scholarly journals Stability and load-displacement behaviour of axially cyclic loaded displacement piles in sands

2022 ◽  
Author(s):  
Siya Rimoy ◽  
Matias Silva ◽  
Richard J. Jardine
Keyword(s):  
Cyclic Loading ◽  
Effective Stress ◽  
Fine Sand ◽  
Diameter Ratio ◽  
Stress Regime ◽  
Cyclic Behaviour ◽  
Pile Diameter ◽  
Calibration Chamber ◽  
High Level ◽  
Cyclic Damage

Uncertainties regarding the axial cyclic behaviour of piles driven in sands led to an extended programme of calibration chamber instrumented pile experiments. Broad trends are identified and interpreted with reference to normalised cyclic loading parameters Qcyclic/QT, Qmean/QT and N. Cyclic damage is shown to be related to changes in the radial effective stress regime close to the shaft. While stable loading leads to little or no change as cycling continues in the sand masses’ effective stress regime, high-level cyclic loading can affect stresses far out into the sand mass. The test systems’ chamber-to-pile diameter ratio has a significant impact on outcomes. Piles installed in loose, fine, sand are far more susceptible to cyclic loading than in denser, coarser sand. Little or no change in pile stiffness was seen in tests that remained within the stable cyclic region, even over 10,000 or more cycles. Unstable tests lost their stiffness rapidly and metastable cases showed intermediate behaviours. The permanent deflections developed under cycling depend on the combined influence of Qcyclic/QT, Qmean/QT and N. While model tests provide many valuable insights into the behaviour of piles driven in sand, they are unable to capture some key features observed in the field.

scholarly journals Effective stress regime around a jacked steel pile during installation ageing and load testing in chalk

2018 ◽  
Vol 55 (11) ◽  
pp. 1577-1591 ◽  
Author(s):  
R.M. Buckley ◽  
R.J. Jardine ◽  
S. Kontoe ◽  
B.M. Lehane
Keyword(s):  
Cyclic Loading ◽  
Effective Stress ◽  
Test Site ◽  
Static Tension ◽  
Load Testing ◽  
Stress Regime ◽  
Effective Stresses ◽  
Axial Cyclic Loading ◽  
Tension Testing ◽  
Static And Cyclic Loading

This paper reports experiments with 102 mm diameter closed-ended instrumented Imperial College piles (ICPs) jacked into low- to medium-density chalk at a well-characterized UK test site. The “ICP” instruments allowed the effective stress regime surrounding the pile shaft to be tracked during pile installation, equalization periods of up to 2.5 months, and load testing under static tension and one-way axial cyclic loading. Installation resistances are shown to be dominated by the pile tip loads. Low installation shaft stresses and radial effective stresses were measured that correlated with local cone penetration test (CPT) tip resistances. Marked shaft total stress reductions and steep stress gradients are demonstrated in the vicinity of the pile tip. The local interface shaft effective stress paths developed during static and cyclic loading displayed trends that resemble those seen in comparable tests in sands. Shaft failure followed the Coulomb law and constrained interface dilation was apparent as the pile experienced drained loading to failure, although with a lesser degree of radial expansion than with sands. Radial effective stresses were also found to fall with time after installation, leading to reductions in shaft capacity as proven by subsequent static tension testing. The jacked, closed-ended, piles’ ageing trends contrast sharply with those found with open piles driven at the same site, indicating that ageing is affected by pile tip geometry and (or) installation method.

scholarly journals Insights, Trends and Challenges Associated with Measuring Coal Relative Permeability

2019 ◽  
Vol 89 ◽  
pp. 01004
Author(s):  
Dylan Shaw ◽  
Peyman Mostaghimi ◽  
Furqan Hussain ◽  
Ryan T. Armstrong
Keyword(s):  
Relative Permeability ◽  
Effective Stress ◽  
History Matching ◽  
Water Saturation ◽  
Laboratory Data ◽  
Stress Regime ◽  
Cross Point ◽  
Irreducible Water Saturation ◽  
Relative Permeability Curves ◽  
The Right

Due to the poroelasticity of coal, both porosity and permeability change over the life of the field as pore pressure decreases and effective stress increases. The relative permeability also changes as the effective stress regime shifts from one state to another. This paper examines coal relative permeability trends for changes in effective stress. The unsteady-state technique was used to determine experimental relativepermeability curves, which were then corrected for capillary-end effect through history matching. A modified Brooks-Corey correlation was sufficient for generating relative permeability curves and was successfully used to history match the laboratory data. Analysis of the corrected curves indicate that as effective stress increases, gas relative permeability increases, irreducible water saturation increases and the relative permeability cross-point shifts to the right.

scholarly journals Experimental and Estimation Studies of Resilient Modulus of Marine Coral Sand under Cyclic Loading

