Graphene oxide nanomaterials are increasingly used in various fields due to their superior properties.In order to study the influence of graphene oxide additives on the performance of modified asphalt,in this study,gr...Graphene oxide nanomaterials are increasingly used in various fields due to their superior properties.In order to study the influence of graphene oxide additives on the performance of modified asphalt,in this study,graphene oxide modified asphalt was prepared and characteristics was studied including the high deformation resistance performance and the self-healing property of modified asphalt.Functional groups and morphology of graphene oxide modified asphalt were described by Fourier transform infrared spectroscopy.The high deformation resistance performance and self-healing effect of asphalt samples were obtained through dynamic slear rheometer(DSR)test.Results shows that graphene oxide dispersions improve the performance of asphalt relatively well compared to graphene oxide powder.There is no chemical reaction between graphene oxide and asphalt,but physical connection.The addition of graphene oxide improved the high deformation resistance of modified asphalt and expedited the self-healing ability of asphalt under fatigue load.展开更多
To disclose the grain crushing effects on the weathered granular soil rheological behavior,a series of rheological tests (odometer compression and triaxial shearing) were carried out.At the same time,the sieving analy...To disclose the grain crushing effects on the weathered granular soil rheological behavior,a series of rheological tests (odometer compression and triaxial shearing) were carried out.At the same time,the sieving analysis tests of these specimens were also executed before and after tests,and the grain crushing degree,Br and n5,were collectively adopted to estimate the grain crushing.The grain crushing degree depends on the stress path,stress level,and load time,especially,the longer load time and more intensive gradient shearing path will increase the grain crushing quantity.The Hardin crushing degrees Br are 0.191,0.118 and 0.085 in the ordinary compression,rheological compression and triaxial rheological shearing,respectively;The grain crushing degrees n5 are 1.9,1.4 and 1.32,respectively.The strain softening phase indicates the grain crushing and diffusive collapse,and the strain hardening phase indicates the rearrangement of these crushed grains and formation of new bearing soil skeleton.The rheological deformation of granular soil can be attributed to the coarse grain crushing and the filling external porosity with crushed fragments.展开更多
The viscoelastic-plastic creep experiments on soft ore-rock in Jinchuan Mine III were performed under circular increment step load and unload. The experimental data were analyzed according to instantaneous elastic str...The viscoelastic-plastic creep experiments on soft ore-rock in Jinchuan Mine III were performed under circular increment step load and unload. The experimental data were analyzed according to instantaneous elastic strain, visco-elastic strain, instantaneous plastic strain and visco-plastic strain. The result shows that instantaneous deformation modulus tends to increase with the increase of creep stress; soft rocks enhance the ability to resist instantaneous elastic deformation and instantaneous plastic deformation during the multi-level of load and unload in the cyclic process. In respect of specimen JC1099, the ratio of visco-elastic strain to visco-plastic strain varies from 3.15 to 6.58, and the ratio has decreasing tendency with stress increase as a whole; creep deformation tends to be a steady state at low stress level; soft rocks creep usually embodies accelerated creep properties at high stress level. With the damaging variable and the hardening function introduced, a nonlinear creep model of soft rocks is established, in which the decay creep is described by the nonlinear hardening function H of viscidity coefficient. The model can describe the accelerated creep of soft rocks since the nonlinear damaging evolvement variable D of deformation parameter of rocks is introduced. Three stages of soft rocks creep can be described with the uniform creep equation in the nonlinear creep model. With this nonlinear creep model applied to the creep experiments of the ore-rock of Jinchuan Mine III, the nonlinear creep model＇s curves are in good agreement with experimental data.展开更多
The initial shear stress and plastic cohesion ( η ) are the most important parameters reflecting the rheological properties of the paste slurry. The rheological parameters as well as the quantitative relationship amo...The initial shear stress and plastic cohesion ( η ) are the most important parameters reflecting the rheological properties of the paste slurry. The rheological parameters as well as the quantitative relationship among the consumption of different fill materials were obtained through the experiment and research on these parameters. They can be used to predict the scope of the values of τ and η in production for a given ratio, which can reduce the conveying resistance of fill slurry along the pipelines and avoid the blockage of the pipelines. It is found that the rheological model of the total tailing slurry belongs to the Bingham type, which has a feature of strong internal structure and large initial shear stress. The calculation formula for the resistance loss of pipelines conforms nicely to the field test and the actual production in Jinchuan Nickel Mine.展开更多
By adopting cyclic increment loading and unloading method, time-independent and time-dependent strains can be separated. It is more reasonable to describe the reversible and the irreversible deformations of sample sep...By adopting cyclic increment loading and unloading method, time-independent and time-dependent strains can be separated. It is more reasonable to describe the reversible and the irreversible deformations of sample separately during creep process. A nonlinear elastic-visco-plastic rheological model is presented to characterize the time-based deformational behavior of hard rock. Specifically, a spring element is used to describe reversible instantaneous elastic deformation. A reversible nonlinear visco-elastic （RNVE） model is developed to characterize recoverable visco-elastic response. A combined model, which contains a fractional derivative dashpot in series with another Hook’s body, and a St. Venant body in parallel with them, is proposed to describe irreversible visco-plastic deformation. Furthermore, a three-stage damage equation based on strain energy is developed in the visco-plastic portion and then nonlinear elastic-visco-plastic rheological damage model is established to explain the trimodal creep response of hard rock. Finally, the proposed model is validated by a laboratory triaxial rheological experiment. Comparing with theoretical and experimental results, this rheological damage model characterizes well the reversible and irreversible deformations of the sample, especially the tertiary creep behavior.展开更多
