TY - JOUR A1 - Kirsch, Ansgar T1 - Experimental investigation of the face stability of shallow tunnels in sand JF - Acta Geotechnica N2 - Various models have been proposed for the prediction of the necessary support pressure at the face of a shallow tunnel. To assess their quality, the collapse of a tunnel face was modelled with small-scale model tests at single gravity. The development of the failure mechanism and the support force at the face in dry sand were investigated. The observed displacement patterns show a negligible influence of overburden on the extent and evolution of the failure zone. The latter is significantly influenced, though, by the initial density of the sand: in dense sand a chimney-wedge-type collapse mechanism developed, which propagated towards the soil surface. Initially, loose sand did not show any discrete collapse mechanism. The necessary support force was neither influenced by the overburden nor the initial density. A comparison with quantitative predictions by several theoretical models showed that the measured necessary support pressure is overestimated by most of the models. Those by Vermeer/Ruse and Léca/Dormieux showed the best agreement to the measurements. Y1 - 2010 U6 - https://doi.org/10.1007/s11440-010-0110-7 SN - 1861-1125 VL - 5 IS - 1 SP - 43 EP - 62 PB - Springer CY - Berlin ER - TY - JOUR A1 - Kirstein, Simon A1 - Müller, Karsten A1 - Walecki-Mingers, Mark A1 - Deserno, Thomas M. T1 - Robust adaptive flow line detection in sewer pipes JF - Automation in construction N2 - As part of a novel approach to automatic sewer inspection, this paper presents a robust algorithm for automatic flow line detection. A large image repository is obtained from about 50,000 m sewers to represent the high variability of real world sewer systems. Automatic image processing combines Canny edge detection, Hough transform for straight lines and cost minimization using Dijkstra's shortest path algorithm. Assuming that flow lines are mostly smoothly connected horizontal structures, piecewise flow line delineation is reduced to a process of selecting adjacent line candidates. Costs are derived from the gap between adjacent candidates and their reliability. A single parameter α enables simple control of the algorithm. The detected flow line may precisely follow the segmented edges (α = 0.0) or minimize gaps at joints (α = 1.0). Both, manual and ground truth-based analysis indicate that α = 0.8 is optimal and independent of the sewer's material. The algorithm forms an essential step to further automation of sewer inspection. Y1 - 2012 U6 - https://doi.org/10.1016/j.autcon.2011.05.009 SN - 1872-7891 (E-Journal) ; 0926-5805 (Print) IS - 21 SP - 24 EP - 31 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Kolymbas, Dimitrios A1 - Fellin, W. A1 - Kirsch, Ansgar T1 - Squeezing due to stress relaxation in foliated rock JF - International journal for numerical and analytical methods in geomechanics Y1 - 2006 U6 - https://doi.org/10.1002/nag.530 SN - 1096-9853 (E-Journal); 0363-9061 (Print) VL - Vol. 30 IS - Iss. 13 SP - 1357 EP - 1367 ER - TY - JOUR A1 - Kramer, Matthias A1 - Valero, Daniel A1 - Chanson, Hubert A1 - Bung, Daniel Bernhard T1 - Towards reliable turbulence estimations with phase-detection probes: an adaptive window cross-correlation technique JF - Experiments in Fluids Y1 - 2019 U6 - https://doi.org/10.1007/s00348-018-2650-9 SN - 1432-1114 VL - 60 EP - Article number 2 PB - Springer CY - Berlin ER - TY - JOUR A1 - Kuhnhenne, Markus A1 - Reger, Vitali A1 - Pyschny, Dominik A1 - Döring, Bernd T1 - Influence of airtightness of steel sandwich panel joints on heat losses JF - E3S Web of Conferences 12th Nordic Symposium on Building Physics (NSB 2020) N2 - Energy saving ordinances requires that buildings must be designed in such a way that the heat transfer surface including the joints is permanently air impermeable. The prefabricated roof and wall panels in lightweight steel constructions are airtight in the area of the steel covering layers. The sealing of the panel joints contributes to fulfil the comprehensive requirements for an airtight building envelope. To improve the airtightness of steel sandwich panels, additional sealing tapes can be installed in the panel joint. The influence of these