scholarly journals Long-Term Cyclic Loading Impact on the Creep Deformation Mechanism in Cohesive Materials

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3907
Author(s):  
Andrzej Głuchowski ◽  
Wojciech Sas
Keyword(s):  
Cyclic Loading ◽  
Pore Pressure ◽  
Ocean Waves ◽  
Triaxial Tests ◽  
Creep Tests ◽  
Damage And Failure ◽  
Wide Range ◽  
Modified Cam Clay ◽  
Cohesive Materials

Long-term cyclic loading is observed in a wide range of human activities, as well as in nature, such as in the case of ocean waves. Cyclic loading can lead to ratcheting which is defined as progressive accumulation of plastic deformation in a material. Long-term cyclic loading causes a time effect (creep), which is a secondary compression effect. In this article, we conducted 15 triaxial tests on four types of cohesive materials in undrained conditions to evaluate the damage and failure mechanism. To characterize the strain and pore pressure development, we modified the Yanbu resistance concept. On the basis of the static creep tests, we concluded that the stress paths for undrained creep behavior have to take into account the pore pressure developed during long-term cyclic loading. Pore pressure build-up and plastic strain accumulation during long-term cyclic loading are dependent on the number of loading cycles. Finally, we proposed the failure criterion, which was based on the Modified Cam-Clay constitutive model.

Cyclic strength of a natural liquefiable sand stabilized with colloidal silica grout

2008 ◽  
Vol 45 (10) ◽  
pp. 1345-1355 ◽  
Author(s):  
J. A. Díaz-Rodríguez ◽  
V. M. Antonio-Izarraras ◽  
P. Bandini ◽  
J. A. López-Molina
Keyword(s):  
Cyclic Loading ◽  
Pore Pressure ◽  
Simple Shear ◽  
Colloidal Silica ◽  
Low Cost ◽  
Silty Sand ◽  
Experimental Program ◽  
Shear Tests ◽  
Liquefaction Resistance ◽  
Wide Range

This paper summarizes the experimental results of a series of cyclic simple shear tests on liquefiable silty sand with and without sample improvement with colloidal silica grout. The objective of the paper is to evaluate the effectiveness of colloidal silica grouting in reducing the liquefaction potential of natural silty sand. Colloidal silica was selected as a stabilizing material due to its low viscosity, wide range of gel times, nontoxicity, and low cost. The soil tested in this experimental program is a poorly graded sand with 11.5% of nonplastic silt from the Port of Lázaro Cárdenas, México. Colloidal silica treated and untreated sand specimens show different pore pressure response and deformation behavior under cyclic loading in simple shear tests. The results indicate that, for a given initial relative density and initial effective vertical stress, liquefiable silty sand specimens stabilized with colloidal silica grout generally exhibit significant gain in liquefaction resistance compared with untreated specimens. It was also found that the colloidal silica grout reduces considerably the rates of pore pressure generation and shear strain of the silty sand specimens subjected to cyclic loading.

scholarly journals Deformation Characteristics of Soft Marine Soil Tested under Cyclic Loading with Low Frequency

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Yu Lu ◽  
Wenbin Fu ◽  
Danxuan Xue
Keyword(s):  
Cyclic Loading ◽  
Pore Pressure ◽  
High Stress ◽  
Low Frequency ◽  
Load Level ◽  
Triaxial Tests ◽  
Deformation Characteristics ◽  
Confining Stress ◽  
The Difference ◽  
Marine Soil

Soft marine soil which could be found widely at the coastal and offshore areas is usually associated with high settlement and instability, especially under cyclic loading. Many research studies have been conducted on its deformation characteristics under the cyclic loading with high frequency, whereas few works have been reported on that under the low-frequency cyclic loading which largely existed in engineering. In this work, a comprehensive series of undrained triaxial tests under cyclic loading with low frequency was conducted to investigate the deformation characteristics of soft marine soil. The results demonstrate that soil specimens accumulate plastic deformation and pore pressure under cyclic loading. Specimens tested under conditions such as high confining stress, high-stress ratio, and long cyclic period generally reveal higher deformation and pore pressure. Meanwhile, the rectangular wave presents the largest contribution to plastic strain and pore pressure, followed by the trapezoidal and triangular waves, respectively, whereas the difference between the various waves decreased gradually with the increasing load level and cyclic period. The undisturbed specimens displayed lower deformations and pore pressures than the reconstructed specimens, whereas the differences are not significant when the confining stress is much higher than the structural yield stress. Furthermore, an empirical model for predicting the evolution of pore pressure is proposed and then validated against the experimental data in both this work and the literature.

