scholarly journals Pore-water pressure development in a frozen saline clay under isotropic loading and undrained shearing

2021 ◽  
Author(s):  
Chuangxin Lyu ◽  
Satoshi Nishimura ◽  
Seyed Ali Ghoreishian Amiri ◽  
Feng Zhu ◽  
Gudmund Reidar Eiksund ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Effective Stress ◽  
Water Pressure ◽  
Frozen Soil ◽  
Hydraulic Pressure ◽  
Physical Analysis ◽  
Rate Dependency ◽  
Frozen Soils ◽  
Unfrozen Water Content ◽  
Pressure Development

AbstractA systematical testing program on frozen Onsøy clay under isotropic loading and undrained shearing at different temperatures (− 3 ~ − 10 °C), strain rates (0.2~5%/h) and initial Terzaghi effective stress (20~400 kPa) was conducted with the focus on pore pressure development. It is meant to increase the understanding and facilitate the development of an ‘effective stress’-based model for multi-physical analysis for frozen soils. This study adopted the pore pressure measurement method suggested by Arenson and Springman (Can Geotech J 42 (2):412–430, 2005. https://doi.org/10.1139/t04-111) and developed a new testing procedure for frozen soils, including a ‘slow’ freezing method for sample preparation and post-freezing consolidation for securing hydraulic pressure equilibrium. The B-value of frozen soils is less than 1 and significantly dependent on temperature and loading history. The dilative tendency or pore pressure development in an undrained shearing condition is found to be dependent on both unfrozen water content and mean stress, which is consistent with unfrozen soils. Besides, the experimental results reported in the literature regarding uniaxial tests show that the shear strength does not share the same temperature- and salinity-dependency for different frozen soil types. The rate dependency of frozen soils is characterized between rate dependency of pure ice and that of the unfrozen soil and is therefore highly determined by the content of ice and the viscous behavior of ice (through temperature dependency). This paper also explains the pore pressure response in freezing and thawing is dependent on volumetric evolution of soil skeleton.

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.

Evaluating the Potential for Damaging Hydraulic Pressure in the Concrete Tie Rail Seat

2010 ◽  
Author(s):  
John C. Zeman ◽  
J. Riley Edwards ◽  
David A. Lange ◽  
Christopher P. L. Barkan
Keyword(s):  
Surface Water ◽  
Effective Stress ◽  
Water Pressure ◽  
Hydraulic Pressure ◽  
Vertical Load ◽  
Critical Problem ◽  
Surface Geometry ◽  
State Of Stress ◽  
Pore Water Pressures ◽  
Prestressed Beam

Rail seat deterioration (RSD) is the most critical problem with concrete tie performance on North American freight railroads. Currently, the problem is not sufficiently understood to allow for effective solutions. RSD is considered to have up to five potential mechanisms, and this paper investigates one of them: hydraulic pressure cracking. A model of the effective stress in a concrete tie rail seat — considering the contributions of a uniform vertical load, a uniform lateral load, a prestressed beam on an elastic foundation, and pore pressure to the state of stress — was created to determine what surface water pressures at the rail seat could lead to damaging pore water pressures in the concrete. A laboratory test setup and procedure were devised to measure the surface water pressure in a laboratory rail seat using tie pads of differing material composition and geometry. Results show that the magnitude of the pressure generated and the rate of pressure dissipation with many load cycles depends on the pad material and surface geometry. Comparing the effective stress model and the measured surface pressures, hydraulic pressure cracking appears to be a feasible mechanism for RSD given the correct combination of dynamic rail seat loads, sufficient moisture, and a tie pad surface that develops high pressure.

