Generator Handbook Our generator handbook provides a basic education in electrical theory and generator operation, including formula for calculating power output and how to use that information to size a generator for your needs. Concrete Vibrators Handbook Our Concrete Vibrator handbook explains the basics of concrete, the purpose of vibrating curing concrete, and the different types of vibrator machines available.
Technical Paper. Generator Motor Starting This short paper will address motor basics, starting current, the impact high transient current has on a generator and the important role transient reactance plays in estimating the generator size in the absence of generator performance data.
Crown the elevation of a road surface at its edges, to encourage drainage. Datum any level surface taken as a plane of reference from which to measure elevations. Elasticity a characteristic of soil which allows deformation during a subjected load, but returns almost to its original configuration after removal of the force. Foot in tamping rollers, one of a number of projections from a cylindrical drum. Frost Line the greatest depth to which ground is expected to freeze in a given location.
Grade usually the surface elevation of the ground at points where it meets a structure. Also, surface slope. Grain Size Curve a soil graph analysis showing the percentage size variations by weight. Granular Material a sandy type of soil with particles that are coarser than cohesive material and do not stick to each other. Gravel a cohesionless aggregate of rock fragments with varying dimensions of 3. Impervious resistant to movement of water. In Situ natural undisturbed soil in place.
Lift a layer of fill as spread or compacted. Liquid Limit the water content at which soil passes from a plastic to a liquid state. Loam a soft, easily worked soil containing sand, silt, clay and decayed vegetation.
Optimum Moisture Content that percent of moisture at which the greatest density of a soil can be obtained through compaction. Pass a working trip or passage of an excavating, grading or compaction machine from point A to point B. One direction only. Permeability a characteristic of soil which allows water to flow through it because of gravity.
Plastic the ability of a soil to be rolled into a fine thread at a certain moisture content. Proctor a method developed by R. It is almost universally used to determine the maximum density of any soil so that specifications may be properly prepared for field construction requirements. Proctor, Modified a moisture density test of more rigid specification than Proctor.
The basic difference is the use of heavier weight dropped from a greater distance in laboratory tests. Quicksand fine sand or silt that is prevented from settling firmly together by upward movement of underground water. Sand a cohesiveless aggregate of round and angular fragments of rock with a particle size between 2. Internal friction and cohesion determine shear resistance. Shrinkage soil volume which is reduced when subjected to moisture; usually occurs in fine grain soils.
Sub-base the layer of material placed to furnish strength to the base of a road. Subgrade the surface produced by grading native earth, or cheap imported materials which serve as a base for more expensive paving. Search for:. Article sections. Soil Compaction Figure 1 Soil compaction is defined as the method of mechanically increasing the density of soil.
Following are important elements in soil compaction: Soil type Soil moisture content Compaction effort required Why compact? There are five principal reasons to compact soil: Increases load-bearing capacity Reduces settling of soil Reduces shrinkage of soil Reduces water seepage, swelling and contraction Provides better stability Types of compaction There are four types of compaction effort on soil or asphalt: Vibration Impact Kneading Pressure These different types of effort are found in the two principal types of compaction force: static and dynamic.
Benefits of Soil Compaction Figure 3 — These illustrations show the results of improper compaction and how proper compaction can ensure a longer structural life, eliminating future foundation problems.
Soil Types and Conditions Every soil type behaves differently with respect to maximum density and optimum moisture. There are three basic soil groups: Cohesive Granular Organic this soil is not suitable for compaction and will not be discussed here Cohesive soils Sieve Test Cohesive soils have the smallest particles. Characteristics Cohesive soils are dense and tightly bound together by molecular attraction. Granular Soils Granular soils range in particle size from.
Characteristics Sand and gravel obtain maximum density in either a fully dry or saturated state. Moisture vs. Why Test? Soil testing accomplishes the following: Measures density of soil for comparing the degree of compaction vs specs Figure 9 Measures the effect of moisture on soil density vs specs Provides a moisture density curve identifying optimum moisture Types of tests Tests to determine optimum moisture content are done in the laboratory.
Compaction Equipment Applications The desired level of compaction is best achieved by matching the soil type with its proper compaction method. Cohesive soils—clay is cohesive; its particles stick together. A rammer is the best choice, or a pad-foot vibratory roller if higher production is needed. Compaction machine characteristics Two factors are important in determining the type of force a compaction machine produces: frequency and amplitude.
Compaction Specifications A word about meeting job site specifications. Generally, compaction performance parameters are given on a construction project in one of two ways: Method Specification—detailed instructions specify machine type, lift depths, number of passes, machine speed and moisture content. This method is outdated, as machine technology has far outpaced common method specification requirements. End-Result Specification—engineers indicate final compaction requirements, thus giving the contractor much more flexibility in determining the best, most economical method of meeting the required specs.
