The study focuses on the creep characteristics of significant yellow sandstone for water conservancy, hydropower, and other waterrelated slope excavation unloading rock-graded loading creep characteristics. It conduct...The study focuses on the creep characteristics of significant yellow sandstone for water conservancy, hydropower, and other waterrelated slope excavation unloading rock-graded loading creep characteristics. It conducts a uniaxial graded loading creep test on yellow sandstone under different pre-peak unloading and wetting-drying cycles. The improved nonlinear Nishihara model was obtained by introducing a nonlinear viscous element with an accelerated creep threshold switch. The sensitivity characteristics of the parameters of the improved creep model were analyzed and a nonlinear creep constitutive model was established, considering the unloading-cyclic intrinsic damage induced by water intrusion. The research results show that:(1)With an increase in the unloading point, the porosity of the rock samples initially decreases and then increases. As the number of cyclic water intrusions rises, the porosity of the rock samples gradually increases, reaching a maximum of 9.58% at an unloading point of 70% uniaxial compression stress(0.7 Rc) after five cycles.(2) Total creep deformation increases with the number of cyclic water intrusions;however, with an increase in the unloading ratio, the original samples show an initial decrease, followed by an increase in creep deformation. With a higher unloading ratio and various instances of cyclic water intrusion, the total creep time of the rock samples,compared to the original samples, is reduced by 21.8%and 23.02%. The creep damage mode gradually changes from shear damage to tensile damage.(3) The sensitivity characteristics of the improved creep model parameters show that transient elasticity modulus E1 is affected by the coupling of unloading and cyclic water intrusion. The viscoelastic modulus E2 and viscous coefficient η1 are mainly affected by unloading and cyclic water intrusion.(4) Based on the strain equivalence principle of damage mechanics, the damage treatment of the parameters in the original model is improved to construct a nonlinear creep constitutive model that considers unloading-cyclic water intrusion damage. A parameter inversion and comparison to the traditional Nishihara model reveal an average relative standard deviation of 0.271%,significantly less than 1%, indicating a more accurate nonlinear creep constitutive model. The research results are crucial for analyzing the long-term stability of water-related steep rocky slopes post-excavation and unloading and for preventing and controlling creep-type landslide disasters.展开更多
Investigating the combined effects of mining damage and creep damage on slope stability is crucial,as it can comprehensively reveal the non-linear deformation characteristics of rock under their joint influence.This s...Investigating the combined effects of mining damage and creep damage on slope stability is crucial,as it can comprehensively reveal the non-linear deformation characteristics of rock under their joint influence.This study develops a fractional-order nonlinear creep constitutive model that incorporates the double damage effect and implements a non-linear creep subroutine for soft rock using the threedimensional finite difference method on the FLAC3D platform.Comparative analysis of the theoretical,numerical,and experimental results reveals that the fractional-order constitutive model,which incorporates the double damage effect,accurately reflects the distinct deformation stages of green mudstone during creep failure and effectively captures the non-linear deformation in the accelerated creep phase.The numerical results show a fitting accuracy exceeding 97%with the creep test curves,significantly outperforming the 61%accuracy of traditional creep models.展开更多
A new unified constitutive model was developed to predict the two-stage creep-aging(TSCA)behavior of Al-Zn-Mg-Cu alloys.The particular bimodal precipitation feature was analyzed and modeled by considering the primary ...A new unified constitutive model was developed to predict the two-stage creep-aging(TSCA)behavior of Al-Zn-Mg-Cu alloys.The particular bimodal precipitation feature was analyzed and modeled by considering the primary micro-variables evolution at different temperatures and their interaction.The dislocation density was incorporated into the model to capture the effect of creep deformation on precipitation.Quantitative transmission electron microscopy and experimental data obtained from a previous study were used to calibrate the model.Subsequently,the developed constitutive model was implemented in the finite element(FE)software ABAQUS via the user subroutines for TSCA process simulation and the springback prediction of an integral panel.A TSCA test was performed.The result shows that the maximum radius deviation between the formed plate and the simulation results is less than 0.4 mm,thus validating the effectiveness of the developed constitutive model and FE model.展开更多
Concrete creep,which is characterised by the gradual,time-dependent deformation under sustained loading,remains a critical factor for structural durability,safety and long-term performance.This review synthesises key ...Concrete creep,which is characterised by the gradual,time-dependent deformation under sustained loading,remains a critical factor for structural durability,safety and long-term performance.This review synthesises key advancements in creep research,tracing its evolution from early foundational experimental studies and empirical models such as Bažant’s B3 to contemporary materials innovations and emerging computational frameworks.Novel contributions and notable developments include the integration of Finite Element Analysis(FEA),Bayesian optimisation,and fractional calculus,which have significantly improved predictive accuracy under diverse and varying environmental conditions.The study characterised the pivotal role material innovation plays in this evolution and progression,with recent focus on the development of high-performance and sustainable concretes.These advanced materials include Ultra-High-Performance Concrete(UHPC),Recycled Aggregate Concrete(RAC),Ground Granulated Blast-Furnace Slag(GGBFS)modified concrete,Rice Husk Ash(RHA)composites,and nano-modified concretes,all aimed at enhancing creep resistance and sustainability.The study also examines the influence of temperature,humidity,and sustained stress on creep behaviour,highlighting the need for robust multiscale models.Emerging trends,such as artificial intelligence,mesoscopic modelling,and eco-efficient materials,are identified as transformative tools for future research and applications.By bridging historical insights with modern innovations,this work provides a strategic framework for the design of resilient,durable,and sustainable infrastructure systems in the face of evolving performance demands and environmental challenges.展开更多
To elucidate the cyclic creep mechanisms in China's impure salt rock after high-temperature damage,cyclic nanoindentation and uniaxial cyclic loading tests were conducted at 25℃,100℃,120℃,and 160℃in this study...To elucidate the cyclic creep mechanisms in China's impure salt rock after high-temperature damage,cyclic nanoindentation and uniaxial cyclic loading tests were conducted at 25℃,100℃,120℃,and 160℃in this study.The results revealed that under cyclic nanoindentation,gypsum mineral exhibited significantly lower indentation depths compared to halite and ankerite minerals,indicating superior resistance to deformation.Additionally,the results demonstrated that high temperature significantly enhances the creep behavior.The maximum indentation depth and creep displacement of minerals,as well as the maximum deformation and creep strain of rock cores,all followed an exponential increase with rising temperatures,with the rate of increase accelerating at higher temperatures.Importantly,it was found that mineral deformation is not the dominant factor in the overall deformation of rock cores;however,the behavior of the mineral phases fundamentally governs the salt rock's mechanical response under stress.Based on these findings,a new constitutive model for cyclic creep was established based on fractional derivatives to accurately characterize the nonlinear cyclic creep characteristics of impure salt rocks at different scales.This model was validated against test data,effectively representing the periodic fluctuations in indentation depth or strain,particularly during the accelerated creep stage.Furthermore,a temperature-dependent correction parameter was introduced,along with a modified Mori-Tanaka method,to upscale microscale results to the macroscale across varying temperatures.This study provides a theoretical foundation for predicting deformation and assessing the stability of salt cavern walls under high-temperature and cyclic loading conditions in deep geological settings.展开更多