The influence of high pore-water pressure on the strength of cohesionless soils

1977 ◽  
Vol 284 (1318) ◽  
pp. 91-130 ◽  
Keyword(s):  
Pore Pressure ◽  
Effective Stress ◽  
Quartz Sand ◽  
Pore Water Pressure ◽  
Pore Space ◽  
Water Pressure ◽  
Experimental Studies ◽  
Interparticle Contact ◽  
Particulate Materials ◽  
Shearing Resistance

The influence on the mechanical properties of saturated particulate materials of the component of stress carried by the water filling the pore space is fundamental to both theoretical and experimental studies in soil mechanics. The rôle of pore pressure in controlling compressibility and shear strength is expressed in Terzaghi’s principle of effective stress to a degree of accuracy which is sufficient for most engineering purposes. However, the precise significance of the small but finite area of interparticle contact has remained uncertain in the application of this equation to shearing resistance. In the present paper the possible errors associated with the use of current expressions for intergranular stress and effective stress are examined. These errors are of significant magnitude at high values of pore pressure and low values of the yield stress of the solid forming the particles. A very accurate experimental investigation has been carried out into the sensitivity of shearing resistance to large changes in pore pressure (up to 41.4 MN/m 2 ), using particulate materials ranging in strength from Quartz sand to lead shot. The results indicate that the simple Terzaghi effective stress equation a' - o - u is consistent with all the observations, though for Quartz sand a range of pore pressure changes an order of magnitude higher is desirable for additional confirmatory evidence.

scholarly journals Snowmelt and slushflows: hydrological and hazard implications

1998 ◽  
Vol 26 ◽  
pp. 381-384 ◽  
Author(s):  
Martin Gude ◽  
Dieter Scherer
Keyword(s):  
Water Pressure ◽  
Hydraulic Pressure ◽  
Minor Importance ◽  
Northern Sweden ◽  
Initiation Mechanism ◽  
Release Process ◽  
Pressure Development ◽  
Transitional Processes ◽  
Water Saturated

In many high-latitude areas, slushflows occur frequently during the snowmelt period but information on the initiation mechanism is rare. Field observations and measurements of slushflows in northwestern Spitsbergen and in northern Sweden demonstrate the role of meltwater accumulation and the hydraulic pressure gradient in the release process. Snow metamorphism is revealed to be of minor importance in the observed events. The monitoring of water-pressure development in a saturated snow cover demonstrates that preferred release areas are within low-gradient valley sections, where meltwater inflow is higher than outflow.Slushflows consist of mudflow-like flowage of water-saturated snow along stream courses. They represent transitional processes between fluvial floods and avalanches. On the other hand, they possess unique characteristics concerning release and movement. The comparative evaluation of definition items for fluvial floods, slushflows and avalanches offers hasic data suitable for a risk assessment.

Cyclic Response of Granular Subsoil Under a Gravity Base Foundation for Offshore Wind Turbines

2011 ◽  
Author(s):  
Stefanus Safinus ◽  
Germa´n Sedlacek ◽  
Udo Hartwig
Keyword(s):  
Service Life ◽  
Pore Pressure ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Analytical Calculation ◽  
Offshore Wind ◽  
Cyclic Loads ◽  
3D Fem ◽  
Offshore Wind Turbines ◽  
Pressure Development

It is essential in the design of gravity foundations under cyclic loading that inadmissibly large reductions of the subsoil bearing capacity due to the accumulated pore water pressure (loss of stability) and tilting of the foundation caused by the accumulation of settlements (loss of serviceability) are ruled out. This paper describes a procedure to predict these phenomena in non-cohesive subsoils. Real irregular loads during the service life of the structure can be idealized into parcels of uniform cyclic loads. Using the “High Cyclic Accumulation Model” proposed by Niemunis [1] the strain accumulation and thus the settlement of the subsoil due to the cyclic loads occurring within the service life of the wind turbine can be estimated. The pore pressure development is analyzed by dividing the mechanism in a pore pressure build-up phase in undrained condition (analytical calculation) and a dissipation phase (3D-FEM-Calculation).

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.

scholarly journals Wave-induced residual pore pressure around a buried pipeline

2021 ◽  
Vol 261 ◽  
pp. 02056
Author(s):  
Zhou-Quan Liao ◽  
Xiao-Li Liu
Keyword(s):  
Pore Pressure ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Wave Loading ◽  
Buried Pipeline ◽  
Marine Structures ◽  
Factors Affecting ◽  
Pressure Development ◽  
Semi Empirical ◽  
Wave Induced