In this study,different influence mechanisms associated with temperatures and pH values were investigated through cemented paste backfill(CPB)systems.CPB samples were prepared with temperatures ranging from 10 to 50℃...In this study,different influence mechanisms associated with temperatures and pH values were investigated through cemented paste backfill(CPB)systems.CPB samples were prepared with temperatures ranging from 10 to 50℃ in 10℃ increments and pH values of 3,7,and 13.Then,the CPB mixture were subjected to rheological tests,thermogravimetric analysis(TG),derivative thermogravimetry analysis(DTG),Fourier-transform infrared spectroscopy(FT-IR),and scanning electron microscopy(SEM).Results demonstrated that the temperatures had significant effects on the rheological properties of CPB,whereas the effects of pH values were relatively unapparent.Higher temperatures(over 20℃)were prone to bring higher shear stress,yield stress,and apparent viscosity with the same pH value condition.However,an overly high temperature(50℃)cannot raise the apparent viscosity.Non-neutral conditions,for pH values of 3 and 13,could strengthen the shear stress and apparent viscosity at the same temperature.Two different yield stress curves could be discovered by uprising pH values,which also led to apparent viscosity of two various curves under the same temperatures(under 50℃).Microscopically,rheological properties of CPB were affected by temperatures and pH values which enhanced or reduced the cement hydration procedures,rates,products and space structures.展开更多
As for ceramic stereolithography technique,the preparation of suitable resin-based ceramic slurry is of primary importance.In this study,the effects of powder characteristics such as specific surface area,particle siz...As for ceramic stereolithography technique,the preparation of suitable resin-based ceramic slurry is of primary importance.In this study,the effects of powder characteristics such as specific surface area,particle size and distribution,particle morphology on the rheological behavior of zirconia resin-based suspensions were investigated intensively.Results show that the specific surface area of the powder is the most important factor affecting slurry viscosity.Choosing low specific surface area and quasi-spherical shaped powder is more likely to obtain low viscosity slurries.In addition,the influence of solid loading on the flow behavior were also studied using Krieger-Dougherty model.Zirconia samples with the relative density of(97.83±0.33)%were obtained after sintering at 1550℃.No obvious abnormal grain growth in the microstructure of the sintered body is observed.Results indicate that after the optimization of the processing parameters with the help of rheology characterization,complex-shaped high-quality zirconia parts can be obtained using the stereolithography technique.展开更多
Considering the rheological properties of rock and soil body,and exploiting the merit of strength reduction technique,a theory of couple analysis is brought forward on the basis of strength reduction theory and rheolo...Considering the rheological properties of rock and soil body,and exploiting the merit of strength reduction technique,a theory of couple analysis is brought forward on the basis of strength reduction theory and rheological properties.Then,the concept and the calculation procedure of the safety factor are established at different time.Making use of finite element software ANSYS,the most dangerous sliding surface of the slope can be obtained through the strength reduction technique.According to the dynamic safety factor based on rheological mechanism,a good forecasting could be presented to prevent and cure the landslide.The result shows that the couple analysis reveals the process of the slope failure with the time and the important influence on the long-term stability due to the rheological parameters.展开更多
The rheological properties of two kinds of oil-based drilling fluids with typically composition were studied at pressures up to 138 MPa and temperatures up to 204 ℃ using the RheoChan 7400 Rheometer.The experimental ...The rheological properties of two kinds of oil-based drilling fluids with typically composition were studied at pressures up to 138 MPa and temperatures up to 204 ℃ using the RheoChan 7400 Rheometer.The experimental results show that the apparent viscosity,plastic viscosity and yield point decrease with the increase of temperature,and increase with the increase of pressure.The effect of pressure on the apparent viscosity,plastic viscosity and yield point is considerable at ambient temperature.However,this effect gradually reduces with the increase of temperature.The major factor influencing the rheological properties of oil-based drilling fluids is temperature instead of pressure in the deep sections of oil wells.On the basis of numerous experiments,the model for predict the apparent viscosity,plastic viscosity and yield point of oil-based drilling fluids at high temperature and pressure was established using the method of regressive analysis.It is confirmed that the calculated data are in good agreement with the measured data,and the correlation coefficients are more than 0.98.The model is convenient for use and suitable for the application in drilling operations.展开更多
To further investigate the one-dimensional(1D)rheological consolidation mechanism of double-layered soil,the fractional derivative Merchant model(FDMM)and the non-Darcian flow model with the non-Newtonian index are re...To further investigate the one-dimensional(1D)rheological consolidation mechanism of double-layered soil,the fractional derivative Merchant model(FDMM)and the non-Darcian flow model with the non-Newtonian index are respectively introduced to describe the deformation of viscoelastic soil and the flow of pore water in the process of consolidation.Accordingly,an 1D rheological consolidation equation of double-layered soil is obtained,and its numerical analysis is performed by the implicit finite difference method.In order to verify its validity,the numerical solutions by the present method for some simplified cases are compared with the results in the related literature.Then,the influence of the revelent parameters on the rheological consolidation of double-layered soil are investigated.Numerical results indicate that the parameters of non-Darcian flow and FDMM of the first soil layer greatly influence the consolidation rate of double-layered soil.As the decrease of relative compressibility or the increase of relative permeability between the lower soil and the upper soil,the dissipation rate of excess pore water pressure and the settlement rate of the ground will be accelerated.Increasing the relative thickness of soil layer with high permeability or low compressibility will also accelerate the consolidation rate of double-layered soil.展开更多
The influence of aging on the evolution of structural,morphological and rheological properties of neat asphalt was investigated by Fourier transform infrared(FTIR),atomic force microscopy(AFM) and dynamic shear rheome...The influence of aging on the evolution of structural,morphological and rheological properties of neat asphalt was investigated by Fourier transform infrared(FTIR),atomic force microscopy(AFM) and dynamic shear rheometer(DSR),respectively.Asphalt was suffered under 20 W/m2 of UV radiant intensity and under the condition of aging time(0,48,96 and 144 h) with film thickness of 100 μm and film thickness of 50,100,200 and 500 μm after aging for 120 h,respectively,at certain UV radiant intensity 20 W/m2.Rheological results tested by DSR exhibit higher the complex shear(stiffness) modulus(G*) and lower phase angle(δ),compared to the virgin at the same test condition.The compositions analysis of asphalt before and after aging show an increase of carbonyl and sulfoxides,while a decrease of aromatic functional groups.With the increase of the component of asphaltene,obvious agglomerates of asphalten appear in neat asphalt surfaces after aging.展开更多