Existing creep constitutive models rarely incorporate studies on the coupling mechanism between creep damage and rock strain softening/hardening.This study analyzed the strain softening and hardening behaviors of argi...Existing creep constitutive models rarely incorporate studies on the coupling mechanism between creep damage and rock strain softening/hardening.This study analyzed the strain softening and hardening behaviors of argillaceous sandstone and sandy mudstone during load-induced failure based on the plastic increment theory.These behaviors were then coupled with an improved Burgers creep model to establish a coupled creep-damage and plastic softening/hardening model.Finally,the validity and engineering applicability of the proposed model were verified through FLAC~(3D)numerical simulations.The numerical simulation results of standard cylindrical specimens show that the established coupling model can effectively reflect the unloading creep deformation law and failure characteristics of argillaceous sandstone and sandy mudstone.Taking the diversion tunnel of a hydropower station in Northwest China as an example for engineering application,the coupled creep-damage and plastic softening/hardening model is introduced into FLAC~(3D)to carry out numerical simulation calculation of the tunnel under excavation and unsupported creep conditions.The results show that the uncoordinated deformation of the upper and lower walls of the surrounding rock of the tunnel is more prominent.When the buried depth of the tunnel increases to 80 m,the monitoring point C in the sandy mudstone area of the upper wall shows nonlinear accelerated deformation under unsupported creep conditions,and the maximum displacement in the horizontal direction reaches 44.5 mm,and the maximum displacement in the vertical direction reaches 53.5 mm.The coupled creep-damage and plastic softening/hardening model established in the research results can well describe the whole process of uncoordinated deformation and failure in the unloading creep process of soft-hard interbedded rock mass.展开更多
The interface between concrete and soil-rock mixture(SRM-concrete interface)under freeze-thaw cycles is very prone to creep damage,threatening the long-term stability of the superstructure in cold regions.However,ther...The interface between concrete and soil-rock mixture(SRM-concrete interface)under freeze-thaw cycles is very prone to creep damage,threatening the long-term stability of the superstructure in cold regions.However,there is no study concerning the characteristics of the nonlinear accelerated creep stage using the existing creep model in SRM-concrete interface.Therefore,shear creep tests were conducted to study the creep displacement and failure modes at the SRM-concrete interface under varying rock contents(15%-65%)and freeze-thaw cycles(0-20 iterations).A modified Burgers viscoelastic-plastic constitutive model is proposed to illustrate the creep failure characteristics of SRM-concrete interface induced by freeze-thaw cycles,which contains a hardening and loosening component.Results reveal a notable decrease in creep deformation correlating with increased rock content at SRM-concrete interface.Notably,the resistance of SRM-concrete interface to shear creep behavior peaks after five freeze-thaw cycles.This modified creep model accurately describes the nonlinear hardening and loosening creep behavior at the SRM-concrete interface,offering a substantial theoretical foundation for studying the longterm deformation and service life of superstructures in cold regions.展开更多
To investigate the temperature susceptibility and nonlinear memory effects of artificially frozen soil creep behavior,this study conducted uniaxial step-loading creep tests under controlled temperatures ranging from-1...To investigate the temperature susceptibility and nonlinear memory effects of artificially frozen soil creep behavior,this study conducted uniaxial step-loading creep tests under controlled temperatures ranging from-10℃to-20℃.The transient creep characteristics and steady-state creep rates of artificially frozen soils were systematically examined with respect to variations in temperature and stress.Experimental results demonstrate that decreasing temperatures lead to a decaying trend in the steady-state creep rate of silty frozen soil,confirming that low-temperature environments significantly inhibit plastic flow while enhancing material stiffness.Based on fractional calculus theory,a fractional derivative creep model was established.By incorporating temperature dependencies,the model was further improved to account for both stress and temperature effects.The model predictions align closely with experimental data,achieving over 91%agreement(standard deviation±1.8%),and effectively capture the stress-strain behavior of artificially frozen soil under varying thermal conditions.This research provides a reliable theoretical foundation for studying deformation characteristics in cold-regions engineering.展开更多
The creep deformation and mechanical properties of 2219 aluminum alloy were experimentally investigated under both tension and compression at the temperature of 165℃for different time.The results indicated that the c...The creep deformation and mechanical properties of 2219 aluminum alloy were experimentally investigated under both tension and compression at the temperature of 165℃for different time.The results indicated that the creep deformation under tensile stress was greater than that under compressive stress.As the stress level increases,the compressive creep rate showed more significant increase.The yield strength after compressive stress creep-ageing was higher than that after stress-free ageing,with the lowest strength observed in the tensile-aged sample.Overall,the average phase length after compressive stress creep-ageing was larger than after tensile stress ageing.Under tensile stress,the number and size of precipitates at small angles to the stress direction were larger than those perpendicular to the stress direction.In contrast,under compressive stress,this relationship was reversed,and the preferential orientation of phases became more pronounced with ageing time.A unified,physics-based creep-ageing constitutive model,accounting for the orientation of precipitation,was developed for both tensile and compressive stress conditions.The predicted results were in good agreement with the experimental data.These findings,along with the developed model,provide a theoretical and simulation basis for precise creep-ageing forming of components under complex stresses.展开更多
Investigations into the long-term creep behavior of Beishan granite in uniaxial compression were conducted.Four levels of axial stress(60,70,87,and 95 MPa)were applied to rock specimens.Contrasting with earlier resear...Investigations into the long-term creep behavior of Beishan granite in uniaxial compression were conducted.Four levels of axial stress(60,70,87,and 95 MPa)were applied to rock specimens.Contrasting with earlier research,the long-term creep data in this work present a substantial advancement in the time dimension.Except for the sample subjected to 60 MPa axial loading,which did not fail after a loading duration of 1650 d,the specimens under the other three stresses all failed after sustained constant loading durations of 1204,1023,and 839 d,respectively.A lower envelope of driving stress-ratio for crystalline rocks was obtained,tending towards approximately 0.45 over an infinite time scale.According to the experimental results,as axial stress increases,both the axial strain accumulated in the transient creep process and the strain rate associated with steady-state creep deformation increase exponentially;however,the share of steady-state creep strain remains nearly constant at about82.53%.A novel damage-based creep model was put forward.It provides an enhanced depiction of the comprehensive creep process in rocks,notably improving the accuracy in forecasting the accelerated creep phase,which significantly impacts the long-term stability of engineering structures.展开更多
