Increase In Dry Density Research Articles

Models of soil compaction due to traffic and their evaluation

Soil compaction by wheeling may cause considerable damage to the structure of the tilled soil and the subsoil and consequently to crop production, workability and the environment. Soil compaction models are reviewed and their evaluation under laboratory or field conditions is discussed. The development of a compaction model includes: (i) modelling the propagation of the loading forces within the soil resulting from forces applied at the soil surface from farm vehicles; (ii) modelling soil stress–strain behaviour. Models predict stress distribution in the soil induced by farm vehicle and change in soil structure: increase in dry bulk density and rut depth formation. We conclude that models based on Boussinesq equations for stress propagation are useful since they use a small number of parameters. They have been successfully evaluated in field conditions for homogeneous soil under a wide range of soil and water conditions. The difference between simulations and observations becomes more apparent when dealing with heterogeneous structures (clods, firm subsoil). The models based on the finite element method (FEM) have been shown to be more adequate for modelling the 3D distribution of stress within the soil induced by wheeling and the complex stress–strain behaviour of soil. Nevertheless, these models require more mechanical parameters and have been evaluated under limited conditions in laboratory bins or in the field with low compaction intensities. This review stresses the need to test FEM soil compaction models, so as to extend the range of conditions where these models can be applied.

Measuring the Effect of Mixed Grading on the Maximum Dry Density of Sands

Abstract During cut and fill operations, compaction using sands from different sources may be carried out. The resulting mixed sand will have different compaction characteristics than those of the parent sands. An increase in dry density will result as the grading moves towards more ideal characteristics for dense packing. Laboratory compaction tests using pluviation and the vibrating hammer method have been carried out to measure this increase in dry density. The resulting value is generally significantly greater than the result predicted by taking the mean value of dry density given by the parent sands.

Activation energy for diffusion of chloride ions in compacted sodium montmorillonite

Diffusion of chloride ions in compacted montmorillonite was studied for a performance assessment as buffer material in geological disposal of high-level radioactive waste. The apparent diffusion coefficients were from 6.8×10 −12 to 2.2×10 −10 m 2 s −1 for sodium montmorillonite at dry densities from 1.0 to 1.8 Mg m −3 at diffusion temperatures from 278 to 323 K. The activation energy increased from 14 kJ mol −1 (lower than that in free water, 17.4 kJ mol −1) to 25 kJ mol −1 (higher than that in free water), as the dry density increased from 1.0 to 1.8 Mg m −3. These facts can be attributed to changes in the predominant diffusion process as dry density increases. The dry density dependence of the activation energy cannot be explained by conventional diffusion models, such as the pore water diffusion model.

Self-Diffusion of Sodium Ions in Compacted Sodium Montmorillonite

Diffusion of sodium ions through compacted sodium montmorillonite in a water-saturated state was studied to obtain fundamental information for performance assessments of geological disposal of high-level radioactive waste.Basal spacings obtained from X-ray diffraction measurements indicated a decrease in the interlamellar spacing with increasing dry density of the montmorillonite; the three-water-layer hydrate was observed at low dry density (≤1.3 Mg/m3), and the two-water-layer hydrate was observed at high dry density (≥1.6 Mg/m3), whereas both were observed at dry densities between 1.4 and 1.5 Mg/m3.Activation energies from 14.1 to 24.7 kJ/mol were obtained from the temperature dependence of the self-diffusion coefficients of sodium ions. Activation energies lower than that for the diffusion of sodium ions in free water were found for montmorillonite specimens with dry densities of ≤1.2 Mg/m3, while higher activation energies were observed at dry densities ≥1.4 Mg/m3.The pore water diffusion model, the general model used for migration of nuclides, is based on geometric parameters; however, findings cannot be explained by only the changes in the geometric parameters. Possible explanations for the dry density dependence of the activation energy are changes in the temperature dependence of the distribution coefficients of sodium ions on the montmorillonite, changes in the diffusion process with an increase in dry density, or both.

