Monotonic and dilatory pore-pressure decay during piezocone tests in clay

1998 ◽  
Vol 35 (6) ◽  
pp. 1063-1073 ◽  
Author(s):  
S E Burns ◽  
P W Mayne
Keyword(s):  
Pore Pressure ◽  
Pore Water Pressure ◽  
Soil Mechanics ◽  
Water Pressure ◽  
Cavity Expansion ◽  
Coefficient Of Consolidation ◽  
Soft Clays ◽  
Fine Grained ◽  
Cavity Expansion Theory ◽  
Pore Pressure Response

During a pause in cone penetration in fine-grained soils, pore-water pressure dissipation tests are performed to evaluate the coefficient of consolidation. For standard piezocones with shoulder filter elements, soft clays and silts show a monotonically decreasing response with time; however, dissipation tests performed in heavily overconsolidated silts and clays show dilatory behavior, with the pore-pressure behavior increasing from the initial measured value to a maximum, and then decreasing to hydrostatic values. This paper presents a theoretical framework which combines cavity-expansion theory and critical-state soil mechanics with an analytical solution to the radial consolidation equation. The method is able to describe the pore-pressure response curve for dissipation tests performed in soils which demonstrate either monotonically decreasing or dilatory pore-pressure behavior.Key words: cavity expansion, consolidation, piezocone, pore pressure.

scholarly journals Experimental insights into consolidation rates during one-dimensional loading with special reference to excess pore water pressure

2020 ◽  
Vol 15 (12) ◽  
pp. 3571-3591
Author(s):  
Bartłomiej Szczepan Olek
Keyword(s):  
Pore Water ◽  
Large Scale ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Small Scale ◽  
Coefficient Of Consolidation ◽  
Consolidation Process ◽  
Factors Affecting ◽  
Fine Grained ◽  
Fine Grained Soil

AbstractConsolidation rate has significant influence on the settlement of structures founded on soft fine-grained soil. This paper presents the results of a series of small-scale and large-scale Rowe cell consolidation tests with pore water pressure measurements to investigate the factors affecting the consolidation process. Permeability and creep/resistance structure factors were considered as the governing factors. Intact and reconstituted marine clay from the Polish Carpathian Foredeep basin as well as clay–sand mixtures was examined in the present study. The fundamental relationship correlating consolidation degrees based on compression and pore water pressure was assessed to indicate the nonlinear soil behaviour. It was observed that the instantaneous consolidation parameters vary as the process progresses. The instantaneous coefficient of consolidation first drastically increases or decreases with increase in the degree of consolidation and stabilises in the middle stage of the consolidation; it then decreases significantly due to viscoplastic effects occurring in the soil structure. Based on the characteristics of the relationship between coefficient of consolidation and degree of dissipation at the base, the consolidation range that complies with theoretical assumptions was established. Furthermore, the influence of coarser fraction in clay–sand mixtures in controlling the consolidation rates is discussed.

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.

Simulation of creep deformation in the foundation of Tar Island Dyke

1995 ◽  
Vol 32 (6) ◽  
pp. 1002-1023 ◽  
Author(s):  
Mohammed M. Morsy ◽  
N.R. Morgenstern ◽  
D.H. Chan
Keyword(s):  
Pore Pressure ◽  
Effective Stress ◽  
Creep Deformation ◽  
Pore Water Pressure ◽  
Soil Mechanics ◽  
Water Pressure ◽  
Pressure Change ◽  
Sensitivity Study ◽  
Stress Model ◽  
Oil Sand

Tar Island Dyke is a 92 m tailing dyke for retaining oil sand tailings and has been operated by Suncor in Fort McMurray, Alberta. Construction of the dyke began in the mid-1960's adjacent to the Athabasca river. The foundation of the dyke consists of a layer of interbedded silts and clay overlying a basal sand stratum. Stresses imposed by the dyke on the foundation clay have been causing continuing movement of the structure over 30 years. Movements of the dyke have been monitored for over 25 years and show significant creep deformation of over 1 m in the foundation clay. Pore pressure in the clay was monitored, with little pore pressure change during this period. Therefore the movement was mostly due to creep rather than consolidation. The unique feature of this case is that the loading due to the dyke has been essentially constant for over 15 years but movement has continued. An effective stress model for creep is adopted to simulate the construction of the Tar Island Dyke. The model is based on critical state soil mechanics and uses secondary consolidation and the Taylor Singh-Mitchell creep relationships. The model is able to capture the movement of the dyke and its foundation, and good agreement is obtained between the calculated and measured deformations. A sensitivity study has been carried out to study the effect of varying the creep parameters on the results of the analysis. Key words : Tar Island Dyke, creep mechanism, finite element, clay foundation, effective stress model, pore-water pressure.