The steady and dynamic rheological behaviors of precipitated calcium carbonate (PCC) suspension in polyethylene glycol (PEG) were investigated on a TA AR2000ex rheometer. Under steady shear consistency index K and flo...The steady and dynamic rheological behaviors of precipitated calcium carbonate (PCC) suspension in polyethylene glycol (PEG) were investigated on a TA AR2000ex rheometer. Under steady shear consistency index K and flow exponent N of suspensions with different volume fractions were determined. The shear-thinning and the discontinuous shear-thickening behavior were observed at different constant frequencies from 10 to 100 rad/s. The relationship between the complex viscosity and the constant frequency were determined. As the volume fraction increases,flow exponent N shows a rapid increase,and it increases dramatically when the discontinuous shear-thickening takes place,while consistency index K decreases. Dynamic oscillatory shear experiments were conducted at constant strain amplitude and constant frequency,respectively. For the frequency sweep,the system shows viscous property in entire range of the frequency investigated,and the complex viscosity shows discontinuous jump at a critical frequency of 10 rad/s. For the strain sweep,on the other hand,at low strain the elastic modulus is strongly dependent on the strain,and the viscous modulus is independent of the strain. But at the critical strain point both of the moduli show an abrupt jump and the system transits from elastic to viscous at a strain of 0.1.展开更多
High temperature rheological properties of fiber modified asphalt binders and impact of the type and content on such properties were studied.Three types of fiber,including polyester(PET),polyacrylonitrile(PAN) and cel...High temperature rheological properties of fiber modified asphalt binders and impact of the type and content on such properties were studied.Three types of fiber,including polyester(PET),polyacrylonitrile(PAN) and cellulose(CEL),a control content(0%) and four levels of fiber content(2%,4%,6% and 8% by total asphalt binder mass) were used with asphalt binders.The high temperature rheological properties,consisting of complex modulus(G*) and phase angle δ,were measured using SHRP's dynamic shear rheometer(DSR) between 46-82 ℃.Experimental results indicate that the changes of G* and tan δ of fiber modified asphalt binders with the increase of test temperature tend to slow down,and the temperature susceptibility is improved obviously compared to that of original asphalt binder.Fiber modification results in the increase of rutting parameter(G*/sin δ) at high temperatures,the decrease of temperature susceptibility,and further improved high temperature performance of asphalt binder.An excellent correlation exhibits between fiber content and high temperature performance of asphalt binder.Moreover,fiber type also has different influences on the improvement of G*/sin δ,G*/sin δ of PET and PAN fiber asphalt binders are both higher than that of CEL fiber,but G*/sin δ of CEL fiber is still higher than that of original asphalt.However,there is a critical fiber content when fibers start to interact with each other.Therefore,based on the critical fiber content and economic consideration,the optimum fiber contents for various fiber-modified asphalt binders are obtained.展开更多
Low-permeability dense reservoirs,including micro-fractured reservoirs,are commonly characterized by high content of clay substances,high original water saturation,high sensitivity to invasive fluids,high capillary pr...Low-permeability dense reservoirs,including micro-fractured reservoirs,are commonly characterized by high content of clay substances,high original water saturation,high sensitivity to invasive fluids,high capillary pressure,complicated structure and anisotropic,high flow-resistance and micro pore throats etc,.Generally they also have lots of natural micro fractures,probably leading to stress sensibility.Main damaging factors in such reservoirs are water-sensibility and water-blocking caused by invasive fluids during drilling and production operations.Once damaged,formation permeability can rarely recovered.Numerous studies have shown that damaging extent of water-blocking ranges from 70% to 90%.Main damaging mechanisms and influencing factors of water-blocking were systematically analyzed.Also some feasible precaution or treating approaches of water-blocking were put forward.In a laboratory setting,a new multi-functional drilling fluid composed mainly of amphion polymer,sulfonation polymer,high effectively preventive water-blocking surfactants,ideal packing temporary bridging agents(TBA) and film-forming agents,etc.,were developed.New low-damage drilling fluids has many advantages,such as good rheological properties,excellent effectiveness of water-blocking prevention,good temporary plugging effect,low filtration and ultra-low permeability(API filtration≤5 mL,HTHP filtration≤10 mL,mud cake frictional coefficient≤0.14,permeability recovery>81%),can efficiently prevent or minimize damage,preserve natural formation and enhance comprehensive development-investment effect in TUHA Jurassic dense sandstone reservoir formation with low-permeability,the only one developing integrated condense gas field.Some references can be provided to similar reservoir formations.展开更多
There are two mechanisms of the coarse surface asperity resistance effect and rubbing resistance effect in the course of the soft rock structural surface creep,of which the former plays a dominant role in hindering th...There are two mechanisms of the coarse surface asperity resistance effect and rubbing resistance effect in the course of the soft rock structural surface creep,of which the former plays a dominant role in hindering the deformation in the starting creep phase,so that the structural surface creep usually displays the strong surface roughness effect,and so does the latter when the asperities in the coarse surface were fractured by shearing.Under the low stress condition,there are only two phases of the decelerating creep and the constant creep for the soft rock structural surface,and as the stress increases and overcomes the rubbing resistance,the accelerating creep failure of the structural surface will happen suddenly.Therefore,a multiple rheological model,which combines the nonlinear NEWTON body(NN) of a certain mass and the empirical plastic body(EM) with the classical SAINT VENANT body,NEWTON body,KELVIN body and HOOKE body,could be used to comprehensively describe the creep characteristics of the soft rock structural surface.Its mechanical parameter values will vary owing to the different surface roughness of the structural surface.The parameters of GH,GK and ηL are positively linearly correlative to the surface roughness.The surface roughness and m are negative exponential function correlation.The long-term strength τS is positively correlative to the surface roughness.展开更多
