Artificial Infiltration in Rock and Soil - A Comparison of Responses in Central Gothenburg using Numerical Models
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Examensarbete för masterexamen
Modellbyggare
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Sammanfattning
Underground constructions can cause lowering of the groundwater table, due to
groundwater leakage into the structure. To minimize the risk of drawdown, artificial infiltration can be implemented which can maintain or raise the groundwater
table to a desired level. Water can be infiltrated either in rock or soil, and observation data has shown that the two materials exhibit different responses. In literature,
limited amount of research has been conducted comparing the responses between
rock and soil infiltrations and it was therefore of interest to investigate this further.
This thesis aimed to compare the responses obtained from rock and soil infiltration
using numerical finite difference modelling. To enable a systematic comparison between the different approaches two types of models were created, using Excel and
GMS MODFLOW. Consequently the thesis also resulted in a comparison between
the models, to conclude which model approach could simulate the observed data but
also to see how the characteristics of the models affected the results. In addition,
a risk object, which in this case is a building sensitive to groundwater fluctuations,
was included to exemplify the results obtained from the models by suggesting the
most suitable infiltration approach. The comparison was applied to a stretch of
the Västlänken project, which is a railway tunnel currently being constructed in
Gothenburg, Sweden.
The results from both models show that the response generated from rock infiltration have more of a linear response, compared to soil infiltration which demonstrated
an exponential trend. The results from the Excel model were correlated to the observed data when it comes to the propagation of the responses, indicating a more
diffusive response in rock compared to soil. The GMS MODFLOW model however,
did not show this type of pattern. Both numerical models managed to simulate the
differences in responses, but to which extent the results coincide with the observed
data varied. For the risk object, it was suggested that rock infiltration might be the
best option since a more linear response makes it easier to predict how much the
levels will be raised. Further, the exponential response from a soil infiltration would
require the infiltration facility to be located close by, which might be difficult since
the area is densely built.
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Ämne/nyckelord
Artificial infiltration, Underground constructions, Numerical modelling, Spreadsheet application, GMS MODFLOW, drawdown