The total thermal resistance of bedding systems can be affected by environmental variables.A computational fluid dynamics(CFD)model of child manikin and duvet bedding system was developed to investigate the effects of...The total thermal resistance of bedding systems can be affected by environmental variables.A computational fluid dynamics(CFD)model of child manikin and duvet bedding system was developed to investigate the effects of air temperature(T_(air),5–25°C)and air velocity(V_(air),0.2–1.0 m/s)on the total thermal resistance(R_(t))of children’s bedding systems composed of duvet with different total filling weights(w,350–1000 g)in three sleep postures(P1,P2,and P3).Heat flux experiments were conducted to validate the CFD model.Results from the simulations indicated that a 1℃rise in T_(air)led to a reduction in R_(t)by 0.09–0.11 clo.Furthermore,R_(t)decreases with the increase in V_(air),and the reduction in R_(t)slows down as V_(air)increases.Variations in T_(air)and V_(air)had the most significant impact on R_(t)in the P2 sleep position and the least effect in the P3 sleep position.Based on the simulation results,a prediction equation for the R_(t)of the children’s bedding systems was established.These research findings offer valuable insights into the scientific selection and design of children’s bedding systems,which are crucial for improving children’s sleep quality.展开更多
The coupling effects of rainfall,earthquake,and complex topographic and geological conditions complicate the dynamic responses and disasters of slope-tunnel systems.For this,the large-scale shaking table tests were ca...The coupling effects of rainfall,earthquake,and complex topographic and geological conditions complicate the dynamic responses and disasters of slope-tunnel systems.For this,the large-scale shaking table tests were carried out to explore the dynamic responses of steep bedding slope-tunnel system under the coupling effect of rainfall and earthquake.Results show that the slope surface and elevation amplification effect exhibit pronounced nonlinear change caused by the tunnel and weak interlayers.When seismic wave propagates to tunnels,the weak interlayers and rock intersecting areas present complex wave field distribution characteristics.The dynamic responses of the slope are influenced by the frequency,amplitude,and direction of seismic waves.The acceleration amplification coefficient initially rises and then falls as increasing seismic frequency,peaking at 20 Hz.Additionally,the seismic damage process of slope is categorized into elastic(2-3 m/s^(2)),elastoplastic(4-5 m/s^(2))and plastic damage stages(≥6.5 m/s^(2)).In elastic stage,ΔMPGA(ratio of acceleration amplification factor)increases with increasing seismic intensity,without obvious strain distribution change.In plastic stage,ΔMPGA begins to gradually plummet,and the strain is mainly distributed in the damaged area.The modes of seismic damage in the slope-tunnel system are mainly of tensile failure of the weak interlayer,cracking failure of tunnel lining,formation of persistent cracks on the slope crest and waist,development and outward shearing of the sliding mass,and buckling failure at the slope foot under extrusion of the upper rock body.This study can serve as a reference for predicting the failure modes of tunnel-slope system in strong seismic regions.展开更多
[Objective] The study was conducted to optimize the operation parameters of water control equipment for deep-litter beddings. [Method] A four-factor three-level orthogonal design was adopted to optimize experimental t...[Objective] The study was conducted to optimize the operation parameters of water control equipment for deep-litter beddings. [Method] A four-factor three-level orthogonal design was adopted to optimize experimental temperature, stopping time of aeration, aeration time and aeration rate by 9 groups of experiments, so as to improve the water removal efficiency of adopted mixed and reduce operation energy consumption. [Result] The average water contents in the mixed bedding under 3 temperatures decreased by 4.58% ±2.91%, 13.17% ±3.77% and 10.8% ±7.72%, respectively; the highest water removal efficiency could be achieved under an experimental temperature at 45 ℃, stopping time of aeration of 15 min, aeration time of 7 min, and an aeration rate at 4 m^3/min, which formed the optimal factor combination mode of the operation parameter of the water control equipment; the effects of various experimental factors on water content in the bedding were in order of aeration ratetemperatureaeration timestopping time of aeration; and the effects of various experimental factors on water removal efficiency in the bedding were in order of temperatureaeration rateaeration timestopping time of aeration. [Conclusion] After the optimization of operation parameters of the water control equipment for the deep-litter bedding, water removal efficiency of the mixed bedding could be improved, and the operation energy consumption of the equipment could be reduced.展开更多
The selection and compatibility of the microbial strains and bedding materials in a deep-litter system is the primary issues for this ecological breeding technology. In this paper, we analyzed and summarized the categ...The selection and compatibility of the microbial strains and bedding materials in a deep-litter system is the primary issues for this ecological breeding technology. In this paper, we analyzed and summarized the categories of microbial strains and bedding materials suitable for a deep-litter system, the fermentation properties of different microbes, the parameter requirements of bedding materials, and the fermentation process led by functional microbial flora in a deep-litter system, with the objective to provide theoretical bases and practical guidance for the promotion of deep-litter breeding method nationwide.展开更多
The thermal insulation of a bedding system is one of the most critical factors affecting sleeping thermal comfort.This study reported a mathematical model to evaluate both local and total thermal insulations of a bedd...The thermal insulation of a bedding system is one of the most critical factors affecting sleeping thermal comfort.This study reported a mathematical model to evaluate both local and total thermal insulations of a bedding system.To determine the geometric parameters in the model,the geometric model of the bedding system was developed using a 3D virtual simulation program.Its reliability was validated by comparing it with the 3D scanning model.The predicted local and total thermal insulations of bedding systems were compared with those measured by the thermal manikin obtained in a previous study.The bedding systems included six down quilts with different filling weights and involved three body postures.The results showed that the predicted thermal insulation values agreed well with the experimental values.The predicted local and total thermal insulations were with acceptable accuracy,whose errors were within 20%and 10%,respectively.Finally,the research discussed the effects of two main parameters(i.e.,the proportions and partial thermal resistances of heat transfer parts)on bedding thermal insulations and provided practical suggestions for regulating bedding thermal insulation.This study has important implications for evaluating the thermal comfort of the bedding system and contributes to improving the sleeping environment.展开更多
The thermal environment is an essential factor that affects sleep quality.In many circumstances,the bed microenvironment is more important than the ambient environment because of the large covered area of the human bo...The thermal environment is an essential factor that affects sleep quality.In many circumstances,the bed microenvironment is more important than the ambient environment because of the large covered area of the human body and the close contact between the bedding system and the human body.The main objective of this research is to establish an effective method to determine bedding system insulation.A thermal manikin was used in the measurement of bedding system insulation.Three different types of quilts,which were filled with cotton,polyester and duvet respectively,were chosen to be tested.In total ten different quilts with different materials and weights were involved in the test.Four regular arrangements of covers were chosen with coverage rates of 94.1%,85.9%,70.6%,and 54.4%to test.A total of 64 bedding systems were tested to build an effective method to determine the bedding system insulation.On the basis of test data,the change of bedding system insulation with coverage was found to be nonlinear.Exponential fitting was applied to establish an insulation evaluation method for bedding system insulation.In addition,the effects of quilt cover and sleepwear on bedding system insulation were discussed and thermal insulation increment caused by quilt cover and sleepwear were estimated.The relationships between neutral indoor temperature and weight per unit area of the quilt for different coverage rates have been quantified based on existing subject experiments.This research provides an effective method to determine bedding system insulation,which can be widely used in thermal comfort research and HVAC system design.展开更多