Based on the sweet potato starch,cationic starch,acetic starch and cationic-acetic compoundedly modified starch were made through chemical denaturalization.The above three kinds of static rheological parameter and dyn...Based on the sweet potato starch,cationic starch,acetic starch and cationic-acetic compoundedly modified starch were made through chemical denaturalization.The above three kinds of static rheological parameter and dynamic rheological parameter were measured,respectively.The experimental result reveals that the thermal stability of starchy viscosity increases after chemical denaturalization.Under the condition of identical shearing rate,the shear stress of cationic-acetic ester compoundedly modified sweet potato starch paste is the largest among these kinds of sweet potato starch.This attributes to a phenomenon of shearing thinning.Furthermore,raw sweet potato starch has a larger gel intensity than that of modified starch.展开更多
A three-dimensional(3D) lattice model for predicting the rheological behavior of asphalt mixtures was presented.In this model asphalt mixtures were described as a two-phase composite material consisting of asphalt san...A three-dimensional(3D) lattice model for predicting the rheological behavior of asphalt mixtures was presented.In this model asphalt mixtures were described as a two-phase composite material consisting of asphalt sand and coarse aggregates distributed randomly.Asphalt sand was regarded as a viscoelastic material and aggregates as an elastic material.The rheological response of asphalt mixture subjected to different constant stresses was simulated.The calibrated overall creep strain shows a good approximation to experimental results.展开更多
Rheological properties of the virgin bitumen and TPS modified bitumen binders with several percentages of TPS additives were studied.All TPS modified bituminous binders were prepared on a laboratory scale.Dynamic shea...Rheological properties of the virgin bitumen and TPS modified bitumen binders with several percentages of TPS additives were studied.All TPS modified bituminous binders were prepared on a laboratory scale.Dynamic shear rheometer(DSR) strain sweep test was made to measure the linear viscoelasticity areas of various bitumen binders at -20-70 ℃,then temperature sweep test and frequency sweep test were made in the linear viscoelasticity areas.Complex modulus master curves were drawn to analyze and compare various bitumen binders' rheological properties.Based on the test results,the ideal percentage of TPS additive was brought forward.The results show that TPS modified bitumen binders have more excellent properties at high,medium and low temperatures compared with original bitumen.The dosages of TPS additive are vital to their properties.展开更多
The rheological properties in the supernatant of peach gum from Prunnus dulcis were discussed in order to provide more scientific technical parameters and references for developing peach gum as a kind of medicinal gum...The rheological properties in the supernatant of peach gum from Prunnus dulcis were discussed in order to provide more scientific technical parameters and references for developing peach gum as a kind of medicinal gum.The rheological properties in the supernatant of peach gum were comparatively studied in different material ratios,temperatures,shaking times,pH values and salinities.The results show that,1) the mathematical model of shear rate with material ratio and shear stress is Y=0.069X12+0.035X2 -1.174,R2=0.942;2) the mathematical model of shear rate with temperature and shear stress is Y=4.936X12+0.023 2X2-1.688,R2=0.937;3) the mathematical model of shear rate with shaking time and shear stress is Y=0.005 192 X13-0.140 73X12+1.249 045X1+ 0.036 546 X2-3.644 29,R2=0.954 3;4) the effects of pH value on the rheological properties in the supernatant of peach gum are comparatively complicated with a varying range of 3-11 and the shear rate shows a change trend of saddle model;5) the mathematical model of shear rate with the concentration of NaCl and shear stress is Y=-0.037 44X1+0.012 93 X2,R2=0.998;6) the mathematical model of shear rate with the concentration of CaCl2 and shear stress is Y=0.025 789X1+0.016 19X2,R2 =0.999;and 7) the mathematical model of shear rate with the concentration of sorbic acid potassium and shear stress is Y=0.079 5X1+0.017 3X2,R2=0.998.The results show that the material ratio,temperature,shaking time,pH value significantly affect the rheological properties in the supernatant of peach gum,and the concentrations of NaCl and CaCl2 also significantly affect the rheological properties expect the concentration of sorbic acid potassium.展开更多
Second lining stability, which is the last protection in tunnel engineering, is critically important. The theological properties of the surrounding rock heavily affect second lining stability. In this work, we used la...Second lining stability, which is the last protection in tunnel engineering, is critically important. The theological properties of the surrounding rock heavily affect second lining stability. In this work, we used laboratory triaxial compressive rheological limestone tests to study nonlinear creep damage characteristics of surrounding rock mass in construction projects. We established a nonlinear creep damage constitutive model for the rock mass, as well as a constitutive model numerical implementation made by programming. Second, we introduced a new foam concrete with higher compression performance and good ductility and studied its mechanical properties through uniaxial and triaxial tests. This concrete was used as the filling material for the reserved deformation layer between the primary support and second lining. Finally, we proposed a high efficiency and accuracy staged optimization method. The minimum reserved deformation layer thickness was established as the optimization goal, and the presence of plastic strain in the second lining after 100 years of surrounding rock creep was used as an evaluation index. Reserved deformation layer thickness optimization analysis reveals no plastic strain in the second lining when the reserved deformation minimum thickness layer is 28.50 cm. The results show that the new foam concrete used as a reserved deformation layer filling material can absorb creep deformation of surrounding rock mass, reduce second lining deformation that leads to plastic strain, and ensure long-term second lining stability.展开更多
基金supported by Gansu Provincial Science and Technology Plan(23CXGA0195)Longnan Science and Technology Plan(2024CX03)。
文摘Graphene oxide nanomaterials are increasingly used in various fields due to their superior properties.In order to study the influence of graphene oxide additives on the performance of modified asphalt,in this study,graphene oxide modified asphalt was prepared and characteristics was studied including the high deformation resistance performance and the self-healing property of modified asphalt.Functional groups and morphology of graphene oxide modified asphalt were described by Fourier transform infrared spectroscopy.The high deformation resistance performance and self-healing effect of asphalt samples were obtained through dynamic slear rheometer(DSR)test.Results shows that graphene oxide dispersions improve the performance of asphalt relatively well compared to graphene oxide powder.There is no chemical reaction between graphene oxide and asphalt,but physical connection.The addition of graphene oxide improved the high deformation resistance of modified asphalt and expedited the self-healing ability of asphalt under fatigue load.