Effect of dry density on Sr-90 diffusion in a compacted Ca-bentonite for a backfill of radioactive waste repository

The transport of radionuclides in compacted bentonite is dominated by the diffusion process. The dry density is an important factor in the diffusion of radionuclides through the compacted bentonite. Through-diffusion tests were performed to investigate the effect of dry density on Sr-90 diffusion. In the diffusion tests the sample used was a bentonite taken from the southeastern area of Korea and the experimental solution was synthetic groundwater spiked with a tracer of Sr-90 (as 90SrCl 2). The dry density was adjusted in the range of 1.0–1.7 Mg/m 3. The distribution coefficient of Sr-90 in the compacted bentonite was much lower than that obtained by a batch test. The formation factor and porosity of the compacted bentonite were decreased with increasing dry density. The apparent and effective diffusion coefficients of Sr-90 were in the range of 1.14 × 10 −12 –1.20 × 10 −12m 2/s, 1.81 × 10 −11 –1.11 × 10 −11m 2/s, respectively, and decreased with increasing dry density of compacted bentonite. It was found for Sr-90 that the higher the dry density increases, the more significant the surface diffusion, as compared with the pore diffusion. The results obtained will be used as basic data for the safety assessment of a repository.

The Effect of Stone Content, Size, and Shape on the Engineering Properties of a Compacted Silty Clay

Research Article| May 01, 1990 The Effect of Stone Content, Size, and Shape on the Engineering Properties of a Compacted Silty Clay ABDUL SHAKOOR; ABDUL SHAKOOR Department of Geology and Water Resources Research Institute, Kent State University, Kent, OH 44240 Search for other works by this author on: GSW Google Scholar BRAD D. COOK BRAD D. COOK Department of Geology and Water Resources Research Institute, Kent State University, Kent, OH 44240 *Present address: Camp Dresser and McKee Inc., 1-Center Plaza, Boston, MA 02106. Search for other works by this author on: GSW Google Scholar Environmental and Engineering Geoscience (1990) xxvii (2): 245–253. https://doi.org/10.2113/gseegeosci.xxvii.2.245 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation ABDUL SHAKOOR, BRAD D. COOK; The Effect of Stone Content, Size, and Shape on the Engineering Properties of a Compacted Silty Clay. Environmental and Engineering Geoscience 1990;; xxvii (2): 245–253. doi: https://doi.org/10.2113/gseegeosci.xxvii.2.245 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentBy SocietyEnvironmental and Engineering Geoscience Search Advanced Search Abstract Large samples of a homogeneous silty clay (CL) of glacial origin and crushed limestone aggregate were obtained to study the compaction characteristics of clay-stone mixtures containing varying proportions of aggregate. Three size gradations of limestone aggregate (#10–#4 sieve, #4–1/2 in., and 1/2 in–3/4 in.) were each admixed with dried clay in 10 percent by weight increments from 10–80 percent. Limestone aggregate, subrounded in an abrasion apparatus, was mixed with the same clay in similar proportions to study the effect of stone shape. The clay-stone mixtures were then compacted by standard Proctor method to determine maximum dry density, optimum moisture content, and void ratio of each mix. Additionally, permeability and unconfined compressive strength tests were conducted on mixtures compacted to a minimum of 95 percent maximum dry density and at ±2 percent optimum water content.Results show that there is an increase in maximum dry density and a corresponding decrease in void ratio as the stone content of a clay-aggregate mixture increases to 60–70 percent by weight regardless of stone size or shape. Permeability is generally not affected for up to 50 percent stone content, but increases 4 to 5 orders of magnitude between 50–70 percent stone. Unconfined compressive strength generally decreases with increasing stone content and stone size. The study shows that the addition of small size stone in small proportions can help improve the density of compacted silty clays without appreciably affecting other properties. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not currently have access to this article.

Density and strength characteristics of lightweight mortar

Experiments were carried out on 42 moist-cured plain mortar specimens and 156 lightweight mortar (LWM) specimens wherein air was introduced in the fresh mix with the aid of a foaming agent and an increased mixer speed. In contrast with that of the normal-weight mortar, increase in dry density and compressive strength has been observed with the increase in water/cement ratio of the mix. Theoretical expressions for predicting the dry density and an empirical formula for predicting the compressive strength of LWM have been suggested.

Behavior of soil under a brief dynamic load

1. The damping coefficients both of cohesive and noncohesive soils practically do not depend on the state of the soils relative to the limit state almost up to loss of strength by the soil specimen. An increase of the initial lateral pressure and dry density of the noncohesive soil as well as a decrease of the moisture content of cohesive soil noticeably reduce the value of the damping coefficients (from 0.6 to 0.05 for noncohesive and from 0.3 to 0.15 for cohesive). The interval of variations of the damping coefficients obtained under conditions of small values of the initial lateral pressure (within 0.1 MPa) and combined stress state leads to the need for an experimental determination of the damping coefficients, at least for similar conditions. 2. The shear moduli for small values of the initial lateral pressure and under conditions of a combined stress state for cohesive soil depend on the level of the initial lateral pressure and for the noncohesive on the change in the moisture content. In the interval of stresses created in the specimen, when the initial lateral pressure does not exceed 0.098 MPa and the average static stress does not exceed 0.3 MPa, the shear moduli are practically proportional to the average stress. 3. Both volumetric strains and distortional strains under a brief dynamic shear load and under conditions of a combined stress state are far less than the strains from an equal static load. In this case, whereas the volumetric strains in shear for noncohesive soil have the character of compacting, for cohesive soils they are always loosening. 4. The description of the process of soil deformation as a result of a brief dynamic load obtained shows the possibility of determining the nonlinear reaction of soil to this load by means of the linear acceleration method, if the system under consideration can be represented as a system with one degree of freedom.