To examine the effect of bedding angle upon burst proneness in terms of energy,phyllites with seven various bedding angles are selected for conventional uniaxial compression and single-cyclic loading eunloading uniaxi...To examine the effect of bedding angle upon burst proneness in terms of energy,phyllites with seven various bedding angles are selected for conventional uniaxial compression and single-cyclic loading eunloading uniaxial compression tests.The ejection and failure during compression process of phyllites are monitored in real-time by high-speed camera system.The results demonstrate that the phyllites with different bedding angles all consistently follow the linear energy storage and dissipation(LESD)law during compression.The ultimate energy storage of phyllites with varying bedding angles can be calculated precisely via using the LESD law.Based on this,four kinds of energy-based rockburst indices are applied to quantitatively assess the burst proneness for phyllites.Combined with the recorded images of high-speed camera system,ejection distance,and mass of rock fragments and powder,the burst proneness for phyllites with various bedding angles is qualitatively evaluated adopting the far-field ejection mass ratio.Next,burst proneness of anisotropic phyllites is assessed quantitatively and qualitatively.It is found that phyllites with bedding angles of 0°,15°,and 90°have a high burst proneness,and that with bedding angle of 30°has a medium burst proneness,whereas the ones with bedding angles of 45°,60°,and 75°have a low burst proneness.Finally,the published experimental data of shale and sandstone specimens with different bedding angles are extracted,and it is preliminarily verified that the bedding angle does not change the LESD law of rocks.展开更多
This study investigates the impact of bedding plane orientation on sodium chloride(NaCl)precipitation in a calcarenite stone,subjected to salt weathering cycles.It involves conducting wetting-drying cycles using sodiu...This study investigates the impact of bedding plane orientation on sodium chloride(NaCl)precipitation in a calcarenite stone,subjected to salt weathering cycles.It involves conducting wetting-drying cycles using sodium chloride on two series of specimens sampled parallel and perpendicular to the bedding plane.Capillary imbibition was carried out using saline solutions of two concentrations(15 g/L and 45 g/L).SEM observations show that,across all contaminated samples,halite precipitates mainly on the surface,in the form of efflorescence,while subflorescence remains negligible.The analysis identifies two distinct halite morphologies:(i)cubic crystals of 2 to 10μm at grain boundaries and(ii)xenomorphic aggregates on pore walls,reflecting that the size and morphology of halite crystals vary according to local nucleation conditions,influenced by the mineralogical composition of the substrates and the degree of supersaturation reached during the cycles.X-ray diffraction analysis revealed significantly higher halite precipitation in samples oriented perpendicular to the sediment bedding(4.53–5.22%)than in those oriented parallel(2.71–4.17%),indicating that bedding plane orientation is a determining factor in weathering processes and the evolution of petrophysical properties.These results demonstrate that capillary transport is intrinsically anisotropic in calcarenite,with bedding orientation controlling both the amount of precipitated salt and the location of crystallizations.This study thus establishes a solid mechanistic framework for predicting salt weathering patterns in stratified heritage stones,and offers concrete perspectives for optimizing conservation strategies in coastal environments.展开更多
Chinaʼs continental shale exhibits favorable geological characteristics and substantial resource potential,yet oil recovery for natural energy extraction remains critically low.Investigating the mechanisms of hydrauli...Chinaʼs continental shale exhibits favorable geological characteristics and substantial resource potential,yet oil recovery for natural energy extraction remains critically low.Investigating the mechanisms of hydraulically induced bedding fracture to generate complex fracture networks in continental shale,and establishing effective flow systems,is of utmost importance.This study employs laboratory experiments and numerical simulations to investigate the flow capacity and percolation behavior of hydraulically induced bedding fractures by different fluids in full-diameter shale cores.Hydraulic stimulation using different fluids generates bedding plane fracture networks,establishing effective flow systems.Eroded and detached shale fragments support localized fractures,thereby increasing their opening and enhancing flow capacity.Cetyltrimethylammonium bromide(CTAB)solution and SiO2 solution reduce the hydration of the shale surface,preventing shale fragments from swelling and disintegrating,leading to more stable percolation behavior.Eroded and spalled shale fragments near the injection point are transported to farther locations,where they help support localized fractures.This process differs from conventional hydraulic fracturing.Under a constant injection rate,the velocity in the smaller flow paths near the closure is significantly higher than that in the main flow paths,leading to pronounced bypass flow behavior.This restricts the percolation of fluid during imbibition in shale cores.The results provide valuable insights into the mechanism of hydraulically induced bedding fracture in continental shale,offering guidance for the effective development of shale reservoirs.展开更多
Pig bedding biochar(PBBC)and Cd-enriched Perilla frutescenswere used for joint remediation of Cd-contaminated soil.Cd-contaminated soil was treated with different concentration of PBBC.The physiological and biochemica...Pig bedding biochar(PBBC)and Cd-enriched Perilla frutescenswere used for joint remediation of Cd-contaminated soil.Cd-contaminated soil was treated with different concentration of PBBC.The physiological and biochemical indicators of P.frutescens was evaluated under different Cd stress,including biomass,antioxidant system.Meanwhile Cd bioavailability,enzyme activity and nutrient bioavailability of the soil were monitored.Results revealed that PBBC at 1%and 5%levels led to decreased diethylenetriaminepentaacetic acid-extractable Cd(DTPA-Cd)content in soil by 19.09%-20.05%and 30.10%-47.08%,respectively.Moreover,PBBC promoted the transformation of exchangeable Cd(EXC-Cd)into a more stable form,enhanced soil enzymes(peroxidase,acid phosphatase,urease,and sucrase)activities,and alleviated P.frutescens's oxidative stress.PBBC increased its biomass,consequently enhancing Cd accumulation in the plant's,thereby improving Phytoextraction rate(PER).1%PBBC showed the best effect,with a total biomass increased 21.42%-26.94%,PERwas enhanced by 39.83%-54.82%.This study justifies that the combining PBBC with P.frutescens enhances Cd removal fromsoil,making the PBBC-P.frutescens a promising choice for treating Cd-polluted soil.展开更多
Weak interlayers play a crucial role in the seismic performance of bedding slopes;however,the effects of structural surface development within these layers remain underexplored.This study presents two scaled models of...Weak interlayers play a crucial role in the seismic performance of bedding slopes;however,the effects of structural surface development within these layers remain underexplored.This study presents two scaled models of bedding slopes,each with different weak interlayers:one with a homogeneous weak layer and another with discontinuous interfaces.Shaking table tests were conducted to compare their seismic performance.The results show that the peak ground acceleration(PGA)values above the weak interlayer in model A were significantly higher than those in model B,with the differences increasing as the input wave amplitude increased.The peak earth pressure(PEP)values at the tensile failure boundary at the rear edge of model A were also higher,whereas those within the weak layer at the toe of model A were lower than those in model B.Deformation analysis revealed that the maximum principal strain in model A initially appeared at the upper part of the tensile failure boundary,while the maximum shear strain was concentrated near the rear edge within the weak layer.In contrast,model B exhibited the opposite strain distribution.These findings provide insight into the impact of weak interlayers on the dynamic response and deformation of bedding slopes,highlighting the importance of considering this factor in seismic landslide investigations and failure mode predictions.展开更多