基金Project(50908233) supported by the National Natural Science Foundation of ChinaProject(200413) supported by Communication Science and Technology Fund of Hunan Province,China
文摘To disclose the grain crushing effects on the weathered granular soil rheological behavior,a series of rheological tests (odometer compression and triaxial shearing) were carried out.At the same time,the sieving analysis tests of these specimens were also executed before and after tests,and the grain crushing degree,Br and n5,were collectively adopted to estimate the grain crushing.The grain crushing degree depends on the stress path,stress level,and load time,especially,the longer load time and more intensive gradient shearing path will increase the grain crushing quantity.The Hardin crushing degrees Br are 0.191,0.118 and 0.085 in the ordinary compression,rheological compression and triaxial rheological shearing,respectively;The grain crushing degrees n5 are 1.9,1.4 and 1.32,respectively.The strain softening phase indicates the grain crushing and diffusive collapse,and the strain hardening phase indicates the rearrangement of these crushed grains and formation of new bearing soil skeleton.The rheological deformation of granular soil can be attributed to the coarse grain crushing and the filling external porosity with crushed fragments.
基金Project(2007CB209400) supported by the Major State Basic Research and Development Program of ChinaProject(50774093) supported by the National Natural Science Foundation of ChinaProject(200801) supported by Open Research Fund of Hunan Provincial Key of Safe Mining Techniques of Coal Mines
文摘The viscoelastic-plastic creep experiments on soft ore-rock in Jinchuan Mine III were performed under circular increment step load and unload. The experimental data were analyzed according to instantaneous elastic strain, visco-elastic strain, instantaneous plastic strain and visco-plastic strain. The result shows that instantaneous deformation modulus tends to increase with the increase of creep stress; soft rocks enhance the ability to resist instantaneous elastic deformation and instantaneous plastic deformation during the multi-level of load and unload in the cyclic process. In respect of specimen JC1099, the ratio of visco-elastic strain to visco-plastic strain varies from 3.15 to 6.58, and the ratio has decreasing tendency with stress increase as a whole; creep deformation tends to be a steady state at low stress level; soft rocks creep usually embodies accelerated creep properties at high stress level. With the damaging variable and the hardening function introduced, a nonlinear creep model of soft rocks is established, in which the decay creep is described by the nonlinear hardening function H of viscidity coefficient. The model can describe the accelerated creep of soft rocks since the nonlinear damaging evolvement variable D of deformation parameter of rocks is introduced. Three stages of soft rocks creep can be described with the uniform creep equation in the nonlinear creep model. With this nonlinear creep model applied to the creep experiments of the ore-rock of Jinchuan Mine III, the nonlinear creep model＇s curves are in good agreement with experimental data.
文摘The initial shear stress and plastic cohesion ( η ) are the most important parameters reflecting the rheological properties of the paste slurry. The rheological parameters as well as the quantitative relationship among the consumption of different fill materials were obtained through the experiment and research on these parameters. They can be used to predict the scope of the values of τ and η in production for a given ratio, which can reduce the conveying resistance of fill slurry along the pipelines and avoid the blockage of the pipelines. It is found that the rheological model of the total tailing slurry belongs to the Bingham type, which has a feature of strong internal structure and large initial shear stress. The calculation formula for the resistance loss of pipelines conforms nicely to the field test and the actual production in Jinchuan Nickel Mine.
基金Project(BK20150005)supported by the Natural Science Foundation of Jiangsu Province for Distinguished Young Scholars,ChinaProject(2015XKZD05)supported by the Fundamental Research Funds for the Central Universities,China
文摘By adopting cyclic increment loading and unloading method, time-independent and time-dependent strains can be separated. It is more reasonable to describe the reversible and the irreversible deformations of sample separately during creep process. A nonlinear elastic-visco-plastic rheological model is presented to characterize the time-based deformational behavior of hard rock. Specifically, a spring element is used to describe reversible instantaneous elastic deformation. A reversible nonlinear visco-elastic （RNVE） model is developed to characterize recoverable visco-elastic response. A combined model, which contains a fractional derivative dashpot in series with another Hook’s body, and a St. Venant body in parallel with them, is proposed to describe irreversible visco-plastic deformation. Furthermore, a three-stage damage equation based on strain energy is developed in the visco-plastic portion and then nonlinear elastic-visco-plastic rheological damage model is established to explain the trimodal creep response of hard rock. Finally, the proposed model is validated by a laboratory triaxial rheological experiment. Comparing with theoretical and experimental results, this rheological damage model characterizes well the reversible and irreversible deformations of the sample, especially the tertiary creep behavior.
