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Item type:Publication, Access status: without files , Effect of installation method on static and dynamic load test response for piles in sand(2020-01-01); ; ; Static load tests (SLTs) are rarely performed on offshore piles, instead relying on dynamic load tests (DLTs). Evaluation techniques for DLTs were developed originally for solid piles, and caution is needed in applying the techniques directly to open-ended piles, particularly for the large-diameter monopiles used for offshore wind turbines. Centrifuge tests are reported here, investigating the influence of pile installation method and sand relative density for pairs of DLTs and SLTs. The piles were successfully driven to penetration of 3-4·6 diameters, which was much deeper than proved possible to jack the piles. Due to limited hammer energy, loads mobilised during the DLTs were less than 25% of the corresponding SLT values. The soil resistance mobilised at limited displacements was lowest for wished-in-place piles, and also for DLTs conducted on shallowly embedded jacked piles. For driven piles, the DLT and SLT results were relatively consistent, with surprisingly similar values for piles driven into loose and dense sand despite significant differences in cone resistance. Given the potential for low mobilisation of soil resistance in DLTs, care is needed when using DLTs for evaluating the static axial pile capacity of open-ended piles of low length-to-diameter ratio.Publicationtype: Journal Article53 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , FE-based identification of pile–soil interactions from dynamic load tests to predict the axial bearing capacity(2019-12-01); The static axial pile bearing capacity depends mainly on the developed pile–soil interaction. Hence, to determine a realistic and reliable ultimate pile bearing capacity, the pile–soil interaction needs to be identified and described precisely.One relevant field for this application is dynamic load tests (DLTs). During a DLT, the pile bearing capacity is deduced from measurements at the pile head. Current procedures of deriving the bearing capacity of open-ended piles from these measurements are lagging behind regarding the description of the pile–soil interaction for open-ended piles and the influence of the pore fluid response.Hence, a new technique based on the finite element method is developed, which captures the key aspects for DLT results correctly and is capable of deriving the static pile bearing capacity. The method is validated against dynamic and static load test data obtained from centrifuge tests on large diameter monopiles. An application to field test data of tubular steel piles is shown. The developed approach seems suitable to assess the static pile bearing capacity based on DLT measurements.Publicationtype: Journal Article29 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Penetration of ship anchors and the influence of submarine cablesImpacts by ship anchors are one of the main reasons for damage to submarine cables. Regulations meet this risk by defining a minimum permanent burial depth of submarine cables. The key parameters for the risk evaluation are the burial depth of the cable as well as the penetration depth of the anchor. In order to meet this risk sufficiently and to reduce the risk of submarine cable damage, the penetration process into the sea bed of the ship anchor has to be understood. Numerical simulations of the anchor penetration in sand are performed, in order to investigate the influence of anchor movement on submarine cables and to identify possible damage mechanisms.Publicationtype: Conference Paper191 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Numerical simulation of stress waves in tubular pilesAn improved insight into pile driving and pile load tests, especially for tubular piles of offshore wind projects, is necessary to optimize pile installation processes and to derive reliable bearing capacities from dynamic load tests. Numerical methods are used to evaluate geotechnical processes. Challenges include the nonlinear pile-soil interaction and inelastic wave propagation in saturated soil. Numerical simulations of pile installation as well as dynamic load tests are conducted to evaluate influences from different soil and driving characteristics. Considered variations include driving frequency, drainage condition of the soil, and pile-soil interaction properties. These conducted numerical simulations based on the finite element method of pile installation show interesting results, such as pile installation time decreasing with impact frequency. Furthermore, the drainage conditions of the soil around the pile and pile-soil interaction properties significantly influence the stress waves inside the pile. A new idea of an evaluation for dynamic load tests on openended piles based on the finite element method is introduced. The unknown parameters within this approach are inversely estimated from stress wave measurements at the pile head using an evolutionary algorithm.Publicationtype: Conference Paper108 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Dynamic load tests on large diameter open-ended piles in sand performed in the centrifugeOffshore infrastructure is commonly founded on piles. In accordance with design guidelines, piling contracts usually include load tests to verify the bearing capacity following pile installation. Offshore, these are generally performed as dynamic load tests (DLT) rather than static load