Load-bearing characteristic of methane hydrate within coarse-grained sediments – Insights from isotropic consolidation

2020 ◽  
Vol 121 ◽  
pp. 104571
Author(s):  
Liang Lei ◽  
Xuerui Gai ◽  
Yongkoo Seol
Keyword(s):  
Methane Hydrate ◽  
Coarse Grained ◽  
Load Bearing ◽  
Isotropic Consolidation ◽  
Bearing Characteristic

scholarly journals Assessment of Seismic Bearing Capacity of a Strip Footing Resting on Reinforced Earth Bed using Pseudo-Static Analysis

2021 ◽  
Vol 31 (2) ◽  
pp. 117-137
Author(s):  
Sagar Jaiswal ◽  
Vinay Bhushan Chauhan
Keyword(s):  
Bearing Capacity ◽  
Dynamic Loading ◽  
Ultimate Load ◽  
Strip Footing ◽  
Shallow Foundation ◽  
Coarse Grained ◽  
Geosynthetic Reinforcement ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Dense Sand

Abstract The use of geosynthetic reinforcement to enhance the ultimate load-bearing capacity and reduce the anticipated settlement of the shallow foundation has gained sufficient attention in the geotechnical field. The improved performance of the shallow foundation is achieved by providing one or more layers of geosynthetics below the foundation. The full wraparound technique proved to be efficient for the confinement of soil mass and reduction in settlement of foundation however lacks the literature to ascertain the performances of such footing under dynamic loading. In view of the above, the present study examines the effect of geosynthetic layers having a finite length with full wraparound ends as a reinforcement layer, placed horizontally at a suitable depth below the foundation using the finite element modeling (FEM) and evaluates the ultimate load-bearing capacity of a strip footing resting on loose and dense coarse-grained earth beds under seismic loading and further compared to those of footing resting on unreinforced earth bed. Moreover, the effect of horizontal seismic acceleration coefficient (kh) on the ultimate load-bearing capacity has been investigated by varying kh from 0.1 to 0.6 at an interval of 0.1, for both reinforced and unreinforced earth bed having loose and dense soil strata. Furthermore, this study demonstrates that by adopting the new practice of using the geosynthetic reinforcement with the full wraparound ends in foundations, it is possible to support relatively heavier structures under static as well as dynamic loading without allowing large footing settlements. From the outcomes of the present study, it is noted that the ultimate load-bearing capacity of footing resting on loose and dense sand bed found to be improved by 60% and 18% for soils having friction angle of 25° and 40°, respectively compared to respective unreinforced earth beds under static condition.

Impact of Variations in Water Concentration on the Nanomechanical Behaviour of Type I Collagen Microfibrils in Annulus Fibrosus

2021 ◽  
Author(s):  
Shambo Bhattacharya ◽  
Devendra Kumar Dubey
Keyword(s):  
Elastic Modulus ◽  
Annulus Fibrosus ◽  
Type I Collagen ◽  
Water Concentration ◽  
Collagen Type I ◽  
Type I ◽  
Load Bearing ◽  
Characteristic Features ◽  
Dynamics Simulations ◽  
Bearing Characteristic

Abstract Changes in water concentration mediated by proteoglycan degradation are characteristic features of intervertebral disc (IVD) degeneration. Change in water concentration alters the chemo-mechanical interactions among the nanoscale biomolecular constituents, affecting the load-bearing property of IVD. Present study investigates the effect of water concentration on the nanomechanics of collagen type I microfibrils in the Annulus Fibrosus using molecular dynamics simulations. Results show, in axial tension, increase in water concentration (WC) from 0% to ~50% increases the elastic modulus from ~2.7 GPa to ~4 GPa. This is attributed to a combination of a shift in deformation from backbone straightening to combined stretching and intermolecular sliding and subsequent strengthening of tropocollagen-water-tropocollagen (TWT) interface by the formation of water bridges and intermolecular electrostatic attractions. Further increase in WC to ~75% reduces the modulus to ~1.8 GPa due to shift in deformation to polypeptide straightening, weakening TWT interface due to reduced electrostatic attraction and increase in number of water molecules in a water bridge. During axial compression, increase in WC to ~50% results in increase in modulus from ~0.8 GPa to ~4.5 GPa. This is attributed to combination of the development of hydrostatic pressure and strengthening of the TWT interface. Further increase in WC to ~75% shifts the load-bearing characteristic from collagen to water, resulting in a decrease in elastic modulus to ~2.8 GPa. Such water-mediated alteration in load-bearing properties act as foundations to hypermobility or stiffening observed in degenerated spine segments.