Evolution of the factor of safety following excavation in clay

2009 ◽  
Vol 46 (5) ◽  
pp. 487-493 ◽  
Author(s):  
J. S. L’Heureux ◽  
S. Leroueil ◽  
J. F. Laflamme
Keyword(s):  
Pore Pressure ◽  
Factor Of Safety ◽  
Clayey Soil ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soil Mass ◽  
Eastern Canada ◽  
Soft Clays ◽  
Clay Deposits ◽  
The Difference

Numerical analyses have been performed to study the evolution of the factor of safety following the excavation of a cut in clay. The analyses consider variable thickness of the clayey soil deposit under the excavation. The results show that, for a given clayey soil, there is a relation between the time for full dissipation of excess pore-water pressure from the soil mass following the excavation and the geometry of the cut (Htot/Hexc). The analytical results agree reasonably well with pore pressure measurements made in excavations in clay deposits from eastern Canada. This suggests that time to reach full pore pressure equilibration following the excavation of a cut in homogenous clayey soil deposits can be predicted when knowledge of the coefficient of swelling–consolidation is available. Lastly, results obtained in the present study show that 50% of the difference between the short- and long-term factors of safety may be lost at values as low as about 8% of the time to reach equilibration of pore pressures. This means that the time during which one can rely on the short-term strength of the clayey soil following the excavation may be relatively short, especially for soft clays.

Unified Analytical Solution for Cylindrical Cavity Expansion of Saturated Soil Based on Large Deformation and Non-Drainage

2010 ◽  
Vol 168-170 ◽  
pp. 2406-2415
Author(s):  
Chun Long Nie
Keyword(s):  
Large Deformation ◽  
Pore Pressure ◽  
Deformation Theory ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Plastic Region ◽  
Cavity Expansion ◽  
Excess Pore Water Pressure ◽  
Cylindrical Cavity Expansion ◽  
Excess Pore

Soil around the cylindrical pore is divided into elastic and plastic regions. In the elastic region, the small deformation theory is applied while in the plastic region, the large deformation theory and unified strength criterion are applied. According to the stress equilibrium equation and the boundary condition of continuous stress and deformation, the theoretical solution to plastic region radius, limit expansion pore pressure excess pore pressure and excess pore water pressure of the cylindrical cavity expansion can be derived when considering large deformation and non-drainage problems. Compared to the theoretical results of Cao L.F., the theoretical calculation results are closer to the field test results which show that the theory has a certain value in engineering application. Through calculations and analysis, it is also derived that expansion pore pressure increase is non-linear with the increase of b value, while the excess pore water pressure is just the opposite.

Type of Slope Failure Identified from Pore Water Pressure and Moisture Content Measurements

2015 ◽  
Vol 744-746 ◽  
pp. 690-694
Author(s):  
Muhammad Rehan Hakro ◽  
Indra Sati Hamonangan Harahap
Keyword(s):  
Moisture Content ◽  
Pore Pressure ◽  
Slope Failure ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Failure Process ◽  
Small Scale ◽  
Content Increase ◽  
Sudden Increase ◽  
Model Slope

Rainfall-induced landslides occur in many parts of the world and causing a lot of the damages. For effective prediction of rainfall-induced landslides the comprehensive understanding of the failure process is necessary. Under different soil and hydrological conditions experiments were conducted to investigate and clarify the mechanism of slope failure. The failure in model slope was induced by sprinkling the rainfall on slope composed of sandy soil in small flume. Series of tests were conducted in small scale flume to better understand the failure process in sandy slopes. The moisture content was measured with advanced Imko TDR (Time Domain Reflectrometry) moisture sensors in addition to measurements of pore pressure with piezometers. The moisture content increase rapidly to reach the maximum possible water content in case of higher intensity of rainfall, and higher intensity of the rainfall causes higher erosion as compared to smaller intensity of the rainfall. The controlling factor for rainfall-induced flowslides was density of the slope, rather than intensity of the rainfall and during the flowslide the sudden increase in pore pressure was observed. Higher pore pressure was observed at the toe of the slope as compared to upper part of the slope.

Experimental study on dual capillary barrier using recycled asphalt pavement materials

2014 ◽  
Vol 51 (10) ◽  
pp. 1165-1177 ◽  
Author(s):  
F.R. Harnas ◽  
H. Rahardjo ◽  
E.C. Leong ◽  
J.Y. Wang
Keyword(s):  
Water Content ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Water Storage ◽  
Pressure Head ◽  
Volumetric Water Content ◽  
Capillary Barrier ◽  
Recycled Asphalt ◽  
Fine Grained ◽  
Drainage Rate