This study aimed to investigate the influence of recycled sand(RS)content and water-binder ratio on the long term performance of recycled sand concrete(RSC).A 220 days drying shrinkage and creep test of RSC was conduc...This study aimed to investigate the influence of recycled sand(RS)content and water-binder ratio on the long term performance of recycled sand concrete(RSC).A 220 days drying shrinkage and creep test of RSC was conducted,and the microhardness of ITZ were analyzed to explain the differences in performance.The experimental results indicate that,when RS content is 50%,the drying shrinkage and creep strain of RSC is the smallest.This is attributed to the highest microhardness in the ITZ when the RS content is 50%.When the RS content is 100%,the shrinkage and creep strains increase due to the high water absorption of RS,which leads to the evaporation of additional water and the deterioration of the ITZ.As the water-binder ratio increases,the drying shrinkage and creep strain of RSC with different RS content increases.According to the EC2 specification and the CEB-FIP specification,the drying shrinkage and creep prediction models for RSC have been established.展开更多
In deep coal mining,surrounding rock is subjected to both high in-situ stress and intense mining disturbances,leading to significant time-dependent behavior.Accurately capturing this behavior is essential for predicti...In deep coal mining,surrounding rock is subjected to both high in-situ stress and intense mining disturbances,leading to significant time-dependent behavior.Accurately capturing this behavior is essential for predicting long-term roadway stability,necessitating the development of a reliable constitutive creep model and numerical simulation approach.In this study,creep experiments were conducted on pre-damaged rock with varying initial damage levels to investigate the time-dependent mechanical properties.Based on the experimental results,an accelerated-creep criterion was proposed,and an elastic-viscoplastic creep damage model(EVPCD)was established that simultaneously considers the effects of time-dependent damage and instantaneous damage caused by stress disturbances on rock creep behavior.Subsequently,the effectiveness of the proposed creep model was verified using experimental data,and the secondary development of the EVPCD model was completed based on the FLAC3D platform.Following this,a long-term stability analysis method of deep surrounding rock that accounts for excavation-and mining-induced disturbances was proposed.Using the main roadway of Xutuan Coal Mine as a case study,numerical simulations were carried out to investigate the time-dependent deformation and failure characteristics of the surrounding rock following excavation and mining disturbance.Combined with on-site monitoring of the surrounding rock damage areas,the results indicate that the EVPCD outperforms the CVISC and Nishihara models in predicting the time-dependent behavior of deep surrounding rock.展开更多
This study presents and verifies a hybrid methodology for reliable determination of parameters in structural rheological models(Zener,Burgers,and Maxwell)describing the viscoelastic behavior of polyurethane specimens ...This study presents and verifies a hybrid methodology for reliable determination of parameters in structural rheological models(Zener,Burgers,and Maxwell)describing the viscoelastic behavior of polyurethane specimens manufactured using extrusion-based 3D printing.Through comprehensive testing,including cyclic compression at strain rates ranging from 0.12 to 120 mm/min(0%-15%strain)and creep/relaxation experiments(10%-30%strain),the lumped parameters were independently determined using both analytical and numerical solutions of the models’differential equations,followed by cross-verification in additional experiments.Numerical solutions for creep and relaxation problems were obtained using finite element analysis,with the three-parameter Mooney-Rivlin model and Prony series employed to simulate elastic and viscous stress components,respectively.Energy dissipation per cycle was quantified during cyclic compression tests.The results demonstrate that all three models adequately describe material behavior within the 0%-15%strain range across various strain rates.Comparative analysis revealed the Burgers model’s superior performance in characterizing creep and stress relaxation at low strain levels.While Zener and Burgers model parameters from uniaxial compression showed limited applicability for energy dissipation calculations,the generalized Maxwell model effectively captured viscoelastic properties across different strain rates.Notably,parameters derived from creep tests provided a more universal assessment of dissipative properties due to optimization based on characteristic curve regions.Both parameter sets described polyurethane’s elastic-hysteretic behavior with approximately 20%error,proving significantly more accurate than the linear strain-time dependence hypothesis.Finite element analysis(FEA)complemented numerical modeling by demonstrating that while the generalized Maxwell model effectively describes initial rapid stress-strain changes,FEA provides superior characterization of steady-state processes.This computational approach yields more physically representative results compared to simplified analytical solutions,despite certain limitations in transient analysis.展开更多
By the methods of uniaxial single-stage loading and graded incremental cyclic loading, the creep experiments were performed on the deep saturated rock from Dongguashan Mine, and the creep curves of saturated rock unde...By the methods of uniaxial single-stage loading and graded incremental cyclic loading, the creep experiments were performed on the deep saturated rock from Dongguashan Mine, and the creep curves of saturated rock under different loading stresses were obtained. By comparing with the creep rule of dry rock in the same location, the creep rule of deep saturated rock was analyzed. Based on the united rheological mechanical model, the rheological model of deep saturated rock was recognized, and the parameters of the model were determined. The results show that the creep curves are very smooth under low stress, but the phenomena of wave and catastrophe turn up under high stress, and the bearing capacity of rock is weakening over time. The rheological properties of saturated and dry rocks are very different under tlie condition of deep high stress, especially when unloading, degradation and damage of rock quality is more serious, and the effect of water cannot be neglected. The H--HIN--NJS model （Schofield-Scott-Blair model） was selected to represent the rheology rule of deep saturated rock, and the fitting curves of model agree well with the experiment data, so the selected model is reasonable.展开更多
