HHT Analysis on Pore Pressure Dissipation of Wave-Induced Fluidization in a Sandy Bed

Wave-induced pore pressure variations during the stage of increasing excess pore pressure consist of the mechanism of generation of fluidization. Moreover, in post-fluidization stage, pore pressure variations not only reveal the dissipation mechanism of fluidization but also the wave-fluidized bed interactions. Past results from a series of lab flume tests have further illustrated that pore pressure variations in a fluidized response are nonlinear and nonsataionary. Hence, the HHT method was further applied to analyze the pore pressure measurements in this study. The results demonstrate that after the dissipation of excess pore pressures the amplitudes of fundamental and higher-frequency components begin to decay. Meanwhile, the amplified amplitudes of fundamental and higher-frequency components during fluidization response would decrease with decreasing thickness of fluidized soil-layer in consecutive tests.

Consolidation of a soil layer subsequent to cessation of deposition

10.1139/t04-105 ◽

2005 ◽

Vol 42 (2) ◽

pp. 678-682

Author(s):

Guofu Zhu ◽

Jian-Hua Yin

Keyword(s):

Pore Pressure ◽

Soil Layer ◽

Average Degree ◽

Excess Pore Pressure ◽

Triangular Distribution ◽

Pressure Distributions ◽

Pore Pressures ◽

Degree Of Consolidation ◽

Excess Pore Pressures ◽

It is necessary in certain cases to estimate the progress of consolidation in a soil layer that has ceased increasing in thickness over time. In this paper, the existing excess pore pressures for two timethickness relations are used as the "initial" pore pressures for analysing the consolidation of soil subsequent to the cessation of deposition. Average degrees of consolidation of the soil layer are presented for one-way drainage and two-way drainage boundary conditions. The average degrees of consolidation are compared with those for uniform and triangular initial excess pore pressure distributions. It is found that the average degree of consolidation for one-way drainage boundaries can be estimated using the value for the triangular distribution. The average degree of consolidation for two-way drainage boundaries is bound by the averages for both the uniform and the triangular initial excess pore pressure distributions.Key words: consolidation, deposition, drainage, settlement, soil.

Experiment and Analysis of Submarine Landslide Model Caused by Elevated Pore Pressure

Journal of Marine Science and Engineering ◽

10.3390/jmse7050146 ◽

2019 ◽

Vol 7 (5) ◽

pp. 146 ◽

Cited By ~ 2

Author(s):

Tao Liu ◽

Yueyue Lu ◽

Lei Zhou ◽

Xiuqing Yang ◽

Lei Guo

Keyword(s):

Pore Pressure ◽

Soil Layer ◽

Initial Crack ◽

Excess Pore Pressure ◽

Deep Soil ◽

Hydrate Decomposition ◽

Dynamic Relationship ◽

Geological Conditions ◽

Shear Slip ◽

Hydrate decomposition is an important potential cause of marine geological disasters. It is of great significance to understand the dynamic relationship between hydrate reservoir system and the overlying seabed damage caused by its decomposition. The purpose of this study is to understand the instability and destruction mechanisms of a hydrated seabed using physical simulations and to discuss the effects of different geological conditions on seabed stability. By applying pressurized gas to the low permeability silt layer, the excess pore pressure caused by the decomposition of hydrate is simulated and the physical appearance process of the overlying seabed damage is monitored. According to the test results, two conclusions were drawn in this study: (1) Under the action of excess pore pressure caused by hydrate decomposition, typical phenomena of overlying seabed damage include pockmark deformation and shear–slip failure. In shallower or steeper strata, shear-slip failure occurs in the slope. The existence of initial crack in the stratum is the main trigger cause. In thicker formations or gentler slopes, the surface of the seabed has a collapse deformation feature. The occurrence of cracks in the deep soil layer is the main failure mechanism. (2) It was determined that the thickness and slope of the seabed, among other factors, affect the type and extent of seabed damage.

