Experimental investigation on the creep behavior of an unsaturated clay

To better understand the long-term deformation of landslides with consideration of the influence of water content variation, a series of triaxial creep tests with suction control was conducted on clay specimens taken from one large-scale landslide in the Three Gorges Reservoir area in China. Results indicate that, in the double-logarithmic coordinates, the axial strain increases linearly and the axial strain-rate decreases linearly with the elapsed time; the axial strain and strain rate increase with increasing deviator stress levels and decreasing matric suction. For theoretical analysis, based on the simulation of the test results by an empirical creep model developed for saturated soils, a linear relationship was established between suction and one of the parameters of the model. Then, a revised model with consideration of suction effects was developed. In the revised model, a power function was adopted for the description of the strain–time relationship and a hyperbolic function was employed for the stress–strain relationship. Verification indicated that the calculated results were in good agreement with the experimental ones.

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Creep Behaviors of Methane Hydrate-Bearing Frozen Sediments

Energies ◽

10.3390/en12020251 ◽

2019 ◽

Vol 12 (2) ◽

pp. 251 ◽

Cited By ~ 4

Author(s):

Yanghui Li ◽

Peng Wu ◽

Xiang Sun ◽

Weiguo Liu ◽

Yongchen Song ◽

...

Keyword(s):

Strain Rate ◽

Methane Hydrate ◽

Axial Strain ◽

Confining Pressure ◽

Creep Tests ◽

Creep Stage ◽

Long Term Stability ◽

Deviator Stress ◽

Strain And Strain Rate

Creep behaviors of methane hydrate-bearing frozen specimens are important to predict the long-term stability of the hydrate-bearing layers in Arctic and permafrost regions. In this study, a series of creep tests were conducted, and the results indicated that: (1) higher deviator stress (external load) results in larger initial strain, axial strain, and strain rate at a specific elapsed time. Under low deviator stress levels, the axial strain is not large and does not get into the tertiary creep stage in comparison with that under high deviator stress, which can be even up to 35% and can cause failure; (2) both axial strain and strain rate of methane hydrate-bearing frozen specimens increase with the enhancement of deviator stress, the decrease of confining pressure, and the decrease of temperature; (3) the specimens will be damaged rather than in stable creep stage during creeping when the deviator stress exceeds the quasi-static strength of the specimens.

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An Experimental Study on the Effect of Prior Plastic Straining on Creep Behavior of 304 Stainless Steel

Journal of Engineering Materials and Technology ◽

10.1115/1.2904207 ◽

1993 ◽

Vol 115 (2) ◽

pp. 200-203 ◽

Cited By ~ 11

Author(s):

Z. Xia ◽

F. Ellyin

Keyword(s):

Stainless Steel ◽

Plastic Strain ◽

Strain Rate ◽

Creep Behavior ◽

Test Procedure ◽

Constant Strain Rate ◽

304 Stainless Steel ◽

Creep Model ◽

Plastic Strain Rate ◽

Creep Tests

Constant strain-rate plastic straining followed by creep tests were conducted to investigate the effect of prior plastic straining on the subsequent creep behavior of 304 stainless steel at room temperature. The effects of plastic strain and plastic strain-rate were delineated by a specially designed test procedure, and it is found that both factors have a strong influence on the subsequent creep deformation. A creep model combining the two factors is then developed. The predictions of the model are in good agreement with the test results.

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Test Study on the Creep Behaviors of Tianjin Clays

E3S Web of Conferences ◽

10.1051/e3sconf/201913607029 ◽

2019 ◽

Vol 136 ◽

pp. 07029

Author(s):

Gang Li ◽

Zhen Yan ◽

Jinli Zhang ◽

Jia Liu ◽

Yu Xi

Keyword(s):

Strain Rate ◽

Axial Strain ◽

Deviatoric Stress ◽

Test Results ◽

Creep Tests ◽

Creep Properties ◽

Test Study ◽

Undisturbed Samples ◽

Calculation Results ◽

Triaxial Creep

The drained triaxial creep tests were carriedout to investigate the relationshipsbetween axial strain and time, axial strain and deviatoricstress, and axial strain rate and time for the undisturbed samples of muddy clay and clay in Tianjin.Based on the creep test results, the Singh-Mitchell modelwas used for creep calculation. The results showed that the muddyclay and clay exhibited typical non-linear creep properties. The axial strain increasedwith time and then gradually tendedto be stable.The strain rate increasedasthe deviatoric stress increased, and the muddy clay and clay showedthe characteristics of attenuation creep under deviatoricstresses. The axial strain of muddy clay wassignificantly larger than that of clay, and reachedthestable state within 3000 minutes.Under low deviatoricstress, the slope of the isochronal curve was smaller; while under high deviatoric stress, the slope of the isochronal curve waslarger.The test results were in good agreement with the calculation results, which indicated that the Singh-Mitchell model wassuitable for describing the creep behaviorsof the undisturbed claysin Tianjin.