A set of uniaxial tensile creep tests at different pre-deformations, aging temperatures and stress levels were carried out for Al-Li-S4 alloy, and the creep behavior and the effects of pre-deformation on mechanical pr...A set of uniaxial tensile creep tests at different pre-deformations, aging temperatures and stress levels were carried out for Al-Li-S4 alloy, and the creep behavior and the effects of pre-deformation on mechanical properties and microstructures were determined under basic thermodynamics conditions of aging forming. The results show that pre-deformation shortens the time of primary creep and raises the second steady-state creep rate. Then, the total creep strain is greater, but in the range of test parameters it is still smaller than that without pre-deformation. In addition, transmission electron microscopy（TEM） observation shows that pre-deformation promotes the formation of T1 phase and θ′ phase and makes them distribute more dispersively, while inhibits the generation of δ′ phase, which leads to the improvement of mechanical properties of the alloy. A unified constitutive model reflecting the effects of aging mechanism, stress levels and different pre-deformations was established. The fitting results agree with the experimental data well.展开更多
The constitutive modeling and springback simulation for AA2524 sheet in creep age forming（CAF） process were presented.A series of creep aging tests were performed on AA2524 at the temperature of 180-200 °C and ...The constitutive modeling and springback simulation for AA2524 sheet in creep age forming（CAF） process were presented.A series of creep aging tests were performed on AA2524 at the temperature of 180-200 °C and under the stress of 140-210 MPa for 16 h.Based on these experimental data,material constitutive equations which can well characterize creep aging behaviors of the tested alloy were developed.The effect of interior stress distributed along the sheet thickness on springback was simulated using FE software MSC.MARC by compiling the established constitutive models into the user subroutine.The simulation results showed that the amount of sheet springback was 61.12% when merely considering tensile stress existing along the sheet thickness;while sheet springback was up to 65.93% when taking both tensile and compressive stresses into account.In addition,an AA2524 rectangular sheet was subjected to CAF experiment in resistance furnace.The springback value of the formed rectangular sheet was 68.2%,which was much closer to 65.93%.This confirms that both tensile and compressive stresses across the sheet thickness should be considered in accurately predicting springback of the sheet after forming,which can be more consistent with experimental results.展开更多
Previous constitutive models of granite shear creep have two limitations：（1） although moisture greatly affects granite shear creep behavior, currently there are no constitutive models that include this factor;（2）...Previous constitutive models of granite shear creep have two limitations：（1） although moisture greatly affects granite shear creep behavior, currently there are no constitutive models that include this factor;（2） there are also no models that include an acceleration stage. This paper presents an improved Burgers constitutive model with the addition of a damage parameter to characterize the moisture effect and uses a nonlinear relation equation between stress and strain for inclusion as the acceleration stage. The damage parameter is determined from granite creep experiment under four different moisture contents（0%, 0.22%, 0.49%, and 0.79%）. The nonlinear relation equation is obtained by fitting a dataset of stain versus time under five different loading stages. To verify the presented model, a creep experiment was conducted on other granite samples and the results show that the model agrees well with the experimental observation data.展开更多
The mechanical behavior of sliding zone soils plays a significant role in landslide. In general, the sliding zone soils are basically in unsaturated state due to rainfall infiltration and reservoir water level fluctua...The mechanical behavior of sliding zone soils plays a significant role in landslide. In general, the sliding zone soils are basically in unsaturated state due to rainfall infiltration and reservoir water level fluctuation. Meanwhile, a large number of examples show that the deformation processes of landslides always take a long period of time, indicating that landslides exhibit a time-dependent property. Therefore, the deforma- tion of unsaturated soils of landslide involves creep behaviors. In this paper, the Burgers creep model for unsaturated soils under triaxial stress state is considered based on the unsaturated soil mechanics. Then, by curve fitting using the least squares method, creep parameters in different matric suction states are obtained based on the creep test data of unsaturated soils in the sliding zones of Qianjiangping landslide. Results show that the predicted results are in good agreement with the experimental data, Finally, to fur- ther explore the creep characteristics of the unsaturated soils in sliding zones, the relationships between parameters of the model and matric suction are analyzed and a revised Burgers creep model is developed correspondingly. Simulations on another group of test data are performed by using the modified Burgers creep model and reasonable results are observed,展开更多
Estimating long-term creep deformation and life of materials is an effective way to ensure the service safety and to reduce the cost of long-term integrity evaluation of high temperature structural materials.Since the...Estimating long-term creep deformation and life of materials is an effective way to ensure the service safety and to reduce the cost of long-term integrity evaluation of high temperature structural materials.Since the 1980 s, the θ projection model has been widely used for predicting creep lives due to its ability to capture the characteristic transitions observed in creep curves obtained under constant true stress conditions. However, the creep rupture behavior under constant load or engineering stress conditions cannot be simulated accurately using this model because of the different stress states. In this paper, creep curves obtained under constant load conditions were analyzed using a modified θ projection model by considering the increase in true stress with creep deformation during the creep tests. This model is expressed as ε = θ_1(1-e^(-θ_2t)) + θ3 e^(θ_4e^θ5^εt)-1, and was validated using the creep curves of K465 and DZ125 superalloys tested at a range of temperatures and engineering stresses. Moreover, it was shown that the predictive capability of the modified θ projection model was significantly improved over the original one, as it reduces the prediction uncertainty from a range of 10% to 20% to below 5%. Meanwhile,it was shown that the model can be reasonably used for predicting constant stress creep conditions, when appropriate parameters are used. The prediction performance of the modified model will be discussed in another paper. The results of this study show great potential for the evaluation and assessment of the service safety of structural materials used in applications where designs are limited by creep deformation.展开更多
Coal exhibits different creep behaviours when filled with different amounts of gas. Creep tests of coal filled with 0 and 0.5 MPa gas were performed, and strain under different axial stress was compared.The three cree...Coal exhibits different creep behaviours when filled with different amounts of gas. Creep tests of coal filled with 0 and 0.5 MPa gas were performed, and strain under different axial stress was compared.The three creep constitutive models which were analysed using the method fitting experimental data for determining which creep model can reflect the creep process of the test best. The results show that the deformation of coal filled with 0.5 MPa gas is more higher than that of coal filled with 0 MPa gas under the same axial stress. Gas plays a positive effect on the deformation of coal process and will accelerate creep process. And gas will reduce coal intensity and change coal creep properties.Compared with Nishihara Model and Extensional Nishihara Model, Burgers Model can reflect the three stages of creep process of coal filled with gas better. The research results can contribute to reveal coal and gas outburst mechanism.展开更多
基金We gratefully acknowledge the financial support from the Key Laboratory of Geological Safety of Coastal Urban Underground Space,Ministry of Natural Resources(BHKF2022Y03)Shandong Provincial Colleges and Universities Youth Innovation Technology Support Program,Education Department of Shandong Province(grant number 2023KJ092).