Shale reservoirs have abundant bedding structures,which deeply alter the mechanical properties of rocks,and thus affect the reservoir stimulation performance.Previous research mostly focuses on the effects of parallel...Shale reservoirs have abundant bedding structures,which deeply alter the mechanical properties of rocks,and thus affect the reservoir stimulation performance.Previous research mostly focuses on the effects of parallel bedding on fracture propagation,while the mechanical properties and mechanisms of fracture propagation remain unclear for rocks with complex wavy bedding(e.g.China’s continentalorigin Gulong shale).Herein,a mixed phase-field fracture model of the wavy-bedding shale was applied,based on the local tension-compression decomposition phase field method(PFM)and geometric structure generation algorithm for the bedding with controllable morphological features.The parametric analysis of fracture propagation behaviors in the case of abundant complex bedding structures showed that with wavy bedding,the vertical fracture propagation rate is far higher than the horizontal propagation rate.Moreover,the development of branch fractures is suppressed during the fracturing process of the wavy-bedding sample,and the stimulated volume is limited,which is different from the characteristic of parallel bedding that promotes horizontal fracture initiation and propagation.The results showed that larger amplitudes,higher frequencies,higher inclination angles,and larger strengths of wavy bedding all promote the formation of vertical penetrating fractures and suppress the growth of branch fractures.Under such circumstances,it is hard to create a well-connected fracture network after fracturing.This research may provide a theoretical basis for understanding fracture behaviors in rocks with such complex wavy bedding.展开更多
Steep bedding slopes are widely distributed in Southwestern China’s mountainous regions and have complex seismic responses and instability risks,causing casualties and property losses.Considering the high-seismic-int...Steep bedding slopes are widely distributed in Southwestern China’s mountainous regions and have complex seismic responses and instability risks,causing casualties and property losses.Considering the high-seismic-intensity environment,the dynamic failure evolution and instability mechanism of high-steep bedding slopes are simulated via the discrete element method and shaking table test.The dynamic response characteristics and cumulative failure effects of slopes subjected to continuous ground motion are investigated.The results show that the dynamic response characteristics of slopes under continuous earthquakes are influenced by geological and topographic conditions.Elevation has a distinct impact on both the slope interior and surface,with amplification effects more pronounced on the surface.The weak interlayers have different influences on the dynamic amplification effect of slopes.Weak interlayers have dynamic magnification effects on the slope surface at relative elevations of 0-0.33 and 0.82-1.0 but have weakening effects between 0.33 and 0.82.Moreover,the weak interlayers also have controlling effects on the dynamic instability mode of slopes.The characteristics of intergranular contact failure,fracture propagation,and displacement distribution are analyzed to reveal the dynamic failure evolution and instability mechanism through the discrete-element model.The dynamic instability process of slopes includes three stages:fracture initiation(0-0.2g),fracture expansion(0.2g-0.3g),and sliding instability(0.3g-0.6g).This work can provide a valuable reference for the seismic stability and reinforcement of complex slopes.展开更多
The increasing demand for mineral resources has significantly deepened the excavation depths of open-pit mines.Large-scale deformation disasters caused by landslides on open pit mine slopes occur frequently,posing sev...The increasing demand for mineral resources has significantly deepened the excavation depths of open-pit mines.Large-scale deformation disasters caused by landslides on open pit mine slopes occur frequently,posing severe threats to human safety and mine operations.Therefore,research on monitoring and early warning technologies for openpit mine landslides is of utmost importance.The emergence of the Newtonian force monitoring and early warning system has introduced an effective new approach for landslide monitoring in open-pit mines and has been successfully applied in the Nanfen openpit mine,where it monitored landslides and issued early warnings up to 16 hours in advance.This study focuses on the bedding rock slope on the footwall of the Nanfen open pit mine,analyzing the geological conditions of the mining area.Through laboratory experiments,the mechanical parameters and mineral composition characteristics of the regional rock mass(greenschist)are obtained.A geological mechanical model of the landslide was then constructed,and the NPR anchor cable numerical analysis model was developed using FLAC3D numerical simulation software to analyze the variation patterns of Newtonian force during landslides.Based on this analysis,the influence of different NPR anchor cable parameters(including anchor cable inclination angle,spacing,and pre-tension force)on the Newtonian force was investigated.Comparative results indicate that the optimal design parameters for the NPR anchor cables are a 25°inclination angle,40 m anchoring spacing,and a 400 kN pre-tension force.Additionally,it was found that the sensitivity of these three key parameters to the Newtonian force load,from highest to lowest,is as follows:pre-tension force,spacing,and inclination angle.This optimal configuration provides practical guidance for the design of NPR anchor cables in Newtonian force monitoring applications,offering theoretical and technical support for future landslide monitoring and early warning.展开更多
Earthquakes contribute to the failure of anti-dip bedding rock slopes(ABRSs)in seismically active regions.The pseudo-static method is commonly employed to assess the ABRSs stability.However,simplifying seismic effects...Earthquakes contribute to the failure of anti-dip bedding rock slopes(ABRSs)in seismically active regions.The pseudo-static method is commonly employed to assess the ABRSs stability.However,simplifying seismic effects as static loads often underestimates rock slope stability.The development of a practical stability analysis approach for ABRSs,particularly in slope engineering design,is imperative.This study proposes a stability evaluation model for ABRSs,incorporating the viscoelastic properties of rock,to quantitatively assess the safety factor and failure surface under seismic conditions.The mathematical description of the pseudo-dynamic method,derived in this study,accounts for the viscoelastic properties of ABRSs and integrates the HoekeBrown failure criterion with the Kelvin-Voigt stress-strain relationship of rocks.Furthermore,to address concurrent translation-rotation failure in ABRSs,upper bound limit analysis is utilized to quantify the safety factor.Through a comparison with existing literature,the proposed method considers the effect of harmonic vibration on the stability of ABRSs.The obtained safety factor is lower than that of the quasi-static method,with the resulting percentage change exceeding 5%.The critical failure surface demonstrates superior positional accuracy compared to the Aydan and Adhikary basal planes,with minimal error observed between the physical model test and the numerical simulation test.The parameter sensitivity analysis reveals that the inclination of ABRSs exhibits the highest sensitivity(Sk)value across the three levels of horizontal seismic coefficient(kh).The study aims to devise an expeditious calculation approach for assessing the stability of ABRSs during seismic events,intending to offer theoretical guidance for their stability analysis.展开更多
