On the Influence of the Grain Size Distribution Curve on Dynamic Properties of Quartz Sand

The paper reports on our effort to extend the well-known Hardin\u27s equation by the influence of the grain size distribution curve. The study is motivated by the fact that Hardin\u27s equation with its commonly used constants can significantly over-estimate the small strain shear modulus Gmax of well-graded sands. Approximately 350 resonant column (RC) tests with additional P-wave measurements have been performed on 33 specially mixed grain size distribution curves of a quartz sand with different mean grain sizes d50, coefficients of uniformity Cu = d60/d10 and fines contents FC. The experiments show that for constant values of void ratio and pressure, the shear modulus Gmax and the small-strain constrained elastic modulus Mmax are independent of the mean grain size, but strongly decrease with increasing coefficient of uniformity. A fines content further reduces the small-strain stiffness. In order to improve the estimation of Gmax and Mmax, the parameters of Hardin\u27s equation have been correlated with Cu and FC. A correlation of Gmax and Mmax with relative density Dr is less accurate. For a certain shear strain amplitude γ, the modulus degradation factor G(γ)/Gmax is smaller for higher Cu-values but does not depend on the fines content. An extension of an empirical formula for the modulus degradation factor is presented

Complex High‐Cyclic Loading in an Accumulation Model for Sand

Experimental evidence indicates that multidimensional cyclic loading of soils causes larger accumulation of deformations than equivalent one-dimensional loading. The response of sand to high-cyclic loading with 10,000 cycles and up to four-dimensional stress paths (i.e., four independent oscillating components) is examined in 120 triaxial and hollow cylinder tests in this work to extend these findings. With increasing number of oscillating stress components, the accumulation of permanent strains tends to increase. It is demonstrated that the definition of the multidimensional strain amplitude incorporated in the high-cycle accumulation (HCA) model can account for this. The validation of the HCA model for complex cyclic loading is complemented by the simulation of model tests on monopile foundations of offshore wind turbines subjected to multidirectional cyclic loading, for which the consideration of spatially variable cyclic loading with nonconstant load amplitudes in the HCA model is discussed. For this purpose, an extension of the HCA model considering multiple strain amplitudes is presented

Complex High‐Cyclic Loading in an Accumulation Model for Sand

Experimental evidence indicates that multidimensional cyclic loading of soils causes larger accumulation of deformations than equivalent one‐dimensional loading. The response of sand to high‐cyclic loading with 10,000 cycles and up to four‐dimensional stress paths (i.e., four independent oscillating components) is examined in 120 triaxial and hollow cylinder tests in this work to extend these findings. With increasing number of oscillating stress components, the accumulation of permanent strains tends to increase. It is demonstrated that the definition of the multidimensional strain amplitude incorporated in the high‐cycle accumulation (HCA) model can account for this. The validation of the HCA model for complex cyclic loading is complemented by the simulation of model tests on monopile foundations of offshore wind turbines subjected to multidirectional cyclic loading, for which the consideration of spatially variable cyclic loading with nonconstant load amplitudes in the HCA model is discussed. For this purpose, an extension of the HCA model considering multiple strain amplitudes is presented

Residual deformations due to long-time cyclic loading with two dimensional strain loops

A cyclic loading with multidimensional strain loops in the soil may be caused by traffic loading, by wind and wave loading (e.g. offshore wind turbines) or by earthquake shaking. The present paper focuses on the accumulation of permanent deformations due to a high-cyclic loading, that means a loading with many cycles of small to intermediate strain amplitudes. Two different strategies for the consideration of multidimensional strain loops in a high-cycle accumulation model are presented. Experimental evidence for the first strategy is provided. However, it is suitable for convex strain loops only. The second strategy can handle also non-convex strain loops, but has not been confirmed experimentally yet. The paper discusses suitable experiments for such prove and documents some preliminary test series

Conspicuous Consumption in the emergent VanLife Community

As the worth of experiential consumption increases, so does the importance of experiential conspicuous consumption. Traveling is an outstanding example for experiential consumption, which resulted in increased research interest in travel as means of conspicuous consumption. The emergent VanLife community is a prime example of experiential consumption, but to this date no connection to conspicuous consumption has been made. This paper explores the underlying motivations for choosing VanLife as a vacation mode and possible connections to conspicuous consumption. For this purpose, a qualitative study was conducted. While the participants could not be directly linked to conspicuous consumption, indirect evidence of conspicuous consumption in the broader VanLife community could be found

Stress- and Strain-Controlled Undrained Cyclic Triaxial Tests on a Fine Sand for a High-Cycle Accumulation Model