文摘The study focuses on the creep characteristics of significant yellow sandstone for water conservancy, hydropower, and other waterrelated slope excavation unloading rock-graded loading creep characteristics. It conducts a uniaxial graded loading creep test on yellow sandstone under different pre-peak unloading and wetting-drying cycles. The improved nonlinear Nishihara model was obtained by introducing a nonlinear viscous element with an accelerated creep threshold switch. The sensitivity characteristics of the parameters of the improved creep model were analyzed and a nonlinear creep constitutive model was established, considering the unloading-cyclic intrinsic damage induced by water intrusion. The research results show that:(1)With an increase in the unloading point, the porosity of the rock samples initially decreases and then increases. As the number of cyclic water intrusions rises, the porosity of the rock samples gradually increases, reaching a maximum of 9.58% at an unloading point of 70% uniaxial compression stress(0.7 Rc) after five cycles.(2) Total creep deformation increases with the number of cyclic water intrusions;however, with an increase in the unloading ratio, the original samples show an initial decrease, followed by an increase in creep deformation. With a higher unloading ratio and various instances of cyclic water intrusion, the total creep time of the rock samples,compared to the original samples, is reduced by 21.8%and 23.02%. The creep damage mode gradually changes from shear damage to tensile damage.(3) The sensitivity characteristics of the improved creep model parameters show that transient elasticity modulus E1 is affected by the coupling of unloading and cyclic water intrusion. The viscoelastic modulus E2 and viscous coefficient η1 are mainly affected by unloading and cyclic water intrusion.(4) Based on the strain equivalence principle of damage mechanics, the damage treatment of the parameters in the original model is improved to construct a nonlinear creep constitutive model that considers unloading-cyclic water intrusion damage. A parameter inversion and comparison to the traditional Nishihara model reveal an average relative standard deviation of 0.271%,significantly less than 1%, indicating a more accurate nonlinear creep constitutive model. The research results are crucial for analyzing the long-term stability of water-related steep rocky slopes post-excavation and unloading and for preventing and controlling creep-type landslide disasters.
基金support from the National Natural Science Foundation of China(No.52308316)the Scientific Research Foundation of Weifang University(Grant No.2024BS42)+2 种基金China Postdoctoral Science Foundation(No.2022M721885)the Key Laboratory of Rock Mechanics and Geohazards of Zhejiang Province(No.ZJRMG-2022-01)supported by Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(NO.SKLGME023017).
文摘Investigating the combined effects of mining damage and creep damage on slope stability is crucial,as it can comprehensively reveal the non-linear deformation characteristics of rock under their joint influence.This study develops a fractional-order nonlinear creep constitutive model that incorporates the double damage effect and implements a non-linear creep subroutine for soft rock using the threedimensional finite difference method on the FLAC3D platform.Comparative analysis of the theoretical,numerical,and experimental results reveals that the fractional-order constitutive model,which incorporates the double damage effect,accurately reflects the distinct deformation stages of green mudstone during creep failure and effectively captures the non-linear deformation in the accelerated creep phase.The numerical results show a fitting accuracy exceeding 97%with the creep test curves,significantly outperforming the 61%accuracy of traditional creep models.
基金supported by the National Key R&D Program of China(No.2021YFB3400900)the National Natural Science Foundation of China(Nos.52175373,52205435)+1 种基金Natural Science Foundation of Hunan Province,China(No.2022JJ40621)the Innovation Fund of National Commercial Aircraft Manufacturing Engineering Technology Center,China(No.COMACSFGS-2022-1875)。
文摘A new unified constitutive model was developed to predict the two-stage creep-aging(TSCA)behavior of Al-Zn-Mg-Cu alloys.The particular bimodal precipitation feature was analyzed and modeled by considering the primary micro-variables evolution at different temperatures and their interaction.The dislocation density was incorporated into the model to capture the effect of creep deformation on precipitation.Quantitative transmission electron microscopy and experimental data obtained from a previous study were used to calibrate the model.Subsequently,the developed constitutive model was implemented in the finite element(FE)software ABAQUS via the user subroutines for TSCA process simulation and the springback prediction of an integral panel.A TSCA test was performed.The result shows that the maximum radius deviation between the formed plate and the simulation results is less than 0.4 mm,thus validating the effectiveness of the developed constitutive model and FE model.
文摘Concrete creep,which is characterised by the gradual,time-dependent deformation under sustained loading,remains a critical factor for structural durability,safety and long-term performance.This review synthesises key advancements in creep research,tracing its evolution from early foundational experimental studies and empirical models such as Bažant’s B3 to contemporary materials innovations and emerging computational frameworks.Novel contributions and notable developments include the integration of Finite Element Analysis(FEA),Bayesian optimisation,and fractional calculus,which have significantly improved predictive accuracy under diverse and varying environmental conditions.The study characterised the pivotal role material innovation plays in this evolution and progression,with recent focus on the development of high-performance and sustainable concretes.These advanced materials include Ultra-High-Performance Concrete(UHPC),Recycled Aggregate Concrete(RAC),Ground Granulated Blast-Furnace Slag(GGBFS)modified concrete,Rice Husk Ash(RHA)composites,and nano-modified concretes,all aimed at enhancing creep resistance and sustainability.The study also examines the influence of temperature,humidity,and sustained stress on creep behaviour,highlighting the need for robust multiscale models.Emerging trends,such as artificial intelligence,mesoscopic modelling,and eco-efficient materials,are identified as transformative tools for future research and applications.By bridging historical insights with modern innovations,this work provides a strategic framework for the design of resilient,durable,and sustainable infrastructure systems in the face of evolving performance demands and environmental challenges.
基金supported by the National Natural Science Foundation of China(Grant No.12402488)the China Postdoctoral Science Foundation(Grant No.2023M742898)the Postdoctoral Fellowship Program of China Postdoctoral Science Foundation(Grant No.GZC20232193).
