scholarly journals Boulder Pickup by Tsunami Surge

2019 ◽  
Vol 13 (05n06) ◽  
pp. 1941006
Author(s):  
Samuel Harry ◽  
Margaret Exton ◽  
Harry Yeh
Keyword(s):  
Pore Water Pressure ◽  
Initial Conditions ◽  
Scale Effects ◽  
Traditional Approach ◽  
Water Pressure ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Flow Conditions ◽  
The Difference ◽  
The Impact

Study of boulder transport by tsunamis is challenging because boulder size, shape, and composition vary greatly; furthermore, flow conditions, topography, and initial conditions are generally unknown. To investigate the mechanism of boulder pickup, experiments of tsunami-like flow past spherical boulders partially buried in a sediment bed are conducted. The experiments are performed in a large centrifuge facility to reduce scale effects and the corresponding dynamic similitude is discussed. The traditional approach to determine boulder pickup is adapted for the case of a half-buried spherical boulder. The adapted model predicts that the boulders are transported, but does not accurately predict the timing of pick up. To investigate the difference in pickup timing, two physical phenomena are discussed: pore-water-pressure dissipation in the soil, and the impact of the free-surface flow on hydrodynamic forces. For a spherical shaped boulder, vertical forces (i.e. buoyant and lift forces) are critical for the initiation of boulder pickup. It was found that spherical boulders that are three-quarter buried in the soil are not transported, even when exposed to flow conditions that would otherwise predict transport.

scholarly journals Impact of the moisture content in medium sands on CPTU test results

2016 ◽  
Vol 48 (3) ◽  
pp. 221-231 ◽  
Author(s):  
Łukasz Zawadzki ◽  
Marek Bajda
Keyword(s):  
Moisture Content ◽  
Unsaturated Soils ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Degree Of Saturation ◽  
Test Results ◽  
Time Dynamic ◽  
Tip Resistance ◽  
The Impact ◽  
Resistance Value

Abstract Soils occurring in the soil “active zone” are in contact with the surface and are directly influenced by external factors (mainly climatic changes) that cause variation in their parameters over time. Dynamic and uncontrolled changes of soil properties e.g. due to rainfall and evapotranspiration processes may affect field test results leading to the misinterpretation of the obtained data. This paper presents investigations on the influence of moisture content changes in sandy soils on CPTU results. For this purpose, a field ground model has been constructed and five CPTU tests with a different moisture content of soil were carried out. During the investigations, the tip resistance (qc), friction on sleeve (fs), and pore water pressure (u2) were measured. Moreover, a TDR probe was applied to determine the distribution of the moisture content in the studied soil columns. Differences between CPT results obtained in saturated and unsaturated soils have been shown. Furthermore, a simple equation to correct the tip resistance value due to the impact of the degree of saturation has been proposed.

Flotation and free surface flow in a model for subglacial drainage. Part 1. Distributed drainage

2012 ◽  
Vol 702 ◽  
pp. 126-156 ◽  
Author(s):  
Christian Schoof ◽  
Ian J. Hewitt ◽  
Mauro A. Werder
Keyword(s):  
Water Pressure ◽  
Computing Time ◽  
Potential Gradient ◽  
Coupled System ◽  
Free Surface Flow ◽  
Travelling Wave ◽  
Surface Flow ◽  
Squeeze Film ◽  
Effective Pressure ◽  
Water Drainage

AbstractWe present a continuum model for melt water drainage through a spatially distributed system of connected subglacial cavities, and consider in this context the complications introduced when effective pressure or water pressure drops to zero. Instead of unphysically allowing water pressure to become negative, we model the formation of a partially vapour- or air-filled space between ice and bed. Likewise, instead of allowing sustained negative effective pressures, we allow ice to separate from the bed at zero effective pressure. The resulting model is a free boundary problem in which an elliptic obstacle problem determines hydraulic potential, and therefore also determines regions of zero effective pressure and zero water pressure. This is coupled with a transport problem for stored water, and the coupled system bears some similarities with Hele-Shaw and squeeze-film models. We present a numerical method for computing time-dependent solutions, and find close agreement with semi-analytical travelling wave and steady-state solutions. As may be expected, we find that ice–bed separation is favoured by high fluxes and low ice surface slopes and low bed slopes, while partially filled cavities are favoured by low fluxes and high slopes. At the boundaries of regions with zero water or effective pressure, discontinuities in water level are frequently present, either in the form of propagating shocks or as stationary hydraulic jumps accompanied by discontinuities in potential gradient.

