Volume change indices during loading and unloading of an unsaturated soil

1992 ◽  
Vol 29 (2) ◽  
pp. 195-207 ◽  
Author(s):  
D. Y. F. Ho ◽  
D. G. Fredlund ◽  
H. Rahardjo
Keyword(s):  
Soil Properties ◽  
Key Words ◽  
Volume Change ◽  
Unsaturated Soil ◽  
Constitutive Relations ◽  
Change Theory ◽  
Glacial Till ◽  
Testing Procedures ◽  
Loading And Unloading ◽  
Oedometer Tests

The paper presents the volume change theory and the designation of associated soil properties that must be measured for an unsaturated soil. The equipment required for the measurement of each of the relevant volume relationships is described. Several testing procedures for obtaining the volume change indices during loading and unloading of an unsaturated soil are presented. Typical results from loading and unloading tests on compacted silt and compacted glacial till specimens are presented and analyzed. The analysis is given in order to illustrate the application of the volume change theory to practical problems. Key words : unsaturated soil, volume change indices, constitutive relations, coefficients of volume change, oedometer tests.

In situ estimation of the coefficient of consolidation in clays

1990 ◽  
Vol 27 (1) ◽  
pp. 58-67 ◽  
Author(s):  
Mohammed G. Kabir ◽  
Alan J. Lutenegger
Keyword(s):  
Key Words ◽  
Pore Pressure ◽  
Reference Values ◽  
Time Factors ◽  
In Situ Tests ◽  
Coefficient Of Consolidation ◽  
Oedometer Test ◽  
Undisturbed Samples ◽  
Oedometer Tests

An investigation was conducted to demonstrate the applicability of cylindrical piezocone and flat piezoblade tests for providing reliable estimates of the coefficient of consolidation in clays. Coefficients of consolidation were calculated from piezocone dissipation tests for different degrees of consolidation using theoretical time factors to provide a comparison with laboratory oedometer tests. Three techniques were developed to calculate the coefficient of consolidation from piezoblade dissipation tests. Results from in situ pore pressure dissipation tests were compared with laboratory oedometer tests performed on undisturbed samples oriented in both the vertical and horizontal directions, to provide reference values of cv and ch. The results of investigations conducted at several clay sites are presented. Key words: in situ tests, piezocone, piezoblade, coefficient of consolidation, oedometer test, clays.

Research of pneumatic conveyor for overloading of fuel pellets

2021 ◽  
pp. 88-96
Author(s):  
N. Spodyniuk ◽  
◽  
L. Horbachenko ◽  
Keyword(s):  
Key Words ◽  
Agricultural Sector ◽  
Raw Materials ◽  
Agricultural Waste ◽  
High Quality ◽  
Fuel Pellets ◽  
Energy Consuming ◽  
Loading And Unloading

The constant development of the country's agricultural sector allows the production of biofuels, such as fuel pellets, from agricultural waste - straw, corn and sunflower husks. However, the transportation of fuel pellets is quite energy consuming. The process of loading and unloading, transportation over long distances requires complex mechanized equipment. The use of a pneumatic conveyor for grain reloading will allow to provide high-quality transportation of fuel pellets. The aim of the article was to investigate the operation of the pneumatic conveyor for overloading fuel pellets, to determine the optimal indicators that affect the productivity of the pneumatic conveyor. Since fuel pellets, as raw materials, are structurally similar to cereals, a study of the pneumatic grain conveyor PTZ-25 was conducted. The dependence of the productivity of the pneumatic conveyor on the lifting height h, m and the length of the pipelines L, m was obtained. The obtained results showed that by reducing the length of the pipelines by four times and the lifting height by half, the productivity of the pneumatic conveyor will increase by 1.15 times. Key words: fuel pellets, pneumatic conveyor, productivity

Method for Quick Prediction of Hydraulic Conductivity and Soil-Water Retention of Unsaturated Soils

2018 ◽  
Vol 2672 (52) ◽  
pp. 108-117 ◽  
Author(s):  
Shaoyang Dong ◽  
Yuan Guo ◽  
Xiong (Bill) Yu
Keyword(s):  
Finite Element ◽  
Hydraulic Conductivity ◽  
Soil Properties ◽  
Soil Water ◽  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Hydraulic Properties ◽  
Water Retention ◽  
Characteristic Curve ◽  
Soil Water Retention

Hydraulic conductivity and soil-water retention are two critical soil properties describing the fluid flow in unsaturated soils. Existing experimental procedures tend to be time consuming and labor intensive. This paper describes a heuristic approach that combines a limited number of experimental measurements with a computational model with random finite element to significantly accelerate the process. A microstructure-based model is established to describe unsaturated soils with distribution of phases based on their respective volumetric contents. The model is converted into a finite element model, in which the intrinsic hydraulic properties of each phase (soil particle, water, and air) are applied based on the microscopic structures. The bulk hydraulic properties are then determined based on discharge rate using Darcy’s law. The intrinsic permeability of each phase of soil is first calibrated from soil measured under dry and saturated conditions, which is then used to predict the hydraulic conductivities at different extents of saturation. The results match the experimental data closely. Mualem’s equation is applied to fit the pore size parameter based on the hydraulic conductivity. From these, the soil-water characteristic curve is predicted from van Genuchten’s equation. The simulation results are compared with the experimental results from documented studies, and excellent agreements were observed. Overall, this study provides a new modeling-based approach to predict the hydraulic conductivity function and soil-water characteristic curve of unsaturated soils based on measurement at complete dry or completely saturated conditions. An efficient way to measure these critical unsaturated soil properties will be of benefit in introducing unsaturated soil mechanics into engineering practice.