Methane in situ explosion fracturing(MISEF)technology improves deep reservoir permeability by generating multiple radial fractures around the wellbore,with fracture propagation significantly influenced by in situ stre...Methane in situ explosion fracturing(MISEF)technology improves deep reservoir permeability by generating multiple radial fractures around the wellbore,with fracture propagation significantly influenced by in situ stress and bedding structures.However,limited experimental studies on the combined effects of triaxial stress and explosive loading,along with detailed characterization of explosive damage,hinder further optimization of this technology.This study introduces an experimental method to simulate MISEF under triaxial stress,using CH4-O2 detonation to generate controllable explosive loads.Bedding shale samples are fractured in a pseudo-triaxial core holder.Micro-computed tomography(μ-CT)and nuclear magnetic resonance(NMR)are used to quantify three-dimensional(3D)fracture characteristics and pore structure evolution.LS-DYNA simulations are employed to elucidate fracture propagation and dynamic behavior.The results show that detonation produces explosive loads with overpressures of 69.929-84.338 MPa and pressure rise rates of up to 555.624 MPa/ms,exhibiting an oscillation-attenuation characteristic.μ-CT reveals 3-5 radial fractures,with 3D fracture volume and surface area decreasing as triaxial stress rises.Hoop stress inhibits fracture propagation more than axial stress.NMR analysis shows that explosive loading converts bound fluid to movable fluid,while in situ stress suppresses this process.With increasing triaxial stress,micropore(T2<10 ms)changes are minimal,while meso/macropore and fracture(T2>10 ms)NMR signals decrease significantly.Higher triaxial stress reduces water overpressure of stress loading chambers and vibrational displacement at sample boundaries.Numerical simulations indicate that explosive loading generates hoop tensile stress,which drives the formation of radial fractures.Triaxial stress increases hoop compressive stress,suppressing fracture propagation.Fractures initiate along bedding planes,forming cross-shaped or T-shaped patterns.展开更多
In the practical slope engineering,the stability of lower sliding mass(region A)with back tensile cracks of the jointed rock slope attracts more attentions,but the upper rock mass(region B)may also be unstable.Therefo...In the practical slope engineering,the stability of lower sliding mass(region A)with back tensile cracks of the jointed rock slope attracts more attentions,but the upper rock mass(region B)may also be unstable.Therefore,in this study,based on the stepped failure mode of bedding jointed rock slopes,considering the influence of the upper rock mass on the lower stepped sliding mass,the improved failure model for analyzing the interaction force(F_(AB))between two regions is constructed,and the safety factors(F_(S))of two regions and whole region are derived.In addition,this paper proposes a method to determine the existence of F_(AB) using their respective acceleration values(a_(A) and a_(B))when regions A and B are unstable.The influences of key parameters on two regions and the whole region are analyzed.The results show that the variation of the F_(AB) and F_(S) of two regions can be obtained accurately based on the improved failure model.The accuracy of the improved failure model is verified by comparative analysis.The research results can explain the interaction mechanism of two regions and the natural phenomenon of slope failure caused by the development of cracks.展开更多
The fracture network of hydraulic crack is significantly influenced by the bedding plane in coalbed methane extraction.Under mode Ⅱ loading,crack deflection holds a key position in hydraulic cracking,especially in hy...The fracture network of hydraulic crack is significantly influenced by the bedding plane in coalbed methane extraction.Under mode Ⅱ loading,crack deflection holds a key position in hydraulic cracking,especially in hydraulic shearing.This study first analyzed the crack deflection theory of layered rock.The semi-circle bending test under asymmetric loading is performed,and the four-dimensional Lattice Spring Model(4D-LSM)is established to examine how the bedding parameters affect coal crack propagation under mode Ⅱ dominant loads.The 4D-LSM results are comparable to the coal loading test results under quasi-mode Ⅱ and the analytical prediction of crack deflection theory.During mode Ⅱ loading,the coal crack propagation is greatly influenced by the angle,strength,and elastic modulus of the bedding plane,while the effects of thickness and spacing of bedding are insignificant.The crack of coal tends to propagate towards the bedding,following a decrease in bedding angle,a decrease in bedding strength,and an increase in elastic modulus.With higher bedding strength,spacing,and thickness,the peak load on the coal sample is higher.The influences of bedding strength,elastic modulus,spacing,and thickness on the peak load of coal samples and its anisotropy gradually decrease.It is proved that compared with the tangential stress ratio and traditional energy release ratio theories,the corrected energy release ratio criterion can more accurately predict the direction of crack deflection of coal,especially under mode Ⅱ loading.The results can provide assistance in the design of initiation pressure and fracturing direction in coal seam hydraulic fracturing.展开更多
To improve understanding of coastal seagrass bed habitats in China,this study investigated seagrass distribution patterns and analyzed water column and sediment parameters of seagrass bed ecosystems on Guanglu,Zhangzi...To improve understanding of coastal seagrass bed habitats in China,this study investigated seagrass distribution patterns and analyzed water column and sediment parameters of seagrass bed ecosystems on Guanglu,Zhangzi,and Haiyang Islands in Changhai County,Dalian City,during August 2022.The findings revealed that seagrass beds were predominantly composed of Zostera marina,Zostera japonica,and Zostera caespitosa,with Zostera marina as the dominant species.All seagrass species exhibited patchy spatial distributions,potentially linked to localized environmental stressors.Seagrass beds on Zhangzi Island exhibited high suspended particulate matter,while those on Haiyang Island showed elevated sediment chemical constituents and low dissolved oxygen in the water column.Among the three sites,Zhangzi Island had the lowest macroalgal coverage,shoot density,and epiphytic biomass.Seagrass beds on Haiyang Island displayed higher epiphytic biomass than the other two islands.Conversely,seagrass beds on Guanglu Island were characterized by lower shoot height and benthic biomass.Although ecological assessment indices classified all three island seagrass beds as grade I(currently stable),persistent anthropogenic disturbances were identified as drivers of gradual degradation,potentially threatening future stability.These findings highlight site-specific habitat characteristics and underscore the importance of targeted conservation strategies.This research provides crucial baseline data for the conservation and management of coastal seagrass beds.展开更多
Additive manufacturing(AM)is an advanced production method for layer-by-layer fabrication,offering a paradigm shift in manufacturing.However,the sustainability of AM processes is poor,since suppliers recommend reusing...Additive manufacturing(AM)is an advanced production method for layer-by-layer fabrication,offering a paradigm shift in manufacturing.However,the sustainability of AM processes is poor,since suppliers recommend reusing 50%-70%of reprocessed powder,contributing to a significant increase in material disposal.To explore the possibility of fully reusing the polymeric material,we conduct a comprehensive characterisation of the powder particulates,in combination with analysis of the final prints.Utilizing optical and scanning electron microscopes,we statistically evaluate the size,morphology,and shape of the particles.Furthermore,tensile strength and deformation of printed bars is evaluated,showcasing the impact of aging on the print properties.The findings reveal that consecutive reuse of used powder significantly influences dimensional accuracy of the printed parts.We detect a 30.63%relative value of shrinkage after six printing iterations,which corresponds to an absolute shrinkage increase by 0.98%.This is significant considering the standard shrinkage for the material used is already 3.2%.Additionally,parts that are printed with reused material exhibit a small increase in elongation at yield,as well as an unexpected rise in tensile strength.Significant agglomeration of small particles is observed in the aged powder,since there are particles of less than 10μm,which are not found in the virgin powder.These results contribute to a better understanding of the issues related to the reusing of aged material,and offer invaluable insights for mitigating the environmental impact that is associated with material disposal in AM.展开更多
基金supported by the National Natural Science Foundation of China(NSFC)(No.51506076).
