scholarly journals Effects of an impermeable layer on pore pressure response to tsunami-like inundation

2022 ◽  
Vol 478 (2257) ◽  
Author(s):  
Margaret Exton ◽  
Harry Yeh
Keyword(s):  
Pore Pressure ◽  
The Body ◽  
Excess Pore Pressure ◽  
Pressure Gradients ◽  
Tsunami Inundation ◽  
Building Foundation ◽  
Soil Stress ◽  
Impermeable Layer ◽  
Pore Pressure Response ◽  
Soil Instability

Tsunami hazards have been observed to cause soil instability resulting in substantial damage to coastal infrastructure. Studying this problem is difficult owing to tsunamis’ transient, non-uniform and large loading characteristics. To create realistic tsunami conditions in a laboratory environment, we control the body force using a centrifuge facility. With an apparatus specifically designed to mimic tsunami inundation in a scaled-down model, we examine the effects of an embedded impermeable layer on soil instability: the impermeable layer represents a man-made pavement, a building foundation, a clay layer and alike. The results reveal that the effective vertical soil stress is substantially reduced at the underside of the impermeable layer. During the sudden runup flow, this instability is caused by a combination of temporal dislocation of soil grains and an increase in pore pressure under the impermeable layer. The instability during the drawdown phase is caused by the development of excess pore-pressure gradients, and the presence of the impermeable layer substantially enhances the pressure gradients leading to greater soil instability. The laboratory results demonstrate that the presence of an impermeable layer plays an important role in weakening the soil resistance under tsunami-like rapid runup and drawdown processes.

scholarly journals TEMPERATURE VARIATIONS IN MIXED-SAND-GRAVEL SEDIMENTS AT A STEEP, MEGA-TIDAL BEACH

2018 ◽  
pp. 59
Author(s):  
Arash Tavakoli ◽  
Nina Stark ◽  
Alex E. Hay
Keyword(s):  
Pore Pressure ◽  
Pore Space ◽  
Beach Erosion ◽  
Excess Pore Pressure ◽  
Pressure Gradients ◽  
Soil Matrix ◽  
Temperature Variations ◽  
Excess Pore Pressures ◽  
The Impact ◽  
Excess Pore

The increasing urbanization of coastal regions makes beach erosion and coastline protection an important field of research (Elko et al., 2014). Excess pore pressures and pore pressure gradients in the soil matrix can impact sediment mobilization and erosion in terms of liquefaction (Sumer, 2014). Despite previous studies, there are still unsolved questions regarding coastal liquefaction due to wave action. Particularly, the role of groundwater dynamics, the impact of wave breaking, sediment reorganization, and potential air content represent unsolved problems. Furthermore, open questions still exist regarding the interaction and roles of excess pore pressure built-up, vertical pressure gradients and horizontal pressure gradients (Foster et al., 2006; Yeh and Mason, 2014; Sumer, 2014; Stark, 2017). We hypothesize that temperature variations may reveal complementary information with regard to pore water fluid behavior, such as pore space saturation, groundwater flows, exfiltration and infiltration processes, and impact of wave forcing. The study presented here shows some preliminary data sets of combined pore pressure and temperature recordings.

scholarly journals Contribution of Pumping Action of Wave-Induced Pore-Pressure Response to Development of Fluid Mud Layer

2019 ◽  
Vol 7 (9) ◽  
pp. 317 ◽  
Author(s):  
Yang ◽  
Zhu ◽  
Liu ◽  
Sun ◽  
Ling ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Fine Particles ◽  
Pore Water Pressure ◽  
Theoretical Calculations ◽  
Water Pressure ◽  
Pressure Response ◽  
Excess Pore Pressure ◽  
Pore Pressure Response ◽  
Wave Induced ◽  
Excess Pore

To investigate the vertical migration response of fine sediments, the pore pressure response of the silty seabed under the action of waves was tested. Under the action of waves, there is an obvious pumping phenomenon in the sludge accumulated by pore pressure. The excess pore water pressure caused by the waves in the seabed is unevenly distributed with respect to depth and there is an extreme value of up to 1.19 kPa. The pressure affects the liquefaction properties of the sludge. According to instantaneous-liquefaction judgment, the liquefaction of surface soil occurs, but the soil is not completely liquefied. Using theoretical calculations, the vertical source supply of floating mud development was analyzed. The pumping effect of the wave-induced excess pore pressure manifests in two aspects, as follows: (1) The centralized migration of splitting channels, which is visible to the naked eye, and (2) the general migration of fine particles between particle gaps at the mesoscopic level, which accounts for up to 22.2% of the migration of fine particles.