2020 ◽  
Vol 8 (4) ◽  
pp. 287 ◽  
Author(s):  
Shao-Heng He ◽  
Qiong-Fang Zhang ◽  
Zhi Ding ◽  
Tang-Dai Xia ◽  
Xiao-Lu Gan
Keyword(s):  
Cyclic Loading ◽  
South China Sea ◽  
Effective Stress ◽  
South China ◽  
Stress Ratio ◽  
Resilient Modulus ◽  
Cyclic Stress ◽  
Marine Transportation ◽  
Cyclic Stress Ratio ◽  
Coral Sand

Coral sand is an important filler resource that can solve the shortage of terrestrial fillers in coastal areas. Recently, the foundations of many infrastructures in the South China Sea have been built with coral sand as fillers, which have been subjected to wave and traffic cyclic loads. Resilient modulus (Mr) is an important design parameter in marine engineering, but there are few studies on the resilient modulus response of coral sand under cyclic loading. A series of drained cyclic triaxial tests were carried out to investigate the effects of the initial mean effective stress (p0) and cyclic stress ratio (ζ) on the resilient modulus response of the coral sand from the South China Sea. The change of fractal dimension (αc) can reflect the rule of particle breakage evolution. The αc of coral sand shows a tendency of almost maintaining stable and then increasing rapidly with the increase of mean effective stress p0 under each cyclic stress ratio ζ. There is a threshold of p0, when the p0 exceeds this threshold, αc will increase significantly with the increase of p0. The increase of p0 has a beneficial effect on the improvement of the Mr, while the increase of ζ has both beneficial and detrimental effects on the improvement of the Mr. A new prediction model of the Mr considering particle breakage was established, which can better predict the Mr of coral sand in the whole stress interval. The research results can provide guidance for the design of marine transportation infrastructures, which can promote the development of marine transportation industry and energy utilization.

A Method for Estimating Creep Deformation of Structures Subjected to Cyclic Loading

1973 ◽  
Vol 40 (4) ◽  
pp. 928-934 ◽  
Author(s):  
J. J. Williams ◽  
F. A. Leckie
Keyword(s):  
Cyclic Loading ◽  
Creep Strain ◽  
Effective Stress ◽  
Creep Test ◽  
Creep Deformation ◽  
Cyclic Creep ◽  
Uniaxial Stress ◽  
Time Varying ◽  
Proportional Loading

A method is proposed for estimating structural creep deformation due to histories of cyclic proportional loading. The method applies to structures composed of materials whose creep strain due to constant uniaxial stress is given by an equation of the form ε(t)/ε0={σ/σ0}n{t/t0}m Knowledge of the form of the creep law for time-varying stress is not required, as use is made of an effective stress obtained from a single cyclic creep test.

scholarly journals Static and dynamic effective stress coefficient of chalk

Geophysics ◽  
2012 ◽  
Vol 77 (2) ◽  
pp. L1-L11 ◽  
Author(s):  
M. Monzurul Alam ◽  
Ida Lykke Fabricius ◽  
Helle Foged Christensen
Keyword(s):  
Pore Pressure ◽  
Effective Stress ◽  
Mechanical Strain ◽  
Mechanical Tests ◽  
Differential Stress ◽  
Stress Regime ◽  
Hydrocarbon Reservoir ◽  
Stress Coefficient ◽  
The Difference ◽  
Stress Dependent

Deformation of a hydrocarbon reservoir can ideally be used to estimate the effective stress acting on it. The effective stress in the subsurface is the difference between the stress due to the weight of the sediment and a fraction (effective stress coefficient) of the pore pressure. The effective stress coefficient is thus relevant for studying reservoir deformation and for evaluating 4D seismic for the correct pore pressure prediction. The static effective stress coefficient [Formula: see text] is estimated from mechanical tests and is highly relevant for effective stress prediction because it is directly related to mechanical strain in the elastic stress regime. The corresponding dynamic effective stress coefficient [Formula: see text] is easy to estimate from density and velocity of acoustic (elastic) waves. We studied [Formula: see text] and [Formula: see text] of chalk from the reservoir zone of the Valhall field, North Sea, and found that [Formula: see text] and [Formula: see text] vary with differential stress (overburden stress-pore pressure). For Valhall reservoir chalk with 40% porosity, [Formula: see text] ranges between 0.98 and 0.85 and decreases by 10% if the differential stress is increased by 25 MPa. In contrast, for chalk with 15% porosity from the same reservoir, [Formula: see text] ranges between 0.85 and 0.70 and decreases by 5% due to a similar increase in differential stress. Our data indicate that [Formula: see text] measured from sonic velocity data falls in the same range as for [Formula: see text], and that [Formula: see text] is always below unity. Stress-dependent behavior of [Formula: see text] is similar (decrease with increasing differential stress) to that of [Formula: see text] during elastic deformation caused by pore pressure buildup, for example, during waterflooding. By contrast, during the increase in differential stress, as in the case of pore pressure depletion due to production, [Formula: see text] increases with stress while [Formula: see text] decreases.