The performance of a capillary barrier cover as a cover system is affected by the ability of the capillary barrier to store water. To increase the water storage of a capillary barrier cover, the dual capillary barrier (DCB) concept is proposed. The objective of this paper is to investigate the water storage of the proposed DCB as compared to the storage of a traditional single capillary barrier (SCB). The investigation is conducted using two one-dimensional infiltration column tests under different rainfall conditions. The results show that a DCB stores more water as compared to SCB. The results show that the fine-grained layers of a DCB have higher volumetric water contents during drainage as compared to that of the fine-grained layer of an SCB. The higher volumetric water content is caused by the fact that the thickness of the layers in a DCB corresponds to a pore-water pressure head range where the material has the highest volumetric water content. In addition, a slower drainage rate is resulted from additional layering in a DCB.

scholarly journals Mechanical response and pore pressure generation in granular filters subjected to uniaxial cyclic loading

2018 ◽  
Vol 55 (12) ◽  
pp. 1756-1768
Author(s):  
Jahanzaib Israr ◽  
Buddhima Indraratna
Keyword(s):  
Cyclic Loading ◽  
Pore Pressure ◽  
Pore Water ◽  
Mechanical Response ◽  
Pore Water Pressure ◽  
Axial Strain ◽  
Water Pressure ◽  
Internal Erosion ◽  
Excess Pore Water Pressure ◽  
Excess Pore

This paper presents results from a series of piping tests carried out on a selected range of granular filters under static and cyclic loading conditions. The mechanical response of filters subjected to cyclic loading could be characterized in three distinct phases; namely, (I) pre-shakedown, (II) post-shakedown, and (III) post-critical (i.e., the occurrence of internal erosion). All the permanent geomechanical changes such, as erosion, permeability variations, and axial strain developments, took place during phases I and III, while the specimen response remained purely elastic during phase II. The post-critical occurrence of erosion incurred significant settlement that may not be tolerable for high-speed railway substructures. The analysis revealed that a cyclic load would induce excess pore-water pressure, which, in corroboration with steady seepage forces and agitation due to dynamic loading, could then cause internal erosion of fines from the specimens. The resulting excess pore pressure is a direct function of the axial strain due to cyclic densification, as well as the loading frequency and reduction in permeability. A model based on strain energy is proposed to quantify the excess pore-water pressure, and subsequently validated using current and existing test results from published studies.

Studying the Geotechnical Properties of Clayey Soil Contaminated by Kerosene

2020 ◽  
Vol 857 ◽  
pp. 383-393
Author(s):  
Mahdi O. Karkush ◽  
Amer G. Jihad
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Contaminated Soil ◽  
Fine Particles ◽  
Clayey Soil ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Chemical Characteristics ◽  
Coefficient Of Consolidation ◽  
Plastic Containers

This study focuses on investigating the impacts of kerosene on the physical, mechanical, and chemical characteristics of clay soil. The soils specimens are contaminated artificially with six ratios of kerosene (5, 10, 20, 30, 40, and 50) % calculated according to the dry weight of soil. The artificial contamination includes air drying of the disturbed soil, then placed in plastic containers and mixed with the field water content and the specified concentration of kerosene to ensure getting homogenous contaminated soil specimens. The contaminated soil specimens left for 30 days in plastic containers covered by nylon sheets to control the water content and prevent volatility of contaminant. The results of tests proved that different ratios of kerosene have different impacts on the engineering and chemical characteristics of soil specimens. The specific gravity, percentages of fine particles, optimum water content, the initial and final void ratio, coefficient of consolidation, swelling index, permeability, the undrained shear strength, effective shear strength parameters, and the rate of reduction of initial pore water pressure are reduced significantly with increasing the content of kerosene in soil. Generally, the concentration of kerosene less than 10% has slight impacts on the studied characteristics of soil specimens.

An effective stress model for creep of clay

1995 ◽  
Vol 32 (5) ◽  
pp. 819-834 ◽  
Author(s):  
Mohammed M. Morsy ◽  
D.H. Chan ◽  
N.R. Morgenstern
Keyword(s):  
Finite Element ◽  
Pore Pressure ◽  
Effective Stress ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Surface Model ◽  
Interpolation Technique ◽  
Stress Integration ◽  
Integration Algorithms ◽  
Double Yield

An effective stress constitutive model to study the problem numerically of creep in the field is presented. A double-yield surface model for the stress–strain–time behaviour of wet clay is described. The model adopts the concept of separating the total deformation into immediate and delayed components. The yield surfaces employed are the modified Cam-clay ellipsoid and the Von Mises cylinder inscribed in the ellipsoid. The proposed numerical scheme incorporates the pore pressure based on field observations into a finite element analysis. An interpolation technique is used to determine the pore pressure at every element. A field example is presented to illustrate the interpolation technique procedure. The scheme not only avoids the complexity of making predictions of pore-water pressure, but also allows the analysis to be carried out in terms of effective stresses based on the actual observed pore pressure. Two stress integration algorithms based on the implicit calculation of plastic strain are implemented and tested for the double-yield surface model. A numerical simulation of stress-controlled drained creep tests confirms the numerical procedure. Key words : constitutive equations, creep, finite element, stress integration algorithms, effective stress approach, pore-water pressure.

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