基金Project(2019zzts678)supported by the Fundamental Research Funds for the Central Universities,China。
文摘In this study,different influence mechanisms associated with temperatures and pH values were investigated through cemented paste backfill(CPB)systems.CPB samples were prepared with temperatures ranging from 10 to 50℃ in 10℃ increments and pH values of 3,7,and 13.Then,the CPB mixture were subjected to rheological tests,thermogravimetric analysis(TG),derivative thermogravimetry analysis(DTG),Fourier-transform infrared spectroscopy(FT-IR),and scanning electron microscopy(SEM).Results demonstrated that the temperatures had significant effects on the rheological properties of CPB,whereas the effects of pH values were relatively unapparent.Higher temperatures(over 20℃)were prone to bring higher shear stress,yield stress,and apparent viscosity with the same pH value condition.However,an overly high temperature(50℃)cannot raise the apparent viscosity.Non-neutral conditions,for pH values of 3 and 13,could strengthen the shear stress and apparent viscosity at the same temperature.Two different yield stress curves could be discovered by uprising pH values,which also led to apparent viscosity of two various curves under the same temperatures(under 50℃).Microscopically,rheological properties of CPB were affected by temperatures and pH values which enhanced or reduced the cement hydration procedures,rates,products and space structures.
基金National Key Research and Development Program of China(2017YFB0310400)National Natural Science Foundation of China(51572277,51702340)+1 种基金Shanghai Sailing Program(17YF1428800)Natural Science Foundation of Shanghai(17ZR1434800)。
文摘As for ceramic stereolithography technique,the preparation of suitable resin-based ceramic slurry is of primary importance.In this study,the effects of powder characteristics such as specific surface area,particle size and distribution,particle morphology on the rheological behavior of zirconia resin-based suspensions were investigated intensively.Results show that the specific surface area of the powder is the most important factor affecting slurry viscosity.Choosing low specific surface area and quasi-spherical shaped powder is more likely to obtain low viscosity slurries.In addition,the influence of solid loading on the flow behavior were also studied using Krieger-Dougherty model.Zirconia samples with the relative density of(97.83±0.33)%were obtained after sintering at 1550℃.No obvious abnormal grain growth in the microstructure of the sintered body is observed.Results indicate that after the optimization of the processing parameters with the help of rheology characterization,complex-shaped high-quality zirconia parts can be obtained using the stereolithography technique.
文摘Considering the rheological properties of rock and soil body,and exploiting the merit of strength reduction technique,a theory of couple analysis is brought forward on the basis of strength reduction theory and rheological properties.Then,the concept and the calculation procedure of the safety factor are established at different time.Making use of finite element software ANSYS,the most dangerous sliding surface of the slope can be obtained through the strength reduction technique.According to the dynamic safety factor based on rheological mechanism,a good forecasting could be presented to prevent and cure the landslide.The result shows that the couple analysis reveals the process of the slope failure with the time and the important influence on the long-term stability due to the rheological parameters.
基金Project(50574061) supported by the National Natural Science Foundation of ChinaProject(IRT0411) supported by the Changjiang Scholars and Innovative Research Team,Ministry of Education
文摘The rheological properties of two kinds of oil-based drilling fluids with typically composition were studied at pressures up to 138 MPa and temperatures up to 204 ℃ using the RheoChan 7400 Rheometer.The experimental results show that the apparent viscosity,plastic viscosity and yield point decrease with the increase of temperature,and increase with the increase of pressure.The effect of pressure on the apparent viscosity,plastic viscosity and yield point is considerable at ambient temperature.However,this effect gradually reduces with the increase of temperature.The major factor influencing the rheological properties of oil-based drilling fluids is temperature instead of pressure in the deep sections of oil wells.On the basis of numerous experiments,the model for predict the apparent viscosity,plastic viscosity and yield point of oil-based drilling fluids at high temperature and pressure was established using the method of regressive analysis.It is confirmed that the calculated data are in good agreement with the measured data,and the correlation coefficients are more than 0.98.The model is convenient for use and suitable for the application in drilling operations.
基金Project(51578511)supported by the National Natural Science Foundation of China。
文摘To further investigate the one-dimensional(1D)rheological consolidation mechanism of double-layered soil,the fractional derivative Merchant model(FDMM)and the non-Darcian flow model with the non-Newtonian index are respectively introduced to describe the deformation of viscoelastic soil and the flow of pore water in the process of consolidation.Accordingly,an 1D rheological consolidation equation of double-layered soil is obtained,and its numerical analysis is performed by the implicit finite difference method.In order to verify its validity,the numerical solutions by the present method for some simplified cases are compared with the results in the related literature.Then,the influence of the revelent parameters on the rheological consolidation of double-layered soil are investigated.Numerical results indicate that the parameters of non-Darcian flow and FDMM of the first soil layer greatly influence the consolidation rate of double-layered soil.As the decrease of relative compressibility or the increase of relative permeability between the lower soil and the upper soil,the dissipation rate of excess pore water pressure and the settlement rate of the ground will be accelerated.Increasing the relative thickness of soil layer with high permeability or low compressibility will also accelerate the consolidation rate of double-layered soil.
