scholarly journals LABORATORY WORK ON TOTAL SUCTION CALIBRATION CURVE FOR WHATMAN #42 FILTER PAPER

2017 ◽  
Vol 1 (1) ◽  
pp. 16
Author(s):  
Yusep Muslih Purwana
Keyword(s):  
Unsaturated Soil ◽  
Salt Solution ◽  
Calibration Curve ◽  
Filter Paper ◽  
Indirect Method ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soil Suction ◽  
The Difference ◽  
Total Suction

<p>Soil suction is one of main parameter in unsaturated soil mechanics as its measurement is as very important as pore water pressure measurement for effective stress concept in saturated soil mechanics.Basically, the measurement of soil suction can be classified into 2 categories; direct and indirect method. In the first method, negative pore water pressure is measured directly to obtain matric suction, whereas in indirect method, suction is obtained indirectly by using salt solution and censor.  Calibration is then required to establish the relationship between concentration of salt solution and censor. Filter paper method is considered as the simplest method and relatively low cost compare to other method. The studies conducted by many investigators indicate that calibration curve from one type to another type of filter paper is quite different. This paper presents the basic concepts of laboratory work on establishing total suction calibration curve for Wahtmann #42 filter paper. The work has been conducted using NaCl and KCl solutions with different molality to generate different suction. The result indicates that the higher molality of solution, the higher suction is generated. The calibration curve from KCl exhibits a bit higher compare to the one from NaCl. The difference of both curves most probably is due to the difference of equilibration period and suction source.</p><p><strong>Keywords</strong>: Calibration curve, filter paper, suction, unsaturated soil</p>

Soil Suction Dispersion and Statistical Analysis with Depth at the Medford Airport

1997 ◽  
Vol 1596 (1) ◽  
pp. 76-83
Author(s):  
James B. Nevels
Keyword(s):  
Standard Deviation ◽  
Filter Paper ◽  
Test Procedure ◽  
Matric Suction ◽  
Soil Suction ◽  
Sample Interval ◽  
The Mean ◽  
The Difference ◽  
T Distribution ◽  
Total Suction

The use of soil suction measurements has steadily increased in geotechnical practice. A current standard test procedure that describes the use of laboratory filter papers as passive sensors to measure the soil matric and total suction is ASTM D5298-94. The principal objective of the research presented here was to evaluate dispersion of suction measurements with depth using the filter paper method described in the ASTM standard. In a single test boring to a depth of 5.33 m, 35 samples were taken at intervals of 152.4 mm. Each sample was separated into four replicate samples. The matric and total suction of each of the 35 sample intervals were then measured, resulting in a total of 278 suction measurements. To manage this volume of tests, the sample size was split approximately in half, and each portion was separately tested. This approach led to severall insights into the test procedure, such as the effect of delay in transferring the filter paper from the specimen container into the metal container. Sampling and testing are described. The dispersion of both the total and the matric suction measurements was characterized in three ways: the range of measurements in each sample interval, the standard deviation of measurements in each sample interval, and an error function defined as the difference between each measurement and the mean for the sample interval. Each of these statistics was plotted as a histogram. A chi-squared test was applied to measure the goodness-of-fit of a t-distribution fitted to the error as defined by the difference between each measurement and the mean for that sample interval. Results indicate precision for total and matric suction measurements of 0.0540 log kPa within one standard deviation. Analysis does not indicate a substantial difference between the error associated with total suction measurements and that associated with matric suction measurements. A brief description of the conventional geotechnical site characterization is presented for the Medford Airport.

scholarly journals Boulder Pickup by Tsunami Surge

2019 ◽  
Vol 13 (05n06) ◽  
pp. 1941006
Author(s):  
Samuel Harry ◽  
Margaret Exton ◽  
Harry Yeh
Keyword(s):  
Pore Water Pressure ◽  
Initial Conditions ◽  
Scale Effects ◽  
Traditional Approach ◽  
Water Pressure ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Flow Conditions ◽  
The Difference ◽  
The Impact