True Shear Parameters of Saturated Clays

1973 ◽  
Vol 10 (4) ◽  
pp. 652-663
Author(s):  
A. Sridharan ◽  
S. Narasimha Rao
Keyword(s):  
Stress Level ◽  
Pore Water Pressure ◽  
Initial Conditions ◽  
Water Pressure ◽  
Triaxial Compression ◽  
Compression Tests ◽  
Strength Parameters ◽  
Test Procedures ◽  
Stress History ◽  
Triaxial Compression Tests

Ever since Hvorslev proposed a failure criterion incorporating intrinsic parameters, several test procedures have come into practice to determine these ‘true’ strength parameters. Several consolidated undrained triaxial compression tests with pore water pressure measurement were conducted on both montmorillonite and kaolinite clays and the results were analyzed using different existing methods. All the methods through which the data were analyzed fail to assign any unique true strength parameters. Even a particular method yields different values depending upon the initial conditions (stress history, water content) of the sample and stress level during testing. It has been reasoned that these variations are due to the probable differences in fabric between the samples which are involved in various methods. There seems to be a unique linear relationship between tan [Formula: see text] and Cc/pe irrespective of the sample state, stress level, and stress history in both undisturbed and remolded conditions for all the procedures adopted.

scholarly journals Numerical simulation of 2D hydrodynamic impact of wedge and ship section at variable velocity

2013 ◽  
Vol 10 (1) ◽  
pp. 49-58 ◽  
Author(s):  
Md. Mashiur Rahaman ◽  
Hiromichi Akimoto ◽  
Md. Ashim Ali
Keyword(s):  
Impact Load ◽  
Time History ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Variable Velocity ◽  
History Of ◽  
Volume Method ◽  
The Impact ◽  
Simulated Time ◽  
Simulated Flow

A commercial CFD code Fluent 6.3® is used to simulate non-linear free surface flow and compute the impact load during variable velocity water entry of 2D wedge and ship section. The code uses the finite volume method to solve the conservation of mass and momentum equations to obtain simulated flow field. The interface between water and air was modeled using volume of fluid (VOF) method. Wedge section with 30 degree dead-rise angle and a ship section are numerically simulated. Time history of impact force and pressures at distinct locations are predicted; and compared with existing experimental results and other numerical methods. Present numerical results compare well with experimental measurements.DOI: http://dx.doi.org/10.3329/jname.v10i1.14383

The importance of accounting vegetation on unsaturated slopes prone to rainfall-induced instabilities – a case study in Norway

2021 ◽  
Author(s):  
Luca Piciullo ◽  
Vittoria Capobianco ◽  
Håkon Heyerdahl
Keyword(s):  
Slope Stability ◽  
Pore Water Pressure ◽  
Initial Conditions ◽  
Water Pressure ◽  
Railway Track ◽  
Climate Conditions ◽  
Birch Trees ◽  
Transient Seepage ◽  
Pressure Regime ◽  
Steep Slopes

<p>In unsaturated steep slopes, the upper unsaturated zone may have a crucial role in the slope stability. In this work we studied a natural slope located adjacent to a railway track in Eastern Norway. Due to its steep inclination, the factor of safety should be always kept under observation. In addition, the climate in Norway is expected to become wetter and warmer, with increased snow melting. Thus the rainfall/snowmelt infiltration play an important role and needs to be monitored properly to avoid any failure. The slope is instrumented since 2016 and both volumetric water content (VWC) and the pore water pressure regime are monitored.</p><p>The modulus SEEP/W of the commercial software GeoStudio (GEO-SLOPE International, Ltd.) was used to model the transient seepage conditions of the slope for a 7-month monitoring period (from June 2019 to December 2019). Several analyses were carried out by changing the initial conditions and the boundary climate conditions of the slope. Regarding the initial conditions, two series of simulations were carried out, one with an initial calibration of the VWC distribution, another one without calibration, hence, by only locating the ground water table at a specific depth and by indicating the maximum negative head (as required by the model). The calibration, instead, consisted in starting the simulation considering a VWC distribution as closer as possible to the in-situ value.</p><p>For each series, a total of three simulations were carried out with different boundary climate conditions, respectively considering only rainfall/snowmelt (R), considering both rainfall/snowmelt and evaporation (Cl), and considering rainfall/snowmelt and evapotranspiration due to vegetation (V). Indeed, the slope is all covered by relatively dense vegetation, with shrubs and birch trees. For the simulations including evaporation and vegetation (Cl and V), the land-climate interaction boundary condition was adopted. Climate functions, such as the pairs temperature-time, relative humidity-time, wind speed-time, were obtained from a close meteorological station. The evaporation was determined by using the Penman-Monteith equation, including vegetation features in the case of vegetated slope. Preliminary results show that the initial calibration is important for the correct back-analyses of the measured data, and that the model is more accurate when accounting for climate boundary conditions and vegetation, which influence also the slope stability conditions.</p><div>The work has been part of the working package "Landslide triggered by hydro-meteorological processes" within the Center for Research-based Innovation (CRI) programme KLIMA2050 (), financed by the Research Council of Norway.</div>

Reinforcement Effect Analysis of Dynamic Drainage Consolidation Based on Finn Constitutive Law