The paper presents a discussion of the isotropic elastic stiffness E in the high-cycle accumulation (HCA) model proposed by Niemunis et al. (2005). The model may be used to predict permanent deformations or excess pore water pressures in non-cohesive soils due to cyclic loading. The stress-dependent bulk modulus K was determined from pairs of drained and undrained cyclic triaxial tests on a fine sand with constant stress amplitude and with similar initial conditions. K was found in good agreement with an earlier study on a medium coarse sand where a correction for membrane penetration effects had to be applied. Undrained cyclic triaxial tests with constant strain amplitude commenced at an anisotropic initial effective stress were performed for Poisson’s ratio ν. It is demonstrated that ν does not depend on amplitude, density and initial pressure. Its increase with the initial stress ratio may be disregarded for practical purposes

Soil-structure interaction: A state-of-the-art review of modeling techniques and studies on seismic response of building structures

The present article aims to provide an overview of the consequences of dynamic soil-structure interaction (SSI) on building structures and the available modelling techniques to resolve SSI problems. The role of SSI has been traditionally considered beneficial to the response of structures. However, contemporary studies and evidence from past earthquakes showed detrimental effects of SSI in certain conditions. An overview of the related investigations and findings is presented and discussed in this article. Additionally, the main approaches to evaluate seismic soil-structure interaction problems with the commonly used modelling techniques and computational methods are highlighted. The strength, limitations, and application cases of each model are also discussed and compared. Moreover, the role of SSI in various design codes and global guidelines is summarized. Finally, the advancements and recent findings on the SSI effects on the seismic response of buildings with different structural systems and foundation types are presented. In addition, with the aim of helping new researchers to improve previous findings, the research gaps and future research tendencies in the SSI field are pointed out

Schlussbericht zum WIR!-Plant³ Projekt

In Paludikultur können unterschiedlichste Rohstoffe hergestellt werden. Das Spektrum geht von Wasserbüffelfleisch für die menschliche Ernährung, über Wirkstoffe gegen Husten bis hin zu Baustoffen (Dachreet oder Dämmplatten) und Energieträger. Es ist davon auszugehen, dass aus klimapoiltischer Sicht in Deutschland hunderttausende Hektar Moore wiedervernässt und ggfs. in Paludikultur gebracht werden, mit dem Ergebnis, dass zunehmend Produkte aus Paludikultur auf den Markt kommen. Die Zertifizierung von Produkten ist ein probates Mittel, diesen Produkten eine Qualität zu bescheinigen, die sie von konventionellen vergleichbaren Produkten abhebt. Ziel der vorliegenden Arbeit ist herauszuarbeiten, wie dies durch eine Zertifizierung von Produkten aus der nassen Moorbewirtschaftung anhand der auf der Erntefläche bereitgestellten Ökosystemleistungen realisiert werden kann. Beispielhaft werden für zwei Untersuchungsgebiete Einsparmöglichkeiten für Treibhausgasemissionen durch Wiedervernässung und Umstellung auf Paludikultur vorgestellt, Umfangreiche Literaturstudien und die Ergebnisse aus drei Workshops wurden herangezogen, um die Grundlagen für eine solche Zertifizierung zu erarbeiten. Entsprechende Vorschläge zum Aufbau eines Zertifizierungssystems für Paludikultur werden vorgestellt und die Bedingungen diskutiert, die bei Paludikulturen im nassen Moor bei der Bewirtschaftung eingehalten werden müssen. Ein Paludikultur-Standard wurde entwickelt und mit entsprechenden Kriterien untersetzt, die mittels verifizierbarer Indikatoren abgeprüft werden können. In einem nächsten Schritt sollte dann die konkrete Umsetzung eines entsprechenden Zertifikats festgelegt werden.Paludiculture can deliver a wide variety of raw materials. The spectrum ranges from water buffalo meat for human consumption, to active ingredients against coughs, to building materials (roof thatch or insulation boards) and energy sources. From a climate perspective, hundreds of thousands of hectares of peatland in Germany will be rewetted and, if necessary, brought into paludiculture, with the result that more and more products based on paludiculture will come onto the market. Product certification is an effective means of certifying the quality of these products, setting them apart from comparable conventional products. The aim of this study is to work out how this can be achieved by certifying products from wet peatland management on the basis of the ecosystem services provided on the harvested area. As an example, potential savings in greenhouse gas emissions through rewetting and conversion to paludiculture are presented for two study sites. Extensive literature studies and the results of three workshops are used to develop the basis for such certification. Corresponding proposals for the development of a certification system for paludiculture are presented and the conditions that must be met for paludiculture in wet peatlands are discussed. A paludiculture standard was developed and underpinned with corresponding criteria that can be checked using verifiable indicators. The next step would be to define the specific implementation of a corresponding certificat