Burbaum U.,CDM Consult GmbH |
Sass I.,TU Darmstadt |
Breuer B.,TU Darmstadt
Geotechnik | Year: 2010
In EPBS tunnel driving, claystones of varying properties causes often serious problems by clogging the TBM. The reason are adhesive forces due to contact of fluids and claystone. The soil sticks on the solid surfaces of the TBM what leads to clogging related to serious delays and increased costs. The adhesion of cohesive soils to solid surfaces depends on the capillary forces of a fluid film inside the soil-solid interface and can be understood as a boundary layer effect. These capillarity forces increase in inverse proportion to the thickness of the fluid film. The surface tension and thickness of fluid film are the main parameters which define the systems properties. This paper addresses the results of research activities on soil-steel surface interactions. Results of adhesion tests using a Lias Alpha claystone example are presented. Consequences for tunnel driving are given.
Lanz J.K.,University of Stuttgart |
Wagner R.,German Aerospace Center |
Wolf U.,Free University of Berlin |
Krochert J.,CDM Consult GmbH |
Neukum G.,Free University of Berlin
Journal of Geophysical Research E: Planets | Year: 2010
We analyzed a small cone field in SW Utopia Planitia that shows striking similarities to volcanic rift zones on Earth. This is of particular interest as the study area lies off any of the volcanic centers of Mars in the northern hemisphere lowlands and is surrounded by material of the Amazonian aged Vastitas Borealis Formation (VBF). We believe that the study area could be the first direct evidence for volcanic activity in Utopia Planitia prior to the resurfacing by VBF material. The most striking characteristics that we observed are (1) a set of broad eruptive fissures showing signs of ongoing extension during cone formation, (2) parallel dike swarms, (3) magmatic intrusions, and (4) a number of lava flows that have erupted from the fissures and pitted cones that surround a larger cone in the center of the study area and that are often associated with, or aligned along, the fissures and dikes. Cratering model ages indicate that the study area is of Late Noachian to Early Hesperian age and is thus distinctly older than the surrounding VBF, falling into the time frame of the main phases of activity in the volcanic centers of Syrtis Major, Elysium Planitia, and the southern highlands. Copyright 2010 by the American Geophysical Union.
Burbaum U.,CDM Consult GmbH |
Kerr A.G.,CDM Ireland Ltd
2012 Proceedings - North American Tunneling, NAT 2012 | Year: 2012
Dublin City Council (DCC) intends to upgrade the Ringsend wastewater treatment works from its present capacity of 1.64 million population equivalent (PE) to 2.1 million PE to meet the future demand projections for the catchment area and ensure compliance with relevant legislation. The proposed treated final effluent discharge option is to divert the existing inshore effluent discharge point into a purpose built long sea outfall tunnel (LSOT) extension, approximately 5-metre in-internal-diameter and 9-kilometre under Dublin Bay eastwards from the City of Dublin. No geological records existed for the Dublin Bay geology at the project outset. Therefore a marine subsurface investigation, incorporating 21 onshore and offshore boreholes and an inter-tidal geophysics exercise (Marine SI), was completed to determine the geology under Dublin Bay and identify the optimum LSOT tunnel route. The results of the Marine SI radically altered the historically inferred understanding of the bay's geology and have presented a range of complex conditions for tunnel alignment design. This paper will present the methodology and interpretation of results of the Marine SI in Dublin Bay and resulting complexities for the LSOT design.
Amstaetter K.,University of Tubingen |
Amstaetter K.,CDM Consult GmbH |
Borch T.,Colorado State University |
Kappler A.,University of Tubingen
Geochimica et Cosmochimica Acta | Year: 2012
Microbial reduction of Fe(III) minerals at neutral pH is faced by the problem of electron transfer from the cells to the solid-phase electron acceptor and is thought to require either direct cell-mineral contact, the presence of Fe(III)-chelators or the presence of electron shuttles, e.g. dissolved or solid-phase humic substances (HS). In this study we investigated to which extent the ratio of Pahokee Peat Humic Acids (HA) to ferrihydrite in the presence and absence of phosphate influences rates of Fe(III) reduction by Shewanella oneidensis MR-1 and the identity of the minerals formed. We found that phosphate generally decreased reduction rates by sorption to the ferrihydrite and surface site blocking. In the presence of low ferrihydrite concentrations (5mM), the addition of HA helped to overcome this inhibiting effect by functioning as electron shuttle between cells and the ferrihydrite. In contrast, at high ferrihydrite concentrations (30mM), the addition of HA did not lead to an increase but rather to a decrease in reduction rates. Confocal laser scanning microscopy images and ferrihydrite sedimentation behaviour suggest that the extent of ferrihydrite surface coating by HA influences the aggregation of the ferrihydrite particles and thereby their accessibility for Fe(III)-reducing bacteria. We further conclude that in presence of dissolved HA, iron reduction is stimulated through electron shuttling while in the presence of only sorbed HA, no stimulation by electron shuttling takes place. In presence of phosphate the stimulation effect did not occur until a minimum concentration of 10mg/l of dissolved HA was reached followed by increasing Fe(III) reduction rates up to dissolved HA concentrations of approximately 240mg/l above which the electron shuttling effect ceased. Not only Fe(III) reduction rates but also the mineral products changed in the presence of HA. Sequential extraction, XRD and 57Fe-Mössbauer spectroscopy showed that crystallinity and grain size of the magnetite produced by Fe(III) reduction in the presence of HA is lower than the magnetite produced in the absence of HA. In summary, this study shows that both the concentration of HA and Fe(III) minerals strongly influence microbial Fe(III) reduction rates and the mineralogy of the reduction products. Thus, deviations in iron (hydr)oxide reactivity with changes in aggregation state, such as HA induced ferrihydrite aggregation, need to be considered within natural environments. © 2012 Elsevier Ltd.
Wawrzyniak C.,CDM Consult GmbH
North American Tunneling 2010 Proceedings, NAT 2010 | Year: 2010
With regard to the new construction of big infrastructure projects more and more tunneling projects are carried out based on functional tenders or as construction projects according to the model of Public Private Partnership (PPP). The special risks are presented from the insurer's point of view using the example of a tunnel collapse. A number of four tunnels consisting of two tubes each were excavated during the new construction of a motorway section in Hungary. In July 2008 a collapse occurred in the tunnel heading with the result that both tubes collapsed on a length of 200 m. In case of PPP projects risks are especially seen in the comparatively high degrees of freedom in the process of interpretation of foundation models as a basis for a further planning. Furthermore, designers of the 100% design and the supervision both are acting on behalf of the construction firm. Moreover there is an increased degree of freedom in the construction itself which also leads to a higher risk potential.