Soil reaction under offshore-structure

The simplest elasticity model of the foundation underlying a slender beam under flexure was conceived by Winkler, requiring local proportionality between soil reactions and beam deflection. Such an approach leads to well-posed elastostatic and elastodynamic problems, but as highlighted by Wieghardt, it provides elastic responses that are not technically significant for a wide variety of engineering applications. Thus, Winkler’s model was replaced by Wieghardt himself by assuming that the beam deflection is the convolution integral between soil reaction field and an averaging kernel. Due to conflict between constitutive and kinematic compatibility requirements, the corresponding elastic problem of an inflected beam resting on a Wieghardt foundation is ill-posed. Modifications of the original Wieghardt model were proposed by introducing fictitious boundary concentrated forces of constitutive type, which are physically questionable, being significantly influenced on prescribed kinematic boundary conditions. Inherent difficulties and issues are overcome in the present research using a displacement-driven nonlocal integral strategy obtained by swapping the input and output fields involved in Wieghardt’s original formulation. That is, nonlocal soil reaction fields are the output of integral convolutions of beam deflection fields with an averaging kernel. Equipping the displacement-driven nonlocal integral law with the bi-exponential averaging kernel, an equivalent nonlocal differential problem, supplemented with non-standard constitutive boundary conditions involving nonlocal soil reactions, is established. As a key implication, the integrodifferential equations governing the elastostatic problem of an inflected elastic slender beam resting on a displacement-driven nonlocal integral foundation are replaced with much simpler differential equations supplemented with kinematic, static, and new constitutive boundary conditions. The proposed nonlocal approach is illustrated by examining and analytically solving exemplar problems of structural engineering. Benchmark solutions for numerical analyses are also detected.

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Chemical and Phytocoenological Characteristics of Two Different Slovak Peatlands

Plants ◽

10.3390/plants10071290 ◽

2021 ◽

Vol 10 (7) ◽

pp. 1290

Author(s):

Danica Fazekašová ◽

Gabriela Barančíková ◽

Juraj Fazekaš ◽

Lenka Štofejová ◽

Ján Halas ◽

...

Keyword(s):

Organic Matter ◽

Soil Profile ◽

Agricultural Land ◽

Nitrogen Supply ◽

Point Of View ◽

Statistical Testing ◽

Plant Residues ◽

Soil Reaction ◽

Chemical Parameters

This paper presents the results of pedological and phytocoenological research focused on the detailed research of chemical parameters (pH, organic carbon, and nutrients), risk elements (As-metalloid, Cd, Co, Cr, Cu, Ni, Pb, and Zn), and species composition of the vegetation of two different peatlands on the territory of Slovakia—Belianske Lúky (a fen) and Rudné (a bog). Sampling points were selected to characterize the profile of the organosol within the peatland, the soil profile between the peatland and the agricultural land, and the soil profile of the outlying agricultural land, which is used as permanent grassland. Based on phytocoenological records, a semi-quantitative analysis of taxa in accordance with the Braun–Blanquet scale was performed. The study revealed that the thickness of the peat horizon of the fen in comparison with the bog is very low. In terms of the quality of organic matter, the monitored peatlands are dominated by fresh plant residues such as cellulose and lignin. Differences between individual types of peatlands were also found in the soil reaction and the supply of nitrogen to the organic matter of peat. The values of the soil exchange reaction were neutral on the fen, as well as slightly alkaline but extremely low on the bog. A significantly higher nitrogen supply was found in the organic matter of the fen in contrast to the bog. At the same time, extremely low content of accessible P and an above-limit content of As in the surface horizons were also found on the fen. From the phytocoenological point of view, 22 plant species were identified on the fen, while only five species were identified on the bog, which also affected the higher diversity (H’) and equitability (e). The results of the statistical testing confirmed the diversity of the studied peatlands and the different impact of environmental variables on plant diversity.

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Compacted Anthropogenic Materials as Backfill for Buried Pipes

Materials ◽

10.3390/ma14040717 ◽

2021 ◽

Vol 14 (4) ◽

pp. 717

Author(s):

Andrzej Głuchowski ◽

Raimondas Šadzevičius ◽

Rytis Skominas ◽

Wojciech Sas

Keyword(s):

Recycled Concrete ◽

Special Treatment ◽

Soil Reaction ◽

Concrete Aggregate ◽

Buried Pipe ◽

Recycled Asphalt ◽

Empirical Parameter ◽

Backfill Material ◽

Constrained Modulus ◽

Natural Aggregates

Buried pipe design requires knowledge about the fill to design the backfill structure. The interaction between the backfill envelope and the pipe impacts the structural performance of the buried pipe. The backfill material and compaction level respond to the backfill’s overall strength and, therefore, for pipe-soil interaction. The strength of backfill material is described in terms of modulus of soil reaction E’ and constrained modulus Eode. As the E’ is an empirical parameter, the Eode can be measured in the laboratory by performing the oedometer tests. In this study, we have performed extensive oedometric tests on five types of anthropogenic materials (AM). Three of them are construction and demolition materials (C–D materials) namely, recycled concrete aggregate (RCA), crushed brick (CB), and recycled asphalt pavement (RAP). Two of them are industrial solid wastes (ISW) namely, fly ash and bottom slag mix (FA + BS) and blast furnace slag (BFS). The results of the tests revealed that AM behaves differently from natural aggregates (NA). In general, the Eode value for AM is lower than for NA with the same gradation. Despite that, some of AM may be used as NA substitute directly (RCA or BFS), some with special treatment like CB and some with extra compaction efforts like RAP or FA + BS.

