Browsing by Author "van der Weij, Oskar"

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    Comparison of constructing of an underground and open-pit parking facility within hard rock in an urban area
    (2024-08-19) Rathnayaka Mudiyanselage, Achintha; van der Weij, Oskar; Insinööritieteiden korkeakoulu; Rinne, Mikael
    Cities are proliferating, attracting more people, where the demand for adequate parking spaces continues to rise while diminishing the free buildable space. Underground parking facilities offer a way around this problem. Building underground can be done in two major ways, either as a parking facility in a tunnel or as an open pit version. In countries where the bedrock is at a shallow depth, even open pit excavations would include hard rock excavations. Given the impact a large excavation would have on nearby existing structures, especially considering the highly disruptive nature of rock excavation techniques, it is important to assess the rock mechanical feasibility of the two options when selecting the appropriate method. Further, it is also vital to determine the environmental impact and overall cost to identify the most favorable approach. This thesis explored a case study of a rock mechanical analysis from the Meilahti hospital area where an open-pit parking facility was proposed. A hypothetical underground tunnel version of the parking facility was developed to assess its rock mechanical viability using 3DEC numerical modeling software and compared the results with the open-pit version. Further, total CO2 emissions related to rock construction works were computed using One click LCA software, and the expected theoretical rock construction-related cost of both options were calculated and compared. Simulated displacements are compared where in the tunnel version the displacements at surrounding structures were ranging from 2…3 mm. In comparison, in the open pit version, the simulated displacements are rather high, even more than 10 mm at some locations. Higher displacements could result in severe fractures in the existing tunnel's shotcrete layer, as well as foundation settlement in surrounding structures, causing shear cracks in the walls. In terms of CO2 output, both variants emit a closer level of CO2 with a slightly low percentage difference in the tunnel version. Further, there was a considerable difference in the total rock construction-related cost where the open pit version would cost nearly 1.5 times as much as the tunnel version. These results can be used as a base guideline to determine the best alternative in densely populated urban regions for any planned underground structure
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    Impact of thermal background stresses on the rock reinforcement of a nuclear waste repository
    (2021-01-25) van der Weij, Oskar; Winderholler, Rodrigo; Insinööritieteiden korkeakoulu; Rinne, Mikael
    The stability of the deep underground spaces in a nuclear waste repository environment is compromised most severely by two factors; the high in-situ stress and thermally induced stresses that take place after the application of bolts and shotcrete. A new approach for modelling the effect of these issues is explored and presented in this thesis. Here the numerical modelling software 3DEC is used to model a hypothetical repository by combining publicly available data from repository projects, showcasing a worst-case scenario for a repository situated in a Precambrian bedrock environment. The construction of the hypothetical model is presented in detail to provide an understanding of modelling a repository in 3DEC. As brittle failure of the rock mass is expected, the elasto-plastic, Mohr-Coulomb based cohesion-softening-friction-hardening has been chosen as the constitutive model for the rock mass. The joint behavior is modelled by the elasto-plastic Coulomb slip constitutive model. The results from the hypothetical scenario are analyzed qualitatively to indicate what are potentially some critical locations and behavior mechanisms that compromise the long-term stability in a nuclear waste repository environment. The thesis elaborates to what extent is 3DEC suitable for evaluating the operational stability of a nuclear waste repository and what kind of damage is plausible in a nuclear waste repository environment. The boundaries of the excavation in large openings in the hypothetical model experience the largest displacements, both due to in-situ and thermal stresses. Some shear and normal displacements in joints are modelled. The thermal phase stresses and displacements cause issues in the integrity of the shotcrete and yielding in the bolts, both in normal and shear. In addition, significant shortcomings in the shotcrete model of 3DEC are discovered.
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    Kokonaiskustannusten suunnittelu ja projektiallianssi työkaluna budjetissa pysymiseen kalliorakennushankkeissa
    (2017-12-03) van der Weij, Oskar; Rinne, Mikael; Insinööritieteiden korkeakoulu; Gustavsson, Henry