tests often used onshore, for economical and practical considerations. Substantial experience exists in evaluating DLT on closed-ended piles. However, DLT on open-ended profiles have not been investigated sufficiently to date, particularly for piles with low length to diameter ratio. In order to derive realistic static axial pile bearing capacities, the processes during DLT taking place in the open-ended pile and soil need to be understood. Centrifuge tests provide the possibility of model tests with defined and reproducible conditions under consideration of realistic stress states. This paper discusses centrifuge test results of static and dynamic load tests on monopiles investigating the effects of pile installation method. The findings of this study provide a basis towards improved understanding of DLT on open-ended piles. © 2018 Taylor & Francis Group, London.Publicationtype: Conference Paper170 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Numerical based identification of pile-soil interaction in terms of the axial pile bearing capacity(Technische Universität Hamburg, Institut für Geotechnik und Baubetrieb, 2018); Publicationtype: Doctoral Thesis135 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Advances in numerical modelling of different ground improvement techniquesCommon ground improvement techniques like deep vibration compaction, vibro replacement stone columns, dynamic compaction or vibratory rolling are still a subject of research. Research fields are for example optimized layouts or estimation of main influencing parameters. A lot of successful scientific research is conducted on piles and piling using various numerical methods. Therefore, it is assumed that numerical models can be used to improve ground improvement methods. In this contribution, different ground improvement techniques and numerical models to simulate the influence of these techniques on the surrounding soil are presented. Furthermore, optimization methods and potentials of ground improvement techniques are shown.Publicationtype: Journal Article182 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Impact on submarine cables due to ship anchor – soil interactionEinfluss von Schiffsanker-Boden-Interaktion auf Seekabel. Eine der Hauptursachen für die Beschädigung von Seekabeln ist die Einwirkung durch Schiffsanker. Beim Ankern dringt der Schiffsanker in den Meeresgrund ein und kann Seekabel auf zwei Wegen beschädigen. Zum einen kann dies durch den direkten Kontakt von Seekabel und Anker und ein entsprechendes Mitziehen erfolgen, andererseits können Seekabel bereits durch die Ankerbewegung und einen damit verbundenen seitlichen Druck auf das Kabel ohne direkten Kontakt beschädigt werden. Um Beschädigungen oder eine Beeinträchtigung der Funktionalität von Seekabeln zu vermeiden, werden Seekabel in einer bestimmten Tiefe verlegt. Um den Einfluss der Verlegetiefe zu untersuchen, wird das Ankereindringverhalten sowie die Interaktion von Seekabel und Meeresgrund mit Hilfe von numerischen Simulationen modelliert. Hierfür wird die gekoppelte Euler-Lagrange Formulierung (CEL) verwendet.Publicationtype: Journal Article150 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , About the influence of one-way loading on the bearing behaviour of precast concrete piles for onshore wind energy plants(2017-03-01); ; ; ; About the influence of one-way loading on the bearing be haviour of precast concrete piles for onshore wind energy plants. Due to the energy transition several wind energy plants are built. Precast impact driven concrete piles represent one option to realise foundation piles onshore. In Germany, the bearing capacity of these piles can be estimated using empirical values taken from current standards or using in-house specifications of plant producers. Cyclic loading of such foundations exceeding 20 [%] of the static characteristic pile bearing capacity have to be considered when estimating the pile bearing capacity. However, the consequences of cyclic loading for the bearing behaviour of precast impact driven concrete piles are not fully understood yet. Therefore, field tests in cohesive and non-cohesive soils considering static and cyclic loading with different load amplitudes have been conducted and are presented within this paper. Using prevalent methods stated in current standards to estimate the bearing capacity of piles under static and cyclic loading are applied to recalculate the results of the field tests. Thereby, the suitability of these methods for estimation of the bearing behaviour of precast impact driven concrete piles under static and cyclic loading is reviewed.Publicationtype: Journal Article121 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Class-A-prediction of lateral pile deformation with respect to vibratory and impact pile drivingDistinctions of lateral loading behavior of vibrated and impact driven piles with respect to their influence on state variables of soils exist. Based on a field test simulations of horizontal load tests subsequent to the simulation of installation processes (vibrated and impact driven) are conducted. Soil behavior and horizontal displacement of the piles are investigated. Characteristics of pile installations as dynamic processes with large deformations and horizontal load tests as static processes have to be reproduced. A link to transfer results between CEL-method used for simulations of pile installations and classic FEM used for simulation of horizontal load tests is established.Publicationtype: Journal Article95