基金Project(200631800076) supported by 2006 West Science and Technology Project of the Department of Transportation
文摘The influence of aging on the evolution of structural,morphological and rheological properties of neat asphalt was investigated by Fourier transform infrared(FTIR),atomic force microscopy(AFM) and dynamic shear rheometer(DSR),respectively.Asphalt was suffered under 20 W/m2 of UV radiant intensity and under the condition of aging time(0,48,96 and 144 h) with film thickness of 100 μm and film thickness of 50,100,200 and 500 μm after aging for 120 h,respectively,at certain UV radiant intensity 20 W/m2.Rheological results tested by DSR exhibit higher the complex shear(stiffness) modulus(G*) and lower phase angle(δ),compared to the virgin at the same test condition.The compositions analysis of asphalt before and after aging show an increase of carbonyl and sulfoxides,while a decrease of aromatic functional groups.With the increase of the component of asphaltene,obvious agglomerates of asphalten appear in neat asphalt surfaces after aging.
基金Projects (50774096, 50606017) supported by the National Natural Science Foundation of China
文摘The steady and dynamic rheological behaviors of precipitated calcium carbonate (PCC) suspension in polyethylene glycol (PEG) were investigated on a TA AR2000ex rheometer. Under steady shear consistency index K and flow exponent N of suspensions with different volume fractions were determined. The shear-thinning and the discontinuous shear-thickening behavior were observed at different constant frequencies from 10 to 100 rad/s. The relationship between the complex viscosity and the constant frequency were determined. As the volume fraction increases,flow exponent N shows a rapid increase,and it increases dramatically when the discontinuous shear-thickening takes place,while consistency index K decreases. Dynamic oscillatory shear experiments were conducted at constant strain amplitude and constant frequency,respectively. For the frequency sweep,the system shows viscous property in entire range of the frequency investigated,and the complex viscosity shows discontinuous jump at a critical frequency of 10 rad/s. For the strain sweep,on the other hand,at low strain the elastic modulus is strongly dependent on the strain,and the viscous modulus is independent of the strain. But at the critical strain point both of the moduli show an abrupt jump and the system transits from elastic to viscous at a strain of 0.1.
基金Project(2004243) supported by the Science and Technology Key Project of Hubei Province,China
文摘High temperature rheological properties of fiber modified asphalt binders and impact of the type and content on such properties were studied.Three types of fiber,including polyester(PET),polyacrylonitrile(PAN) and cellulose(CEL),a control content(0%) and four levels of fiber content(2%,4%,6% and 8% by total asphalt binder mass) were used with asphalt binders.The high temperature rheological properties,consisting of complex modulus(G*) and phase angle δ,were measured using SHRP's dynamic shear rheometer(DSR) between 46-82 ℃.Experimental results indicate that the changes of G* and tan δ of fiber modified asphalt binders with the increase of test temperature tend to slow down,and the temperature susceptibility is improved obviously compared to that of original asphalt binder.Fiber modification results in the increase of rutting parameter(G*/sin δ) at high temperatures,the decrease of temperature susceptibility,and further improved high temperature performance of asphalt binder.An excellent correlation exhibits between fiber content and high temperature performance of asphalt binder.Moreover,fiber type also has different influences on the improvement of G*/sin δ,G*/sin δ of PET and PAN fiber asphalt binders are both higher than that of CEL fiber,but G*/sin δ of CEL fiber is still higher than that of original asphalt.However,there is a critical fiber content when fibers start to interact with each other.Therefore,based on the critical fiber content and economic consideration,the optimum fiber contents for various fiber-modified asphalt binders are obtained.
基金Project(50574061) supported by the National Natural Science Foundation of China
文摘Low-permeability dense reservoirs,including micro-fractured reservoirs,are commonly characterized by high content of clay substances,high original water saturation,high sensitivity to invasive fluids,high capillary pressure,complicated structure and anisotropic,high flow-resistance and micro pore throats etc,.Generally they also have lots of natural micro fractures,probably leading to stress sensibility.Main damaging factors in such reservoirs are water-sensibility and water-blocking caused by invasive fluids during drilling and production operations.Once damaged,formation permeability can rarely recovered.Numerous studies have shown that damaging extent of water-blocking ranges from 70% to 90%.Main damaging mechanisms and influencing factors of water-blocking were systematically analyzed.Also some feasible precaution or treating approaches of water-blocking were put forward.In a laboratory setting,a new multi-functional drilling fluid composed mainly of amphion polymer,sulfonation polymer,high effectively preventive water-blocking surfactants,ideal packing temporary bridging agents(TBA) and film-forming agents,etc.,were developed.New low-damage drilling fluids has many advantages,such as good rheological properties,excellent effectiveness of water-blocking prevention,good temporary plugging effect,low filtration and ultra-low permeability(API filtration≤5 mL,HTHP filtration≤10 mL,mud cake frictional coefficient≤0.14,permeability recovery>81%),can efficiently prevent or minimize damage,preserve natural formation and enhance comprehensive development-investment effect in TUHA Jurassic dense sandstone reservoir formation with low-permeability,the only one developing integrated condense gas field.Some references can be provided to similar reservoir formations.
基金Projects(50774093,50490274) supported by the National Natural Science Foundation of China
文摘There are two mechanisms of the coarse surface asperity resistance effect and rubbing resistance effect in the course of the soft rock structural surface creep,of which the former plays a dominant role in hindering the deformation in the starting creep phase,so that the structural surface creep usually displays the strong surface roughness effect,and so does the latter when the asperities in the coarse surface were fractured by shearing.Under the low stress condition,there are only two phases of the decelerating creep and the constant creep for the soft rock structural surface,and as the stress increases and overcomes the rubbing resistance,the accelerating creep failure of the structural surface will happen suddenly.Therefore,a multiple rheological model,which combines the nonlinear NEWTON body(NN) of a certain mass and the empirical plastic body(EM) with the classical SAINT VENANT body,NEWTON body,KELVIN body and HOOKE body,could be used to comprehensively describe the creep characteristics of the soft rock structural surface.Its mechanical parameter values will vary owing to the different surface roughness of the structural surface.The parameters of GH,GK and ηL are positively linearly correlative to the surface roughness.The surface roughness and m are negative exponential function correlation.The long-term strength τS is positively correlative to the surface roughness.
