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
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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
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