文摘The total thermal resistance of bedding systems can be affected by environmental variables.A computational fluid dynamics(CFD)model of child manikin and duvet bedding system was developed to investigate the effects of air temperature(T_(air),5–25°C)and air velocity(V_(air),0.2–1.0 m/s)on the total thermal resistance(R_(t))of children’s bedding systems composed of duvet with different total filling weights(w,350–1000 g)in three sleep postures(P1,P2,and P3).Heat flux experiments were conducted to validate the CFD model.Results from the simulations indicated that a 1℃rise in T_(air)led to a reduction in R_(t)by 0.09–0.11 clo.Furthermore,R_(t)decreases with the increase in V_(air),and the reduction in R_(t)slows down as V_(air)increases.Variations in T_(air)and V_(air)had the most significant impact on R_(t)in the P2 sleep position and the least effect in the P3 sleep position.Based on the simulation results,a prediction equation for the R_(t)of the children’s bedding systems was established.These research findings offer valuable insights into the scientific selection and design of children’s bedding systems,which are crucial for improving children’s sleep quality.
基金supported by the National Natural Science Foundation of China (Grant No.52109125)the Natural Science Foundation of Jiangsu Province,China (Grant No.BK20231217)the Key Laboratory of Geomechanics and Geotechnical Engineering Safety,Chinese Academy of Sciences (Grant No.SKLGME023001).
文摘The coupling effects of rainfall,earthquake,and complex topographic and geological conditions complicate the dynamic responses and disasters of slope-tunnel systems.For this,the large-scale shaking table tests were carried out to explore the dynamic responses of steep bedding slope-tunnel system under the coupling effect of rainfall and earthquake.Results show that the slope surface and elevation amplification effect exhibit pronounced nonlinear change caused by the tunnel and weak interlayers.When seismic wave propagates to tunnels,the weak interlayers and rock intersecting areas present complex wave field distribution characteristics.The dynamic responses of the slope are influenced by the frequency,amplitude,and direction of seismic waves.The acceleration amplification coefficient initially rises and then falls as increasing seismic frequency,peaking at 20 Hz.Additionally,the seismic damage process of slope is categorized into elastic(2-3 m/s^(2)),elastoplastic(4-5 m/s^(2))and plastic damage stages(≥6.5 m/s^(2)).In elastic stage,ΔMPGA(ratio of acceleration amplification factor)increases with increasing seismic intensity,without obvious strain distribution change.In plastic stage,ΔMPGA begins to gradually plummet,and the strain is mainly distributed in the damaged area.The modes of seismic damage in the slope-tunnel system are mainly of tensile failure of the weak interlayer,cracking failure of tunnel lining,formation of persistent cracks on the slope crest and waist,development and outward shearing of the sliding mass,and buckling failure at the slope foot under extrusion of the upper rock body.This study can serve as a reference for predicting the failure modes of tunnel-slope system in strong seismic regions.
基金Supported by the Fund for Independent Innovation of Agricultural Sciences in Jiangsu Province(CX(13)3073)Jiangsu Science and Technology Support Program(BE2014-342-1)~~
文摘[Objective] The study was conducted to optimize the operation parameters of water control equipment for deep-litter beddings. [Method] A four-factor three-level orthogonal design was adopted to optimize experimental temperature, stopping time of aeration, aeration time and aeration rate by 9 groups of experiments, so as to improve the water removal efficiency of adopted mixed and reduce operation energy consumption. [Result] The average water contents in the mixed bedding under 3 temperatures decreased by 4.58% ±2.91%, 13.17% ±3.77% and 10.8% ±7.72%, respectively; the highest water removal efficiency could be achieved under an experimental temperature at 45 ℃, stopping time of aeration of 15 min, aeration time of 7 min, and an aeration rate at 4 m^3/min, which formed the optimal factor combination mode of the operation parameter of the water control equipment; the effects of various experimental factors on water content in the bedding were in order of aeration ratetemperatureaeration timestopping time of aeration; and the effects of various experimental factors on water removal efficiency in the bedding were in order of temperatureaeration rateaeration timestopping time of aeration. [Conclusion] After the optimization of operation parameters of the water control equipment for the deep-litter bedding, water removal efficiency of the mixed bedding could be improved, and the operation energy consumption of the equipment could be reduced.
基金Supported by the Special Fund for the Independent Innovation of Agricultural Sciences and Technology in Jiangsu Province[cx(12)1001-04]~~
文摘The selection and compatibility of the microbial strains and bedding materials in a deep-litter system is the primary issues for this ecological breeding technology. In this paper, we analyzed and summarized the categories of microbial strains and bedding materials suitable for a deep-litter system, the fermentation properties of different microbes, the parameter requirements of bedding materials, and the fermentation process led by functional microbial flora in a deep-litter system, with the objective to provide theoretical bases and practical guidance for the promotion of deep-litter breeding method nationwide.
基金supported by the MOE (Ministry of Education of China) Project of Humanities and Social Sciences (No.20YJCZH063).
文摘The thermal insulation of a bedding system is one of the most critical factors affecting sleeping thermal comfort.This study reported a mathematical model to evaluate both local and total thermal insulations of a bedding system.To determine the geometric parameters in the model,the geometric model of the bedding system was developed using a 3D virtual simulation program.Its reliability was validated by comparing it with the 3D scanning model.The predicted local and total thermal insulations of bedding systems were compared with those measured by the thermal manikin obtained in a previous study.The bedding systems included six down quilts with different filling weights and involved three body postures.The results showed that the predicted thermal insulation values agreed well with the experimental values.The predicted local and total thermal insulations were with acceptable accuracy,whose errors were within 20%and 10%,respectively.Finally,the research discussed the effects of two main parameters(i.e.,the proportions and partial thermal resistances of heat transfer parts)on bedding thermal insulations and provided practical suggestions for regulating bedding thermal insulation.This study has important implications for evaluating the thermal comfort of the bedding system and contributes to improving the sleeping environment.
基金This work was supported by the National Natural Science Foundation of China(No.52178079,No.51838007)China Postdoctoral Science Foundation(No.2021M701940)Shuimu Tsinghua Scholar Program(No.2020SM003).
文摘The thermal environment is an essential factor that affects sleep quality.In many circumstances,the bed microenvironment is more important than the ambient environment because of the large covered area of the human body and the close contact between the bedding system and the human body.The main objective of this research is to establish an effective method to determine bedding system insulation.A thermal manikin was used in the measurement of bedding system insulation.Three different types of quilts,which were filled with cotton,polyester and duvet respectively,were chosen to be tested.In total ten different quilts with different materials and weights were involved in the test.Four regular arrangements of covers were chosen with coverage rates of 94.1%,85.9%,70.6%,and 54.4%to test.A total of 64 bedding systems were tested to build an effective method to determine the bedding system insulation.On the basis of test data,the change of bedding system insulation with coverage was found to be nonlinear.Exponential fitting was applied to establish an insulation evaluation method for bedding system insulation.In addition,the effects of quilt cover and sleepwear on bedding system insulation were discussed and thermal insulation increment caused by quilt cover and sleepwear were estimated.The relationships between neutral indoor temperature and weight per unit area of the quilt for different coverage rates have been quantified based on existing subject experiments.This research provides an effective method to determine bedding system insulation,which can be widely used in thermal comfort research and HVAC system design.
基金supported by the National Natural Science Foundation of China(Grant No.42077244).