Lime Sludge Stabilization of Sand for Capping Sanitary Landfills

Absence of adequate quantities of suitable capping material, such as clay, is a major problem at many landfill sites. The research presented in this paper was undertaken to develop alternative capping materials by stabilizing river sand with sludge additives. Different percentages of sewage sludge and lime sludge were blended with river sand and the mixtures were evaluated for their suitability as capping materials. An effective capping material, when compacted properly, should maximize density, reduce permeability, and maintain stability with respect to slope failure and volume changes. Results from this evaluation procedure suggest that sewage sludge is not effective in stabilizing sand for capping purposes. The addition of sewage sludge decreases maximum dry density from 102 lbs/ft 3 (1.63 Mg/m 3 ) for pure sand to 76.5 lbs/ft 3 (1.22 Mg/m 3 ) for the 40 percent mixture, whereas the permeability remains in the 10 −4 cm/sec range. Contrary to sewage sludge, lime sludge effectively stabilizes sand and can be used to produce a feasible capping material. With the addition of lime sludge, the maximum dry density increases from 105.6 lbs/ft 3 (1.69 Mg/m 3 ) for pure sand to 108.0 lbs/ft 3 (1.73 Mg/m 3 ) for the 10 percent mixture, and then decreases to 99.6 lbs/ft 3 (1.6 Mg/m 3 ) for the 50 percent mixture. The permeability decreases from an initial value of 8.4 × 10 −4 cm/sec for 0 percent sludge content to a low of 1 × 10 −6 cm/sec at 40 percent sludge content. On the basis of these results, the 20 percent lime sludge mix is considered to provide the best compromise between high density and low permeability in a compacted state. The 20 percent mix is also expected to be stable with respect to volume changes and slope failure as indicated by durability testing, shear strength parameters, and stability analysis.

Fatigue of immature baboon cortical bone

Strain-controlled uniaxial fatigue and monotonic tensile tests were conducted on turned femoral cortical bone specimens obtained from baboons at various ages of maturity. Fatigue loading produced a progressive loss in stiffness and an increase in hysteresis prior to failure, indicating that immature primate cortical bone responds to repeated loading in a fashion similar to that previously observed for adult human cortical bone. Bone fatigue resistance under this strain controlled testing decreased during maturation. Maturation was also associated with an increase in bone dry density, ash fraction and elastic modulus. The higher elastic modulus of more mature bone meant that these specimens were subjected to higher stress levels during testing than more immature bone specimens. Anatomical regions along the femoral shaft exhibited differences in strength and fatigue resistance.

A simplified approach for mix design based on shape factors of coarse aggregates

The stability of granular materials and bituminous mixes increases with increase in dry density or decrease in voids in the mix. Therefore the proportions of materials in the mix are designed to obtain a desired gradation which yields maximum density.

Influence of maize cropping on the soil structure of two soils in the Waikato district, New Zealand

Abstract Modification of soil physical properties resulting from the change of land lise from pasture to various periods of continuous maize cropping on two Waikato soils was investigated. Under present management practices on the two soils, maize cropping produced a deterioration of soil structure as indicated by changes in field properties, a slight increase in dry bulk density, a decrease in aggregate size, and a decrease in soil aggregate stability. On one soil an equilibrium in the state of soil structure was established after 3 years of maize cropping, and further cropping resulted in little modification of the physical properties. On the .;econd soil, however, the first two years of maize cropping were beneficial in terms of decreasing dry bulk density and increasing porosity, but these benefits were later lost with continued cropping.