Experimental Study on the Distribution of Wave-Induced Excess Pore Pressure in a Sandy Seabed around a Mat Foundation

Journal of Marine Science and Engineering ◽

10.3390/jmse7090304 ◽

2019 ◽

Vol 7 (9) ◽

pp. 304

Author(s):

Yuan ◽

Liao ◽

Zhou

Keyword(s):

Pore Pressure ◽

Numerical Study ◽

Experimental Results ◽

Excess Pore Pressure ◽

Offshore Platforms ◽

Pressure Area ◽

Mat Foundation ◽

Mat Foundations ◽

Wave Induced ◽

Mat foundations are widely used in jack-up offshore platforms to support and transfer loads. Regarding mat foundations working on the seabed, the excess wave-induced pore pressure is critical to seabed stability, which may finally cause structural failure. Therefore, it is important to investigate the distribution of the excess pore pressure in the seabed around the mat foundation. In this study, experiments were performed to study the excess pore pressure distribution around a mat foundation in scale considering the true load state by recording wave profiles and pore pressures inside a sandy seabed. To guarantee the reliability of experiments, a numerical study was conducted and compared with the experimental results. Experimental results indicate that with the existence of the mat foundation, the excess pore pressure is higher at the region, the range of which is the width of the model mat (Wm) before the structure. The maximum pore pressure appears at 0.55 Wm in front of the center of the mat foundation. In addition, the current significantly increases the range of high pore pressure area and the amplitude of the excess pore pressure. As the mat orientation changes, the position of the maximum pore pressure changes from the front to the edge of the mat.

Re-mobilization of pile shaft friction after an earthquake

10.1139/cgj-2012-0261 ◽

2013 ◽

Vol 50 (9) ◽

pp. 979-988 ◽

Cited By ~ 4

Author(s):

M.E. Stringer ◽

S.P.G. Madabhushi

Keyword(s):

Hydraulic Conductivity ◽

Load Distribution ◽

Axial Load ◽

Soil Layer ◽

Pile Group ◽

Excess Pore Pressure ◽

Vertical Loading ◽

Soil Settlement ◽

Excess Pore Pressures ◽

During strong earthquakes, significant excess pore pressures can develop in saturated soils. After shaking ceases, the dissipation of these pressures can cause significant soil settlement, creating downward-acting frictional loads on piled foundations. Additionally, if the piles do not support the full axial load at the end of shaking, then the proportion of the superstructure’s vertical loading carried by the piles may change as a result of the soil settlement, further altering the axial load distribution on piles as the soil consolidates. In this paper, the effect of hydraulic conductivity and initial post-shaking pile head loading is investigated in terms of the changing axial load distribution and settlement responses. The investigation is carried out by considering the results from four dynamic centrifuge experiments in which a 2 × 2 pile group was embedded in a two-layer profile and subjected to strong shaking. It is found that large contrasts in hydraulic conductivity between the two layers of the soil model affected both the pile group settlements and axial load distribution. Both these results stem from the differences in excess pore pressure dissipation, part of which took place very rapidly when the underlying soil layer had a large hydraulic conductivity.

Pore Pressure Response to Groundwater Fluctuations in Saturated Double-Layered Soil

Mathematical Problems in Engineering ◽

10.1155/2015/389089 ◽

2015 ◽

Vol 2015 ◽

pp. 1-11 ◽

Cited By ~ 3

Author(s):

Hongwei Ying ◽

Lisha Zhang ◽

Kanghe Xie ◽

Dazhong Huang

Keyword(s):

Pressure Distribution ◽

Pore Pressure ◽

Dimensionless Parameter ◽

Pore Water Pressure ◽

Water Pressure ◽

Layered Soil ◽

Excess Pore Pressure ◽

Groundwater Fluctuation ◽

Excess Pore Pressures ◽

Analytical solutions are developed for one-dimensional consolidation of double-layered saturated soil subjected to groundwater fluctuations. The solutions are derived by an explicit mathematical procedure using Duhamel’s theorem in conjunction with a Fourier series, when groundwater fluctuation is described by a general time-dependent function and assumed to be the pore water pressure variations at the upper boundary. Taking as an example the harmonic groundwater fluctuation, the relevant response of the excess pore water pressure is discussed in detail, and the main influencing factors of the excess pore pressure distribution are analyzed. A dimensionless parameterθhas been introduced because it significantly affects the phase and the amplitude of excess pore pressures. The influences of the coefficients of permeability and compressibility of soil on the excess pore pressure distribution are different and cannot be incorporated into the coefficient of consolidation in double-layered soil. The relative permeability ratio of two clayey soils also plays an important role on the curves of the distributions of the excess pore pressures. The effects of the thickness of the soil layer on the excess pore pressure distribution should be considered together with the dimensionless parameterθand the permeability and compressibility of the double-layered soil system.