文摘To examine the effect of bedding angle upon burst proneness in terms of energy,phyllites with seven various bedding angles are selected for conventional uniaxial compression and single-cyclic loading eunloading uniaxial compression tests.The ejection and failure during compression process of phyllites are monitored in real-time by high-speed camera system.The results demonstrate that the phyllites with different bedding angles all consistently follow the linear energy storage and dissipation(LESD)law during compression.The ultimate energy storage of phyllites with varying bedding angles can be calculated precisely via using the LESD law.Based on this,four kinds of energy-based rockburst indices are applied to quantitatively assess the burst proneness for phyllites.Combined with the recorded images of high-speed camera system,ejection distance,and mass of rock fragments and powder,the burst proneness for phyllites with various bedding angles is qualitatively evaluated adopting the far-field ejection mass ratio.Next,burst proneness of anisotropic phyllites is assessed quantitatively and qualitatively.It is found that phyllites with bedding angles of 0°,15°,and 90°have a high burst proneness,and that with bedding angle of 30°has a medium burst proneness,whereas the ones with bedding angles of 45°,60°,and 75°have a low burst proneness.Finally,the published experimental data of shale and sandstone specimens with different bedding angles are extracted,and it is preliminarily verified that the bedding angle does not change the LESD law of rocks.
文摘This study investigates the impact of bedding plane orientation on sodium chloride(NaCl)precipitation in a calcarenite stone,subjected to salt weathering cycles.It involves conducting wetting-drying cycles using sodium chloride on two series of specimens sampled parallel and perpendicular to the bedding plane.Capillary imbibition was carried out using saline solutions of two concentrations(15 g/L and 45 g/L).SEM observations show that,across all contaminated samples,halite precipitates mainly on the surface,in the form of efflorescence,while subflorescence remains negligible.The analysis identifies two distinct halite morphologies:(i)cubic crystals of 2 to 10μm at grain boundaries and(ii)xenomorphic aggregates on pore walls,reflecting that the size and morphology of halite crystals vary according to local nucleation conditions,influenced by the mineralogical composition of the substrates and the degree of supersaturation reached during the cycles.X-ray diffraction analysis revealed significantly higher halite precipitation in samples oriented perpendicular to the sediment bedding(4.53–5.22%)than in those oriented parallel(2.71–4.17%),indicating that bedding plane orientation is a determining factor in weathering processes and the evolution of petrophysical properties.These results demonstrate that capillary transport is intrinsically anisotropic in calcarenite,with bedding orientation controlling both the amount of precipitated salt and the location of crystallizations.This study thus establishes a solid mechanistic framework for predicting salt weathering patterns in stratified heritage stones,and offers concrete perspectives for optimizing conservation strategies in coastal environments.
基金supported by the Frontier and Fundamental Research of Active Nanofluids Flooding for Enhanced Oil Recovery through Discontinuous and Variable-circle Modes in High Temperature and High Salinity Offshore Oilfields(U22B6005)National Natural Science Foundation of China(No.52274037)Study on Key Issues of Enhanced Oil Recovery of Gulong Shale Oil(DQYT-2022-JS-761).
文摘Chinaʼs continental shale exhibits favorable geological characteristics and substantial resource potential,yet oil recovery for natural energy extraction remains critically low.Investigating the mechanisms of hydraulically induced bedding fracture to generate complex fracture networks in continental shale,and establishing effective flow systems,is of utmost importance.This study employs laboratory experiments and numerical simulations to investigate the flow capacity and percolation behavior of hydraulically induced bedding fractures by different fluids in full-diameter shale cores.Hydraulic stimulation using different fluids generates bedding plane fracture networks,establishing effective flow systems.Eroded and detached shale fragments support localized fractures,thereby increasing their opening and enhancing flow capacity.Cetyltrimethylammonium bromide(CTAB)solution and SiO2 solution reduce the hydration of the shale surface,preventing shale fragments from swelling and disintegrating,leading to more stable percolation behavior.Eroded and spalled shale fragments near the injection point are transported to farther locations,where they help support localized fractures.This process differs from conventional hydraulic fracturing.Under a constant injection rate,the velocity in the smaller flow paths near the closure is significantly higher than that in the main flow paths,leading to pronounced bypass flow behavior.This restricts the percolation of fluid during imbibition in shale cores.The results provide valuable insights into the mechanism of hydraulically induced bedding fracture in continental shale,offering guidance for the effective development of shale reservoirs.
基金supported by the Science and Technology Innovation of Fujian Agriculture and Forestry University(Nos.KFB23079 and KFB23065).
文摘Pig bedding biochar(PBBC)and Cd-enriched Perilla frutescenswere used for joint remediation of Cd-contaminated soil.Cd-contaminated soil was treated with different concentration of PBBC.The physiological and biochemical indicators of P.frutescens was evaluated under different Cd stress,including biomass,antioxidant system.Meanwhile Cd bioavailability,enzyme activity and nutrient bioavailability of the soil were monitored.Results revealed that PBBC at 1%and 5%levels led to decreased diethylenetriaminepentaacetic acid-extractable Cd(DTPA-Cd)content in soil by 19.09%-20.05%and 30.10%-47.08%,respectively.Moreover,PBBC promoted the transformation of exchangeable Cd(EXC-Cd)into a more stable form,enhanced soil enzymes(peroxidase,acid phosphatase,urease,and sucrase)activities,and alleviated P.frutescens's oxidative stress.PBBC increased its biomass,consequently enhancing Cd accumulation in the plant's,thereby improving Phytoextraction rate(PER).1%PBBC showed the best effect,with a total biomass increased 21.42%-26.94%,PERwas enhanced by 39.83%-54.82%.This study justifies that the combining PBBC with P.frutescens enhances Cd removal fromsoil,making the PBBC-P.frutescens a promising choice for treating Cd-polluted soil.
基金funding support from the National Nature Science Foundation of China(Grant No.41931296)the Open Research Project of Sichuan Provincial Key Laboratory for Major Hazard Source Monitoring and Control(Grant No.KFKT2023-4)the 57#Project(Grant No.JH2024015).
文摘Weak interlayers play a crucial role in the seismic performance of bedding slopes;however,the effects of structural surface development within these layers remain underexplored.This study presents two scaled models of bedding slopes,each with different weak interlayers:one with a homogeneous weak layer and another with discontinuous interfaces.Shaking table tests were conducted to compare their seismic performance.The results show that the peak ground acceleration(PGA)values above the weak interlayer in model A were significantly higher than those in model B,with the differences increasing as the input wave amplitude increased.The peak earth pressure(PEP)values at the tensile failure boundary at the rear edge of model A were also higher,whereas those within the weak layer at the toe of model A were lower than those in model B.Deformation analysis revealed that the maximum principal strain in model A initially appeared at the upper part of the tensile failure boundary,while the maximum shear strain was concentrated near the rear edge within the weak layer.In contrast,model B exhibited the opposite strain distribution.These findings provide insight into the impact of weak interlayers on the dynamic response and deformation of bedding slopes,highlighting the importance of considering this factor in seismic landslide investigations and failure mode predictions.
基金supported by the Technology Project of CNPC(Grant No.2023ZZ08)the National Natural Science Foundation of China(Grant No.52274058)the USTC Research Funds of the Double First-Class Initiative(Grant No.YD2090002025).
