scholarly journals FEM modelling of soil behaviour under compressive loads

2017 ◽  
Vol 163 ◽  
pp. 012001 ◽  
Author(s):  
N Ungureanu ◽  
V Vlăduţ ◽  
S Şt Biriş
Keyword(s):  
Fem Modelling ◽  
Compressive Loads ◽  
Soil Behaviour

A multiscale homogenization procedure to predict the elasto-viscoplastic behavior of polymer-based nanocomposites

2021 ◽  
pp. 096739112110233
Author(s):  
Mohammad Hassan Shojaeefard ◽  
Abolfazl Khalkhali ◽  
Sharif Khakshournia
Keyword(s):  
Design Procedure ◽  
Polymeric Matrix ◽  
Elastic Behavior ◽  
Algorithm Optimization ◽  
Multiphase Materials ◽  
Rate Dependent ◽  
Main Challenge ◽  
Compressive Loads ◽  
Structural Parts ◽  
The Impact

It has been demonstrated that adding a few percent of nanoscale reinforcements, leads to remarkable improvement in mechanical properties of the polymers such as stiffness, damping, and energy absorption. These lightweight materials are attractive substitutes for the heavy metallic structural parts in the automotive, military, aerospace and many other industries. However, due to complexity of these multiphase materials, accurate modeling of their behavior in real loading cases is still ambiguous. The impact simulation is a vital step in design procedure of a vehicle, where a strain rate-dependent model of its components is required. In this paper, an elasto-viscoplastic modeling procedure of the polymer-based nanocomposites, assuming the elastic behavior of the nano-phase is presented; whereas the polymeric matrix deformation is dependent to the loading rate and is characterized by the method of Genetic algorithm optimization-based fitting to the experimental observations. By introducing a modified Halpin-Tsai method, the nanocomposite is then modeled as a homogenized material where the modification algorithm is the main challenge. A combination of approaches including parametric analysis, central composite design of experiments and response surface method is proposed to modify the tangent modulus of the polymeric matrix to be passed as the input to the Halpin-Tsai equations. Finally, the procedure is implemented to a set of epoxy-GNP nanocomposites under unidirectional compressive loads with different rates and the stress-strain curves are predicted with a decent precision.

scholarly journals Recommended Procedures to Assess Critical State Locus from Triaxial Tests in Cohesionless Remoulded Samples

Geotechnics ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 95-127
Author(s):  
António Viana da Fonseca ◽  
Diana Cordeiro ◽  
Fausto Molina-Gómez
Keyword(s):  
Critical State ◽  
Review Paper ◽  
State Theory ◽  
Soil Freezing ◽  
Triaxial Tests ◽  
Cohesionless Soils ◽  
Saturation Condition ◽  
Testing Procedures ◽  
Laboratory Procedures ◽  
Soil Behaviour

The critical state theory is a robust conceptual framework for the characterisation of soil behaviour. In the laboratory, triaxial tests are used to assess the critical state locus. In the last decades, the equipment and testing procedures for soil characterisation, within the critical state framework, have advanced to obtain accurate and reliable results. This review paper summarises and describes a series of recommended laboratory procedures to assess the critical state locus in cohesionless soils. For this purpose, results obtained in the laboratory from different cohesionless soils and triaxial equipment configurations are compiled, analysed and discussed in detail. The procedures presented in this paper reinforce the use of triaxial cells with lubricated end platens and an embedded connection piston into the top-cap, together with the verification of the full saturation condition and the measurement end-of-test water content—preferable using the soil freezing technique. The experimental evidence and comparison between equipment configurations provide relevant insights about the laboratory procedures for obtaining a reliable characterisation of the critical state locus of cohesionless geomaterials. All the procedures recommended herein can be easily implemented in academic and commercial geotechnical laboratories.

scholarly journals Comparison of Geotechnical Properties of Laterite, Kaolin and Peat

2015 ◽  
Vol 773-774 ◽  
pp. 1438-1442 ◽  
Author(s):  
Siti Aimi Nadia Mohd Yusoff ◽  
I. Bakar ◽  
Devapriya Chitral Wijeyesekera ◽  
Adnan Zainorabidin ◽  
Aziman Madun
Keyword(s):  
Specific Gravity ◽  
Moisture Content ◽  
Initial Moisture Content ◽  
General Information ◽  
Geotechnical Properties ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Proctor Test ◽  
Construction Operation ◽  
Soil Behaviour