scholarly journals Bucket foundation model testing under tensile axial loading

2017 ◽  
Vol 54 (5) ◽  
pp. 720-728 ◽  
Author(s):  
Evelina Vaitkune ◽  
Lars Bo Ibsen ◽  
Benjaminn Nordahl Nielsen
Keyword(s):  
Cyclic Loading ◽  
Pore Pressure ◽  
Load Capacity ◽  
Tensile Loading ◽  
Quality Data ◽  
Soil Conditions ◽  
Bucket Foundation ◽  
Foundation Model ◽  
Loading Tests

The present study focusses on bucket foundation behaviour under long-term cyclic loading. The paper analyses testing results of a bucket foundation model exposed to cyclic tensile loading. The model, with dimensions of 1 m in diameter and 0.5 m in skirt length, was, installed in dense water-saturated sand. Slow monotonic loading tests and cyclic tensile loading tests were performed (up to 40 000 load cycles) including tests with mean cyclic loading in tension, which is a unique testing condition. High-quality data were documented for load, displacement, and pore pressure response. Conclusions have been drawn regarding static and cyclic loading stiffness and displacement development during long-term cyclic loading. Four cyclic loading tests induced partially drained soil conditions and showed that pore pressure can accumulate during the long-term loading. Post-cyclic monotonic tensile loading tests showed up to 25% reduction in load capacity of the foundation. The research results provide valuable information for the design of an upwind bucket foundation under a jacket structure.

Effect of initial pore pressure on undrained shear behaviour of fine-grained gassy soil

2017 ◽  
Vol 54 (11) ◽  
pp. 1592-1600 ◽  
Author(s):  
Y. Hong ◽  
L.Z. Wang ◽  
Charles W.W. Ng ◽  
B. Yang
Keyword(s):  
Pore Pressure ◽  
Fossil Fuels ◽  
Oil And Gas ◽  
Shear Behaviour ◽  
Excess Pore Pressure ◽  
Triaxial Tests ◽  
Fine Grained ◽  
Wide Range ◽  
The Stability ◽  
Undrained Shear

Many of the world reserves of fossil fuels are located at various water depths in fine-grained sediment under the seabed. The fine-grained sediment contains relatively large biogas bubbles, which has been posing challenges to the stability of offshore foundations supporting oil and gas platforms. Although fine-grained gassy soil was found to exhibit different undrained shear strengths (cu) by altering the initial pore pressure, ui (relevant to water depth), systematic studies concerning the effect of ui on undrained shear behaviours of the soil are still lacking. This study reports a series of undrained triaxial tests aiming to compare and investigate the responses of reconstituted fine-grained gassy soil with the same consolidation pressure ([Formula: see text]), but at a wide range of varying ui (0–1000 kPa). The shearing-induced excess pore pressure (Δu) in the gassy specimens highly depends on ui. It can be either smaller than that of the saturated specimen with the same [Formula: see text] (due to partial dissipation of Δu into relatively large bubbles at low ui) or larger than that of the saturated specimen (related to collapse of relatively small bubbles at high ui). Consequently, the presence of bubbles had beneficially increased cu at relatively low ui (ui/[Formula: see text] < 0.6), and vice versa. The critical stress ratio of the reconstituted fine-grained gassy soil, however, did not appear to be altered by ui.

TIME TO THE END OF PRIMARY CONSOLIDATION (EOP) OF SOFT CLAYEY SOILS: CONCERNING THE EFFECT OF ATTERBERG’S LIMIT AND CYCLIC LOADING HISTORY

2019 ◽  
Vol 128 (2B) ◽  
pp. 29-41
Author(s):  
Trần Thanh Nhàn
Keyword(s):  
Cyclic Loading ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Clayey Soils ◽  
Loading History ◽  
Cyclic Shear ◽  
Wide Range ◽  
Primary Consolidation ◽  
Time Required

In order to observe the end of primary consolidation (EOP) of cohesive soils with and without subjecting to cyclic loading, reconstituted specimens of clayey soils at various Atterberg’s limits were used for oedometer test at different loading increments and undrained cyclic shear test followed by drainage with various cyclic shear directions and a wide range of shear strain amplitudes. The pore water pressure and settlement of the soils were measured with time and the time to EOP was then determined by different methods. It is shown from observed results that the time to EOP determined by 3-t method agrees well with the time required for full dissipation of the pore water pressure and being considerably larger than those determined by Log Time method. These observations were then further evaluated in connection with effects of the Atterberg’s limit and the cyclic loading history.

