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FEM-simulering av nedbrytning hos obundet material vid upprepad belastning

Hammadi, Domiyan LU (2012) In TVGT-5000 VGTM01 20112
Geotechnical Engineering
Abstract
Traditionally, the underground problems have been handled in the topic geotechnical engineering. Within geotechnical engineering FEM has in recent years begun to be used to solve problems in the soil mechanics. The soil mechanical relations are also applicable to the superstructure materials. The usage of the same tools on the entire road structure increases the chances to catch the degradation of the road structure.

Design of a road structure is done by determination of sufficient layer thicknesses so that the road structure shows an acceptable degradation rate. In addition, high requirements are set for the unbound materials in order to have good bearing capacity characteristics during the design life.

To ensure a well designed... (More)
Traditionally, the underground problems have been handled in the topic geotechnical engineering. Within geotechnical engineering FEM has in recent years begun to be used to solve problems in the soil mechanics. The soil mechanical relations are also applicable to the superstructure materials. The usage of the same tools on the entire road structure increases the chances to catch the degradation of the road structure.

Design of a road structure is done by determination of sufficient layer thicknesses so that the road structure shows an acceptable degradation rate. In addition, high requirements are set for the unbound materials in order to have good bearing capacity characteristics during the design life.

To ensure a well designed road construction, the road construction must meet the requirements and not show a serious deficiency on the bearing capacity. Calculations should not rest solely on experiences and previous experiments, because the empirical design methods have some uncertainty. The risk is that the road becomes under-dimensioned, which creates high costs for maintenance work. Much damages have been discovered due to the deficiencies and limitations with these methods.

To perform different tests is both costly and time consuming so that new numerical methods have been developed. In the numerical methods one uses a finite element program to simulate a road construction. A finite element program will provide various possibilities, such as editing of road structure layer thicknesses, usage of different computational models and graphical presentation of results.

The purpose of this project is to apply a computational model using the finite element program COMSOL MULTIPHYSICS, where two different models for the nonlinear behaviour of unbound granular materials are implemented. One of the models is a stressdependent model called the k-θ model. The second model describes the permanent deformation. It is called Gidel model and is a function of the number of load cycles. Calculations have been performed for two different road structures where the results have been compared to earlier modelling of the results of the Sunninge HVS-test.

The results show that it is possible to implement equations by using the finite element program COMSOL MULTIPHYSICS to describe the behaviour of the unbound granular materials. The displacements vary depending on the thickness, amount of stored moisture and the size of the load. High load in connection with a thin asphalt layer and an amount of stored moisture in the unbound materials make the displacements become large. Comparison between the calculated values and the values obtained from the modelling of the results of the Sunninge HVS-test shows that the calculated values of the displacements are smaller. (Less)
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author
Hammadi, Domiyan LU
supervisor
organization
course
VGTM01 20112
year
type
H3 - Professional qualifications (4 Years - )
subject
keywords
Geotechnical engineering, Road design, Numerical methods, COMSOL MULTIPHYSICS, Unbound granular material, k-θ model, Permanent deformation, HVS-test
publication/series
TVGT-5000
report number
TVGT-5049
ISSN
0281-6679
language
Swedish
id
3163974
date added to LUP
2012-11-12 10:39:01
date last changed
2015-03-24 15:50:38
@misc{3163974,
  abstract     = {Traditionally, the underground problems have been handled in the topic geotechnical engineering. Within geotechnical engineering FEM has in recent years begun to be used to solve problems in the soil mechanics. The soil mechanical relations are also applicable to the superstructure materials. The usage of the same tools on the entire road structure increases the chances to catch the degradation of the road structure.

Design of a road structure is done by determination of sufficient layer thicknesses so that the road structure shows an acceptable degradation rate. In addition, high requirements are set for the unbound materials in order to have good bearing capacity characteristics during the design life.

To ensure a well designed road construction, the road construction must meet the requirements and not show a serious deficiency on the bearing capacity. Calculations should not rest solely on experiences and previous experiments, because the empirical design methods have some uncertainty. The risk is that the road becomes under-dimensioned, which creates high costs for maintenance work. Much damages have been discovered due to the deficiencies and limitations with these methods.

To perform different tests is both costly and time consuming so that new numerical methods have been developed. In the numerical methods one uses a finite element program to simulate a road construction. A finite element program will provide various possibilities, such as editing of road structure layer thicknesses, usage of different computational models and graphical presentation of results.

The purpose of this project is to apply a computational model using the finite element program COMSOL MULTIPHYSICS, where two different models for the nonlinear behaviour of unbound granular materials are implemented. One of the models is a stressdependent model called the k-θ model. The second model describes the permanent deformation. It is called Gidel model and is a function of the number of load cycles. Calculations have been performed for two different road structures where the results have been compared to earlier modelling of the results of the Sunninge HVS-test.

The results show that it is possible to implement equations by using the finite element program COMSOL MULTIPHYSICS to describe the behaviour of the unbound granular materials. The displacements vary depending on the thickness, amount of stored moisture and the size of the load. High load in connection with a thin asphalt layer and an amount of stored moisture in the unbound materials make the displacements become large. Comparison between the calculated values and the values obtained from the modelling of the results of the Sunninge HVS-test shows that the calculated values of the displacements are smaller.},
  author       = {Hammadi, Domiyan},
  issn         = {0281-6679},
  keyword      = {Geotechnical engineering,Road design,Numerical methods,COMSOL MULTIPHYSICS,Unbound granular material,k-θ model,Permanent deformation,HVS-test},
  language     = {swe},
  note         = {Student Paper},
  series       = {TVGT-5000},
  title        = {FEM-simulering av nedbrytning hos obundet material vid upprepad belastning},
  year         = {2012},
}