Comparison of Modelling Strategies for Ground Settlements due to Groundwater Drawdown Multi-criteria analysis for comparison of three software packages
Typ
Examensarbete för masterexamen
Program
Infrastructure and environmental engineering (MPIEE), MSc
Publicerad
2021
Författare
Ögger, Frida
Johansson, Linnea
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
When performing construction projects below the groundwater level, groundwater
leakage into the construction can occur, which can lead to settlements. This Mas ter’s thesis aims at comparing three different software packages for calculation of
settlements caused by groundwater drawdown in an aquifer situated below com pressible soils. The different software packages used are: a stochastic settlement
model that considers creep effects and parameter uncertainties, the Soft Soil Creep
model available in Plaxis 2D and the Chalmers model with creep available in GS Set tlement. To evaluate the appropriateness of them, settlement calculations for both
1D and 2D soil models are performed, together with a multi-criteria analysis (MCA).
The 1D modelling results show that all three approaches exhibit the same elastic and elasto-plastic behaviour. For comparison of the creep behaviour between Plaxis
2D and GS Settlement, differences arise due to model formulations. GS Settlement
seems to predict lower creep settlements than Plaxis for stress states around the
preconsolidation pressure. For drawdowns that highly exceed the preconsolidation
pressure, GS Settlement instead predicts higher settlements compared to Plaxis.
The stochastic settlement model does not include creep effects, but the additional
deformation is captured by the parameter uncertainty interval for drawdowns near
the preconsolidation pressure and higher. When comparing 2D effects of consol idation, the ability for the stochastic settlement model to capture the additional
settlements predicted by Plaxis 2D is ambiguous.
The results in this thesis highlight the differences between the three software pack ages. The MCA shows that the stochastic settlement model has a good capability
in handling spatial uncertainties, but is disadvantageous due to the low level of intu ition. Plaxis can handle complex geometries, but the calculation is time demanding.
GS Settlement is more intuitive with lower calculation effort required, but lacks the
ability of performing calculations with complex geometries. The MCA further em phasises that the ability to implement the theoretical framework of a groundwater
drawdown together with modelling a drawdown over a large area is considered of
high importance. To make it less subjective, further prerequisites which define the
features of the project is needed. Hence, this comparison can serve as a support for
future projects to achieve a versatile analysis in a structured way.
Beskrivning
Ämne/nyckelord
Ground settlements , Multi-criteria analysis , Analytical modelling , Groundwater drawdown , Soft clays , Plaxis 2D , GS Settlement