文摘Shale reservoirs have abundant bedding structures,which deeply alter the mechanical properties of rocks,and thus affect the reservoir stimulation performance.Previous research mostly focuses on the effects of parallel bedding on fracture propagation,while the mechanical properties and mechanisms of fracture propagation remain unclear for rocks with complex wavy bedding(e.g.China’s continentalorigin Gulong shale).Herein,a mixed phase-field fracture model of the wavy-bedding shale was applied,based on the local tension-compression decomposition phase field method(PFM)and geometric structure generation algorithm for the bedding with controllable morphological features.The parametric analysis of fracture propagation behaviors in the case of abundant complex bedding structures showed that with wavy bedding,the vertical fracture propagation rate is far higher than the horizontal propagation rate.Moreover,the development of branch fractures is suppressed during the fracturing process of the wavy-bedding sample,and the stimulated volume is limited,which is different from the characteristic of parallel bedding that promotes horizontal fracture initiation and propagation.The results showed that larger amplitudes,higher frequencies,higher inclination angles,and larger strengths of wavy bedding all promote the formation of vertical penetrating fractures and suppress the growth of branch fractures.Under such circumstances,it is hard to create a well-connected fracture network after fracturing.This research may provide a theoretical basis for understanding fracture behaviors in rocks with such complex wavy bedding.
基金Project(52108361)supported by the National Natural Science Foundation of ChinaProjects(BK20231217,BK20220265)supported by the Basic Research Program of Jiangsu Province,China+5 种基金Project(sklhse-KF-2025-D-02)supported by the Open Research Fund Program of the State Key Laboratory of Hydroscience and Engineering,ChinaProject(2023ZB15)supported by the Independent Research Project of the State Key Laboratory of Subtropical Building and Urban Science,ChinaProject(SKLGME023001)supported by the Key Laboratory of Geomechanics and Geotechnical Engineering Safety,the Chinese Academy of SciencesProject(2025A04J3992)supported by the Basic and Applied Basic Research Project of the Guangzhou Science and Technology Bureau,ChinaProject(SKLGP2022Z015)supported by the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project,ChinaProjects(2023YFS0436,2024NSFSC1715)supported by the Science and Technology Department of Sichuan Province,China。
文摘Steep bedding slopes are widely distributed in Southwestern China’s mountainous regions and have complex seismic responses and instability risks,causing casualties and property losses.Considering the high-seismic-intensity environment,the dynamic failure evolution and instability mechanism of high-steep bedding slopes are simulated via the discrete element method and shaking table test.The dynamic response characteristics and cumulative failure effects of slopes subjected to continuous ground motion are investigated.The results show that the dynamic response characteristics of slopes under continuous earthquakes are influenced by geological and topographic conditions.Elevation has a distinct impact on both the slope interior and surface,with amplification effects more pronounced on the surface.The weak interlayers have different influences on the dynamic amplification effect of slopes.Weak interlayers have dynamic magnification effects on the slope surface at relative elevations of 0-0.33 and 0.82-1.0 but have weakening effects between 0.33 and 0.82.Moreover,the weak interlayers also have controlling effects on the dynamic instability mode of slopes.The characteristics of intergranular contact failure,fracture propagation,and displacement distribution are analyzed to reveal the dynamic failure evolution and instability mechanism through the discrete-element model.The dynamic instability process of slopes includes three stages:fracture initiation(0-0.2g),fracture expansion(0.2g-0.3g),and sliding instability(0.3g-0.6g).This work can provide a valuable reference for the seismic stability and reinforcement of complex slopes.
基金supported by collaborative innovation center for prevention and control of mountain geological hazards of Zhejiang province(Project number:PCMGH-2022-06)。
文摘The increasing demand for mineral resources has significantly deepened the excavation depths of open-pit mines.Large-scale deformation disasters caused by landslides on open pit mine slopes occur frequently,posing severe threats to human safety and mine operations.Therefore,research on monitoring and early warning technologies for openpit mine landslides is of utmost importance.The emergence of the Newtonian force monitoring and early warning system has introduced an effective new approach for landslide monitoring in open-pit mines and has been successfully applied in the Nanfen openpit mine,where it monitored landslides and issued early warnings up to 16 hours in advance.This study focuses on the bedding rock slope on the footwall of the Nanfen open pit mine,analyzing the geological conditions of the mining area.Through laboratory experiments,the mechanical parameters and mineral composition characteristics of the regional rock mass(greenschist)are obtained.A geological mechanical model of the landslide was then constructed,and the NPR anchor cable numerical analysis model was developed using FLAC3D numerical simulation software to analyze the variation patterns of Newtonian force during landslides.Based on this analysis,the influence of different NPR anchor cable parameters(including anchor cable inclination angle,spacing,and pre-tension force)on the Newtonian force was investigated.Comparative results indicate that the optimal design parameters for the NPR anchor cables are a 25°inclination angle,40 m anchoring spacing,and a 400 kN pre-tension force.Additionally,it was found that the sensitivity of these three key parameters to the Newtonian force load,from highest to lowest,is as follows:pre-tension force,spacing,and inclination angle.This optimal configuration provides practical guidance for the design of NPR anchor cables in Newtonian force monitoring applications,offering theoretical and technical support for future landslide monitoring and early warning.
基金funding support from the National Natural Science Foundation of China(Grant No.42072303)the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project(Grant No.SKLGP2021Z004).
文摘Earthquakes contribute to the failure of anti-dip bedding rock slopes(ABRSs)in seismically active regions.The pseudo-static method is commonly employed to assess the ABRSs stability.However,simplifying seismic effects as static loads often underestimates rock slope stability.The development of a practical stability analysis approach for ABRSs,particularly in slope engineering design,is imperative.This study proposes a stability evaluation model for ABRSs,incorporating the viscoelastic properties of rock,to quantitatively assess the safety factor and failure surface under seismic conditions.The mathematical description of the pseudo-dynamic method,derived in this study,accounts for the viscoelastic properties of ABRSs and integrates the HoekeBrown failure criterion with the Kelvin-Voigt stress-strain relationship of rocks.Furthermore,to address concurrent translation-rotation failure in ABRSs,upper bound limit analysis is utilized to quantify the safety factor.Through a comparison with existing literature,the proposed method considers the effect of harmonic vibration on the stability of ABRSs.The obtained safety factor is lower than that of the quasi-static method,with the resulting percentage change exceeding 5%.The critical failure surface demonstrates superior positional accuracy compared to the Aydan and Adhikary basal planes,with minimal error observed between the physical model test and the numerical simulation test.The parameter sensitivity analysis reveals that the inclination of ABRSs exhibits the highest sensitivity(Sk)value across the three levels of horizontal seismic coefficient(kh).The study aims to devise an expeditious calculation approach for assessing the stability of ABRSs during seismic events,intending to offer theoretical guidance for their stability analysis.
基金the National Key Research and Development Program of China(Grant No.2020YFA0711800)Jiangsu Provincial Innovation Capacity Building Program(Jiangsu Safety Emergency Equipment Technology Innovation Center(Grant No.BM2022013)the National Natural Science Foundation of China(Grant No.12372373).
