Long-term settlement of model rock-socketed piers

Very little information is available concerning the long-term settlement behaviour of drilled pier foundations socketed into rock. This paper summarizes the results of laboratory investigations of the long-term settlement (creep) behaviour of model socketed pier foundations. The testing program included seven model piers constructed with different materials and different load-support conditions. The primary models were two small-diameter concrete piers constructed in soft shale. For all models tested the results indicated similarly shaped time–displacement curves, having two distinct regions. The initial portion of the curves represents a region of primary creep and the remaining portion represents a zone of secondary creep having a much lower rate of displacement. A comparison of short-term (1 day, which is a normal maximum duration of a full-scale load test) and long-term (200 days) settlements for the model piers showed an 84–245% increase in settlements. In addition, some information concerning load transfer with time in the model piers and available data from loading tests on large-scale socketed piers are included. Key words: socketed pier foundations, long-term settlement, creep model tests, soft rock.

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Nonlinear Creep Model of Deep Gangue Backfilling Material and Time-Dependent Characteristics of Roof Deformation in Backfilling Mining

Geofluids ◽

10.1155/2020/8816871 ◽

2020 ◽

Vol 2020 ◽

pp. 1-10

Author(s):

Peng Huang ◽

Jixiong Zhang ◽

Qi Zhang ◽

Ntigurirwa Jean Damascene ◽

Yuming Guo

Keyword(s):

Large Scale ◽

High Stress ◽

Viscoelastic Model ◽

Creep Model ◽

Mine Pressure ◽

Nonlinear Creep ◽

Viscoelastic Foundation ◽

The Impact ◽

Roof Deformation

With the gradual increase in mining depth of coal resource exploitation, deep backfilling mining has effectively solved the impact of strong deep mine pressure and strong mining disturbances. However, after deep backfilling mining, the backfilling material is subjected to high stress for a long time, and its viscoelasticity has a significant impact on the roof control effect. This paper uses a large-scale bulk confinement test device to analyze the viscoelastic properties of gangue, establishes a high-precision fractional viscoelastic creep model, and identifies the gangue parameters. The established fractional viscoelastic model was used as the foundation model of the beam, and the roof model based on the fractional viscoelastic foundation was solved. The top deformation characteristics of elastic foundation and fractional foundation were compared and analyzed, and the time effect, viscoelastic effect, and order effect of the fractional order viscoelastic foundation beam were discussed. The results show that the viscosity of gangue increased under the action of deep high stress. As time increased, the roof deformation also increased. In order to more effectively control the long-term deformation of the roof, the viscosity coefficient of the backfilling material should be greater than 20 MPa. This research provides relevant guidance for the requirements of backfilling materials for deep backfilling mining and the prediction of long-term dynamic deformation of the roof in underground excavations.

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Modelling creep deformation in floating ice

Canadian Journal of Civil Engineering ◽

10.1139/l02-082 ◽

2003 ◽

Vol 30 (1) ◽

pp. 28-41 ◽

Cited By ~ 5

Author(s):

K van Steenis ◽

F E Hicks ◽

T M Hrudey ◽

S Beltaos

Keyword(s):

Large Scale ◽

Field Experiments ◽

Numerical Models ◽

Ice Sheet ◽

Transversely Isotropic ◽

Element Model ◽

Ice Cover ◽

Load Test ◽

Drilling Rig

The ability to predict the response of an ice sheet to long-term loading is important in many situations. In northern regions, ice sheets have been used as construction platforms, drilling rig platforms, airfields, parking lots, and festival platforms. Numerical models can be used to predict the deflection of an ice sheet over time and, together with a failure criterion based on allowable deflection, can facilitate the safe use of an ice cover under long-term loading situations. In this study, a two-dimensional axisymmetric finite element model was developed to model the behaviour of a homogeneous, transversely isotropic, infinite ice cover under long-term loading. The model was validated using 33 sets of long-term load test data from large-scale field experiments performed on lake, bay, and reservoir ice and was shown to be capable of reliably predicting deflections under a variety of loading scenarios.Key words: bearing capacity of ice, long-term loading, ice platforms.

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A practical creep model for concrete elements under eccentric compression

Materials and Structures ◽

10.1617/s11527-019-1432-z ◽

2019 ◽

Vol 52 (6) ◽

Author(s):

Haidong Huang ◽

Reyes Garcia ◽

Shan-Shan Huang ◽

Maurizio Guadagnini ◽

Kypros Pilakoutas

Keyword(s):

