As the soil compacts the voids are reduced and this causes the dry unit weight or dry density to increase. Heavily compacted soils contain few large pores, less total pore volume and, consequently, a greater density. Soils field testing north dakota department of transportation. The determination of maximum dry density and optimum moisture content of soil is a measure of compaction level of soils. Both the tests help to determine the optimum moisture content that is required for soil to attain maximum compaction i. At this moisture content the soil can be compacted most ef. Increasing the water content for a saturated soil results in a reduction in dry unit weight. The appropriate decompaction technique will depend largely on the characteristics of a reclaimed site, including clay content, soil moisture and the severity and depth of compaction table 1. Soil compaction decrease in soil volume and porosity, or increase in soil bulk density, due to mechanical stress on soil, for example, from traffic of agricultural machinery.
Soil moisture content rausser college of natural resources. At lower moisture content, the capillary tension inhibits the tendency of the soil particles to move around and be compacted. Soil moisture conditions consideration for soil compaction. Jul 07, 2008 modulus of compacted soils depends not only on dry unit weight and moisture but also on matric suction and soil structure or fabric resulting from the compaction process. Natural soil reconsolidation wellgraded soils more susceptible to natural compaction than poorly graded soils 0 20 40 60 80 100 10 0. Effect of soil moisture in the analysis of undrained shear. The size and shape of a site will also affect the accessibility and manoeuverability of equipment. As water is added to a soil at low moisture content it becomes easier for the particles to move past one another during the application of the compacting forces.
Guidelines for the stabilization of subgrade soils in. Over the past decade the size of iowa farms has increased, leading to larger and heavier equipment. Dcp criteria for chemical modified soils were developed at optimum moisture content. The moisture content at which the greatest value of dry density is reached for the given amount of compaction is the optimum moisture content omc, and the corresponding dry density is the maximum dry density. The soil is then removed from the mould and is mixed with the original sample. Soane, in encyclopedia of soils in the environment, 2005. In this paper we study the relationships between soil moisture and temperature at the surface and various. Laboratory 2 soil density i objectives measure particle density, bulk density, and moisture content of a soil and to relate to total pore space. Compacted soils usually have unsatisfactory physical conditions for plant growth, but the extent of loss of productivity depends on soil type, plant species, and weather conditions. However, these relationships in the as compacted state i. Soil structure also affects the shape of the soil moisture characteristic curve. Soils field testing compute and record dry density to nearest 0.
Note significant increase in water content on the dry side of the compaction curve this is why it is so important to moisture condition expensive soils wet of optimum moisture content. The dry unit weight after compaction first increases as the moisture content increases. There are potential penetration problems at 145 psi. Factors affecting compaction of soil types of soil. It affects infiltration, rooting depthrestrictions, available water capacity, soil porosity, plant nutrient availability, and soil. Effects of compaction increased soil erosion effects of compaction increased soil erosion.
Ct 417 method of testing soils and waters for sulfate content ct 422 method of testing soils and waters for chloride content aashto m 145 standard specification for classification of soils and soilaggregate mixtures for highway construction purposes aashto t 180d standard method of test for moisturedensity relations of soils stabilization. Therefore, it is useful if simple correlation equations can be developed to estimate the compaction. Soils containing gypsum lose water of crystallisation on heating. A compacted soil has a reduced rate of both water infiltration and drainage. Compacted soils usually have unsatisfactory physical conditions for plant growth, but the extent of loss of productivity depends on soil type, plant species, and weather conditions effects on germination and establishment.
Moisture exists in soil within the pore spaces between soil aggregates, called interaggregate pore space, and within pores in the soil aggregates themselves, called intraaggregate pore space. About 2% more water is added in the sample and the test is repeated. Determination of moisture content in soil protocol. Effect of moisture the response of soil to moisture is very important, as the soil must carry the load yearround. Moisture content and compactive effort, which can be controlled, are important factors influencing soil compaction. Moisture density curve for a mediumtextured soil for a given compactive effort. Bulk density can be managed, using measures that limit compaction and build soil organic matter. The nuclear gauge is specifically designed to measure the moisture content and density of soils, aggregates, cement and lime treated materials, and to measure the density of bituminous concrete. From the above two known weights w and w solid, the weight of water m. The loam soil showed rather higher values of bulk density than the other two soils fig. The bulk density increased with increased moisture content. The focus of this work is to explain possible connections between surface temperature and soil moisture in order to carry out suchataskinthefuture. Soil compaction compaction is the application of mechanical. This process is an essential part of the construction of any structure, as it strengthens the soil.
