summer teleconnection patterns,reflecting significant changes in wave propagation patterns that have occurred since the late 1990s.
基金supported by the Sichuan Science and Technology Program of China(2024NSFSC0097,2023NSFSC0004)the National Natural Science Foundation of China(42377143,52225403).
文摘The mainstream method for extracting shale gas involves hydraulic fracturing to create fracture networks.However,as extraction depth increases,notable issues such as rapid production decline,low recovery rates,high water consumption,and resource waste become apparent.Identifying new and efficient auxiliary rock-breaking technologies is crucial for overcoming these challenges.The laser,successfully utilized in industrial production,medical treatment,and technological research,offers unique features such as good directionality,coherence,and high energy density,providing novel possibilities for addressing the limitations of existing deep reservoir transformation.This research focuses on a novel laser-assisted rock-breaking technology,with shale featuring different bedding angles as the subject of investigation.The investigation methodically explored how shale responded to thermal fracture at high temperatures when exposed to laser irradiation with different spot diameter.It investigates the spatiotemporal evolution characteristics of the shale temperature field under laser irradiation,the propagation features of cracks on shale surface,and the physicochemical fracture mechanisms.The research yields the following results:(1)The region of thermal influence of the irradiation surface can be divided into three regions based on the change of rise curve of temperature in the shale surface.(2)Based on the scanning electron microscopy(SEM)testing,combined with the macroscopic and microscopic morphological characteristics of shale fracture surfaces,it reveals significantly distinct zoning characteristics in the roughness of the rock sample’s fracture surfaces after laser irradiation.(3)The thermal fracturing process of shale under laser irradiation involves chemical reactions of constituent minerals and stress generated by the thermal expansion of shale oil in the reservoir.(4)The damage and fracture of shale under the irradiation of laser show significant bedding effect,and there are three modes of rock sample failure:Pattern T(thermal failure),Pattern T-B(thermal and bedding synergistic failure),and Pattern B(bedding failure).The research findings presented in this article serve as a foundation and reference for the theory and technology of laser-assisted shale gas extraction.