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Effect of Differentiated Nitrogen Fertilization on the Enzymatic Activity of the Soil for Sweet Potato (Ipomoea batatas L. [Lam.]) Cultivation

Agronomy ◽

10.3390/agronomy10121970 ◽

2020 ◽

Vol 10 (12) ◽

pp. 1970

Author(s):

Barbara Sawicka ◽

Barbara Krochmal-Marczak ◽

Piotr Pszczółkowski ◽

Elżbieta Jolanta Bielińska ◽

Anna Wójcikowska-Kapusta ◽

...

Keyword(s):

Enzymatic Activity ◽

Total Nitrogen ◽

Nitrogen Fertilization ◽

Ipomoea Batatas ◽

Polynomial Regression ◽

Sandy Loam ◽

C:N Ratio ◽

Soil Reaction ◽

Research Station ◽

Fourth Degree

The experiment was conducted between 2015–2017 in the Research Station for Cultivar Testing in Uhnin (51°34′ N, 23°02′ E), in Luvisols developed from sandy loam soils. Soil samples for the tests of enzymatic activity were collected after the crop was harvested. The measurements included: the content of dehydrogenases, phosphatases, urease and protease, as well as total organic carbon, total nitrogen and mineral nitrogen in soil, based on standard methods. The research results point to changes in the enzymatic activity of light soil under the influence of varied nitrogen fertilization. In objects fertilized with this ingredient, the activity of the analysed enzymes was significantly higher than in the control soil, except for combinations fertilised with 150 kg ha−1 N characterised by the highest accumulation of N-NO3− in soil. The activity of dehydrogenases, phosphatases and urease changed as the nitrogen dose increased. The polynomial regression analysis enabled a better understanding of those dependences. In the case of dehydrogenases, phosphatases and urease, a third-degree curvilinear relation of enzymatic activity to nitrogen fertilisation was observed (a fourth-degree relation was found, with a coefficient R2 in those equations amounting to =0.958, 0.977, 0.979, respectively) and in the case of protease activity, a fourth-degree relation, with coefficient R2 = 0.989. However, soil acidity did not have a significant influence on either the enzymatic activity or physico-chemical characteristics of soil under the cultivation of sweet potatoes. The C:N ratio turned out to be significantly negatively related to the content of the enzymes dehydrogenase (Adh), phosphatase (AF), urease (AU) and protease (AP) as well as the content of total nitrogen, especially its ammonium form (N-NH4). The obtained results indicate the usefulness of research on enzymatic activity as an indicator of soil reaction to nitrogen fertilization and will enable maintenance of the optimal biological balance of cultivated soils.

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Dynamic analysis of an offshore structure on an elastic-plastic foundation-soil system

Computers and Geotechnics ◽

10.1016/0266-352x(86)90007-8 ◽

1986 ◽

Vol 2 (2) ◽

pp. 101-123

Author(s):

J.G.A. Munro ◽

C.J. Cudworth ◽

A.A. Rodger

Keyword(s):

Dynamic Analysis ◽

Offshore Structure ◽

Foundation Soil ◽

Soil System ◽

Elastic Plastic

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A Parametric Study of Low-Frequency Damping of Mooring System

Volume 8A: Ocean Engineering ◽

10.1115/omae2014-23391 ◽

2014 ◽

Author(s):

Minglu Chen ◽

Shan Huang ◽

Nigel Baltrop ◽

Ji Chunyan ◽

Liangbi Li

Keyword(s):

Low Frequency ◽

Structure Design ◽

The Body ◽

Body Motion ◽

Mooring Line ◽

Offshore Structure ◽

Frequency Oscillation ◽

Low Frequency Oscillation ◽

Line System ◽

Irregular Wave

Mooring line damping plays an important role to the body motion of moored floating platforms. Meanwhile, it can also make contributions to optimize the mooring line system. Accurate assessment of mooring line damping is thus an essential issue for offshore structure design. However, it is difficult to determine the mooring line damping based on theoretical methods. This study considers the parameters which have impact on mooring-induced damping. In the paper, applying Morison formula to calculate the drag and initial force on the mooring line, its dynamic response is computed in the time domain. The energy dissipation of the mooring line due to the viscosity was used to calculate mooring-induced damping. A mooring line is performed with low-frequency oscillation only, the low-frequency oscillation superimposed with regular and irregular wave-frequency motions. In addition, the influences of current velocity, mooring line pretension and different water depths are taken into account.

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A New Spectral Method for Modeling Dynamic Ice Actions

23rd International Conference on Offshore Mechanics and Arctic Engineering, Volume 3 ◽

10.1115/omae2004-51360 ◽

2004 ◽

Author(s):

Tuomo Ka¨rna¨ ◽

Yan Qu ◽

Walter L. Ku¨hnlein

Keyword(s):

Dynamic Response ◽

Spectral Density ◽

Time Correlation ◽

General Purpose ◽

Density Functions ◽

Offshore Structure ◽

Spectral Density Functions ◽

Ice Force ◽

Ice Forces ◽

Scale Data

This paper presents a method of evaluating the response of a vertical offshore structure that is subjected to dynamic ice actions. The model concerns a loading scenario where a uniform ice sheet is drifting and crushing against the structure. Full scale data obtained at the lighthouse Norstro¨msgrund is used in the derivation of a method that applies both to narrow and wide structures. A large amount of events with directly measured local forces was used to derive formulas for spectral density functions of the ice force. A non-dimensional formula that was derived for the autospectrum applies for all ice thicknesses. Coherence functions are used to define the cross-spectra of the local ice forces. The two kind of spectral density functions for local forces can be used to evaluate the spectral density of the total ice force. The method takes account of both the spatial and time correlation between the local forces. Accordingly, the model provides a tool to consider the non-simultaneous characteristics of the local ice pressures while assessing the total ice force. The model can be used in conjunction with general purpose FE programs to evaluate the dynamic response of an offshore structure.

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