Seabed instability caused by cyclic wave loading is one of the main factors affecting the foundation instability of marine structures, and it is a key problem that needs to be paid attention in the design of marine structures. Based on Biot’s consolidation theory and a semi-empirical formula for calculating residual pore water pressure, the wave-induced residual seabed response around a buried pipeline was investigated by numerical simulation. The correctness of the numerical results is verified by comparing with experimental results. Effect of the self-weight of the buried pipeline on residual pore pressure development and the characteristics of residual pore pressure near the pipeline are discussed.

scholarly journals Observations of heterogeneous pore pressure distributions in clay-rich materials

2012 ◽  
Vol 76 (8) ◽  
pp. 3115-3129 ◽  
Author(s):  
R. J. Cuss ◽  
J. F. Harrington ◽  
C. C. Graham ◽  
S. Sathar ◽  
A. E. Milodowski
Keyword(s):  
High Pressure ◽  
Pore Pressure ◽  
Effective Stress ◽  
Gas Flow ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Opalinus Clay ◽  
Boom Clay ◽  
Pore Pressures ◽  
Stress States

AbstractThe concept of effective stress is one of the basic tenets of rock mechanics where the stress acting on a rock can be viewed as the total stress minus the pore water pressure. In many materials, including clay-rich rocks, this relationship has been seen to be imperfect and a coefficient (χ) is added to account for the mechanical properties of the clay matrix. Recent experimental results during the flow testing (both gas and water) of several rocks (Callovo-Oxfordian claystone, Opalinus Clay, Boom Clay) and geomaterials (bentonite, kaolinite) has given evidence for stable high pressure differentials. The design of the experiments allows multiple measurements of pore pressure, which commonly shows a complex distribution for several different experimental geometries. The observed stable high pressure differentials and heterogeneous pore pressure distribution makes the describing of stress states in terms of effective stress complex. Highly localized pore pressures can be sustained by argillaceous materials and concepts of evenly distributed pore pressures throughout the sample (i.e. conventional effective stress) do not fit many clay-rich rocks if the complexities observed on the micro-scale are not incorporated, especially when considering the case of gas flow.

scholarly journals Snowmelt and slushflows: hydrological and hazard implications

1998 ◽  
Vol 26 ◽  
pp. 381-384 ◽  
Author(s):  
Martin Gude ◽  
Dieter Scherer
Keyword(s):  
Water Pressure ◽  
Hydraulic Pressure ◽  
Minor Importance ◽  
Northern Sweden ◽  
Initiation Mechanism ◽  
Release Process ◽  
Pressure Development ◽  
Transitional Processes ◽  
Water Saturated

In many high-latitude areas, slushflows occur frequently during the snowmelt period but information on the initiation mechanism is rare. Field observations and measurements of slushflows in northwestern Spitsbergen and in northern Sweden demonstrate the role of meltwater accumulation and the hydraulic pressure gradient in the release process. Snow metamorphism is revealed to be of minor importance in the observed events. The monitoring of water-pressure development in a saturated snow cover demonstrates that preferred release areas are within low-gradient valley sections, where meltwater inflow is higher than outflow.Slushflows consist of mudflow-like flowage of water-saturated snow along stream courses. They represent transitional processes between fluvial floods and avalanches. On the other hand, they possess unique characteristics concerning release and movement. The comparative evaluation of definition items for fluvial floods, slushflows and avalanches offers hasic data suitable for a risk assessment.

Predicting Unfrozen Water Contents in Frozen Soils

1966 ◽  
Vol 3 (2) ◽  
pp. 53-60 ◽  
Author(s):  
Howard B Dillon ◽  
O B Andersland
Keyword(s):  
Water Content ◽  
Freezing Point ◽  
Soil Mechanics ◽  
Frozen Soil ◽  
Unfrozen Water ◽  
Silty Clay ◽  
Frozen Soils ◽  
Unfrozen Water Content ◽  
Experimental Values ◽  
Water Contents

A relationship between temperature and certain soil properties including specific surface area, activity ratio, and the expandable clay lattice, is presented for predicting the unfrozen water content of frozen soils. Data on experimental calorimetric determinations for ice content of two frozen clays and a frozen silty clay are given. Predicted unfrozen water contents are compared with experimental values for eleven soils with good agreement in all cases. Temperatures close to and above the freezing point depression of the soil are excluded. Knowledge of the unfrozen water content in frozen soils permits a more realistic approach to a variety of problems in frozen soil mechanics.

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