02 Fakultät Bau- und Umweltingenieurwissenschaften

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/3

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Institute: search.filters.UBSInstitut.Fakultätsübergreifend / Sonstige EinrichtungAuthor: search.filters.author.Moormann, Christian

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Now showing 1 - 3 of 3
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    Influence of weathering on pore size distribution of soft rocks
    (2022) Knopp, Julia; Steger, Hagen; Moormann, Christian; Blum, Philipp
    Soft rocks can weather and lose their structure within a short time due to drying out and rewetting. Thus they are very sensitive to weathering. Since these rocks are often found in the shallow subsurface, they are of great practical relevance in the foundation of constructions. The rock properties change during the weathering process. Particularly relevant is the softening of the material and the decrease of its mechanical properties, which are determined typically using mechanical laboratory or field tests. The objective of this study is to examine in more detail how the microstructure of rocks changes over the course of weathering, which results in a decrease in mechanical properties. Sulfate rocks of the Grabfeld-Formation in Stuttgart, Germany were investigated. Using XRD analyses it was revealed that initially a chemical weathering processes occurs whereby the rocks leach out, followed by a physical weathering process. Investigations with a mercury porosimeter showed that during chemical weathering the intraaggregate pore content greatly increases, whereas the proportion of interaggregate pores only slightly increases.
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    Introducing tree-based-regression models for prediction of hard rock TBM performance with consideration of rock type
    (2022) Salimi, Alireza; Rostami, Jamal; Moormann, Christian; Hassanpour, Jafar
    Prediction of machine performance is a fundamental step for planning, cost estimation/control and selection of the machine type when using a tunnel boring machine (TBM). Penetration rate (PR) and machine utilization (U) are the two principal measures of TBM performance for evaluating the feasibility of using a machine in a given ground condition. However, despite the widespread use of TBMs and established track records, accurate estimation of machine performance could still be a challenge, particularly in complex geological conditions. Since different types of rocks have varied texture (cementation and grain size), and respond differently to cutting forces in the TBM tunnelling, incorporating the effects of rock type in performance prediction models can improve the accuracy of the estimates. The aim of this study was to develop models for predicting penetration rate of hard rock TBMs in different types of rock based on field penetration index (FPI), using multivariable regression analysis and machine learning algorithm, including classification and regression tree (CART). The proposed models offer estimated FPIs in different rock types, rock strength, and rock mass properties in the form of graphs (diagrams), which can be used to estimate TBM penetration rate. The proposed models have been developed based on the analysis of a comprehensive database of TBM performance in various rock types and offers more accurate estimates of machine performance by incorporating many of the key parameters available in typical geotechnical reports and contract documents. The models also exhibit sensitivity to rock mass parameters for predicting the penetration rate.
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    Sustainable heating and cooling management of urban quarters
    (2022) Kugler, Till; Schittenhelm, Corinna; Volkmer, Stephan; Ryba, Meinhard; Moormann, Christian; Kurth, Detlef; Koenigsdorff, Roland
    An important component for a renewable and sustainable heat energy supply is the consideration of urban quarters. For this purpose, the locally available energy sources, a local energy generation system, and the energy distribution in urban quarters should be considered. In the IWAES project presented here, a bidirectional low-temperature heat network was developed, thus it falls into the category of fifth-generation heat networks. It also makes use of existing urban water management infrastructure. The innovative concept is based on the approach of modifying sewers so that they can transport thermal energy between users in the same quarter and extract thermal energy from wastewater. The overall goal is to generate thermal energy and balance the different thermal needs. This is particularly useful in mixed-use quarters, as the peak loads of different uses occur at different times. The supply concept also envisages integrating other thermal energy sources available in the quarter as well as storage options into the supply concept. As a framework for the technical aspects, a precise urban planning concept is needed that provides the legal framework for land use and urban development and coordinates and implements the developed concept - through so-called energy master planning. A life cycle assessment shows the ecological impact of the developed concept compared to a conventional energy solution. It also shows the savings potential of the developed concept compared to an urban quarter supplied conventionally with heating and de-centrally with cooling. The assessment outlines the dual use of the pre-existing infrastructure, such as the wastewater system, significantly reduces CO2 equivalents. Another result is that the sustainability of the system depends significantly on the used mix of electric sources.