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Study of the Long-Term Deformation Characteristics of Municipal Sludge Solidified Soil under the Coupling Action of Dry-Wet Cycles and Initial Static Deviatoric Stress

Advances in Civil Engineering ◽

10.1155/2020/8824414 ◽

2020 ◽

Vol 2020 ◽

pp. 1-15

Author(s):

Aiwu Yang ◽

Shaokun Yang ◽

Guofang Xu ◽

Wei Zhang

Keyword(s):

Small Deformation ◽

Deviatoric Stress ◽

Creep Model ◽

Hyperbolic Function ◽

Deformation Characteristics ◽

Municipal Sludge ◽

Creep Tests ◽

Short Period ◽

Deviatoric Stresses

A self-developed curing agent is used to solidify the municipal sludge taken from Tianjin. Then, the long-term deformation characteristics of the sludge solidified soil are investigated by means of unconsolidated undrained creep tests with different dry-wet cycles for considering the influence of climate. The experimental results show that the attenuation rate of the shear peak strength of municipal sludge solidified soil decreases gradually with the increase of the number of dry-wet cycles, and the strength remains unchanged when the number of dry-wet cycles is greater than 10. The variation laws under different initial static deviatoric stresses are basically identical. When the applied stress is less than the yield stress of the sludge solidified soil, the duration curves of creep show only attenuated stage, i.e., with very small deformation, and the deformation reaches a constant in a short period of time. When the deviatoric stress reaches the long-term strength of the soil, the instantaneous deformation of the sludge solidified soil becomes large and damage occurs quickly. Under the same deviatoric stress, the creep deformation increases with the increase of the number of dry-wet cycles. When the load applied in each step is of the same magnitude, the higher the initial static deviatoric stress is, the larger the deformation of sludge solidified soil will be. It is found that the stress-strain relationship and the relationship between creep strain and time can be well described by an exponential function and a hyperbolic function, respectively. On this basis, a creep model is proposed for the long-term deformation considering the effect of dry-wet cycle times and initial static deviatoric stress. The model is further validated by comparing the predictions with the test results under different deviatoric stresses; the good agreement between which shows the potential application of the model to relevant practical engineering.

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An Empirical Creep Law From a Single Test

Journal of Basic Engineering ◽

10.1115/1.3657292 ◽

1962 ◽

Vol 84 (2) ◽

pp. 236-238

Author(s):

Iain Finnie

Keyword(s):

Strain Rate ◽

Creep Test ◽

Constant Load ◽

Constant Stress ◽

Single Test ◽

Creep Tests ◽

Stress Strain ◽

Strain And Strain Rate ◽

Single Constant

A method is described by which an empirical creep law, relating stress, strain, and strain rate, may be obtained from a single constant-load creep test. An example to illustrate the method is given, and the empirical creep law is compared with the results of several constant stress creep tests.

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Uniaxial Constant Compressive Stress Creep Tests on Sea Ice

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.2827235 ◽

1995 ◽

Vol 117 (4) ◽

pp. 283-289 ◽

Cited By ~ 6

Author(s):

N. K. Sinha ◽

C. Zhan ◽

E. Evgin

Keyword(s):

Compressive Strength ◽

Sea Ice ◽

Strain Rate ◽

Compressive Stress ◽

Axial Strain ◽

Acoustic Emissions ◽

Constant Strain Rate ◽

Rate Sensitivity ◽

Load Test ◽

Creep Tests

First-year columnar-grained sea ice from Resolute Passage (74° 42′ N, 94° 50′ W), off Barrow Strait in the Canadian High Arctic, was tested under constant uniaxial compressive stress applied normal to the length of the columns. Creep tests were performed at 263 K, 253 K, and 243 K in the stress range of 0.7 to 2.5 MPa, using prismatic samples with dimensions of 50 mm × 100 mm × 250 mm. Because three-dimensional creep data are extremely useful for developing constitutive equations, axial strain was measured in conjunction with the measurements of two lateral strains and acoustic emissions. The deformations were measured using displacement gages mounted on the samples. A description of the experimental procedures and the observations are presented here. One-to-one correspondence has been obtained between the present results on the dependence of minimum creep rate on stress and previous data on the dependence of uniaxial compressive strength on strain rate under constant strain rate. The strain-rate sensitivity of compressive strength can, therefore, be obtained from creep tests which can be performed by using simple dead-load test systems.