基金Project(2007FJ1007) supported by the Science Foundation of Hunan Province,China
文摘Based on the sweet potato starch,cationic starch,acetic starch and cationic-acetic compoundedly modified starch were made through chemical denaturalization.The above three kinds of static rheological parameter and dynamic rheological parameter were measured,respectively.The experimental result reveals that the thermal stability of starchy viscosity increases after chemical denaturalization.Under the condition of identical shearing rate,the shear stress of cationic-acetic ester compoundedly modified sweet potato starch paste is the largest among these kinds of sweet potato starch.This attributes to a phenomenon of shearing thinning.Furthermore,raw sweet potato starch has a larger gel intensity than that of modified starch.
基金Project(10672063) supported by the National Natural Science Foundation of China
文摘A three-dimensional(3D) lattice model for predicting the rheological behavior of asphalt mixtures was presented.In this model asphalt mixtures were described as a two-phase composite material consisting of asphalt sand and coarse aggregates distributed randomly.Asphalt sand was regarded as a viscoelastic material and aggregates as an elastic material.The rheological response of asphalt mixture subjected to different constant stresses was simulated.The calibrated overall creep strain shows a good approximation to experimental results.
基金Project(NCET-05-0656) supported by Education Ministry for the New Century Excellent Talents,China
文摘Rheological properties of the virgin bitumen and TPS modified bitumen binders with several percentages of TPS additives were studied.All TPS modified bituminous binders were prepared on a laboratory scale.Dynamic shear rheometer(DSR) strain sweep test was made to measure the linear viscoelasticity areas of various bitumen binders at -20-70 ℃,then temperature sweep test and frequency sweep test were made in the linear viscoelasticity areas.Complex modulus master curves were drawn to analyze and compare various bitumen binders' rheological properties.Based on the test results,the ideal percentage of TPS additive was brought forward.The results show that TPS modified bitumen binders have more excellent properties at high,medium and low temperatures compared with original bitumen.The dosages of TPS additive are vital to their properties.
基金Project(2006BAD18B02) supported by the 11th Five-Year Plan of National Key Technology R&D Program of ChinaProject(07006B) supported by Youth Fund of Central South University of Forestry and Technology,ChinaProject(080929) supported the Education Fund of Hunan Province,China
文摘The rheological properties in the supernatant of peach gum from Prunnus dulcis were discussed in order to provide more scientific technical parameters and references for developing peach gum as a kind of medicinal gum.The rheological properties in the supernatant of peach gum were comparatively studied in different material ratios,temperatures,shaking times,pH values and salinities.The results show that,1) the mathematical model of shear rate with material ratio and shear stress is Y=0.069X12+0.035X2 -1.174,R2=0.942;2) the mathematical model of shear rate with temperature and shear stress is Y=4.936X12+0.023 2X2-1.688,R2=0.937;3) the mathematical model of shear rate with shaking time and shear stress is Y=0.005 192 X13-0.140 73X12+1.249 045X1+ 0.036 546 X2-3.644 29,R2=0.954 3;4) the effects of pH value on the rheological properties in the supernatant of peach gum are comparatively complicated with a varying range of 3-11 and the shear rate shows a change trend of saddle model;5) the mathematical model of shear rate with the concentration of NaCl and shear stress is Y=-0.037 44X1+0.012 93 X2,R2=0.998;6) the mathematical model of shear rate with the concentration of CaCl2 and shear stress is Y=0.025 789X1+0.016 19X2,R2 =0.999;and 7) the mathematical model of shear rate with the concentration of sorbic acid potassium and shear stress is Y=0.079 5X1+0.017 3X2,R2=0.998.The results show that the material ratio,temperature,shaking time,pH value significantly affect the rheological properties in the supernatant of peach gum,and the concentrations of NaCl and CaCl2 also significantly affect the rheological properties expect the concentration of sorbic acid potassium.
基金Projects(51409154,41372289)supported by the National Natural Science Foundation of ChinaProjects(2015JQJH106,2014TDJH103)supported by Research Fund of Shandong University of Science and Technology,China
文摘Second lining stability, which is the last protection in tunnel engineering, is critically important. The theological properties of the surrounding rock heavily affect second lining stability. In this work, we used laboratory triaxial compressive rheological limestone tests to study nonlinear creep damage characteristics of surrounding rock mass in construction projects. We established a nonlinear creep damage constitutive model for the rock mass, as well as a constitutive model numerical implementation made by programming. Second, we introduced a new foam concrete with higher compression performance and good ductility and studied its mechanical properties through uniaxial and triaxial tests. This concrete was used as the filling material for the reserved deformation layer between the primary support and second lining. Finally, we proposed a high efficiency and accuracy staged optimization method. The minimum reserved deformation layer thickness was established as the optimization goal, and the presence of plastic strain in the second lining after 100 years of surrounding rock creep was used as an evaluation index. Reserved deformation layer thickness optimization analysis reveals no plastic strain in the second lining when the reserved deformation minimum thickness layer is 28.50 cm. The results show that the new foam concrete used as a reserved deformation layer filling material can absorb creep deformation of surrounding rock mass, reduce second lining deformation that leads to plastic strain, and ensure long-term second lining stability.