Significance of unsaturated soil properties on stability analyses against extreme rainfall conditions

2021 ◽  
pp. 193-203
Author(s):  
Brena Li En Tan ◽  
Alfrendo Satyanaga ◽  
Mărgărit-Mircea Nistor ◽  
Martin Wijaya ◽  
Harianto Rahardjo
Keyword(s):  
Soil Properties ◽  
Unsaturated Soil ◽  
Extreme Rainfall ◽  
Stability Analyses

The Active Zone: Unsaturated Soil Volume Change Due to Normal Cycles and Anomalies at Depth

2018 ◽  
Author(s):  
John T. Bryant ◽  
Hayden Fischer ◽  
M. Kabir Hossain ◽  
Jeong Yeon Cheon
Keyword(s):  
Volume Change ◽  
Unsaturated Soil ◽  
Active Zone ◽  
Soil Volume

Constitutive Behavior and Testing of Structural Adhesives

1987 ◽  
Vol 40 (10) ◽  
pp. 1393-1402 ◽  
Author(s):  
Erol Sancaktar
Keyword(s):  
Mechanical Model ◽  
Material Characterization ◽  
Constitutive Relations ◽  
Superposition Principle ◽  
Surface Preparation ◽  
Ring Test ◽  
Stress Strain ◽  
Testing Procedures ◽  
Structural Adhesives

Material characterization of structural adhesives in the bulk and bonded forms is discussed. Constitutive relations used for describing stress–strain data are reviewed. The difficulties associated with adhesive characterization in the bonded form are cited. Common testing procedures for adhesive characterization in the bulk and bonded forms are reviewed. In presenting the constitutive relations used in material characterization of structural adhesives, deformation theories introduced by Hencky are reviewed first. The modifications made in this theory to render it rate dependent and bilinear are discussed and applications to adhesive characterization are cited. Application of linear viscoelasticity, mechanical model characterization, and its use in describing the dependence of adhesive and cohesive strengths on rate, temperature, and bond thickness are presented. The time–temperature superposition principle and three-dimensional stress–strain relations in integral and differential operator forms are reviewed. Frequent assumptions for dilatation and distortion operations are presented. Procedures for describing nonlinear viscoelastic behavior are reviewed. It is pointed out that the extent of nonlinearity is dependent on both the stress level and the time scale. The use of nonlinear spring and dashpot elements, nonlinear differential operators, and perturbation of elastic and viscous coefficients are cited. Prandtl’s incremental theory of plasticity and its extension in the form of over-stress theory is presented. The incorporation of this over-stress idea into the viscoelastic mechanical model characterization is discussed. The modified Bingham model and the Chase–Goldsmith model developed in this fashion and their application to adhesive material characterization are presented. The use of empirical relations for the description of creep behavior is discussed. Prediction of shear behavior based on bulk tensile data is demonstrated. It is suggested that characterization of adhesive behavior in the bonded form should include the application of stress analysis, fracture mechanics, polymer chemistry and surface analysis techniques. In testing bonded samples the use of thick adherend symmetric single lap geometry or napkin ring test geometry is advised and it is suggested that the specimens should be prepared with the same surface preparation and cure techniques.

Prediction of available potassium in Ontario soils by electro-ultrafiltration and chemical extraction

1992 ◽  
Vol 72 (2) ◽  
pp. 159-167 ◽  
Author(s):  
Liangxue Liu ◽  
T. E. Bates ◽  
T. S. Tran
Keyword(s):  
Organic Matter ◽  
Soil Properties ◽  
Key Words ◽  
Soil Ph ◽  
Chemical Extraction ◽  
K Uptake ◽  
Chemical Methods ◽  
Exchangeable Calcium ◽  
Time Required

The extractions of soil K by electroultrafiltration (EUF) and by chemical methods were compared as predictors of plant-available K for greenhouse-grown alfalfa on 38 Ontario soils. The relation of soil properties to the amount of K extracted by EUF fractions was also examined. The contents of silt and clay were negatively correlated with EUF-K at 50 V and 22 °C and positively correlated with EUF-K at 400 V and 80 °C. Soil pH and organic matter were not significantly correlated with the amounts of K extracted in the EUF-K fractions. The EUF extraction of K was influenced by the presence of carbonate or high exchangeable calcium in soils. Similar correlations were obtained between K uptake and K extracted by chemical methods and the sum of EUF-K fractions. When used along with other soil properties, EUF-K fractions and K extracted by chemical methods predicted availability of soil K with roughly equal ability. The model using the sum of K extracted by EUF at 50, 200 and 400 V is the simplest one and contains three variables, K, K2 and Ca2. The use of EUF is limited due to cost of equipment and time required for analysis, unless a number of nutrients can be accurately determined on one extract. Among the chemical methods, equations developed using three nonacidic extradants, NaCl, ABDTPA and NH4OAc explained more variation in K uptake than two acidic extractants, Mehlich 3 and 0.1 M HNO3. The NaCl model, ABDTPA model and NH4OAc model contained the same variables and had similar R2 values (0.88–0.91). Key words: Available K, chemical methods, electro-ultrafiltration, EUF-K fractions, K uptake

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