Lateral resistance of short piles near slopes - a review of calculation methods
(2020) In TVBK-5278 VBKM01 20201Division of Structural Engineering
Department of Building and Environmental Technology
- Abstract (Swedish)
- Vid konstruktion av bullerskärmar så väljs vanligtvis pålning som grundläggningstyp. Det finns flera modeller som kan approximera ett krav på minsta pållängd beroende på olika typer jordförhållande och vindlast. Om pålen ska placeras vid en slänt blir dock beräkningarna betydligt mer osäkra då inverkan av en slänt på den horisontella stabiliteten är svår att uppskatta.
Denna rapport har analyserat och jämfört flera olika metoder för att approximera vilken pållängd som behövs i friktionsjord vid angiven vindlast och för olika typer av markförhållanden. Detta gjordes genom en parameterstudie där inverkan av följande parametrar studerades: bullerskärmens höjd, släntens lutning, avståndet mellan påle och slänt, jorden tyngd samt jorden... (More) - Vid konstruktion av bullerskärmar så väljs vanligtvis pålning som grundläggningstyp. Det finns flera modeller som kan approximera ett krav på minsta pållängd beroende på olika typer jordförhållande och vindlast. Om pålen ska placeras vid en slänt blir dock beräkningarna betydligt mer osäkra då inverkan av en slänt på den horisontella stabiliteten är svår att uppskatta.
Denna rapport har analyserat och jämfört flera olika metoder för att approximera vilken pållängd som behövs i friktionsjord vid angiven vindlast och för olika typer av markförhållanden. Detta gjordes genom en parameterstudie där inverkan av följande parametrar studerades: bullerskärmens höjd, släntens lutning, avståndet mellan påle och slänt, jorden tyngd samt jorden friktionsvinkel. Genom att sedan jämföra resultaten från parameterstudien, samt en finita element analys, så kunde vissa slutsatser dras angående relevansen av de olika metoderna för användande av dem i praktiken.
Slutsatser som drogs var att ett par av metoderna verkade leverera approximerade pållängder med en hög säkerhetsmarginal medan en av metoderna verkade approximera verkligheten bättre, med lägre säkerhetsmarginaler. Dock var en av metoderna som gav hög säkerhetsmarginal betydligt mer tidskrävande än den andra och skulle inte rekommenderas, då resultaten mellan dessa metoder var väldigt lika. Slutsatser kunde görasangående att en av metoderna var mest lämpad om kraven på säkerhetsmarginalerna var höga, medan metoden som gav lägre säkerhetsmargin skulle rekommenderas för design av pelare i ett tidigt skede som sedan verifieras av mer avancerade beräkningar i ett senare skede, samt för optimering av materialanvändningen i pålarna.
Det som var den avgörande skillnaden mellan metoderna var hur de tog hänsyn till släntens inverkan på jordens horistontallastkapacitet och verkade vara mer eller mindre helt avgörande för hur lång påle som approximerades. (Less) - Abstract
- When designing noise screens, piling is usually the chosen foundation type. There are several approximating models that can be used to determine the required pile length; these depend on the soil conditions and wind loads. However, if the pile is placed near a slope, the calculations will be considerably more uncertain as the impact of a slope on the horizontal stability of the pile is difficult to estimate.
This thesis has analysed and compared several different methods to determine the required pile length in friction soils for a specific wind load and different types of ground conditions. This was done by carrying out a parametric study where the influence of the following parameters was studied for each design method: the height of... (More) - When designing noise screens, piling is usually the chosen foundation type. There are several approximating models that can be used to determine the required pile length; these depend on the soil conditions and wind loads. However, if the pile is placed near a slope, the calculations will be considerably more uncertain as the impact of a slope on the horizontal stability of the pile is difficult to estimate.
This thesis has analysed and compared several different methods to determine the required pile length in friction soils for a specific wind load and different types of ground conditions. This was done by carrying out a parametric study where the influence of the following parameters was studied for each design method: the height of the noise screen, the angle of the slope, the distance between the pile and the slope, the unit weight of the soil, and the internal friction angle of the soil. By comparing the results of the parametric study, as well as a finite element analysis, some conclusions could be drawn regarding the relevance of the different methods for use in practice.
The conclusions that were drawn were that one method was in close agreement with the FE model, whereas the other two gave more conservative results. However, one of the methods that produced pile lengths with high safety margin was significantly more time consuming to use and would therefore not be recommended since there was a method producing similar results but with just a fraction of the time spent doing the calculations.
The method comparison revealed that one method provided results quite consistent with the FE-model while two methods consistently resulted in longer piles and with similar pile lengths to each other. Out of the latter two, one method is computationally more expensive and therefore provide few advantages over the other two methods. Conclusively, the designer can select one of the simpler methods depending on the desired level of conservativeness.
The crucial difference between the methods was how they considered the impact of the slope on the lateral load capacity of the soil and these seemed to be the decisive parameters for the lengths of the piles that the different methods approximated. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9022841
- author
- Jönebratt, Tomas LU
- supervisor
- organization
- alternative title
- Horisontallastkapacitet för korta pålar nära slänter
- course
- VBKM01 20201
- year
- 2020
- type
- H3 - Professional qualifications (4 Years - )
- subject
- keywords
- Lateral load capacity, Horizontal load capacity, Piles near slopes, Approximate design methods, Soil, Geotechnical engineering, Friction soil, Wind load, Ultimate limit state, Noise screens
- publication/series
- TVBK-5278
- report number
- TVBK-5278
- ISSN
- 0349-4969
- language
- English
- additional info
- Examinator: Jonas Niklewski
- id
- 9022841
- date added to LUP
- 2020-06-26 13:16:14
- date last changed
- 2020-06-26 13:16:14
@misc{9022841,
abstract = {{When designing noise screens, piling is usually the chosen foundation type. There are several approximating models that can be used to determine the required pile length; these depend on the soil conditions and wind loads. However, if the pile is placed near a slope, the calculations will be considerably more uncertain as the impact of a slope on the horizontal stability of the pile is difficult to estimate.
This thesis has analysed and compared several different methods to determine the required pile length in friction soils for a specific wind load and different types of ground conditions. This was done by carrying out a parametric study where the influence of the following parameters was studied for each design method: the height of the noise screen, the angle of the slope, the distance between the pile and the slope, the unit weight of the soil, and the internal friction angle of the soil. By comparing the results of the parametric study, as well as a finite element analysis, some conclusions could be drawn regarding the relevance of the different methods for use in practice.
The conclusions that were drawn were that one method was in close agreement with the FE model, whereas the other two gave more conservative results. However, one of the methods that produced pile lengths with high safety margin was significantly more time consuming to use and would therefore not be recommended since there was a method producing similar results but with just a fraction of the time spent doing the calculations.
The method comparison revealed that one method provided results quite consistent with the FE-model while two methods consistently resulted in longer piles and with similar pile lengths to each other. Out of the latter two, one method is computationally more expensive and therefore provide few advantages over the other two methods. Conclusively, the designer can select one of the simpler methods depending on the desired level of conservativeness.
The crucial difference between the methods was how they considered the impact of the slope on the lateral load capacity of the soil and these seemed to be the decisive parameters for the lengths of the piles that the different methods approximated.}},
author = {{Jönebratt, Tomas}},
issn = {{0349-4969}},
language = {{eng}},
note = {{Student Paper}},
series = {{TVBK-5278}},
title = {{Lateral resistance of short piles near slopes - a review of calculation methods}},
year = {{2020}},
}