文摘To elucidate the cyclic creep mechanisms in China's impure salt rock after high-temperature damage,cyclic nanoindentation and uniaxial cyclic loading tests were conducted at 25℃,100℃,120℃,and 160℃in this study.The results revealed that under cyclic nanoindentation,gypsum mineral exhibited significantly lower indentation depths compared to halite and ankerite minerals,indicating superior resistance to deformation.Additionally,the results demonstrated that high temperature significantly enhances the creep behavior.The maximum indentation depth and creep displacement of minerals,as well as the maximum deformation and creep strain of rock cores,all followed an exponential increase with rising temperatures,with the rate of increase accelerating at higher temperatures.Importantly,it was found that mineral deformation is not the dominant factor in the overall deformation of rock cores;however,the behavior of the mineral phases fundamentally governs the salt rock's mechanical response under stress.Based on these findings,a new constitutive model for cyclic creep was established based on fractional derivatives to accurately characterize the nonlinear cyclic creep characteristics of impure salt rocks at different scales.This model was validated against test data,effectively representing the periodic fluctuations in indentation depth or strain,particularly during the accelerated creep stage.Furthermore,a temperature-dependent correction parameter was introduced,along with a modified Mori-Tanaka method,to upscale microscale results to the macroscale across varying temperatures.This study provides a theoretical foundation for predicting deformation and assessing the stability of salt cavern walls under high-temperature and cyclic loading conditions in deep geological settings.
基金funded by the Natural Science Foundation of China(Grant No.U22A20600)。
文摘Existing creep constitutive models rarely incorporate studies on the coupling mechanism between creep damage and rock strain softening/hardening.This study analyzed the strain softening and hardening behaviors of argillaceous sandstone and sandy mudstone during load-induced failure based on the plastic increment theory.These behaviors were then coupled with an improved Burgers creep model to establish a coupled creep-damage and plastic softening/hardening model.Finally,the validity and engineering applicability of the proposed model were verified through FLAC~(3D)numerical simulations.The numerical simulation results of standard cylindrical specimens show that the established coupling model can effectively reflect the unloading creep deformation law and failure characteristics of argillaceous sandstone and sandy mudstone.Taking the diversion tunnel of a hydropower station in Northwest China as an example for engineering application,the coupled creep-damage and plastic softening/hardening model is introduced into FLAC~(3D)to carry out numerical simulation calculation of the tunnel under excavation and unsupported creep conditions.The results show that the uncoordinated deformation of the upper and lower walls of the surrounding rock of the tunnel is more prominent.When the buried depth of the tunnel increases to 80 m,the monitoring point C in the sandy mudstone area of the upper wall shows nonlinear accelerated deformation under unsupported creep conditions,and the maximum displacement in the horizontal direction reaches 44.5 mm,and the maximum displacement in the vertical direction reaches 53.5 mm.The coupled creep-damage and plastic softening/hardening model established in the research results can well describe the whole process of uncoordinated deformation and failure in the unloading creep process of soft-hard interbedded rock mass.
基金The National Natural Science Foundation of China(Grant No.42271144,Grant No.42071100)the Project of Shaanxi Province Qinchuangyuan"scientists&engineers"team construction(Grant No.2022KXJ-086)the Project of Application Fundamental Research of China Communications Construction(Grant No.2022-ZJKJ-PTJS07)。
文摘The interface between concrete and soil-rock mixture(SRM-concrete interface)under freeze-thaw cycles is very prone to creep damage,threatening the long-term stability of the superstructure in cold regions.However,there is no study concerning the characteristics of the nonlinear accelerated creep stage using the existing creep model in SRM-concrete interface.Therefore,shear creep tests were conducted to study the creep displacement and failure modes at the SRM-concrete interface under varying rock contents(15%-65%)and freeze-thaw cycles(0-20 iterations).A modified Burgers viscoelastic-plastic constitutive model is proposed to illustrate the creep failure characteristics of SRM-concrete interface induced by freeze-thaw cycles,which contains a hardening and loosening component.Results reveal a notable decrease in creep deformation correlating with increased rock content at SRM-concrete interface.Notably,the resistance of SRM-concrete interface to shear creep behavior peaks after five freeze-thaw cycles.This modified creep model accurately describes the nonlinear hardening and loosening creep behavior at the SRM-concrete interface,offering a substantial theoretical foundation for studying the longterm deformation and service life of superstructures in cold regions.
基金National Key Research and Development Program of China“Structural Stability Assessment Techniques and Demonstration for Masonry Ancient Pagodas”(2023YFF0906005)。
文摘To investigate the temperature susceptibility and nonlinear memory effects of artificially frozen soil creep behavior,this study conducted uniaxial step-loading creep tests under controlled temperatures ranging from-10℃to-20℃.The transient creep characteristics and steady-state creep rates of artificially frozen soils were systematically examined with respect to variations in temperature and stress.Experimental results demonstrate that decreasing temperatures lead to a decaying trend in the steady-state creep rate of silty frozen soil,confirming that low-temperature environments significantly inhibit plastic flow while enhancing material stiffness.Based on fractional calculus theory,a fractional derivative creep model was established.By incorporating temperature dependencies,the model was further improved to account for both stress and temperature effects.The model predictions align closely with experimental data,achieving over 91%agreement(standard deviation±1.8%),and effectively capture the stress-strain behavior of artificially frozen soil under varying thermal conditions.This research provides a reliable theoretical foundation for studying deformation characteristics in cold-regions engineering.
基金Project(JCKY2023205B003)supported by the Defense Industrial Technology Development Program,China。
文摘The creep deformation and mechanical properties of 2219 aluminum alloy were experimentally investigated under both tension and compression at the temperature of 165℃for different time.The results indicated that the creep deformation under tensile stress was greater than that under compressive stress.As the stress level increases,the compressive creep rate showed more significant increase.The yield strength after compressive stress creep-ageing was higher than that after stress-free ageing,with the lowest strength observed in the tensile-aged sample.Overall,the average phase length after compressive stress creep-ageing was larger than after tensile stress ageing.Under tensile stress,the number and size of precipitates at small angles to the stress direction were larger than those perpendicular to the stress direction.In contrast,under compressive stress,this relationship was reversed,and the preferential orientation of phases became more pronounced with ageing time.A unified,physics-based creep-ageing constitutive model,accounting for the orientation of precipitation,was developed for both tensile and compressive stress conditions.The predicted results were in good agreement with the experimental data.These findings,along with the developed model,provide a theoretical and simulation basis for precise creep-ageing forming of components under complex stresses.