Study of boulder transport by tsunamis is challenging because boulder size, shape, and composition vary greatly; furthermore, flow conditions, topography, and initial conditions are generally unknown. To investigate the mechanism of boulder pickup, experiments of tsunami-like flow past spherical boulders partially buried in a sediment bed are conducted. The experiments are performed in a large centrifuge facility to reduce scale effects and the corresponding dynamic similitude is discussed. The traditional approach to determine boulder pickup is adapted for the case of a half-buried spherical boulder. The adapted model predicts that the boulders are transported, but does not accurately predict the timing of pick up. To investigate the difference in pickup timing, two physical phenomena are discussed: pore-water-pressure dissipation in the soil, and the impact of the free-surface flow on hydrodynamic forces. For a spherical shaped boulder, vertical forces (i.e. buoyant and lift forces) are critical for the initiation of boulder pickup. It was found that spherical boulders that are three-quarter buried in the soil are not transported, even when exposed to flow conditions that would otherwise predict transport.

Second Canadian Geotechnical Colloquium: Appropriate concepts and technology for unsaturated soils

1979 ◽  
Vol 16 (1) ◽  
pp. 121-139 ◽  
Author(s):  
D. G. Fredlund
Keyword(s):  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Three Dimensional ◽  
Earth Pressure ◽  
Saturated Soil ◽  
Engineering Practice ◽  
The Matrix ◽  
Matrix Suction

A practical science has not been fully developed for unsaturated soils for two main reasons. First, there has been the lack of an appropriate science with a theoretical base. Second, there has been the lack of an appropriate technology to render engineering practice financially viable.This paper presents concepts that can be used to develop an appropriate engineering practice for unsaturated soils. The nature of an unsaturated soil is first described along with the accompanying stress conditions. The basic equations related to mechanical properties are then proposed. These are applied to practical problems such as earth pressure, limiting equilibrium, and volume change.An attempt is made to demonstrate the manner in which saturated soil mechanics must be extended when a soil is unsaturated. Two variables are required to describe the stress state of an unsaturated soil (e.g., (σ – ua) and (ua – uW). There is a smooth transition from the unsaturated case to the saturated case since the pore-air pressure becomes equal to the pore-water pressure as the degree of saturation approaches 100%. Therefore, the matrix suction (i.e., (ua – uW) goes to 0 and the pore-water pressure can be substituted for the pore-air pressure (i.e., (σ – uW)).The complete volumetric deformation of an unsaturated soil requires two three-dimensional constitutive surfaces. These converge to one two-dimensional relationship for a saturated soil. The shear strength for an unsaturated soil is a three-dimensional surface that reduces to the conventional Mohr–Coulomb envelope for a saturated soil.The manner of applying the volumetric deformation equations and the shear strength equation to practical problems is demonstrated. For earth pressure and limiting equilibrium problems, the unsaturated soil can be viewed as a saturated soil with an increased cohesion. The increase in cohesion is proportional to the matrix suction of the soil. For volume change problems it is necessary to have an indication of the relationship between the various soil moduli.There is a need for further experimental studies and case histories to substantiate the proposed concepts and theories.

scholarly journals Numerical Analysis of the Effects of Crack Characteristics on the Stress and Deformation of Unsaturated Soil Slopes

Water ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 194 ◽  
Author(s):  
Liuxin Yang ◽  
Enlong Liu
Keyword(s):  
Pore Water ◽  
Unsaturated Soil ◽  
Crack Width ◽  
Evaporation Rate ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Infiltration Rate ◽  
Soil Slope ◽  
Soil Slopes ◽  
Stress And Deformation

Cracks induced by evaporation or rainfall have a great influence on the stability of unsaturated soil slopes, which can lead to landslides during the rainfall process. In order to study the effect of crack characteristics on the evolution of stress and deformation of unsaturated soil slopes, a series of numerical analyses under different conditions were performed using a coupled elastoplastic finite element program that we developed for unsaturated soil. When carrying out the numerical analyses, the effective stress for unsaturated soil proposed by Bishop and an elastoplastic double-hardening constitutive model for the soil skeleton were employed. The varying parameters, including the crack location, the discharge speed, evaporation rate, infiltration rate, and tensile strength, were investigated to study the coupling process of pore water pressure and deformation in the process of evaporation and rainfall infiltration. The numerical results showed that the minimum pore water pressure of the soil slope at the end of evaporation/rainfall decreased gradually and the crack width increased gradually as the crack set closer to the slope; the larger the discharge speed of pore air, the greater the crack width. With the increase in the evaporation rate, the pore water pressure of the soil slope reduced and the crack initiated earlier and became wider. As the infiltration rate increased, the pore water pressure of the soil slope and the crack width increased, but the decreasing duration became shorter. The change of tensile strength had little effect on the pore water pressure, but the development of the crack width changed with evaporation and rainfall infiltration.