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Laboratory Experimental Study on Pullout Behavior of Mortar Grouted GFRP Soil Nails

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.168-170.1069 ◽

2010 ◽

Vol 168-170 ◽

pp. 1069-1072

Author(s):

Zhong Yu Liu ◽

Chong Wu Ma ◽

Zhuo Zhao

Keyword(s):

Large Scale ◽

Axial Strain ◽

Hyperbolic Function ◽

Overburden Pressure ◽

Soil Nails ◽

Pullout Resistance ◽

Pull Out ◽

Glass Fiber Reinforced ◽

Dilatancy Effect ◽

Pullout Load

A large-scale laboratory apparatus has been built to study the pullout behavior of mortar grouted glass fiber reinforced polymer (GFRP) soil nails. The axial strain along the nail length and the displacement of the nail head under different pullout loads are measured, and the ultimate pullout load under the overburden pressure is obtained. Then, the influence of the overburden pressure on the ultimate value of the interface friction force is investigated. The experimental results illustrate that the pullout behavior of mortar grouted GFRP soil nails is similar to that of mortar grouted steel soil nails, and the relation between the displacement and the pullout load can be described with the hyperbolic function. In addition, the dilatancy effect of the soil near the nail during pull out should be taken into account in estimating the pullout resistance of soil nails in dense fills.

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A new theoretical creep model of an epoxy-graphene composite based on experimental investigation: effect of graphene content

Journal of Composite Materials ◽

10.1177/0021998319895806 ◽

2020 ◽

Vol 54 (18) ◽

pp. 2461-2472 ◽

Cited By ~ 1

Author(s):

Ata Khabaz-Aghdam ◽

Bashir Behjat ◽

Lucas F M da Silva ◽

E A S Marques

Keyword(s):

Creep Strain ◽

Weight Ratio ◽

Neat Epoxy ◽

Creep Model ◽

Reinforced Composites ◽

Creep Tests ◽

Strain And Strain Rate ◽

Electron Microscopy Analysis ◽

Microscopy Analysis ◽

Creep Models

In this paper, the creep behavior of an epoxy-based adhesive reinforced with different weight fractions of graphene up to 0.5 wt% was studied. Creep tests were performed in three stress levels, using the ultimate strength of the neat epoxy as a reference. Results indicated that the presence of graphene up to 0.5 wt% reduces the creep strain and strain rate of the epoxy. However, the dominant behavior in the creep of epoxy–graphene composites is the creep pattern of the neat epoxy. These experimental observations led to development of theoretical creep models to an appropriate creep model for graphene-reinforced composites by introducing a new function of the graphene weight ratio. A scanning electron microscopy analysis indicated that the strong bond between the graphene surface and epoxy matrix limits the mobility of the molecular chains of the neat epoxy and therefore reduces the creep strain.

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The effects of strain and strain rate on residual microstructures in copper

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100143687 ◽

1986 ◽

Vol 44 ◽

pp. 420-421

Author(s):

M. F. Stevens ◽

P. S. Follansbee

Keyword(s):

Strain Rate ◽

Applied Stress ◽

Threshold Stress ◽

Rate Sensitivity ◽

Viscous Drag ◽

Strain Rates ◽

Strain And Strain Rate ◽

Threshold Strength ◽

Mechanism Transition ◽

Intrinsic Strength

The strain rate sensitivity of a variety of materials is known to increase rapidly at strain rates exceeding ∼103 sec-1. This transition has most often in the past been attributed to a transition from thermally activated guide to viscous drag control. An important condition for imposition of dislocation drag effects is that the applied stress, σ, must be on the order of or greater than the threshold stress, which is the flow stress at OK. From Fig. 1, it can be seen for OFE Cu that the ratio of the applied stress to threshold stress remains constant even at strain rates as high as 104 sec-1 suggesting that there is not a mechanism transition but that the intrinsic strength is increasing, since the threshold strength is a mechanical measure of intrinsic strength. These measurements were made at constant strain levels of 0.2, wnich is not a guarantee of constant microstructure. The increase in threshold stress at higher strain rates is a strong indication that the microstructural evolution is a function of strain rate and that the dependence becomes stronger at high strain rates.

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