Prestressed Concrete ◽

Creep Behaviour ◽

Concrete Structures ◽

Creep Model ◽

Small Scale ◽

Compressive Creep ◽

Eccentric Compression ◽

Shrinkage And Creep ◽

Concrete Elements

AbstractMany prestressed concrete bridges are reported to suffer from excessive vertical deflections and cracking during their service life. Creep softens the structure significantly, and therefore an accurate prediction of creep is necessary to determine long-term deflections in elements under eccentric axial compression such as prestressed concrete girders. This study proposes a modification to the creep damage model of Model Code 2010 to account for the effect of load eccentricity. The modified creep model considers damage due to differential drying shrinkage. Initially, the creep behaviour of small scale concrete specimens under eccentric compression load is investigated experimentally. Twelve small-scale concrete prisms were subjected to eccentric axial loading to assess their shrinkage and creep behaviour. The main parameters investigated include the load eccentricity and exposure conditions. Based on the experimental results, an inverse analysis is conducted to determine the main parameters of the modified creep model. Subsequently, a numerical hygro-mechanical simulation is carried out to examine the effect of load eccentricity on the development of shrinkage and creep, and on the interaction between drying, damage and creep. The results indicate that eccentric loading leads to different tensile and compressive creep through the cross section, which contradicts the current design approach that assumes that tensile and compressive creep are identical. The proposed model also predicts accurately the long-term behaviour of tests on reinforced concrete elements available in the literature. This study contributes towards further understanding of the long-term behaviour of concrete structures, and towards the development of advanced creep models for the design/assessment of concrete structures.

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Overview of the French research on the evolution of spent fuel rod after discharge from the reactor

MRS Proceedings ◽

10.1557/proc-1193-605 ◽

2009 ◽

Vol 1193 ◽

Cited By ~ 1

Author(s):

C. Ferry ◽

C. Cappelaere ◽

C. Jegou ◽

J.P. Piron ◽

M. Firon ◽

...

Keyword(s):

Creep Behaviour ◽

Creep Model ◽

Spent Fuel ◽

Secondary Phases ◽

Water Contact ◽

Fuel Rod ◽

Safety Margins ◽

The Matrix ◽

The One

AbstractSince 2006, French research on spent fuel has focused on the main issues related to transport and extended in-pool storage of spent fuel assembly. Studies on creep behaviour of irradiated cladding have resulted in a new creep model which is valid over a wide domain of temperature, internal pressure and time. Under nominal conditions, no evolution of the spent fuel rod is expected during in-pool storage. In case of defective fuel rods in the storage pool, the consequences of fuel alteration on the initial defect of the cladding depend on the matrix alteration rate and nature of the secondary phases formed. Considering the optional scenario of direct disposal, the long-term behaviour of the spent fuel is investigated focusing on helium consequences before water contact on the one hand and on the influence of repository conditions on matrix alteration on the other hand. The aim of the on-going studies is to improve the safety margins initially introduced in the radionuclide source term models.

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Creep behaviour of a buffer material for nuclear fuel waste vault

Canadian Geotechnical Journal ◽

10.1139/t85-074 ◽

1985 ◽

Vol 22 (4) ◽

pp. 541-550 ◽

Cited By ~ 14

Author(s):

Raymond N. Yong ◽

Prapote Boonsinsuk ◽

Demos Yiotis

Keyword(s):

Finite Element ◽

Nuclear Fuel ◽

Host Rock ◽

Creep Behaviour ◽

Creep Model ◽

Secondary Creep ◽

Full Size ◽

Waste Container ◽

Buffer Material ◽

Nuclear Fuel Waste

In the Canadian nuclear fuel waste disposal concept currently under study, one of the prime candidate procedures is the borehole emplacement technique. Each fuel waste container will be placed in a 1.1 m diameter hole in the floor of a disposal vault in deep plutonic rock. The container will be surrounded by buffer material consisting of a mixture of clay and sand. This study examines the creep behaviour of the buffer material in the borehole during interaction with the waste container and the host rock. It simulated the buffer – container – host rock interaction through a small-scale physical model using the loading pressures anticipated in the full-size system. The results from the model tests were compared with those predicted by a finite element analytical model. The creep behaviour of the full-size system was then predicted using the analytical model.From the results, it is evident that the creep behaviour of the buffer material depends significantly on interaction within the container – buffer – host rock system, overburden pressure, and water uptake. At relatively low overburden pressures, the waste container might settle, causing a separation between the buffer material and the container top. However, this could be alleviated by the swelling properties of the buffer material. The secondary creep rates are negligible, and creep in the buffer material is primarily governed by the primary creep stage. Key words: creep, model test, swelling soil, soil deformation, unsaturated soil, finite element analysis.