Prediction of impending failure of embankments on soft ground

2003 ◽  
Vol 40 (1) ◽  
pp. 209-220 ◽  
Author(s):  
Gavan Hunter ◽  
Robin Fell
Keyword(s):  
Pore Pressure ◽  
Factor Of Safety ◽  
Ground Deformation ◽  
Lateral Displacement ◽  
Deformation Behaviour ◽  
Vertical Displacement ◽  
Pressure Response ◽  
Excess Pore Pressure ◽  
Soft Ground ◽  
Pore Pressure Response

The deformation behaviour and excess pore pressure response of 13 well-monitored embankments on soft ground that were constructed to failure have been analyzed. The analysis shows that by monitoring lateral displacement at the toe of the embankment and vertical displacement at the toe and about 5 m beyond the toe, the onset of impending failure of embankments on soft ground can be detected while the slope is at about 70–90% of the failure height. This equates to an actual factor of safety of around 1.25. Monitoring of borehole inclinometers at the toe of the embankment, cracking of the embankment, and the pore pressure response and deformation during pauses in construction can provide useful additional data for detection of an impending failure.Key words: embankment on soft ground, deformation, pore pressure, failure, factor of safety.

The Effect of Partial Drainage on Measurements by a Piezoball Penetrometer

2011 ◽  
Author(s):  
Hamed Mahmoodzadeh ◽  
Noel Boylan ◽  
Mark Randolph ◽  
Mark Cassidy
Keyword(s):  
Pore Pressure ◽  
Penetration Resistance ◽  
Strength Properties ◽  
Excess Pore Pressure ◽  
Soil Conditions ◽  
Pressure Transducers ◽  
Site Investigations ◽  
Pore Pressure Response ◽  
The University ◽  
Ball Penetrometers

Full-flow penetrometers such as the T-bar and ball are now widely used in offshore site investigations to measure penetration resistance and then infer the strength properties of the seabed. To provide additional data on flow properties of the soil and increase the number of parameters that can be obtained from these tests, ball penetrometers fitted with pore pressure transducers, known as piezoballs, are now being used. Depending on the soil characteristics and rate of penetration, the soil conditions during penetration may vary from undrained to fully drained. The drainage condition during penetration will influence both the measured penetration resistance and excess pore pressure response and therefore influence any parameters interpreted. This paper examines the effect of drainage condition on piezoball measurements during penetration in a muddy silt sample collected from offshore Australia. Tests were conducted in the beam centrifuge at the University of Western Australia using a miniature piezoball, with pore pressure measurement at the equator position. The effect of drainage condition was examined by conducting tests at various rates of penetration, ranging from undrained to fully drained conditions. Methods of interpreting the results of a partially drained penetration test in order to deduce the undrained penetration resistance are also discussed.

Pore-pressure response beneath a ring foundation on clay

1979 ◽  
Vol 16 (3) ◽  
pp. 551-566 ◽  
Author(s):  
K. Y. Lo ◽  
D. E. Becker
Keyword(s):  
Pore Pressure ◽  
Load Transfer ◽  
Earth Pressure ◽  
Pressure Response ◽  
Excess Pore Pressure ◽  
Coefficient Of Consolidation ◽  
Continuous Sampling ◽  
Total Settlement ◽  
Rate Of Dissipation ◽  
Pore Pressure Response

A 9 m diameter and 22 m high concrete silo with a ring footing was instrumented and its performance monitored. The instrumentation included 12 pressure cells, 7 piezometers, 9 settlement cells, and 12 settlement pins. Continuous sampling and vane testing, together with field determination of permeability and coefficient of earth pressure at rest, were also carried out.The subsoil conditions at the site consist of a 3 m crust overlying an 18 m thick soft to firm, slightly overconsolidated clay stratum, which is underlain by bedrock.This paper presents the results of field observation in general, with particular emphasis on the pore-pressure response. It was found that, in spite of the relatively low factor of safety against bearing capacity failure and the considerable load transfer, the maximum measured excess pore pressure amounts to only 40% of the measured applied stress at the silage–soil interface. Important dissipation of pore pressure during loading occurred. The postfilling rate of dissipation of pore pressure was also rapid, due to the high field value of the coefficient of consolidation. Consistently, the total settlement observed up to date was also small.An analysis of the results is carried out for the interpretation of the favourable performance. The implication to the design of similar foundations is also discussed.