Modern prevention and active longevity programs on the basis of disruptive domestic technologies: positive experience and prospects for application

2020 ◽  
pp. 66-73
Author(s):  
A. Simonova ◽  
S. Chudakov ◽  
R. Gorenkov ◽  
V. Egorov ◽  
A. Gostry ◽  
...  
Keyword(s):  
Personalized Medicine ◽  
Early Detection ◽  
Laboratory Diagnostics ◽  
Positive Experience ◽  
Practical Application ◽  
Wide Range ◽  
Integrated Program ◽  
Long Term Experience ◽  
Early Detection And Prevention

The article summarizes the long-term experience of practical application of domestic breakthrough technologies of preventive personalized medicine for laboratory diagnostics of a wide range of socially significant non-infectious diseases. Conceptual approaches to the formation of an integrated program for early detection and prevention of civilization diseases based on these technologies are given. A vision of the prospects for the development of this area in domestic and foreign medicine has been formed.

To the 70th anniversary of World Meteorological Organization. Scientific and technical cooperation of Hydrometeorological Center of the USSR/Russia in the Programs of World Meteorological Organization

2020 ◽  
pp. 117-138
Author(s):  
S.V. Borshch ◽  
◽  
R.M. Vil’fand ◽  
D.B. Kiktev ◽  
V.M. Khan ◽  
...  
Keyword(s):  
Environmental Monitoring ◽  
High Efficiency ◽  
World Meteorological Organization ◽  
70Th Anniversary ◽  
Technical Level ◽  
Technical Cooperation ◽  
Wide Range

The paper presents the summary and results of long-term and multi-faceted experience of international scientific and technical cooperation of Hydrometeorological Center of Russia in the field of hydrometeorology and environmental monitoring within the framework of WMO programs, which indicates its high efficiency in performing a wide range of works at a high scientific and technical level. Keywords: World Meteorological Organization, major WMO programs, representatives of Hydrometeorological Center of Russia in WMO

Research on the Economic Organization Environmental Impact

2017 ◽  
Vol 68 (3) ◽  
pp. 599-601
Author(s):  
Dan Paul Stefanescu ◽  
Oana Roxana Chivu ◽  
Claudiu Babis ◽  
Augustin Semenescu ◽  
Alina Gligor
Keyword(s):  
Economic Activity ◽  
Economic Organization ◽  
Economic Activities ◽  
Environmental Implications ◽  
Minimal Impact ◽  
Wide Range ◽  
Material Environment ◽  
Negative Effect ◽  
Harmful Effects

Any economic activity carried out by an organization, can generate a wide range of environmental implications. Particularly important, must be considered the activities that have a significant negative effect on the environment, meaning those which pollute. Being known the harmful effects of pollution on the human health, the paper presents two models of utmost importance, one of the material environment-economy interactions balance and the other of the material flows between environmental factors and socio-economic activities. The study of these models enable specific conditions that must be satisfied for the economic processes friendly coexist to the environment for long term, meaning to have a minimal impact in that the residues resulting from the economic activity of the organization to be as less harmful to the environment.

Long-term Effects of Triazol Growth Regulators on Stem Elongation of Rhododendron and Kalmia

HortScience ◽  
1997 ◽  
Vol 32 (3) ◽  
pp. 436E-436
Author(s):  
Martin P.N. Gent
Keyword(s):  
Dose Response ◽  
Growth Regulator ◽  
Stem Elongation ◽  
Spray Application ◽  
Long Term Effects ◽  
Potted Plants ◽  
Response Coefficient ◽  
Wide Range ◽  
Second Year

The persistence of effects of paclobutrazol or uniconazol on stem elongation was determined for several years after large-leaf Rhododendron and Kalmia latifolia were treated with a single-spray application of these triazol growth-regulator chemicals. Potted plants were treated in the second year from propagation, and transplanted into the field in the following spring. The elongation of stems was measured in the year of application and in the following 2 to 4 years. Treatments with a wide range of doses were applied in 1991, 1992, or 1995. For all except the most-dilute applications, stem elongation was retarded in the year following application. At the highest doses, stem growth was inhibited 2 years following application. The results could be explained by a model of growth regulator action that assumed stem elongation was inversely related to amount of growth regulator applied. The dose response coefficient for paclobutrazol was less than that for uniconazol. The dose that inhibited stem elongation one-half as much as a saturating dose was about 0.5 and 0.05 mg/plant, for paclobutrazol and uniconazol, respectively. The dose response coefficient decreased exponentially with time after application, with an exponential time constant of about 2/year. The model predicted a dose of growth regulator that inhibited 0.9 of stem elongation immediately after application would continue to inhibit 0.5 of stem elongation in the following year.

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