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Flexural Creep Effects On Permanent Wood Foundation Made Of Structural Insulated Foam-Timber Panels

10.32920/ryerson.14650095.v1 ◽

2021 ◽

Author(s):

Mahmoud Shaaban Sayed Ahmed

Keyword(s):

Experimental Testing ◽

Creep Behaviour ◽

Expanded Polystyrene ◽

Load Test ◽

Soil Pressure ◽

Creep Tests ◽

Structural Capacity ◽

Wood Frame ◽

Term Creep

A Permanent Wood Foundation (PWF) is a panel composed of expanded polystyrene insulation and preserved stud cores laminated between oriented-strand boards and preserved plywood. This thesis presents the experimental testing on selected PWFs' sizes to investigate their long-term creep behaviour under sustained soil pressure. The long-term creep tests were performed over eight months, followed by loading the tested panels to destruction to determine their axial compressive strength. The ultimate load test results showed that the structural qualification of PWF is "as good as" the structural capacity of the conventional wood-frame buildings. The obtained experimental ultimate compressive resistance and flexural resistance, along with the developed long-term creep deflection of the wall under lateral soil pressure can be used in the available Canadian Wood Council (CWC) force-moment interaction equation to establish design tables of such wall panels under gravity loading and soil pressure.

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Hydraulic System Pump Controlled Motor Speed Control Performance Research

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.926-930.1361 ◽

2014 ◽

Vol 926-930 ◽

pp. 1361-1364

Author(s):

Ye Tian ◽

Li Chen Gu

Keyword(s):

Control System ◽

Hydraulic System ◽

Large Scale ◽

Load Transfer ◽

Speed Control ◽

Simulation Software ◽

Load Test ◽

Motor Speed ◽

Speed Control System ◽

Set Up

With the direction of large-scale, heavy machinery field, hydraulic system performance requirements also more and more high; This article is based on the mechanical and electrical integration of liquid hydraulic system test platform as the background, by the variable pump control motor speed control system as the research object, and describes the control principle of the system, established the mathematical model of the system, on the simulation software AMESim corresponding dynamic simulation model is set up, by changing the input variable pump rotation speed and system load test, and the output of the motor speed response has carried on the simulation, the simulation result in accordance with the expected on the trend of basic, therefore, the pump control motor speed control system between speed and power as a power source and load transfer mechanism is feasible.

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Curve Fitting for Damage Evolution through Regression Analysis for the Kachanov–Rabotnov Model to the Norton–Bailey Creep Law of SS-316 Material

Materials ◽

10.3390/ma14195518 ◽

2021 ◽

Vol 14 (19) ◽

pp. 5518

Author(s):

Mohsin Sattar ◽

Abdul Rahim Othman ◽

Maaz Akhtar ◽

Shahrul Kamaruddin ◽

Rashid Khan ◽

...

Keyword(s):

Creep Behavior ◽

Creep Deformation ◽

Curve Fitting ◽

Elevated Temperatures ◽

Creep Behaviour ◽

Creep Damage ◽

Tertiary Creep ◽

Creep Model ◽

Secondary Creep ◽

Dog Bone

In a number of circumstances, the Kachanov–Rabotnov isotropic creep damage constitutive model has been utilized to assess the creep deformation of high-temperature components. Secondary creep behavior is usually studied using analytical methods, whereas tertiary creep damage constants are determined by the combination of experiments and numerical optimization. To obtain the tertiary creep damage constants, these methods necessitate extensive computational effort and time to determine the tertiary creep damage constants. In this study, a curve-fitting technique was proposed for applying the Kachanov–Rabotnov model into the built-in Norton–Bailey model in Abaqus. It extrapolates the creep behaviour by fitting the Kachanov–Rabotnov model to the limited creep data obtained from the Omega-Norton–Bailey regression model and then simulates beyond the available data points. Through the Omega creep model, several creep strain rates for SS-316 were calculated using API-579/ASME FFS-1 standards. These are dependent on the type of the material, the flow stress, and the temperature. In the present work, FEA creep assessment was carried out on the SS-316 dog bone specimen, which was used as a material coupon to forecast time-dependent permanent plastic deformation as well as creep behavior at elevated temperatures and under uniform stress. The model was validated with the help of published experimental creep test data, and data optimization for sensitivity study was conducted by applying response surface methodology (RSM) and ANOVA techniques. The results showed that the specimen underwent secondary creep deformation for most of the analysis period. Hence, the method is useful in predicting the complete creep behavior of the material and in generating a creep curve.

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Flexural Creep Effects On Permanent Wood Foundation Made Of Structural Insulated Foam-Timber Panels

10.32920/ryerson.14650095 ◽

2021 ◽

Author(s):

Mahmoud Shaaban Sayed Ahmed

Keyword(s):

Experimental Testing ◽

Creep Behaviour ◽

Expanded Polystyrene ◽

Load Test ◽

Soil Pressure ◽

Creep Tests ◽

Structural Capacity ◽

Wood Frame ◽

Term Creep

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Evolution of Large-Scale Coronal Structures

International Astronomical Union Colloquium ◽

10.1017/s0252921100024945 ◽

1994 ◽

Vol 144 ◽

pp. 29-33

Author(s):

P. Ambrož

Keyword(s):

Magnetic Field ◽

Field Line ◽

Large Scale ◽

Coronal Magnetic Field ◽

Source Surface ◽

Solar Cycles ◽

Characteristic Relationship ◽

The Magnetic Field ◽

Coronal Structures

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.

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