Soil compaction patterns caused by off-road vehicles in eastern canadian agricultural soils

The interaction between vehicles and soils of varying properties and moisture contents can cause serious compaction and soil structure problems. This situation always confronts the farmer, who has to deal with the soil effects, and should be of foremost interest to agricultural machine manufacturers and dealers as well as other off-road vehicle users in order that they may employ the best vehicle configuration for various conditions. This study is oriented towards evaluating compaction behaviour under various loads, different soil conditions, number of passes, and tire sizes. Contour plots of change in dry density compared to the original density were obtained under the tire path cross sections for different loads, number of passes and soil moisture conditions. The increase in dry density change, determined for different numbers of passes, was sharp up to five passes and levelled off for further increases in the number of passes. Increase in dry density became as great as 30 pcf (0.48 g/cm 3), illustrating the detrimental effect of repeated passes of a vehicle in the field.

Thermal Conductivity of Saturated Leda Clay

Synopsis The thermal conductivity of saturated remoulded Leda clay, a soil of post-glacial marine origin, increased from 5·5 to 7 B.t.u. in/sq.ft hour°F for an increase in dry density of 20 lb/cu.ft (75–95 lb/cu.ft) and decreased from 7 to 6 B.t.u. in/sq.ft hour°F for an increase of clay size particles from 39 to 60%. The undisturbed soil appeared to have a higher thermal conductivity in the direction normal to the ground surface than in the remoulded condition, but insufficient results are available on which to base conclusions. Extrapolating the thermal conductivity to 100% solids gave a value of 1l·8 B.t.u. in/sq.ft hour°F.The use of the value for the solid fraction in De Vries's method for predicting the conductivity gave reasonable agreement with measured results. La conductibilité calorifique d'argile de Leda remoulée saturée, sol d'origine marine de perioda pré-glacière, a augmenté de 5,5 à 7 unités thermiques britanniques en pieds carrés/heures/degrés Fahrenheit pour un accroissement en densité sèche de 20 livres par pied cube (75–95 livres par pied cube) et a diminué de 7 à 6 unités thermiques britanniques en pieds carrés/heures/degrés Fahrenheit pour un accroissement de dimensions des particules d'argile de 39 à 60%. Le sol intact a révélé une conductibilité thermique plus haute dans la direction perpendiculaire à la surface du sol dans une condition remaniée, mais les résultats obtenus sont insuffsants pour en tirer des conclusions. En extrapolant la conductibilité thermique à 100% les solides ont donné une valeur de 11, s unités thermiques britanniques en pieds carrés/heures/degrés Fahrenheit. L'emploi de la valeur pour la fraction solide d'apres la méthode De Vries pour prédire la conductibilité s'accorde raisonnablement avec les résultats relevés.

Theory and practice of soil densification

THE THERMAL RESISTIVITY of soils is an important factor in the economy of systems of buried electric power cables. This resistivity is a function of the volume fractions of the solid, liquid, and gaseous phases of which soils are normally composed, and of their structural arrangement. Inasmuch as the solid phases usually possess lower thermal resistivities than the liquid and gaseous phases and, because the latter are greatly affected by external factors such as weather and topography and, hence, are subject to cyclic variations, the volume proportion and the structural arrangement of the solid soil constituents determine the maximum theoretical thermal resistivity of a soil. The dry densities of soils are often used instead of the volume proportions of solids. An increase in dry density by one pound per cubic foot results in an average decrease of thermal resistivity of 3 per cent. Soil systems, as found in nature or as obtained by normal backfilling practices, are usually neither at their most loose nor at their densest possible state. Between these two states, there is normally a difference of about 36 pounds with the natural state often having a density of about 12 pounds above the most loose. This indicates the potentialities of decreasing the thermal resistance of soils by means of better and more appropriate compaction methods.

Theory and Practice of Soil Densifcation

THE THERMAL RESISTIVITY of soils is an important factor in the economy of systems of buried electric power cables. This resistivity is a function of the volume fractions of the solid, liquid, and gaseous phases of which soils are normally composed, and of their structural arrangement. Inasmuch as the solid phases usually possess lower thermal resistivities than the liquid and gaseous phases and, because the latter are greatly affected by external factors such as weather and topography and, hence, are subject to cyclic variations, the volume proportion and the structural arrangement of the solid soil constituents determine the maximum theoretical thermal resistivity of a soil. The dry densities of soils are often used instead of the volume proportions of solids. An increase in dry density by one pound per cubic foot results in an average decrease of thermal resistivity of 3 per cent. Soil systems, as found in nature or as obtained by normal backfilling practices, are usually neither at their most loose nor at their densest possible state. Between these two states, there is normally a difference of about 36 pounds with the natural state often having a density of about 12 pounds above the most loose. This indicates the potentialities of decreasing the thermal resistance of soils by means of better and more appropriate compaction methods.