Design of a 720-mm Square Direct Shear Box and Investigation of the Impact of Boundary Conditions on Large-Scale Measured Strength

2020 ◽  
Vol 43 (6) ◽  
pp. 20190344
Author(s):  
Sandra Linero Molina ◽  
Leonie Bradfield ◽  
Stephen G. Fityus ◽  
John V. Simmons ◽  
Arcesio Lizcano
Keyword(s):  
Boundary Conditions ◽  
Large Scale ◽  
Direct Shear ◽  
Shear Box ◽  
The Impact ◽  
Measured Strength

Large Scale Laboratory Direct Shear Tests on Ice

1975 ◽  
Vol 12 (2) ◽  
pp. 169-178 ◽  
Author(s):  
W. D. Roggensack
Keyword(s):  
Large Scale ◽  
Stress Conditions ◽  
Direct Shear ◽  
Shear Tests ◽  
Principal Stresses ◽  
Lake Ice ◽  
Direct Shear Tests ◽  
Strength Determination ◽  
Crystal Diameter ◽  
Shear Box

This paper presents the results of a series of large scale direct shear tests performed on lake ice. Test specimens were oriented with the principal stresses acting in the plane of the ice sheet, approximately normal to the long axes of the columnar crystals. Sample dimensions were large in comparison with mean crystal diameter, reducing the possibility of deviations introduced by size effects. Although a number of assumptions are made concerning stress conditions at failure, results for uniform, artificially ‘seeded’ test pond ice indicate a failure mechanism that is frictional and consistent with triaxial test data reported elsewhere. Post-peak shear resulted in the formation of a distinct failure zone that also displayed a frictional response. The direct shear test described is robust and simple, does not require elaborate sample preparation, and may present an alternative method of strength determination for ice mechanics problems where the shear box configuration duplicates field stress conditions and constraints.

Hydrogeological simulation of sedimentary basin evolution during a glacial cycle

2021 ◽  
Author(s):  
Christian Silbermann
Keyword(s):  
Boundary Conditions ◽  
Large Scale ◽  
Sedimentary Basin ◽  
Long Term Evolution ◽  
Nuclear Waste Repository ◽  
Glacial Cycle ◽  
Thermal Problem ◽  
Term Evolution ◽  
The Impact

<p><strong>Co-authors: Francesco Parisio, Thomas Nagel</strong></p><p>Glaciation cycles affect the long-term evolution of geosystems by crustal deformation, ground freezing and thawing, as well as large-scale hydrogeological changes. In order to properly understand the present and future conditions of potential nuclear waste repository sites, we need to simulate the past history. <br>For this, a sedimentary basin is considered here as a large-scale hydrogeological benchmark study. The long-term evolution during one glacial cycle is simulated using the open-source multi-field finite element code <em>OpenGeoSys</em>. The impact of the glacial loading (weight and induced shear) is taken into account using appropriate time-dependent stress boundary conditions. As a preliminary study, the hydro-mechanically coupled problem and the thermal problem are considered separately. For comparison with a previously published study by Bense et al. (2008), the entire displacement field is prescribed and the groundwater evolution (hydraulic problem) is regarded. Then, the displacement is only prescribed by means of boundary conditions. The impact of different constitutive assumptions on the deformation and hydraulic behavior is analyzed. The thermal problem is used to simulate the evolution of frost bodies in the subsurface beneath and ahead of the glacier.</p><p>V. F. Bense and M. A. Person. Transient hydrodynamics within intercratonic sedimentary basins during glacial cycles. Journal of Geophysical Research,<br>113(F4):F04005, 10 2008.</p>

A Method to Control the Environmental Wind Profile in Idealized Simulations of Deep Convection with Surface Friction

2019 ◽  
Vol 147 (11) ◽  
pp. 3935-3954 ◽  
Author(s):  
Daniel T. Dawson II ◽  
Brett Roberts ◽  
Ming Xue
Keyword(s):  
Boundary Conditions ◽  
Large Scale ◽  
Wind Profile ◽  
Cloud Model ◽  
Lower Boundary ◽  
Surface Friction ◽  
Gradient Force ◽  
Pressure Gradient Force ◽  
Simple Method ◽  
The Impact