sealing tapes was evaluated by measurements carried out by the RWTH Aachen University - Sustainable Metal Building Envelopes. Different installation situations were evaluated by carrying out airtightness tests for different joint distances. In addition, the influence on the heat transfer coefficient was also evaluated using the Finite Element Method (FEM). The combination of obtained air volume flow and transmission losses enables to create an "effective heat transfer coefficient" due to transmission and infiltration. This summarizes both effects in one value and is particularly helpful for approximate calculations on energy efficiency. Y1 - 2020 U6 - https://doi.org/10.1051/e3sconf/202017205008 VL - 172 IS - Art. 05008 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Leandro, J. A1 - Bung, Daniel Bernhard A1 - Carvalho, R. T1 - Measuring void fraction and velocity fields of a stepped spillway for skimming flow using non-intrusive methods JF - Experiments in fluids Y1 - 2014 U6 - https://doi.org/10.1007/s00348-014-1732-6 SN - 0723-4864 (Print) ; 1432-1114 (Online) IS - 55 SP - Art. 1732 PB - Springer Nature CY - Heidelberg ER - TY - JOUR A1 - Lopes, Pedro A1 - Leandro, Jorge A1 - Carvalho, Rita F. A1 - Bung, Daniel Bernhard T1 - Alternating skimming flow over a stepped spillway JF - Environmental Fluid Mechanics Y1 - 2017 U6 - https://doi.org/10.1007/s10652-016-9484-x SN - 1573-1510 VL - 17 IS - 2 SP - 303 EP - 322 PB - Springer CY - Berlin ER - TY - JOUR A1 - Oertel, Mario A1 - Bung, Daniel Bernhard T1 - Stability and scour development of bed material on crossbar block ramps JF - International journal of sediment research N2 - Block ramps are ecologically oriented drop structures with adequate energy dissipation and partially moderate flow velocities. A special case is given with crossbar block ramps, where the upstream and downstream level difference is reduced by a series of basins. To prevent the total structure from failing, the stability of single boulders within the crossbars and the bed material in between must be guaranteed. The present paper addresses the stability of bed material and scour development for various flow regimes. Any bed material erosion may affect the stability of the crossbar boulders, which in turn can result in major damages of the ramp. Therefore new design approaches are developed to choose an appropriate bed material size and to avoid failures of crossbar block ramp structures. Y1 - 2015 U6 - https://doi.org/10.1016/j.ijsrc.2014.12.003 SN - 1001-6279 VL - 30 IS - 4 SP - 344 EP - 350 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Oertel, Mario A1 - Bung, Daniel Bernhard T1 - Initial stage of two-dimensional dam-break waves: laboratory versus VOF JF - Journal of hydraulic research N2 - Since several decades, dam-break waves have been of main research interest. Mathematical approaches have been developed by analytical, physical and numerical models within the past 120 years. During the past 10 years, the number of research investigations has increased due to improved measurement techniques as well as significantly increased computer memories and performances. In this context, the present research deals with the initial stage of two-dimensional dam-break waves by comparing physical and numerical model results as well as analytical approaches. High-speed images and resulting particle image velocimetry calculations are thereby compared with the numerical volume-of-fluid (VOF) method, included in the commercial code FLOW-3D. Wave profiles and drag forces on placed obstacles are analysed in detail. Generally, a good agreement between the laboratory and VOF results is found. KW - VOF KW - PIV KW - physical model KW - numerical model KW - drag force KW - dam-break Y1 - 2012 U6 - https://doi.org/10.1080/00221686.2011.639981 SN - 1814-2079 (E-Journal); 0022-1686 (Print) VL - 50 IS - 1 SP - 89 EP - 97 PB - Taylor & Francis CY - London ER - TY - JOUR A1 - Valero, D. A1 - Bung, Daniel Bernhard A1 - Crookston, B. M. T1 - Closure to “Energy Dissipation of a Type III Basin under Design and Adverse Conditions for Stepped and Smooth Spillways” JF - Journal of Hydraulic Engineering Y1 - 2019 U6 - https://doi.org/10.1061/(ASCE)HY.1943-7900.0001669 VL - 146 IS - 2 PB - ASCE CY - Reston, Va. ER -