Roots usually cannot penetrate soil compacted to 300 psi or more. Rain, for example, may transform soil into a plastic state or even into a liquid. Similarly, soils compacted to wet of optimum will produce more stress even for smaller stress. Road builders make use of this principle when they apply water to dry soil to make it compact more easily. The e 0moisture content relation exhibits a similar trend to moisturedensity and shear strengthmoisture content relations fig. Compaction can result from equipment traffic, especially on wet soils, and tillage pans. In construction of highway embankments, earth dams and many other engineering structures, loose soils must be compacted to increase their unit weights. Initially then, as the moisture content increases so does the dry.
The mould along with the compacted soil is then weighed to get the mass of the compacted soil. In this method of moisture content determination of soil, a known weight w of the representative wet soil sample is dried over night in an oven operating at temperatures between 105c and 110c. Using both the rheological and the conventional soil parameters to evaluate the compaction of the soils, the optimum combination of the principal variables was studied. To determine any of these ratios for a particular soil sample, the water mass must be determined by drying the soil to. Many factors influence the degree with which the soil is compacted. The determination of maximum dry density and optimum moisture content of the soil is a measure of compaction level of soils. Moisture content this is a measurement of how much moisture a soil is holding in its void spaces.
In this study, the soil materials with varying moisture content were compacted with the same duration and settings. Part 2 why do we compact soil missouri university of. Therefore, a moisture content determined by this method will be affected by approximately 0. The moisture content will decrease with an increase in atmospheric temperature. For the purpose of this study soil specimen were compacted and the optimum moisture content was identi. Modulus of compacted soils depends not only on dry unit weight and moisture but also on matric suction and soil structure or fabric resulting from the compaction process. The e 0 moisture content relation exhibits a similar trend to moisture density and shear strength moisture content relations fig. Maximum dry density of soil and optimum moisture content test. Soil compaction occurs when soil particles are pressed together, reducing pore space between them figure 1. Because of the importance of compaction in most earth works. Soilmoisture properties of subgrade soils transportation. Ii introduction a particle density soil particle density g cm3 is mass of soil solids ovendry per unit volume of soil solids. The relation between the moisture content and dry unit weight for saturated soil is shown on the graph in figure 3. In some literature the moisture content is expressed in wet weight basis that is defined as the ratio between water mass and the mass of wet soil.
Compaction properties of silty soils in relation to soil. The bhps showed a strong correlation between measured temperature rise and water content but in its current configuration is. Oct 28, 2016 factors affecting compaction soil type in poorly graded sands the dry unit weight initially decreases as the moisture content increases and then increases to a maximum value with further increase in moisture content. Density of soil in place by the nuclear gauge soil density testing flow chart setting. Soil compacted at moisture content greater than the optimum moisture content has exactly the opposite characteristics to the one compacted below it. Guidelines for the stabilization of subgrade soils in california. The importance of understanding and controlling soil moisture cannot be overstated. A representative sample is taken from the centre of compacted soil for moisture content test. Bulk density is an indicator of soil compaction and soil health. However, these relationships in the ascompacted state i.
Moreover, the difference in the bulk density among these three soils seemed to decrease as the moisture content increased and. The moisture probe may only be used for granular soils and may not be used in soils with organic material. Hence, stressstrain curve, in this case, is much flatter and plastictype failure occurs at a larger strain. Compact material to at least 95 percent of the maximum dry density with moisture content no less than 4. Moisture vs soil density moisture content of the soil is vital to proper compaction.
Moisture content tests of the soil are required to be conducted during mixing and the day after mixing and shall be at or above the optimum moisture content. Prediction of compaction and compressibility characteristics. Influence of moisture content on intelligent soil compaction. Compact soils result in cloddy seedbeds after primary. Soil structure also affects the shape of the soil moisture characteristic curve, particularly in the high matric potential range. The red color in the spectrum indicated the strength of acceleration signal at fundamental and harmonic and subharmonic. The soil moisture content may be expressed by weight as the ratio of the mass of water present to the dry to the dry weight of the soil sample, or by volume as ratio of volume of water to the total volume of the soil sample.