Abstract In idealized, horizontally homogeneous, cloud model simulations of convective storms, the action of surface friction can substantially modify the near-ground environmental wind profile over time owing to the lack of a large-scale pressure gradient force to balance the frictional force together with the Coriolis force. This situation is undesirable for many applications where the impact of an unchanging environmental low-level wind shear on the simulated storm behavior is the focus of investigation, as it introduces additional variability in the experiment and accordingly complicates interpretation of the results. Partly for this reason, many researchers have opted to perform simulations with free-slip lower boundary conditions, which with appropriate boundary conditions allows for more precise control of the large-scale environmental wind profile. Yet, some recent studies have advocated important roles of surface friction in storm dynamics. Here, a simple method is introduced to effectively maintain any chosen environmental wind profile in idealized storm simulations in the presence of surface friction and both resolved and subgrid-scale turbulent mixing. The method is demonstrated through comparisons of simulations of a tornadic supercell with and without surface friction and with or without invoking the new method. The method is compared with similar techniques in the literature and potential extensions and other applications are discussed.

scholarly journals Targets-specified grids-tailored sub-model approach for fast large-scale high-resolution 2D urban flood modelling

2020 ◽  
Author(s):  
Guohan Zhao ◽  
Thomas Balstrøm ◽  
Ole Mark ◽  
Marina B. Jensen
Keyword(s):  
High Resolution ◽  
Boundary Conditions ◽  
Real Time ◽  
Large Scale ◽  
Screening Method ◽  
Urban Flood ◽  
The Impact ◽  
Mean Square Errors ◽  
Impact Zones ◽  
Model Approach

Abstract. The accuracy of two-dimensional urban flood models (2D models) is improved when high-resolution Digital Elevation Models (DEMs) is used, but the entailed high spatial discretisation results in excessive computational expenses, thus prohibiting the use of 2D models in real-time forecasting at a large scale. This paper presents a sub-model approach to tailoring high-resolution 2D model grids according to specified targets, and thus such tailor-made sub-model yields fast processing without significant loss of accuracy. Among the numerous sinks detected from full-basin high-resolution DEMs, the computationally important ones are determined using a proposed Volume Ratio Sink Screening method. Also, the drainage basin is discretised into a collection of sub-impact zones according to those sinks' spatial configuration. When adding full-basin distributed static rainfall, the drainage basin's flow conditions are modelled as a 1D static flow by using a fast-inundation spreading algorithm. Next, sub-impact zones relevant to the targets' local inundation process can be identified by tracing the 1D flow continuity, and thus suggest the critical computational cells from the high-resolution model grids on the basis of the spatial intersection. In MIKE FLOOD's 2D simulations, those screened cells configure the reduced computational domains as well as the optimised boundary conditions, which ultimately enables the fast 2D prediction in the tailor-made sub-model. To validate the method, model experiments were designed to test the impact of the reduced computational domains and the optimised boundary conditions separately. Further, the general applicability and the robustness of the sub-model approach were evaluated by targeting at four focus areas representing different catchment terrain morphologies as well as different rainfall return periods of 1–100 years. The sub-model approach resulted in a 45–553 times faster processing with a 99 % reduction in the number of computational cells for all four cases; the predicted flood extents, depths and flow velocities showed only marginal discrepancies with Root Mean Square Errors (RMSE) below 1.5 cm. As such, this approach reduces the 2D models' computing expenses significantly, thus paving the way for large-scale high-resolution 2D real-time forecasting.

The Large-Scale Direct Shear Test on Gravel Soil with Different Water Content in Badong of Three Gorges Reservoir Region

2011 ◽  
Vol 243-249 ◽  
pp. 2035-2038 ◽  
Author(s):  
Le Hua Wang ◽  
Jia Cheng Wang ◽  
Jian Lin Li
Keyword(s):  
Water Content ◽  
Three Gorges Reservoir ◽  
Large Scale ◽  
Direct Shear Test ◽  
Shear Test ◽  
Direct Shear ◽  
Cut Slope ◽  
Three Gorges ◽  
Gravel Soil ◽  
The Impact

The high cut slope of reservoir-bank road and city buildings are mostly earth-rock mixture after excavation. The strength behavior of the gravelly soil is important for mechanism of landslide triggering and soil erosion in Badong high cut slope. With the impact of rainfall, the water content of gravel soil increases, and the water table changes, this eventually affects the mechanical properties of gravel soils. Taking high cut slope which formed in the course of relocation in Three Gorges Reservoir as its background, the paper selected the gravel soil of typical high cut slope in Badong new town; and through on-site survey, analysis of geological conditions, indoor large-scale direct shear test, combined with laboratory test results, it discussed the influence of high cut slope gravel soil shear strength parameters by different water content of sample. At the end of this paper, it draws some beneficial conclusions.