scholarly journals Stability and Consolidation of Sediment Tailings Incorporating Unsaturated Soil Mechanics

Fluids ◽  
2021 ◽  
Vol 6 (12) ◽  
pp. 423
Author(s):  
Alfrendo Satyanaga ◽  
Martin Wijaya ◽  
Qian Zhai ◽  
Sung-Woo Moon ◽  
Jaan Pu ◽  
...  
Keyword(s):  
Unsaturated Soil ◽  
Pore Water Pressure ◽  
Soil Mechanics ◽  
Water Pressure ◽  
High Water ◽  
Degree Of Saturation ◽  
High Water Content ◽  
Consolidation Process ◽  
Time Required ◽  
Unsaturated Zones

Tailing dams are commonly used to safely store tailings without damaging the environment. Sand tailings (also called Sediment tailings) usually have a high water content and hence undergo consolidation during their placement. As the sediment tailings are usually placed above the ground water level, the degree of saturation and permeability of the sediment tailing is associated with the unsaturated condition due to the presence of negative pore-water pressure or suction. Current practices normally focus on the analyses saturated conditions. However, this consolidation process requires the flow of water between saturated and unsaturated zones to be considered. The objective of this study is to investigate the stability and consolidation of sediment tailings for the construction of road pillars considering the water flow between saturated and unsaturated zones. The scope of this study includes the unsaturated laboratory testing of sediments and numerical analyses of the road pillar. The results show that the analyses based on saturated conditions overestimate the time required to achieve a 90% degree of consolidation. The incorporation of the unsaturated soil properties is able to optimize the design of slopes for road pillars into steeper slope angles.

Effectiveness of Capillary Barrier and Vegetative Slope Covers in Maintaining Soil Suction

2016 ◽  
pp. 51-69
Author(s):  
Harianto Rahardjo ◽  
S. Krisnanto ◽  
E.C. Leong
Keyword(s):  
Shear Strength ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Matric Suction ◽  
Numerical Analyses ◽  
Soil Suction ◽  
Vetiver Grass ◽  
Capillary Barrier ◽  
Maximum Rainfall

Capillary barrier and vegetative slope covers can be used to improve slope stability during rainfall by maintaining matric suction in the slope. A study was performed to investigate the effectiveness of capillary barrier system (CBS) and vegetative slope covers (Orange Jasmine and Vetiver grass) in maintaining soil suction. Performance of slopes with and without slope covers was investigated using field instrumentations and numerical analyses. Laboratory tests were performed to measure hydraulic and shear strength properties of the soil, the soils with Orange Jasmine and Vetiver grass root, and CBS materials. Numerical analyses were performed to investigate the variation of pore-water pressure profiles at a selected location and factor of safety during low, high, and maximum rainfall intensities. Pore-water pressures measured in the field were used to calibrate the numerical models. Laboratory test results showed that the presence of root increased the shear strength of soil. Numerical analyses and field monitoring results showed that the slope with covers can maintain negative pore-water pressure better than the original slope. Performance of Orange Jasmine, Vetiver grass, and CBS in maintaining matric suction in the slope is essentially similar during low, high, and maximum rainfall intensities.