Vibro-Stone Column Reinforcement Mechanism and Numerical Analysis

2012 ◽  
Vol 446-449 ◽  
pp. 1940-1943
Author(s):  
Yang Liu ◽  
Hong Xiang Yan
Keyword(s):  
Numerical Simulation ◽  
Numerical Analysis ◽  
Pore Pressure ◽  
Numerical Procedure ◽  
Numerical Results ◽  
Excess Pore Pressure ◽  
Stone Column ◽  
Reinforcement Mechanism ◽  
Consolidation Theory ◽  
Excess Pore

Numerical simulation of vibro-stone column is taken to simulate the installation of vibro-stone column. A relationship based on test is adopted to calculate the excess pore pressure induced by vibratory energy during the installation of vibro-stone column. A numerical procedure is developed based on the formula and Terzaghi-Renduric consolidation theory. Finally numerical results of composite stone column are compared single stone column.

scholarly journals How deep does sand deposits in the Alentejo basin (Gulf of Cadiz) reach? Evaluating slope stability from bottom-current activities through time

2020 ◽  
Author(s):  
Davide Mencaroni ◽  
Roger Urgeles ◽  
Jonathan Ford ◽  
Jaume Llopart ◽  
Cristina Sànchez Serra ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Sediment Supply ◽  
Excess Pore Pressure ◽  
Bottom Current ◽  
Gulf Of Cadiz ◽  
Strait Of Gibraltar ◽  
Gulf Of Cádiz ◽  
The Stability ◽  
Iberian Margin ◽  
Excess Pore

<p>Contourite deposits are generated by the interplay between deepwater bottom-currents, sediment supply and seafloor topography. The Gulf of Cadiz, in the Southwest Iberian margin, is a famous example of extensive contourite deposition driven by the Mediterranean Outflow Water (MOW), which exits the Strait of Gibraltar, flows northward following the coastline and distributes the sediments coming from the Guadalquivir and Guadiana rivers. The MOW and related contourite deposits affect the stability of the SW Iberian margin in several ways: on one hand it increases the sedimentation rate, favoring the development of excess pore pressure, while on the other hand, by depositing sand it allows pore water pressure to dissipate, potentially increasing the stability of the slope.</p><p>In the Gulf of Cadiz, grain size distribution of contourite deposits is influenced by the seafloor morphology, which splits the MOW in different branches, and by the alternation of glacial and interglacial periods that affected the MOW hydrodynamic regimes. Fine clay packages alternates with clean sand formations according to the capacity of transport of the bottom-current in a specific area. Generally speaking, coarser deposits are found in the areas of higher MOW flow energy, such as in the shallower part of the slope or in the area closer to the Strait of Gibraltar, while at higher water depths the sedimentation shifts to progressively finer grain sizes as the MOW gets weaker. Previous works show that at present-day the MOW flows at a maximum depth of 1400 m, while during glacial periods the bottom-current could have reached higher depths.</p><p>In this study we derived the different maximum depths at which the MOW flowed by analyzing the distribution of sands at different depths along the Alentejo basin slope, in the Northern sector of the Gulf of Cadiz.</p><p>Here we show how changes in sand distribution along slope, within the stratigraphic units deposited between the Neogene and the present day, are driven by glacial – interglacial period alternation that influenced the hydrodynamic regime of the MOW.</p><p>By deriving the depositional history of sand in the Alentejo basin, we are able to correlate directly the influence that climatic cycles had on the MOW activity. Furthermore, by interpreting new multi-channel seismic profiles we have been able to derive a detailed facies characterization of the uppermost part of the Gulf of Cadiz.</p><p>An accurate definition of sand distribution along slope plays an important role in evaluating the stability of the slope itself, e.g. to understand if the sediments may be subjected to excess pore pressure generation. As sand distribution is a direct function of the bottom-current transport capacity, the ultimate goal of this study is to understand how climate variations can affect the stability of submarine slope by depositing contourite-related sand.</p>

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