基金financially supported by the China Atomic Energy Authority(CAEA)through the Geological Disposal Programthe National Natural Science Foundation of China(No.42307258)the China National Nuclear Corporation Fundamental Research Project(No.CNNC-JCYJ-202307)。
文摘Investigations into the long-term creep behavior of Beishan granite in uniaxial compression were conducted.Four levels of axial stress(60,70,87,and 95 MPa)were applied to rock specimens.Contrasting with earlier research,the long-term creep data in this work present a substantial advancement in the time dimension.Except for the sample subjected to 60 MPa axial loading,which did not fail after a loading duration of 1650 d,the specimens under the other three stresses all failed after sustained constant loading durations of 1204,1023,and 839 d,respectively.A lower envelope of driving stress-ratio for crystalline rocks was obtained,tending towards approximately 0.45 over an infinite time scale.According to the experimental results,as axial stress increases,both the axial strain accumulated in the transient creep process and the strain rate associated with steady-state creep deformation increase exponentially;however,the share of steady-state creep strain remains nearly constant at about82.53%.A novel damage-based creep model was put forward.It provides an enhanced depiction of the comprehensive creep process in rocks,notably improving the accuracy in forecasting the accelerated creep phase,which significantly impacts the long-term stability of engineering structures.
基金Funded by the National Key Research and Development Program of China(No.2020YFC1909905)the Science and Technology Research and Development Plan of China National Railway Group Co.,Ltd.(No.L2022G009)the New Cornerstone Science Foundation through the XPLORER PRIZE。
文摘This study aimed to investigate the influence of recycled sand(RS)content and water-binder ratio on the long term performance of recycled sand concrete(RSC).A 220 days drying shrinkage and creep test of RSC was conducted,and the microhardness of ITZ were analyzed to explain the differences in performance.The experimental results indicate that,when RS content is 50%,the drying shrinkage and creep strain of RSC is the smallest.This is attributed to the highest microhardness in the ITZ when the RS content is 50%.When the RS content is 100%,the shrinkage and creep strains increase due to the high water absorption of RS,which leads to the evaporation of additional water and the deterioration of the ITZ.As the water-binder ratio increases,the drying shrinkage and creep strain of RSC with different RS content increases.According to the EC2 specification and the CEB-FIP specification,the drying shrinkage and creep prediction models for RSC have been established.
基金funded by the National Natural Science Foundation of China(Nos.52004098,U24B2041,and 52274079)the Key Research and Development Program of Henan Province(No.251111320400)+1 种基金the Key Research Project Plan for Higher Education Institutions in Henan Province(Nos.24A570006 and 25A570002)the Scientific and Technological Research Project in Henan Province(No.242102320061).
文摘In deep coal mining,surrounding rock is subjected to both high in-situ stress and intense mining disturbances,leading to significant time-dependent behavior.Accurately capturing this behavior is essential for predicting long-term roadway stability,necessitating the development of a reliable constitutive creep model and numerical simulation approach.In this study,creep experiments were conducted on pre-damaged rock with varying initial damage levels to investigate the time-dependent mechanical properties.Based on the experimental results,an accelerated-creep criterion was proposed,and an elastic-viscoplastic creep damage model(EVPCD)was established that simultaneously considers the effects of time-dependent damage and instantaneous damage caused by stress disturbances on rock creep behavior.Subsequently,the effectiveness of the proposed creep model was verified using experimental data,and the secondary development of the EVPCD model was completed based on the FLAC3D platform.Following this,a long-term stability analysis method of deep surrounding rock that accounts for excavation-and mining-induced disturbances was proposed.Using the main roadway of Xutuan Coal Mine as a case study,numerical simulations were carried out to investigate the time-dependent deformation and failure characteristics of the surrounding rock following excavation and mining disturbance.Combined with on-site monitoring of the surrounding rock damage areas,the results indicate that the EVPCD outperforms the CVISC and Nishihara models in predicting the time-dependent behavior of deep surrounding rock.
文摘This study presents and verifies a hybrid methodology for reliable determination of parameters in structural rheological models(Zener,Burgers,and Maxwell)describing the viscoelastic behavior of polyurethane specimens manufactured using extrusion-based 3D printing.Through comprehensive testing,including cyclic compression at strain rates ranging from 0.12 to 120 mm/min(0%-15%strain)and creep/relaxation experiments(10%-30%strain),the lumped parameters were independently determined using both analytical and numerical solutions of the models’differential equations,followed by cross-verification in additional experiments.Numerical solutions for creep and relaxation problems were obtained using finite element analysis,with the three-parameter Mooney-Rivlin model and Prony series employed to simulate elastic and viscous stress components,respectively.Energy dissipation per cycle was quantified during cyclic compression tests.The results demonstrate that all three models adequately describe material behavior within the 0%-15%strain range across various strain rates.Comparative analysis revealed the Burgers model’s superior performance in characterizing creep and stress relaxation at low strain levels.While Zener and Burgers model parameters from uniaxial compression showed limited applicability for energy dissipation calculations,the generalized Maxwell model effectively captured viscoelastic properties across different strain rates.Notably,parameters derived from creep tests provided a more universal assessment of dissipative properties due to optimization based on characteristic curve regions.Both parameter sets described polyurethane’s elastic-hysteretic behavior with approximately 20%error,proving significantly more accurate than the linear strain-time dependence hypothesis.Finite element analysis(FEA)complemented numerical modeling by demonstrating that while the generalized Maxwell model effectively describes initial rapid stress-strain changes,FEA provides superior characterization of steady-state processes.This computational approach yields more physically representative results compared to simplified analytical solutions,despite certain limitations in transient analysis.
基金Project (50774095) supported by the National Natural Science Foundation of ChinaProject (200449) supported by China National Outstanding Doctoral Dissertations Special Funds
文摘By the methods of uniaxial single-stage loading and graded incremental cyclic loading, the creep experiments were performed on the deep saturated rock from Dongguashan Mine, and the creep curves of saturated rock under different loading stresses were obtained. By comparing with the creep rule of dry rock in the same location, the creep rule of deep saturated rock was analyzed. Based on the united rheological mechanical model, the rheological model of deep saturated rock was recognized, and the parameters of the model were determined. The results show that the creep curves are very smooth under low stress, but the phenomena of wave and catastrophe turn up under high stress, and the bearing capacity of rock is weakening over time. The rheological properties of saturated and dry rocks are very different under tlie condition of deep high stress, especially when unloading, degradation and damage of rock quality is more serious, and the effect of water cannot be neglected. The H--HIN--NJS model （Schofield-Scott-Blair model） was selected to represent the rheology rule of deep saturated rock, and the fitting curves of model agree well with the experiment data, so the selected model is reasonable.
