scholarly journals The mechanisms underlying long-term shaft resistance enhancement of energy pile in clays

2020 ◽  
Author(s):  
Saeed Yazdani ◽  
Sam Helwany ◽  
Guney Olgun
Keyword(s):  
Normal Load ◽  
Comprehensive Analysis ◽  
Normal Stresses ◽  
Lateral Stress ◽  
Energy Pile ◽  
Shaft Resistance ◽  
Energy Piles ◽  
Constant Normal Stiffness ◽  
Constant Normal Load

Although there are several studies indicating that heating increases the long-term shaft resistance of energy piles, the mechanisms by which heating causes this increase have not been adequately evaluated yet. This article aims to perform comprehensive analysis and discussion to assess the important factors contributing to this increase by integrating the findings from three recently published papers studying the thermo-mechanical behavior of clay and clay-pile interface. In these three studies, reconstituted kaolin clay was used, and cyclic and monotonic heat ranging between 24° C and 34°C were applied to the clay and interface. The interface was sheared under two stiffness boundary conditions; Constant Normal Stiffness (CNS) and Constant Normal Load (CNL), where the normal stresses varied between 100 kPa and 300 kPa. The analysis performed in this article reveals that the increase in strength of interface under CNL condition is primarily attributed to clay stiffening at interface. However, the increase in shaft resistance under CNS condition is primarily attributed to the heating-induced increase of effective lateral stress, although clay stiffening at interface also partially contributes to the total increase of shaft resistance.

scholarly journals Thermal effects on mechanical behaviour of soil–structure interface

2020 ◽  
Vol 57 (1) ◽  
pp. 32-47 ◽  
Author(s):  
Soheib Maghsoodi ◽  
Olivier Cuisinier ◽  
Farimah Masrouri
Keyword(s):  
Shear Strength ◽  
Mechanical Behaviour ◽  
Soil Structure ◽  
Clayey Soil ◽  
Normal Load ◽  
Shear Characteristics ◽  
Constant Normal Stiffness ◽  
Constant Normal Load ◽  
Dense State ◽  
Interface Behaviour

Mechanical behaviour of the soil–structure interface plays a major role in the shear characteristics and bearing capacity of foundations. In thermoactive structures, due to nonisothermal conditions, the interface behaviour becomes more complex. The objective of this study is to investigate the effects of temperature variations on the mechanical behaviour of soils and the soil–structure interface. Constant normal load (CNL) and constant normal stiffness (CNS) tests were performed on the soil and soil–structure interface in a direct shear device at temperatures of 5, 22, and 60 °C. Fontainebleau sand and kaolin clay were used as proxies for sandy and clayey soils. The sandy soil was prepared in a dense state and the clayey soil was prepared in a normally consolidated state. Results show that the applied thermal variations have a negligible effect on the shear strength of the sand and sand–structure interface under CNL and CNS conditions, and the soil and soil–structure interface behaviour could be considered thermally independent. In clay samples, an increase in the temperature increased the cohesion and consequently the shear strength, due to thermal contraction during heating. The temperature rise had less impact on the shear strength in the case of the clay–structure interface than in the clay samples. The adhesion of the clay–structure interface is less than the cohesion of the clay samples.

scholarly journals Thermo-mechanical behaviour of clay-structure interface

2019 ◽  
Vol 92 ◽  
pp. 10002 ◽  
Author(s):  
Soheib Maghsoodi ◽  
Olivier Cuisinier ◽  
Farimah Masrouri
Keyword(s):  
Shear Strength ◽  
Mechanical Behaviour ◽  
Soil Structure ◽  
Normal Load ◽  
Active Structures ◽  
Shear Characteristics ◽  
Constant Normal Stiffness ◽  
Constant Normal Load ◽  
Effects Of Temperature ◽  
Interface Behaviour

The mechanical behaviour of the soil-structure interface plays a major role in the shear characteristics and bearing capacity of foundations. In thermo-active structures, due to non-isothermal conditions, the interface behaviour becomes more complex. The objective of this study is to investigate the effects of temperature variations on the mechanical behaviour of soils and soil-structure interface. Constant normal load (CNL) and constant normal stiffness (CNS) tests were performed on soil and soil-structure interface in a direct shear device at temperatures of 5, 22 and 60 °C. Kaolin clay was used as proxy for clayey soils. The results showed that, in clay samples the temperature increase, increased the cohesion and consequently the shear strength, due to thermal contraction during heating. The temperature rise had less impact on the shear strength in the case of the clay-structure interface than in the clay samples. The adhesion of the clay-structure interface, is less than the cohesion of the clay samples.

scholarly journals Comprehensive analysis and insights gained from long-term experience of the Spanish DILI registry

2021 ◽  
Author(s):  
Camilla Stephens ◽  
Mercedes Robles-Diaz ◽  
Inmaculada Medina-Caliz ◽  
Miren Garcia-Cortes ◽  
Aida Ortega-Alonso ◽  
...  
Keyword(s):  
Comprehensive Analysis ◽  
Long Term Experience

Comprehensive Analysis of Long-Term Outcomes after HeartMate 3 LVAD Implantation Depending on Surgical Access

2021 ◽  
Vol 40 (4) ◽  
pp. S180-S181
Author(s):  
R. Antończyk ◽  
A. Biełka ◽  
M. Kalinowski ◽  
J. Waszak ◽  
J. Małyszek-Tumidajewicz ◽  
...  
Keyword(s):  
Comprehensive Analysis ◽  
Long Term Outcomes ◽  
Surgical Access

scholarly journals Field Test and Numerical Simulation on the Long-Term Thermal Response of PHC Energy Pile in Layered Foundation

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3873
Author(s):  
Guozhu Zhang ◽  
Ziming Cao ◽  
Yiping Liu ◽  
Jiawei Chen
Keyword(s):  
Thermal Conductivity ◽  
Heat Exchange ◽  
Temperature Variation ◽  
Thermal Response ◽  
Ground Temperature ◽  
Short Term ◽  
Energy Pile ◽  
Backfill Soil ◽  
Short And Long Term

Investigation on the long-term thermal response of precast high-strength concrete (PHC) energy pile is relatively rare. This paper combines field experiments and numerical simulations to investigate the long-term thermal properties of a PHC energy pile in a layered foundation. The major findings obtained from the experimental and numerical studies are as follows: First, the thermophysical ground properties gradually produce an influence on the long-term temperature variation. For the soil layers with relatively higher thermal conductivity, the ground temperature near to the energy pile presents a slowly increasing trend, and the ground temperature response at a longer distance from the center of the PHC pile appears to be delayed. Second, the short- and long-term thermal performance of the PHC energy pile can be enhanced by increasing the thermal conductivity of backfill soil. When the thermal conductivities of backfill soil in the PHC pile increase from 1 to 4 W/(m K), the heat exchange amounts of energy pile can be enhanced by approximately 30%, 79%, 105%, and 122% at 1 day and 20%, 47%, 59%, and 66% at 90 days compared with the backfill water used in the site. However, the influence of specific heat capacity of the backfill soil in the PHC pile on the short-term or long-term thermal response can be ignored. Furthermore, the variation of the initial ground temperature is also an important factor to affect the short-and-long-term heat transfer capacity and ground temperature variation. Finally, the thermal conductivity of the ground has a significant effect on the long-term thermal response compared with the short-term condition, and the heat exchange rates rise by about 5% and 9% at 1 day and 21% and 37% at 90 days as the thermal conductivities of the ground increase by 0.5 and 1 W/(m K), respectively.

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