This paper compares some geotechnical properties of Kaolin, Laterite and Peat. Laterite was collected from Bukit Banang while Peat sample was collected from Parit Nipah, both locations were in Batu Pahat, Johor. Meanwhile, kaolin that was used in this research was manufactured kaolin. These soil samples were subjected to routine laboratory analysis and resulting data were analyzed statistically using a correlation analysis. A laboratory testing program consists of “Basic properties test” to obtain general information on the materials (e.g Natural moisture content, Atterberg Limit, Specific gravity, grain size analysis, chemical composition and pH) and “Geotechnical properties tests” to measure specific properties that characterize soil behaviour for design and constructability assessments (e.g Standard Proctor Test, Unconfined Compressive Strength and CBR).The results showed that the Natural/initial moisture content for laterite, peat and kaolin is 22.54%, 480.61% and 0.22% respectively. Meanwhile Specific gravity for each soil was in the range 1.50-2.79.It was also found that the pH of all soil is acidic which lay in the range of 3.76-5.95.The UCS for the optimally compacted sample of laterite is 445.77 kPa, kaolin is 199.23 kPa and for peat is 58.70 kPa. This paper summarizes the result of analysis performed on all tests conducted. Based on the results, the geotechnical property of the soil is a highly dependent with the type of soil and therefore, determining the soil characterization and the soil strength should be considered during the planning phase of any earthwork construction operation.

scholarly journals New Evaluation Procedure for Multi-Dimensional Mechanical Strains and Tangent Moduli of Breast Implants: IDEAL IMPLANT® Structured Breast Implant Compared to Silicone Gel Implants

2019 ◽  
Vol 6 (2) ◽  
pp. 43 ◽  
Author(s):  
Harold J. Brandon ◽  
Larry S. Nichter ◽  
Dwight D. Back
Keyword(s):  
Breast Implant ◽  
Capsular Contracture ◽  
Compressive Load ◽  
Evaluation Procedure ◽  
Shape Stability ◽  
Silicone Gel ◽  
Tangent Moduli ◽  
Compressive Loads ◽  
Cohesive Gel ◽  
The Ideal

The IDEAL IMPLANT® Structured Breast Implant is a dual lumen saline-filled implant with capsular contracture and deflation/rupture rates much lower than single-lumen silicone gel-filled implants. To better understand the implant’s mechanical properties and to provide a potential explanation for these eight-year clinical results, a novel approach to compressive load testing was employed. Multi-dimensional strains and tangent moduli, metrics describing the shape stability of the total implant, were derived from the experimental load and platen spacing data. The IDEAL IMPLANT was found to have projection, diametric, and areal strains that were generally less than silicone gel implants, and tangent moduli that were generally greater than silicone gel implants. Despite having a relatively inviscid saline fill, the IDEAL IMPLANT was found to be more shape stable compared to gel implants, which implies potentially less interaction with the capsule wall when the implant is subjected to compressive loads. Under compressive loads, the shape stability of a higher cross-link density, cohesive gel implant was unexpectedly found to be similar to or the same as a gel implant. In localized diametric compression testing, the IDEAL IMPLANT was found to have a palpability similar to a gel implant, but softer than a cohesive gel implant.

Effects of Stress Path and Stress History on the Stiffness of Reconstituted London Clay

1986 ◽  
Vol 2 (1) ◽  
pp. 139-144 ◽  
Author(s):  
J. H. Atkinson ◽  
J. S. Evans ◽  
D. Richardson
Keyword(s):  
Stress Path ◽  
Triaxial Tests ◽  
Soil Parameters ◽  
Stress History ◽  
Strain Behaviour ◽  
Reconstituted Soil ◽  
Path Dependent ◽  
London Clay ◽  
Soil Behaviour

AbstractSoil behaviour is stress history dependent and stress path dependent and soil parameters, particularly those for stress-strain behaviour, measured in conventional triaxial tests may not represent the behaviour of soil in many civil engineering works.To obtain more realistic parameters it may be necessary to conduct laboratory tests which more closely represent in situ conditions before and during construction.The paper describes equipment developed at The City University to carry out stress path tests simply and economically. A series of CU triaxial tests and stress path tests on reconstituted soil illustrate the dependence of measured soil parameters on stress history and stress path.

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