Surpressions interstitielles développées par le fonçage dans les sols cohérents

10.1139/t79-088 ◽

1979 ◽

Vol 16 (4) ◽

pp. 814-827

Author(s):

M. Peignaud

Keyword(s):

Pore Pressure ◽

Excess Pore Pressure ◽

Overburden Pressure ◽

Pore Pressures ◽

Excess Pore Pressures ◽

Plastic Clays ◽

The Laboratoire Régional des Ponts et Chaussées, Angers (France) has investigated the excess pore pressures developed during the driving of a piezometer probe at different rates on four sites. Attention is drawn to the important differences between the pore pressures measured during penetration and at rest.During driving, negative excess pore pressures are measured. When the piezometer is stopped the pore pressures become large and positive. For the soils tested, i.e., plastic to highly plastic clays, the maximum excess pore pressure at rest may be estimated from the total overburden pressure. [Journal translation]

A New Technique for Reduction of Excess Pore Pressures During Pile Driving

10.1139/t74-043 ◽

1974 ◽

Vol 11 (3) ◽

pp. 423-430 ◽

Cited By ~ 4

Author(s):

Robert D. Holtz ◽

Per Boman

Keyword(s):

Pore Pressure ◽

Alternative Methods ◽

New Technique ◽

Excess Pore Pressure ◽

Relative Reduction ◽

Pile Driving ◽

Pore Pressures ◽

A New Technique ◽

Excess Pore Pressures ◽

A new technique is described whereby excess pore pressures induced during pile driving in soft, varved silts and clays were economically reduced to a safe level. The technique was applied to piles at a bridge site south of Stockholm, Sweden, where a small slide had occurred during pile driving. A new paper–plastic drain was attached to the wood piles during driving, and two pulling tests indicated that the drain was undamaged under normal driving conditions. The excess pore pressure generated during the driving of some 13 test piles without drains and 48 piles with drains was measured. The data indicated at least a 50% relative reduction in excess pore pressure when the drain was used. In addition, the cost of the technique was considerably less than alternative methods for dealing with dangerous excess pore water pressures resulting from piling in similar soils. The technique has been successfully applied at two other piling sites in Sweden.

Analysis of the Pore Pressure Changes Following the Excavation of a Slope

10.1139/t75-047 ◽

1975 ◽

Vol 12 (3) ◽

pp. 429-440 ◽

Cited By ~ 9

Author(s):

Kurt D. Eigenbrod

Keyword(s):

Pore Pressure ◽

Field Data ◽

Pressure Measurements ◽

Pore Pressures ◽

Field Evidence ◽

Slope Excavation ◽

Order Of Magnitude ◽

Excess Pore Pressures ◽

Pressure Changes ◽

In a numerical analysis the pore pressure changes due to excavation of a slope and the subsequent dissipation of excess pore pressures were calculated. The analytical results of the pore pressure changes due to unloading of a slope agree reasonably well with pore pressure measurements in comparable embankments. This suggests that pore pressures immediately after slope excavation can be predicted analytically in homogeneous materials.The results of an analysis dealing with the dissipation of excess pore pressures due to unloading can also be substantiated by field evidence; however, only few comparable field data are available. For many slopes it can be noted that the time for full dissipation is of the same order of magnitude as the time between excavation and failure. This suggests that many failures might be caused by the delayed equalization of pore pressures.

International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts ◽

Evaluation of excess pore pressures and drainage conditions around driven piles using the cone penetration test with pore pressure measurements. Note

10.1016/0148-9062(91)93420-b ◽

1991 ◽

Vol 28 (1) ◽

pp. A23

Keyword(s):

Pore Pressure ◽

Cone Penetration Test ◽

Pressure Measurements ◽

Penetration Test ◽

Driven Piles ◽

Cone Penetration ◽

Pore Pressures ◽

Excess Pore Pressures ◽

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

Coastal Engineering Proceedings ◽

10.9753/icce.v36.sediment.59 ◽

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 ◽

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.