Fortunately, this is the trend, allowing the contractor to take advantage of the latest technology available. Equipment types Rammers Figure 18 Rammers deliver a high impact force high amplitude making them an excellent choice for cohesive and semi-cohesive soils. The heavier the plate, the more compaction force it Roller Types Figure 19 generates. Tire pressures on some machines can be decreased while rolling to adjust ground contact pressure for different job conditions Safety and General Guidelines As with all construction equipment , there are many safety practices that should be followed while using compaction equipment.
Shoring Trench work brings a new set of safety practices and regulations for the compaction equipment operator. Adhesion a property of soil which causes the particles to stick together. Bank Gravel a natural mixture of cobbles, gravel, sand and fines. Bank Yards soil or rock measured in its original position before digging. Berm an artificial ridge of earth, generally side- slopes of a roadbed. Binder fines which fill voids or hold gravel together when dry. Borrow Pit an excavation from which fill material is taken.
BPR U. Bureau of Public Roads. Rammer Handbook Please Click Here. Vibratory Plate Compactors. Forward - Vibratory plates are low amplitude and high frequency, designed to compact granular soils and asphalt. Gasoline or diesel engines drive one or two eccentric weights at a high speed to develop compaction force. The resulting vibrations cause forward motion. The engine and handle are vibration-isolated from the vibrating plate. The heavier the plate, the more compaction force it generates.
Frequency range is usually vpm to vpm. Plates used for asphalt have a water tank and sprinkler system to prevent asphalt from sticking to the bottom of the baseplate. Vibration is the one principal compaction effect.
Reversible Plate Compactors. In addition to some of the standard vibratory plate features, reversible plates have two eccentric weights that allow smooth transition for forward or reverse travel, plus increased compaction force as the result of dual weights.
Due to their weight and force, reversible plates are ideal for semi-cohesive soils. A reversible is possibly the best compaction buy dollar for dollar.
Multiquip Rollers. Single-Drum Patching Rollers: The ideal solution for asphalt patching jobs too small to be handled with tandem rollers. Dependability and performance make these rollers a favorite of contractors, highway repair agencies and municipalities. A fully enclosed hydrostatic-drive system offers infinitely variable speed control, smooth acceleration and braking.
Many municipalites use rollers as their preferred asphalt patching tool. Tandem Drum Rollers: Double-drum rollers easily tackle large asphalt compaction jobs and feature built-in water tanks, hydrostatic drive and spray bars. A well-graded soil consists of a widerange of particle sizes with the smaller particles filling voidsbetween larger particles.
The result is a dense structure that lendsitself well to compaction. Clay has a particle sizerange of. Silt ranges from. Clay isused in embankment fills and retaining pond beds. CharacteristicsCohesive soils are dense and tightly bound together by molecularattraction. They are plastic when wet and can be molded, butbecome very hard when dry. Proper water content, evenlydistributed, is critical for proper compaction. Cohesive soils usuallyrequire a force such as impact or pressure.
Silt has a noticeablylower cohesion than clay. However, silt is still heavily reliant onwater content. Granular soils are known fortheir water-draining properties. CharacteristicsSand and gravel obtain maximum density in either a fully dry orsaturated state. Testing curves are relatively flat so density can beobtained regardless of water content. The tables on the following pages give a basic indication of soilsused in particular construction applications.
When dry. Granular soils, finesands and silts. Coarse grains canbe seen. Feels grittywhen rubbed betweenfingers. When water and soilare shaken in palm ofhand, they mix. Whenshaking is stopped,they separate. Very little or noplasticity. Little or no cohesivestrength when dry. Soil sample willcrumble easily. Cohesive soils, mixesand clays.
Grains cannot be seenby naked eye. Feelssmooth and greasywhen rubbed betweenfingers. When water and soilPlastic and sticky. Crumbleswith difficulty. Slowsaturation in water. Rain, for example, may transformsoil into a plastic state or even into a liquid.
In this state, soil hasvery little or no load-bearing ability. Moisture vs soil densityMoisture content of the soil is vital to proper compaction. Moisture acts as a lubricant within soil, sliding the particlestogether. Too little moisture means inadequate compaction—the particles cannot move past each other to achieve density. Too much moisture leaves water-filled voids and subsequentlyweakens the load-bearing ability.
The highest density for mostsoils is at a certain water content for a given compaction effort. The drier the soil, the more resistant it is to compaction. In awater-saturated state the voids between particles are partiallyfilled with water, creating an apparent cohesion that binds themtogether. This cohesion increases as the particle size decreases as in clay-type soils.
Soil density testsTo determine if proper soil compactionis achieved for any specific construction application, several methods weredeveloped. The most prominent by far issoil density.
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