基金Project(2014CB046602)supported by the National Basic Research Program of ChinaProject(51235010)supported by the National Natural Science Foundation of China
文摘A set of uniaxial tensile creep tests at different pre-deformations, aging temperatures and stress levels were carried out for Al-Li-S4 alloy, and the creep behavior and the effects of pre-deformation on mechanical properties and microstructures were determined under basic thermodynamics conditions of aging forming. The results show that pre-deformation shortens the time of primary creep and raises the second steady-state creep rate. Then, the total creep strain is greater, but in the range of test parameters it is still smaller than that without pre-deformation. In addition, transmission electron microscopy（TEM） observation shows that pre-deformation promotes the formation of T1 phase and θ′ phase and makes them distribute more dispersively, while inhibits the generation of δ′ phase, which leads to the improvement of mechanical properties of the alloy. A unified constitutive model reflecting the effects of aging mechanism, stress levels and different pre-deformations was established. The fitting results agree with the experimental data well.
基金Project(2014CB046602)supported by the National Basic Research Program of ChinaProject(20120162110003)supported by Ph D Programs Foundation of Ministry of Education of China
文摘The constitutive modeling and springback simulation for AA2524 sheet in creep age forming（CAF） process were presented.A series of creep aging tests were performed on AA2524 at the temperature of 180-200 °C and under the stress of 140-210 MPa for 16 h.Based on these experimental data,material constitutive equations which can well characterize creep aging behaviors of the tested alloy were developed.The effect of interior stress distributed along the sheet thickness on springback was simulated using FE software MSC.MARC by compiling the established constitutive models into the user subroutine.The simulation results showed that the amount of sheet springback was 61.12% when merely considering tensile stress existing along the sheet thickness;while sheet springback was up to 65.93% when taking both tensile and compressive stresses into account.In addition,an AA2524 rectangular sheet was subjected to CAF experiment in resistance furnace.The springback value of the formed rectangular sheet was 68.2%,which was much closer to 65.93%.This confirms that both tensile and compressive stresses across the sheet thickness should be considered in accurately predicting springback of the sheet after forming,which can be more consistent with experimental results.
基金supported by the National Natural Science Foundation of China (No. 41172281)the National Basic Research Program of China (No. 2011CB710604)the Opening Foundation of the State Key Laboratory of Continental Dynamics, Northwest University (No. 201210126)
文摘Previous constitutive models of granite shear creep have two limitations：（1） although moisture greatly affects granite shear creep behavior, currently there are no constitutive models that include this factor;（2） there are also no models that include an acceleration stage. This paper presents an improved Burgers constitutive model with the addition of a damage parameter to characterize the moisture effect and uses a nonlinear relation equation between stress and strain for inclusion as the acceleration stage. The damage parameter is determined from granite creep experiment under four different moisture contents（0%, 0.22%, 0.49%, and 0.79%）. The nonlinear relation equation is obtained by fitting a dataset of stain versus time under five different loading stages. To verify the presented model, a creep experiment was conducted on other granite samples and the results show that the model agrees well with the experimental observation data.
基金Supported by the National Natural Science Foundation of China (50879044)Master's Degree Thesis Excellent Training Funds of Three Gorges University(2011PY008)
文摘The mechanical behavior of sliding zone soils plays a significant role in landslide. In general, the sliding zone soils are basically in unsaturated state due to rainfall infiltration and reservoir water level fluctuation. Meanwhile, a large number of examples show that the deformation processes of landslides always take a long period of time, indicating that landslides exhibit a time-dependent property. Therefore, the deforma- tion of unsaturated soils of landslide involves creep behaviors. In this paper, the Burgers creep model for unsaturated soils under triaxial stress state is considered based on the unsaturated soil mechanics. Then, by curve fitting using the least squares method, creep parameters in different matric suction states are obtained based on the creep test data of unsaturated soils in the sliding zones of Qianjiangping landslide. Results show that the predicted results are in good agreement with the experimental data, Finally, to fur- ther explore the creep characteristics of the unsaturated soils in sliding zones, the relationships between parameters of the model and matric suction are analyzed and a revised Burgers creep model is developed correspondingly. Simulations on another group of test data are performed by using the modified Burgers creep model and reasonable results are observed,
基金the National Key Research and Development Program of China(Grant No.2017YFB0702902)the National Natural Science Foundation of China(Grant Nos.51631008and 51771019)+1 种基金the National High Technology Research Program of China(Grant No.2012AA03A513)the 111 Project(No.B170003)
文摘Estimating long-term creep deformation and life of materials is an effective way to ensure the service safety and to reduce the cost of long-term integrity evaluation of high temperature structural materials.Since the 1980 s, the θ projection model has been widely used for predicting creep lives due to its ability to capture the characteristic transitions observed in creep curves obtained under constant true stress conditions. However, the creep rupture behavior under constant load or engineering stress conditions cannot be simulated accurately using this model because of the different stress states. In this paper, creep curves obtained under constant load conditions were analyzed using a modified θ projection model by considering the increase in true stress with creep deformation during the creep tests. This model is expressed as ε = θ_1(1-e^(-θ_2t)) + θ3 e^(θ_4e^θ5^εt)-1, and was validated using the creep curves of K465 and DZ125 superalloys tested at a range of temperatures and engineering stresses. Moreover, it was shown that the predictive capability of the modified θ projection model was significantly improved over the original one, as it reduces the prediction uncertainty from a range of 10% to 20% to below 5%. Meanwhile,it was shown that the model can be reasonably used for predicting constant stress creep conditions, when appropriate parameters are used. The prediction performance of the modified model will be discussed in another paper. The results of this study show great potential for the evaluation and assessment of the service safety of structural materials used in applications where designs are limited by creep deformation.
基金supported by National Natural Science Funds of China (No. 51304212)Specialized Research Fund for the Doctoral Program of Higher Education (No. 20120023120005)+2 种基金Beijing Higher Education Young Elite Teacher Project (No. YETP0930)Fun-damental Research Funds for the Central Universities (No. 2009QZ09)Open Foundation of State Key Laboratory of Coal Resources and Safe Mining (No. SKLCRSM11KFB04)
文摘Coal exhibits different creep behaviours when filled with different amounts of gas. Creep tests of coal filled with 0 and 0.5 MPa gas were performed, and strain under different axial stress was compared.The three creep constitutive models which were analysed using the method fitting experimental data for determining which creep model can reflect the creep process of the test best. The results show that the deformation of coal filled with 0.5 MPa gas is more higher than that of coal filled with 0 MPa gas under the same axial stress. Gas plays a positive effect on the deformation of coal process and will accelerate creep process. And gas will reduce coal intensity and change coal creep properties.Compared with Nishihara Model and Extensional Nishihara Model, Burgers Model can reflect the three stages of creep process of coal filled with gas better. The research results can contribute to reveal coal and gas outburst mechanism.
