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 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 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 Some Aspects of Shear Behavior of Soft Soil–Concrete Interfaces and Its Consequences in Pile Shaft Friction Modeling

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2578
Author(s):  
Jakub Konkol ◽  
Kamila Mikina
Keyword(s):  
Shear Strength ◽  
Normal Load ◽  
Soft Soil ◽  
Load Condition ◽  
Initial Stiffness ◽  
Friction Modeling ◽  
Interface Failure ◽  
Friction Behavior ◽  
Constant Normal Load ◽  
Concrete Interface

This paper examines the stiffness degradation and interface failure load on soft soil–concrete interface. The friction behavior and its variability is investigated. The direct shear tests under constant normal load were used to establish parameters to hyperbolic interface model which provided a good approximation of the data from instrumented piles. Four instrumented piles were used to obtain reference soil–concrete interface behavior. It was found that the variability of the friction characteristics is the highest for organic clays and the lowest for organic silts. The intact samples exhibit lower shear strength than reconstituted ones. The adhesion varies significantly depending on interface and soil type, which can result in high scatter of the skin friction prediction. The analysis of parameters variability can be used to determine the upper and lower bound of friction behavior on the interface at constant normal load condition. The backward shearing results in decrease in shear strength up to 40% of the precedent forward phase but higher initial stiffness by a factor of between 2 and 3. Presented research provides basic shear and stiffness parameters for four soft soils (organic clay, organic silt, peat, and silty loam) and gives information about variability of interface characteristics.

scholarly journals Simulation of direct shear tests using a forces on fracture surfaces (FFS) approach

2021 ◽  
Vol 80 (8) ◽  
Author(s):  
Thomas Frühwirt ◽  
Daniel Pötschke ◽  
Heinz Konietzky
Keyword(s):  
Normal Load ◽  
Crystalline Rock ◽  
Rock Joints ◽  
Direct Shear ◽  
Shear Tests ◽  
Data Set ◽  
Direct Shear Tests ◽  
Complex Process ◽  
Shear Characteristics ◽  
Constant Normal Stiffness

AbstractThe aim of this work is to provide a complete data set of direct shear tests and to propose a corresponding simulation approach. Tests have been conducted on crystalline rock samples applying constant normal load (CNL) and constant normal stiffness (CNS) boundary conditions. A physical consistent algorithm which explicitly calculates the forces acting on the fracture surface (FFS) has been developed. This FFS approach can explain the occurrence of surface degradation and shows the main shear characteristics. After all, shearing of rough rock joints remains a complex process and the differences between laboratory and simulation results are still significant in some cases. All data and input files are provided free for download and testing.

scholarly journals A Study on Shear Strength under Constant Normal Load Conditions by Using 3DEC

2014 ◽  
Vol 24 (1) ◽  
pp. 46-54
Author(s):  
Young-Mok Noh ◽  
Hong-Ju Mun ◽  
Ki-Ho Kim ◽  
Won-Yil Jang
Keyword(s):  
Shear Strength ◽  
Normal Load ◽  
Constant Normal Load ◽  
Load Conditions
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