2012 ◽  
Vol 170-173 ◽  
pp. 2390-2394
Author(s):  
Gui Hua Yang ◽  
Wei Yu ◽  
Huai Qi Li
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Constitutive Law ◽  
Effect Analysis ◽  
Engineering Construction ◽  
Drainage Channels ◽  
Speed Up ◽  
Effective Drainage ◽  
The Impact

In coastal areas, soft soil treatment is the challenge which must be faced in process of engineering construction. Among numerous treatment methods, dynamic drainage consolidation method is a new and effective method. In this paper, The Finn constitutive law reflecting dynamic pore pressure has been applied to dynamic drainage consolidation analysis. The results show pore water pressure behaves a pulse response proces for the impact, vertical drainage systerm increase the effective drainage channels, speed up the drainage process.

scholarly journals Influence of Rainfall Intensity on the Stability of Unsaturated Soil Slope: Case Study of R523 Road in Thulamela Municipality, Limpopo Province, South Africa

2020 ◽  
Vol 10 (24) ◽  
pp. 8824
Author(s):  
Fhatuwani Sengani ◽  
François Mulenga
Keyword(s):  
Slope Failure ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Extreme Rainfall ◽  
Limpopo Province ◽  
Slope Instability ◽  
Soil Slope ◽  
Numerical Software ◽  
The Impact

The purpose of this paper was to analyze the impact of extreme rainfall on the recurrence of slope instability using the Thulamela Municipality roads (R523) as a case study. To this end, the historical rainfall data of the area of study were analyzed between 1988 and 2018. The results show that a significant increase in rainfall is usually experienced in the summer months of December and January. Following this, the factor of safety (FoS) of slopes of silt clay, clay, and clay loam soils were estimated using the SLIDE simulator (Numerical software “Finite Element Method (FEM)”) under sunny to rainy conditions of the area. A complementary model, FLACSlope (Numerical software “Finite Difference Method (FDM)”), was utilized to simulate FoS and pore water pressure in sunny and rainy conditions of the area. Simulation results show that extreme rainfall has the ability to reduce the shear strength and resistance of the soil slope material. This may explain the recurrent landslides noted in the area. Finally, the water pore pressure has been simulated to increase with the increased water table, which generally pushes the soil particles apart and reduces the stress between the particles resulting in soil slope failure. Extreme rainfall alters the phase of the material solid in a manner that may require further research for a better understanding.

scholarly journals One-dimensional simulation of fire injection heights in contrasted meteorological scenarios with PRM and Meso-NH models

2013 ◽  
Vol 6 (1) ◽  
pp. 721-790 ◽  
Author(s):  
S. Strada ◽  
S. R. Freitas ◽  
C. Mari ◽  
K. M. Longo ◽  
R. Paugam
Keyword(s):  
Boundary Layer ◽  
Initial Conditions ◽  
Eddy Diffusivity ◽  
Radiosonde Data ◽  
Convective Boundary ◽  
Meteorological Model ◽  
Physically Based ◽  
The Mediterranean ◽  
The Difference ◽  
The Impact

Abstract. Wild-fires release huge amounts of aerosol and hazardous trace gases in the atmosphere. The residence time and the dispersion of fire pollutants in the atmosphere can range from hours to days and from local to continental scales. These various scenarios highly depend on the injection height of smoke plumes. The altitude at which fire products are injected in the atmosphere is controlled by fire characteristics and meteorological conditions. Injection height however is still poorly accounted in chemistry transport models for which fires are sub-grid scale processes which need to be parametrised. Only recently, physically-based approaches for estimating the fire injection heights have been developed which consider both the convective updrafts induced by the release of fire sensible heat and the impact of background meteorological environment on the fire convection dynamics. In this work, two different models are used to simulate fire injection heights in contrasted meteorological scenarios: a Mediterranean arson fire and two Amazonian deforestation fires. A Eddy-Diffusivity/Mass-Flux approach, formerly developed to reproduce convective boundary layer in the non-hydrostatic meteorological model Meso-NH, is compared to the 1-D Plume Rise Model. For both models, radiosonde data and re-analyses from the European Center for Medium-Range Weather Forecasts (ECMWF) have been used as initial conditions to explore the sensitivity of the models responses to different meteorological forcings. The two models predict injection heights for the Mediterranean fire between 1.7 and 3.3 km with the Meso-NH/EDMF model systematically higher than the 1-D PRM model. Both models show a limited sensitivity to the meteorological forcings with a 20–30% difference in the injection height between radiosondes and ECMWF data for this case. Injection heights calculated for the two Amazonian fires ranges from 5 to 6.5 km for the 1-D PRM model and from 2 to 4 km for the Meso-NH/EDMF model. The difference of smoke plume heights between the two models can reach 3–4 km. A large difference is obtained for the windy-wet Amazonian fire by the 1-D PRM model with a injection height 1.5 km higher when ECMWF re-analyses are used compared to the run with the radiosonde forcing. For the Mediterranean case, both models forecast a plume injection height above the boundary layer, although there are evidences that this particular fire propagated near the surface, highlighting the current limitations of the two approaches.

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