scholarly journals The influence of stress level on the ratcheting magnitude and progress rate in steel alloys under uniaxial loading conditions

2021 ◽  
Author(s):  
Prasanth Chandrasekar
Keyword(s):  
Cyclic Loading ◽  
Plastic Strain ◽  
Strain Rate ◽  
Loading Condition ◽  
Stress Amplitude ◽  
Fatigue Loading ◽  
Mean Stress ◽  
Cyclic Loading Condition ◽  
Ratcheting Strain ◽  
Cyclic Damage

Engineering materials in their service life undergo symmetric or asymmetric fatigue loading, which leads to fatigue damage in the material. Ratcheting damage is due to the application of mean stress under cyclic loading condition. From deformation behavior perspective, application of mean stress under stress-controlled fatigue loading gives rise to accumulation of plastic strain in the material. Ratcheting strain increases with an increase in applied mean stress and stress amplitude. In addition, ratcheting behavior will increase in cyclic damage with the rise in strain accumulation and it can be illustrated by a shift in the hysteresis loop towards large plastic strain amplitudes. This study focuses on the ratcheting behavior of different steel materials under uniaxial cyclic loading condition and suggests a suitable method to arrest ratcheting by loading the materials at zero ratcheting strain rate condition with specified mean stress and stress amplitudes. The three dimensional surface is created with stress amplitude, mean stress and ratcheting strain rate for different steel materials. This represents a graphical surface zone to study the ratcheting strain rates for various mean stress and stress amplitude combinations.

scholarly journals The Operational Technique of Increasing Service Life Time of the Major Components of the Fighter Aircraft Engine Rotors

2021 ◽  
Vol 51 (3) ◽  
pp. 65-73
Author(s):  
Serhii Pashchenko ◽  
Artem Shulhin ◽  
Volodimyr Samuleev ◽  
Оleksandr Lobunko ◽  
Оleg Dobridenko
Keyword(s):  
Life Cycle ◽  
Cyclic Loading ◽  
Operating Time ◽  
Aircraft Engine ◽  
Individual Characteristics ◽  
Fighter Aircraft ◽  
Previous Operation ◽  
Operational Technique ◽  
Cyclic Damage ◽  
Engine Rotors

Abstract The operational technique for the major components of the fighter aircraft engine rotors has been introduced basing on the real conditions of their cyclic loading in each flight or ground test and a priori information on their previous operation. It has been confirmed that the obtained technical solutions not only conform to the current methods of accounting for the depletion of the life cycle of the Afterburning Turbofan Engine (ATE) but also introduce additional opportunities to consider individual characteristics and conditions of their cyclic loading throughout the overall operating time. A method for estimating the depletion of the life cycle in accordance with the Total Accumulated Cycle (TAC) has been proposed. It allows us to compare the actual operating time of the ATE in hours and the accumulated value of cyclic damage to the engine and its major components (within the TAC parameter) during the previous operation.

scholarly journals Research on the Design of Miniature Pile Foundation for Transmission Line

2019 ◽  
Vol 136 ◽  
pp. 02022
Author(s):  
Xinmin Yu ◽  
Xianri Wang
Keyword(s):  
Transmission Line ◽  
Bearing Capacity ◽  
Pile Foundation ◽  
Small Diameter ◽  
Diameter Ratio ◽  
Pile Diameter ◽  
Working Surface ◽  
Bored Piles ◽  
Pile Length ◽  
Small Working

Micro-pile is a kind of small diameter bored piles, also known as root pile, pile diameter is generally 150-400mm, length-diameter ratio is generally greater than 30,and pile length is usually not more than 30m. Compared with ordinary pile, micro-pile has the advantages of fast construction speed, small working surface, high bearing capacity and small settlement.

An experimental study on cyclic behaviour of reinforced concrete connections

2007 ◽  
Vol 34 (4) ◽  
pp. 565-575 ◽  
Author(s):  
Gerson Moacyr Sisniegas Alva ◽  
Ana Lúcia Homce de Cresce El Debs ◽  
Mounir Khalil El Debs
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Cyclic Loading ◽  
Seismic Analysis ◽  
Reinforcement Rate ◽  
Shear Capacity ◽  
Transverse Reinforcement ◽  
Rc Beam ◽  
Concrete Compressive Strength ◽  
Cyclic Behaviour

Beam-column joints are considered critical regions within the structural system — especially under seismic loading — requiring careful design. Results from tests on four exterior reinforced concrete (RC) beam-column subassemblages are presented in this paper as part of an experimental investigation on the behaviour of RC beam-column connections under reversal cyclic loading. The influence of joint transverse reinforcement rate and concrete compressive strength on the RC beam-column connection behaviour was investigated. It is concluded that concrete compressive strength is the major factor that governs the joint shear capacity. The experimental results also indicated that joint transverse reinforcement affects the load-displacement response of such connections.Key words: cyclic loading, seismic analysis, reinforced concrete structures, beam-column connection.

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