September 2014 class g2 in accordance with tex901k for specimens with a mass greater than 200 g. In contrast, sand grains cannot be molded together. It has a great impact on the consistency of the soil, its density, and its compactability. High soil moisture increases soil compaction caused by field traffic and machinery. Determining moisture content in soil materials txdot designation. The degree of compaction of the soil largely depends upon the quantity of moisture in it however, if the moisture increases beyond a certain limit, compacting strength starts to decrease. This spring most parts of iowa have had plenty of rainfall, causing many producers to enter fields at lessthanideal soil conditions. Inherent factors affecting bulk density and available water. The combined effects of compactive effort, type of compaction, moisture content at compaction, and moisture gain after compaction on the physical parameters ar1d engineering proper ties were noted and compared for field and laboratoryprepared soil. Inherent factors affecting bulk density and available. Interpreting compaction indicators the impact of compaction on crop productivity.
When the moisture content is gradually increased and the same compaction effort, the weight of the soil solids in a unit volume gradually increases. As soil moisture levels increase, infiltration rates decrease. They defined the wilting range as the range in moisture content of the soil. Laboratory 2 soil density i objectives ii introduction. Compacted or impervious soil layers have pore space and less restrict water movement through the soil profile. Each combination of these variables results in a different state of the compacted soil. The principal variables which affect the state of compacted soil are the type of soil, the moisture content, and the amount and type of compaction energy. Pdf effect of moisture content on soil density compaction. Pdf effect of soil moisture content and dry density on cohesive. For a particular compaction effort, the dry density of soil increases with the moisture content of the soil up to the optimum moisture content beyond which it decreases. This critical value varies with soil type and moisture content of the soil when tested schuler et al. Effects of soil properties, water content, and compactive.
Factors affecting compaction soil type in poorly graded sands the dry unit weight initially decreases as the moisture content increases and then increases to a maximum value with further increase in moisture content. Ii introduction a particle density soil particle density g cm3 is mass of soil solids ovendry per unit volume of soil. Performancebased measurement of optimum moisture for soil. Compaction can prevent the build up of large water pressures that cause soil to. Strength and deformation parameters of compacted soil are known to be related to soil.
If, with increasing moisture content, the wet mass of compacted soil markedly increases and then starts to decrease, the optimum moisture content probably has been straddled adequately. Compaction of soil is the compression of soil particles into a smaller volume, which reduces the size of pore space available for air and water. Soils are compacted more readily when soil moisture is at or near. Laboratory determination of compaction properties namely the maximum dry density and optimum moisture content is both time consuming and costly. So that deformation characteristics of compacted soils can be compared at various moisture contents, compactive efforts, and methods of compaction, the creep modulus e. Maximum soil compaction occurs when soil moisture is at or near field capacity figure 1 because soil moisture works as a lubricant between soil particles under heavy pressure from field equipment. If it is suspected that gypsum is present in the soil, dry the moisture content samples at not more that 80 c, for a longer period and report the method used. Ct 417 method of testing soils and waters for sulfate content ct 422 method of testing soils and waters for chloride content aashto m 145 standard specification for classification of soils and soil aggregate mixtures for highway construction purposes aashto t 180d standard method of test for moisture density relations of soils stabilization. However, equipment size is only one factor among many causes of the soil. This can be measured by mainly two methods standard proctor compaction test and modified proctor compaction test. Compaction of soil process, necessity and theory of compaction.
Both the test helps to determine the optimum moisture content that is required for a soil to attain maximum. To further understand the compaction behavior of these forest and range soils, six representative soils of different textural characteristics were subjected to proctor compaction, with 30, 50, and 100 blows at three to four. The response of soil to moisture is very important, as the soil must carry the load yearround. Performancebased measurement of optimum moisture for. Soils typically contain a finite amount of water, which can be expressed as the soil moisture content. The microwave oven may be used for most soil types except for soils that. Soil mechanics physical properties of soils and compaction page 7 fig. Soil compaction compaction, in general, is the densification of soil by removal of air, which requires mechanical energy. Compaction of soil process, necessity and theory of. Experiments were carried out in a sandy loam soil at soil moisture content of 10.