Re-mobilization of pile shaft friction after an earthquake

2013 ◽  
Vol 50 (9) ◽  
pp. 979-988 ◽  
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 ◽  
Excess Pore

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.

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

2011 ◽  
Author(s):  
Shiaw-Yih Tzang ◽  
Yung-Lung Chen ◽  
Shan-Hwei Ou
Keyword(s):  
Pore Pressure ◽  
Soil Layer ◽  
Excess Pore Pressure ◽  
Pressure Measurements ◽  
Flume Tests ◽  
Dissipation Mechanism ◽  
Frequency Components ◽  
Excess Pore Pressures ◽  
Wave Induced ◽  
Excess Pore

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

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 ◽  
Excess Pore

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 time–thickness 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.

scholarly journals Sustainable Measures for Protection of Structures Against Earthquake Induced Liquefaction

2021 ◽  
Author(s):  
Gopal S. P. Madabhushi ◽  
Samy Garcia-Torres
Keyword(s):  
Soil Liquefaction ◽  
Excess Pore Pressure ◽  
Economic Losses ◽  
Element Analysis ◽  
Centrifuge Testing ◽  
Centrifuge Tests ◽  
Liquefiable Soil ◽  
Recent Earthquakes ◽  
Excess Pore Pressures ◽  
Excess Pore

AbstractSoil liquefaction can cause excessive damage to structures as witnessed in many recent earthquakes. The damage to small/medium-sized buildings can lead to excessive death toll and economic losses due to the sheer number of such buildings. Economic and sustainable methods to mitigate liquefaction damage to such buildings are therefore required. In this paper, the use of rubble brick as a material to construct earthquake drains is proposed. The efficacy of these drains to mitigate liquefaction effects was investigated, for the first time to include the effects of the foundations of a structure by using dynamic centrifuge testing. It will be shown that performance of the foundation in terms of its settlement was improved by the rubble brick drains by directly comparing them to the foundation on unimproved, liquefiable ground. The dynamic response in terms of horizontal accelerations and rotations will be compared. The dynamic centrifuge tests also yielded valuable information with regard to the excess pore pressure variation below the foundations both spatially and temporally. Differences of excess pore pressures between the improved and unimproved ground will be compared. Finally, a simplified 3D finite element analysis will be introduced that will be shown to satisfactorily capture the settlement characteristics of the foundation located on liquefiable soil with earthquake drains.

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

2019 ◽  
Vol 7 (5) ◽  
pp. 146 ◽  
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 ◽  
Excess Pore

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.

scholarly journals Dynamic, In-situ, Nonlinear-Inelastic Response and Post-Cyclic Strength of a Plastic Silt Deposit

2021 ◽  
Author(s):  
Amalesh Jana ◽  
Armin W. Stuedlein
Keyword(s):  
Shear Strain ◽  
Low Frequency ◽  
Seismic Energy ◽  
Cyclic Strength ◽  
Excess Pore Pressure ◽  
Inelastic Response ◽  
Pore Pressures ◽  
Excess Pore Pressures ◽  
Excess Pore

This study presents the use of controlled blasting as a source of seismic energy to obtain the coupled, dynamic, linear-elastic to nonlinear-inelastic response of a plastic silt deposit. Characterization of blast-induced ground motions indicate that the shear strain and corresponding residual excess pore pressures (EPPs) are associated with low frequency near- and far-field shear waves that are within the range of earthquake frequencies, whereas the effect of high frequency P-waves are negligible. Three blasting programs were used to develop the initial and pre-strained relationships between shear strain, EPP, and nonlinear shear modulus degradation. The initial threshold shear strain to initiate soil nonlinearity and to trigger generation of residual EPP ranging from 0.002 to 0.003% and 0.008 to 0.012%, respectively, where the latter corresponded to ~30% of Gmax. Following pre-straining and dissipation of EPPs within the silt deposit, the shear strain necessary to trigger residual excess pore pressure increased two-fold. Greater excess pore pressures were observed in-situ compared to that of intact direct simple shear (DSS) test specimens at a given shear strain amplitude. The reduction of in-situ undrained shear strength within the blast-induced EPP field measured using vane shear tests compared favorably with that of DSS test specimens.

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

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
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 ◽  
Excess Pore

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

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 ◽  
Excess Pore

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

1974 ◽  
Vol 11 (3) ◽  
pp. 423-430 ◽  
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 ◽  
Excess Pore

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.

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 Effect of Deep Mixing Grid Spacing On The Settlement of Liquefied Soil, Using Numerical Approach

2022 ◽  
Author(s):  
Fereshteh Rahmani ◽  
Seyed Mahdi Hosseini
Keyword(s):  
Pore Pressure ◽  
Ground Improvement ◽  
Pressure Ratio ◽  
Soil Layer ◽  
Excess Pore Pressure ◽  
Analysis Model ◽  
Liquefaction Mitigation ◽  
Deep Mixing ◽  
Liquefiable Soil ◽  
Excess Pore

Abstract Liquefaction occurs in a loose and saturated sand layer, induces quite large damages to infrastructures, the importance of liquefaction mitigation has been emphasized to minimize earthquake disasters for many years. Many kinds of ground improvement techniques based on various improvement principles have been developed for liquefaction mitigation. Among them, deep mixing method with grid pattern was developed for liquefaction mitigation in the 1990s, where the grid of stabilized column walls functions to restrict the generation of excess pore pressure by confining the soil particle movement during earthquake. In this study, a parametric study of the grid-form deep mixing wall is performed using numerical modeling with GID+OpenSees interface V2.6.0. The finite element method with a three-dimensional analysis model can be used to estimate the foundation settlement over liquefiable soil layer. The validity of the developed model was evaluated by comparing the results obtained from the model with the results of numerical studies and the experimental centrifuge test to investigate the effect of deep mixing grid wall on the settlement and generation of excess pore pressure ratio of liquefiable soil. Based on the analysis, the settlement for improved soil was 69% smaller than the settlement for unimproved soil. The results also indicated that the grid wall space, relative density, and stiffness ratio between soil-cement columns and enclosed soil plays an important role in the occurrence of liquefaction and volumetric strains.

Sign in / Sign up

Export Citation Format

Share Document