The value of information of deformation zones in bedrock for grouting design
Typ
Bachelor Thesis
Program
Infrastructure and environmental engineering (MPIEE), MSc
Publicerad
2024
Författare
Eliasson, William
Thorsson, Martin
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Understanding of site-specific geological characteristics is of high importance in underground
construction. In tunnelling, consideration must be given to possible modes of water transport in the
rock since leakage could result in significant consequences for nearby nature and construction. Core
drilling techniques are often utilized to characterize rock masses, but these are expensive and only
give information specific to a given point of sampling. Hence, a balance must be maintained
between the economical cost of conducting these investigations and the benefit they provide in
terms of information. The aim of this project is to exemplify a methodology of applying Multiple
point statistics (MPS) and Value of information analysis (VOIA) to evaluate the value of performing
further core drilling investigations in a tunnelling project for the purpose of grouting design. This
methodology has been showcased through application on the on-going tunnelling project
Kolmårdstunneln, which is part of the bigger project Ostlänken, Sweden. The MPS algorithm SNESIM
was used in the SGeMS software to construct a geostatistical model, whereafter two different
grouting designs (A1 and A2) were evaluated using VOIA and compared in terms of their respective
construction costs and their associated risk of failure- represented as the expected economic
consequence for underestimating the occurrence of deformation zones in the tunnel. This
evaluation comprised of two stages; a prior analysis which features a probability of failure
dependent on the modelled rock mass in the tunnel, and a pre-posterior analysis, where the
probability of failure has been adjusted using a virtual core drilling campaign and Bayesian updating.
For the context of this case study, the value of information of a campaign was calculated by
comparing the prior and pre-posterior results. It could be concluded that the campaign was not
worth conducting since conducting the campaign would not have led to a different decision being
made. The proposed method shows potential, but further research is necessary regarding several
aspects.
Beskrivning
Ämne/nyckelord
Multiple point statistics , Geostatistical modelling , SNESIM , SGeMS , Value of information analysis , Deformation zones , Bayesian updating