scholarly journals Investigation of Physical Characteristics of Non-Structural Lightweight Aggregate Blocks

2016 ◽  
Author(s):  
Hamid Reza Ashrafi ◽  
Marzieh Sadat Moayyeri ◽  
Peyman Beiranvand
Keyword(s):  
Compressive Strength ◽  
Water Absorption ◽  
Construction Materials ◽  
Lightweight Aggregate ◽  
Coarse Grained ◽  
Mechanical Resistance ◽  
Lightweight Aggregates ◽  
Dead Load ◽  
Load Bearing ◽  
Materials Used

Today, the style of light construction materials used in building is one of the most important factors in reducing building's dead load and better performance of the structures in the earthquake. One of the ways to reduce the structure weight is to use lightweight blocks instead of using traditional materials. The main purpose of this research is to compare density, compressive strength and water absorption volume of non-load-bearing lightweight blocks made of natural and artificial lightweight aggregates. Scoria lightweight aggregates of Sanandaj, Ghorveh mine, pumice in Tabriz, Bostanabad mine, and Leca in Leca enterprise have been used to make the samples. Given the importance of the materials used, grading of coarse-grained materials has been conducted based on the standard of 7657 and grading of fine materials have been conducted based on the standard of 302.The experiments' results show that Scoria blocks due to hard texture, and high mechanical resistance of their lightweight aggregates, have had higher compressive strength, and density and lower water absorption volume compared to pumice and Lika lightweight aggregate blocks. Pumice blocks despite having desirable compressive strength and lower density compared to the two other blocks have higher water absorption volume, and do not meet the standard conditions. This same factor causes it faces with less interest. Among these Lika blocks with density of 1151.94 (kg per cubic meter) below 2000 kilograms per cubic meter of Iran density standard of 7782 (28-day compressive strength of 2.57 MPa), higher than 2.5 MPa of Iran compressive strength standard of 7782 (and water absorption volume of 282.92 kg per cubic meter) below 288 kilograms per cubic meter of Iran water absorption volume standard of 7782 (as a non-load-bearing lightweight block) have been diagnosed desirable.

scholarly journals Investigation of in situ salinity and methane hydrate dissociation in coarse-grained sediments by slow, stepwise depressurization

2019 ◽  
Vol 109 ◽  
pp. 128-144 ◽  
Author(s):  
Stephen C. Phillips ◽  
Peter B. Flemings ◽  
Kehua You ◽  
Dylan W. Meyer ◽  
Tiannong Dong
Keyword(s):  
Methane Hydrate ◽  
Coarse Grained ◽  
Hydrate Dissociation

scholarly journals Compressive characteristics of methane hydrate-bearing sands under isotropic consolidation

2021 ◽  
Vol 61 (2) ◽  
pp. 506-519
Author(s):  
Koji Nakashima ◽  
Yukio Nakata ◽  
Masayuki Hyodo ◽  
Norimasa Yoshimoto ◽  
Shotaro Hiraoka ◽  
...  
Keyword(s):  
Methane Hydrate ◽  
Isotropic Consolidation

scholarly journals Transition from ductile to brittle failure of sodium silicate glasses: a numerical study

MRS Advances ◽  
2016 ◽  
Vol 1 (24) ◽  
pp. 1797-1802 ◽  
Author(s):  
Gergely Molnár ◽  
Patrick Ganster ◽  
Anne Tanguy ◽  
János Török ◽  
Guillaume Kermouche
Keyword(s):  
Sodium Silicate ◽  
Mechanical Response ◽  
Numerical Study ◽  
Maximum Load ◽  
Sodium Content ◽  
Silicate Glasses ◽  
Coarse Grained ◽  
Load Bearing ◽  
High Sodium ◽  
Low Sodium

ABSTRACTUsing molecular statics calculations, sodium silicate glasses are expanded in an isotropic manner to analyze the composition dependence of the mechanical response.Increasing the amount of sodium makes the systems more ductile. The tensile strength is reduced and the final load bearing strain limit is increased.Hydrostatic strain hardening appears in the ductile samples. To explain this phenomena, the density is coarse-grained to identify microscopic defects. In samples containing a significant amount of sodium, a large amount of nano-voids appear before reaching the maximum load bearing capacity. In high sodium content silicates these cracks may cause the hardening observed in the pressure results.In samples with low sodium content, the failure is abrupt and only a large crack is observed. Increasing the amount of long term but weaker Na-O interactions, instead of the short range Si-O ones could explain the observed transition.