scholarly journals SCALE EFFECT ON THE SHEAR STRENGTH OF TWO-LAYER SOIL REINFORCED BY GEOGRID

2018 ◽  
Vol 30 (1) ◽  
Author(s):  
Sakine Tamassoki ◽  
Reza Z. Moayed ◽  
Mohammad Ashkani ◽  
Hamidreza Rahimi
Keyword(s):  
Shear Strength ◽  
Bearing Capacity ◽  
Scale Effect ◽  
Large Scale ◽  
Direct Shear ◽  
Shear Tests ◽  
Element Analysis ◽  
Direct Shear Tests ◽  
Granular Base ◽  
Shear Box

Geosynthetics are used to reinforce soils and improve their mechanical characteristics,especially when soft low-bearing capacity soils are encountered in civil engineering projects.Particularly, in roads, geosynthetics are placed between the interface of granular materials andsoft-soil sub grade to improve composite layers’ bearing capacity. This paper presents the resultsof the finite element analysis of the two-layer soil(granular base-clayey sub grade) reinforced bygeogrid and discusses the effect of the reinforcement on the shear strength. As the primary aim ofthe study, the numerical model was calibrated in comparison with the experimental results oflarge scale direct shear tests. The results showed that the shear strength improved in the two-layersoil which had been reinforced by geogrid. The predictions made by the developed model werefound to be in line with the experimental data obtained from large scale direct shear tests. Asanother aim of the study, different dimensions of shear box were used for modelling in order toinvestigate the scale effect on the shear strength of double-layered soil (clay-sand). The resultsshowed that the increase in the dimensions of the reinforced shear box leads to the enhancementof peak shear strength. Moreover, several analyses were conducted on geogrid in shear box withdifferent dimensions in fixed and unfixed states. The results demonstrated that the shear strengthof treated geogrid was higher than the shear strength of those in which untreated geogrid wasutilized.

scholarly journals Large Scale Direct Shear Box Tests on Gravels

Teknik Dergi ◽  
2020 ◽  
Author(s):  
Ali Anıl YUNATCI ◽  
Kemal Onder CETIN
Keyword(s):  
Large Scale ◽  
Direct Shear ◽  
Shear Box

Impact of COVID-19 on Nuclear Medicine in Germany, Austria and Switzerland: An International Survey in April 2020

2020 ◽  
Vol 59 (04) ◽  
pp. 294-299 ◽  
Author(s):  
Lutz S. Freudenberg ◽  
Ulf Dittmer ◽  
Ken Herrmann
Keyword(s):  
Nuclear Medicine ◽  
Health Systems ◽  
Personal Protective Equipment ◽  
Large Scale ◽  
Diagnostic Procedures ◽  
Protective Equipment ◽  
Current Crisis ◽  
Web Based ◽  
Public Versus Private ◽  
The Impact

Abstract Introduction Preparations of health systems to accommodate large number of severely ill COVID-19 patients in March/April 2020 has a significant impact on nuclear medicine departments. Materials and Methods A web-based questionnaire was designed to differentiate the impact of the pandemic on inpatient and outpatient nuclear medicine operations and on public versus private health systems, respectively. Questions were addressing the following issues: impact on nuclear medicine diagnostics and therapy, use of recommendations, personal protective equipment, and organizational adaptations. The survey was available for 6 days and closed on April 20, 2020. Results 113 complete responses were recorded. Nearly all participants (97 %) report a decline of nuclear medicine diagnostic procedures. The mean reduction in the last three weeks for PET/CT, scintigraphies of bone, myocardium, lung thyroid, sentinel lymph-node are –14.4 %, –47.2 %, –47.5 %, –40.7 %, –58.4 %, and –25.2 % respectively. Furthermore, 76 % of the participants report a reduction in therapies especially for benign thyroid disease (-41.8 %) and radiosynoviorthesis (–53.8 %) while tumor therapies remained mainly stable. 48 % of the participants report a shortage of personal protective equipment. Conclusions Nuclear medicine services are notably reduced 3 weeks after the SARS-CoV-2 pandemic reached Germany, Austria and Switzerland on a large scale. We must be aware that the current crisis will also have a significant economic impact on the healthcare system. As the survey cannot adapt to daily dynamic changes in priorities, it serves as a first snapshot requiring follow-up studies and comparisons with other countries and regions.

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