Gas pressure in unsaturated offshore soils

1990 ◽  
Vol 27 (1) ◽  
pp. 79-89 ◽  
Author(s):  
S. J. Wheeler ◽  
W. K. Sham ◽  
S. D. Thomas
Keyword(s):  
Surface Tension ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Gas Pressure ◽  
Cavity Expansion ◽  
Total Stress ◽  
Pressure Surface ◽  
Reconstituted Soil ◽  
The Difference

Direct measurement of gas pressure within unsaturated offshore soils is very difficult because the gas occurs in the form of large, discrete bubbles. However, consideration of the soil structure and analysis of a continuum model for the soil suggest two independent sets of limits for the gas bubble pressure. Surface tension effects limit the difference between gas pressure and pore-water pressure, while cavity expansion and contraction considerations limit the difference between gas pressure and mean total stress. If the gas pressure lies within these limits, it should remain almost unaffected by changes to the total stress or pore-water pressure. These suggestions are supported by results from an oedometer test on a reconstituted soil sample containing large bubbles of methane gas. Key words: bubbles, cavity expansion, gas, oedometer tests, offshore geotechnics, pore pressure, surface tension, unsaturated.

Stress–strain behaviour of unsaturated soil in true triaxial tests

2002 ◽  
Vol 39 (3) ◽  
pp. 608-619 ◽  
Author(s):  
Hajime Matsuoka ◽  
De'an Sun ◽  
Akiteru Kogane ◽  
Nobuhiko Fukuzawa ◽  
Wataru Ichihara
Keyword(s):  
Unsaturated Soil ◽  
Failure Criterion ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Triaxial Tests ◽  
Principal Stresses ◽  
True Triaxial ◽  
Triaxial Apparatus ◽  
True Triaxial Apparatus ◽  
True Triaxial Tests

A suction-controlled true triaxial apparatus for unsaturated soil was developed from the existing true triaxial apparatus for sand by attaching a device to supply matric suction to specimens. Using the developed apparatus, true triaxial tests (σ1 [Formula: see text] σ2 [Formula: see text] σ3; where σ1, σ2, and σ3 are the three different principal stresses) on an unsaturated silty soil were carried out under constant suction using the negative pore-water pressure method (s = –uw > 0; ua = 0) for applying the matric suction, s (s = ua – uw; where ua is the pore-air pressure and uw is the pore-water pressure). It was found that the true triaxial test results under three different principal stresses are uniquely arranged on the "extended spatially mobilized plane (extended SMP)" for frictional and cohesive materials that is modified from the original SMP for frictional materials by introducing "a bonding stress, σ0 (= c·cotϕ, where c is cohesion and ϕ is the internal friction angle)." It was also found that the shear strengths of the unsaturated silty clay obtained by the true triaxial apparatus nearly agree with the extended SMP failure criterion (Î1Î2/Î3 = constant, where Î1, Î2, and Î3 are the first, second, and third invariants of the translated stress tensor). The measured stress-strain-strength behaviour of the unsaturated soil in three-dimensional (3D) stresses can be well simulated by an elastoplastic model with the transformed stress based on the extended SMP criterion and a special hardening parameter.Key words: failure criterion, shear strength, special shear test, suction, stress path, unsaturated soil.

Improving consolidation of dredged slurry by vacuum preloading using prefabricated vertical drains (PVDs) with varying filter pore sizes

2020 ◽  
Vol 57 (2) ◽  
pp. 294-303 ◽  
Author(s):  
Jun Wang ◽  
Yongli Yang ◽  
Hongtao Fu ◽  
Yuanqiang Cai ◽  
Xiuqing Hu ◽  
...  
Keyword(s):  
Pore Size ◽  
Fine Particles ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Vacuum Preloading ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Pore Sizes ◽  
Filter Surface ◽  
The Difference

Prefabricated vertical drains (PVDs) have been used extensively to accelerate the consolidation rate of dredged slurry. While some fine particles from dredged slurry can easily squeeze through the filter into the drainage channel, many cannot. As such, these soil particles deposit on the filter surface causing partial clogging of the drainage path. Although the pore size of filter is recognized as an important factor that influences PVD clogging, the standards for determining the pore size of the filter are lacking. To this end, the traditional gradient ratio tests with four different filter pore sizes were conducted, and the results show that the permeability of the filter at a given head increases with the increase in the pore size of the filter. To remove the effect of the difference between static hydraulic gradient and vacuum pressure, the vacuum preloading tests with varying pore sizes of filters were further conducted. Through these vacuum preloading tests, the degree of vacuum, settlement, pore-water pressure, water content, vane shear strength, and other parameters of PVDs with various filter pore sizes were obtained, and the optimal pore size of filter was determined.

Sign in / Sign up

Export Citation Format

Share Document