文摘Methane in situ explosion fracturing(MISEF)technology improves deep reservoir permeability by generating multiple radial fractures around the wellbore,with fracture propagation significantly influenced by in situ stress and bedding structures.However,limited experimental studies on the combined effects of triaxial stress and explosive loading,along with detailed characterization of explosive damage,hinder further optimization of this technology.This study introduces an experimental method to simulate MISEF under triaxial stress,using CH4-O2 detonation to generate controllable explosive loads.Bedding shale samples are fractured in a pseudo-triaxial core holder.Micro-computed tomography(μ-CT)and nuclear magnetic resonance(NMR)are used to quantify three-dimensional(3D)fracture characteristics and pore structure evolution.LS-DYNA simulations are employed to elucidate fracture propagation and dynamic behavior.The results show that detonation produces explosive loads with overpressures of 69.929-84.338 MPa and pressure rise rates of up to 555.624 MPa/ms,exhibiting an oscillation-attenuation characteristic.μ-CT reveals 3-5 radial fractures,with 3D fracture volume and surface area decreasing as triaxial stress rises.Hoop stress inhibits fracture propagation more than axial stress.NMR analysis shows that explosive loading converts bound fluid to movable fluid,while in situ stress suppresses this process.With increasing triaxial stress,micropore(T2<10 ms)changes are minimal,while meso/macropore and fracture(T2>10 ms)NMR signals decrease significantly.Higher triaxial stress reduces water overpressure of stress loading chambers and vibrational displacement at sample boundaries.Numerical simulations indicate that explosive loading generates hoop tensile stress,which drives the formation of radial fractures.Triaxial stress increases hoop compressive stress,suppressing fracture propagation.Fractures initiate along bedding planes,forming cross-shaped or T-shaped patterns.
基金Projects(52208369,52309138,52108320)supported by the National Natural Science Foundation of ChinaProjects(2023NSFSC0284,2025ZNSFSC0409)supported by the Sichuan Science and Technology Program,ChinaProject(U22468214)supported by the Joint Fund Project for Railway Basic Research by the National Natural Science Foundation of China and China State Railway Group Co.,Ltd.
文摘In the practical slope engineering,the stability of lower sliding mass(region A)with back tensile cracks of the jointed rock slope attracts more attentions,but the upper rock mass(region B)may also be unstable.Therefore,in this study,based on the stepped failure mode of bedding jointed rock slopes,considering the influence of the upper rock mass on the lower stepped sliding mass,the improved failure model for analyzing the interaction force(F_(AB))between two regions is constructed,and the safety factors(F_(S))of two regions and whole region are derived.In addition,this paper proposes a method to determine the existence of F_(AB) using their respective acceleration values(a_(A) and a_(B))when regions A and B are unstable.The influences of key parameters on two regions and the whole region are analyzed.The results show that the variation of the F_(AB) and F_(S) of two regions can be obtained accurately based on the improved failure model.The accuracy of the improved failure model is verified by comparative analysis.The research results can explain the interaction mechanism of two regions and the natural phenomenon of slope failure caused by the development of cracks.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52225402,U1910206)the National Key Research and Development Project of China(Grant No.2022YFC3004602).
文摘The fracture network of hydraulic crack is significantly influenced by the bedding plane in coalbed methane extraction.Under mode Ⅱ loading,crack deflection holds a key position in hydraulic cracking,especially in hydraulic shearing.This study first analyzed the crack deflection theory of layered rock.The semi-circle bending test under asymmetric loading is performed,and the four-dimensional Lattice Spring Model(4D-LSM)is established to examine how the bedding parameters affect coal crack propagation under mode Ⅱ dominant loads.The 4D-LSM results are comparable to the coal loading test results under quasi-mode Ⅱ and the analytical prediction of crack deflection theory.During mode Ⅱ loading,the coal crack propagation is greatly influenced by the angle,strength,and elastic modulus of the bedding plane,while the effects of thickness and spacing of bedding are insignificant.The crack of coal tends to propagate towards the bedding,following a decrease in bedding angle,a decrease in bedding strength,and an increase in elastic modulus.With higher bedding strength,spacing,and thickness,the peak load on the coal sample is higher.The influences of bedding strength,elastic modulus,spacing,and thickness on the peak load of coal samples and its anisotropy gradually decrease.It is proved that compared with the tangential stress ratio and traditional energy release ratio theories,the corrected energy release ratio criterion can more accurately predict the direction of crack deflection of coal,especially under mode Ⅱ loading.The results can provide assistance in the design of initiation pressure and fracturing direction in coal seam hydraulic fracturing.
基金Dalian Science and Technology Innovation Fund under contract No.2024JJ11PT007Dalian Science and Technology Program for Innovation Talents of Dalian under contract No.2022RJ06+2 种基金Science and Technology Program of Liaoning Province under contract Nos.2022JH2/101300222 and 2022JH2/101300183Scientific Research Project of Education Department of Liaoning Province under contract No.LJ232410158056Research Funds for Undergraduate Universities of Liaoning Province under contract No.2024JBPTZ001。
文摘To improve understanding of coastal seagrass bed habitats in China,this study investigated seagrass distribution patterns and analyzed water column and sediment parameters of seagrass bed ecosystems on Guanglu,Zhangzi,and Haiyang Islands in Changhai County,Dalian City,during August 2022.The findings revealed that seagrass beds were predominantly composed of Zostera marina,Zostera japonica,and Zostera caespitosa,with Zostera marina as the dominant species.All seagrass species exhibited patchy spatial distributions,potentially linked to localized environmental stressors.Seagrass beds on Zhangzi Island exhibited high suspended particulate matter,while those on Haiyang Island showed elevated sediment chemical constituents and low dissolved oxygen in the water column.Among the three sites,Zhangzi Island had the lowest macroalgal coverage,shoot density,and epiphytic biomass.Seagrass beds on Haiyang Island displayed higher epiphytic biomass than the other two islands.Conversely,seagrass beds on Guanglu Island were characterized by lower shoot height and benthic biomass.Although ecological assessment indices classified all three island seagrass beds as grade I(currently stable),persistent anthropogenic disturbances were identified as drivers of gradual degradation,potentially threatening future stability.These findings highlight site-specific habitat characteristics and underscore the importance of targeted conservation strategies.This research provides crucial baseline data for the conservation and management of coastal seagrass beds.
文摘Additive manufacturing(AM)is an advanced production method for layer-by-layer fabrication,offering a paradigm shift in manufacturing.However,the sustainability of AM processes is poor,since suppliers recommend reusing 50%-70%of reprocessed powder,contributing to a significant increase in material disposal.To explore the possibility of fully reusing the polymeric material,we conduct a comprehensive characterisation of the powder particulates,in combination with analysis of the final prints.Utilizing optical and scanning electron microscopes,we statistically evaluate the size,morphology,and shape of the particles.Furthermore,tensile strength and deformation of printed bars is evaluated,showcasing the impact of aging on the print properties.The findings reveal that consecutive reuse of used powder significantly influences dimensional accuracy of the printed parts.We detect a 30.63%relative value of shrinkage after six printing iterations,which corresponds to an absolute shrinkage increase by 0.98%.This is significant considering the standard shrinkage for the material used is already 3.2%.Additionally,parts that are printed with reused material exhibit a small increase in elongation at yield,as well as an unexpected rise in tensile strength.Significant agglomeration of small particles is observed in the aged powder,since there are particles of less than 10μm,which are not found in the virgin powder.These results contribute to a better understanding of the issues related to the reusing of aged material,and offer invaluable insights for mitigating the environmental impact that is associated with material disposal in AM.