The Alteration of the Pore Spaces in Sandstones

1973 ◽  
Vol 31 ◽  
pp. 210-211
Author(s):  
R. E. Ferrell ◽  
G. G. Paulson
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
The Other ◽  
Coarse Grained ◽  
Depositional Fabric ◽  
Soluble Components ◽  
Scanning Electron ◽  
Shape And Size

The pore spaces in sandstones are the result of the original depositional fabric and the degree of post-depositional alteration that the rock has experienced. The largest pore volumes are present in coarse-grained, well-sorted materials with high sphericity. The chief mechanisms which alter the shape and size of the pores are precipitation of cementing agents and the dissolution of soluble components. Each process may operate alone or in combination with the other, or there may be several generations of cementation and solution.The scanning electron microscope has ‘been used in this study to reveal the morphology of the pore spaces in a variety of moderate porosity, orthoquartzites.

On the Origin of the Microscystalline Structure in Rapidly Solidified IN-100 Powder

1977 ◽  
Vol 35 ◽  
pp. 260-261
Author(s):  
J. M. Walsh ◽  
K. P. Gumz ◽  
J. C. Whittles ◽  
B. H. Kear
Keyword(s):  
The Other ◽  
Coarse Grained ◽  
Microcrystalline Structure ◽  
Routine Examination ◽  
Atomization Process ◽  
Centrifugal Atomization ◽  
Splat Quenching ◽  
Powder Particles ◽  
Dendritic Microstructures ◽  
Rapidly Solidified

During a routine examination of the microstructure of rapidly solidified IN-100 powder, produced by a newly-developed centrifugal atomization process1, essentially two distinct types of microstructure were identified. When a high melt superheat is maintained during atomization, the powder particles are predominantly coarse-grained, equiaxed or columnar, with distinctly dendritic microstructures, Figs, la and 4a. On the other hand, when the melt superheat is reduced by increasing the heat flow to the disc of the rotary atomizer, the powder particles are predominantly microcrystalline in character, with typically one dendrite per grain, Figs, lb and 4b. In what follows, evidence is presented that strongly supports the view that the unusual microcrystalline structure has its origin in dendrite erosion occurring in a 'mushy zone' of dynamic solidification on the disc of the rotary atomizer.The critical observations were made on atomized material that had undergone 'splat-quenching' on previously solidified, chilled substrate particles.

Correlation between dislocation, grain boundary and interface of duplex SS in stress corrosion cracking(SCC)

1990 ◽  
Vol 48 (4) ◽  
pp. 928-929
Author(s):  
Wang Zheng-fang ◽  
Z.F. Wang
Keyword(s):  
Stainless Steel ◽  
Thermal Cycle ◽  
Secondary Phase ◽  
Corrosion Cracking ◽  
Coarse Grained ◽  
Test Environment ◽  
Fine Grained ◽  
Evaluation Test ◽  
Welding Thermal Cycle ◽  
Micro Analysis

The main purpose of this study highlights on the evaluation of chloride SCC resistance of the material,duplex stainless steel,OOCr18Ni5Mo3Si2 (18-5Mo) and its welded coarse grained zone(CGZ).18-5Mo is a dual phases (A+F) stainless steel with yield strength:512N/mm2 .The proportion of secondary Phase(A phase) accounts for 30-35% of the total with fine grained and homogeneously distributed A and F phases(Fig.1).After being welded by a specific welding thermal cycle to the material,i.e. Tmax=1350°C and t8/5=20s,microstructure may change from fine grained morphology to coarse grained morphology and from homogeneously distributed of A phase to a concentration of A phase(Fig.2).Meanwhile,the proportion of A phase reduced from 35% to 5-10°o.For this reason it is known as welded coarse grained zone(CGZ).In association with difference of microstructure between base metal and welded CGZ,so chloride SCC resistance also differ from each other.Test procedures:Constant load tensile test(CLTT) were performed for recording Esce-t curve by which corrosion cracking growth can be described, tf,fractured time,can also be recorded by the test which is taken as a electrochemical behavior and mechanical property for SCC resistance evaluation. Test environment:143°C boiling 42%MgCl2 solution is used.Besides, micro analysis were conducted with light microscopy(LM),SEM,TEM,and Auger energy spectrum(AES) so as to reveal the correlation between the data generated by the CLTT results and micro analysis.

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