Methods of Compaction - Civil Engineering …

1 1 CHAPTER VMechanical ModificationMethods of Compaction Laboratory Procedure Shallow Surface Compaction Deep Compaction Techniques Hydromechanical Compaction2 SOIL COMPACTIONIt is the most obvious and simple way of increasing the stabilityand supporting capacity of soil (improving the physical properties of soil)Soil Compaction is the process of increasing the unit weight of soil by forcing solids into a tighter state and reducing air. This is accomplished by applying staticor dynamic loads to the densification include Compaction is one kind of densification that isrealized by rearrangement of soil particles without outflow of water.

2 Soil is compacted by removing air and waterfrom its pore space. There exists a certain amount of moisture that a soil can have where a maximum unit weight is obtained. It does not involve fluid flow, but with moisture is another kind of densification with fluid flow away. Consolidation is primarily for clayeysoils. Water is squeezed outfrom its pores under of Action* Ramming* Vibration* Static Rollers4 RammingRammers have a low frequency (800blows/minute), and a higher stroke ( " to height). As the machine operates the ramming action breaks down the soil, pushes the particles closer together, and forces air out of the machines are distinguished bytheir high frequency (2,000 to 6,000blows/minute) and a low amplitude.

3 The vibratory action sets the soil particles in motion, which rearranges them into adenser improves characteristics of soils:1- Increases Strength2- Decreases permeability3- Reduces settlement of foundation4- Increases slope stability of embankmentsSoil Compaction can be achieved either by static or dynamic loading6 Laboratory ProcedureGenerally before any soil Compaction occurs,various samples of the proposed embankment or fill are analyzed in the Lab. One such lab test is Proctor Compaction Proctor Compaction test is a test that compacts the soil material at various moisture contents.

4 There are two Proctor teststhat are defined by the American Association of Highway Officials and American Standard Testing Material: The Standard Proctor test (ASTM D-698, AASHTO T-99), and The Modified Proctor test (ASTM D-1557 and AASHTO T-180). Laboratory Proctor Compaction Test78910 The Standard Proctor Testis generally used for fills requiring the minimal sub-grade Compaction ,such as small parking lots, and building the Modified Proctoris generally used for fills that will support large loads,such as: Roadways, Airport Runways, and Concrete Parking Aprons.

5 Relative Compaction or Degree of CompactionRelative Compaction = d(field)/ d(max)lab d(field): Dry density achieved in the field. d(max)lab: Max. dry density (from a Proctor Compaction test)11 Generally a contractor is given a percentage of optimum Compaction that must be attained in the field. This is referred to as the Relative Compaction , R(%) or Degree of Compaction . Relative Compaction generally range from 90% -95% as compared to the modified proctor and 95% - 100% as compared to the standard Proctor. Generally granular fillsare required to be compacted to 95% - 100% in the field.

6 1213 NUCLEAR DENSITY TESTIt consists of a special device that send outgamma raysand detects how they travelthrough the amount of gamma rays receivedback into the device correlates with the unit weight of the soil. It also measures the moisture contentof the soil in a similar way using alpha Surface CompactionShallow Compaction in the field is accomplished by rolling or compactionof soils is mainly done with various types of rollers. 14 The four most common types of rollers are: 1. Sheepsfoot rollers,used mainly for Clayey and Silty Smooth-drum rollers,Used primarily for Granular Soils.

7 3. Vibratory Rollers,Used primarily for Granular Soils. Rubber-tired rollersfor clay RollerThis roller compacts all fine-grained materials, including materials that will break down or degrade under the roller feet, but it will not compact cohesionlessgranular materials. 15 The number of passes necessaryfor this type of roller to obtain the required densities must be determined for each type of soil encountered. The roller compacts from the bottom up and is used especially for plastic materials. The lift thicknessfor sheepsfoot rollers is limited to 6 inches (15cm)in compacted depth.

8 16 Steel-Wheeled RollerAlthough extensively used, it is normally operated in conjunction withone of the other three types of Compaction rollers. It is used for compacting granular materialsin thin lifts. Probably its most effective use in subgrade work is in the final finish of a surface,following immediately behind the blade, forming a dense and watertight surface. 17 Steel-Wheeled Roller18 Rubber Tired RollersTamping-Foot RollerA tamping-foot roller is a modification of the sheepsfoot roller. The tamping feet are trapezoidal pads attached to a drum.

9 Tamping-foot rollers are normally self-propelled,and the drum may be capable of tamping-foot roller is suitable for use with a wide range of soil RollerFoot RollerPneumatic rubber-tired rollerFor compacting clay soil. Clays are more difficult to compact than sands and gravels, because they must be brought to the right range of water content before they can be compacted to high densities. Static pressure, as exerted by the wheels of this rubber-tired roller, compacts clays rubber-tired rollerVibratory Platesare designed for consistent Compaction 22 SOME SIMPLE RULES ON Compaction AND CONSOLIDATIONIf your fill is a cohesive / clay soil, it must NOT be too wet, and it must NOT be too dry, a reasonable "rule of thumb" for cohesive (clay)

10 Soils is the moisture content range +/- 2% of the Plastic soil fills in thin layers, maximum 200mm, compact each fully before placing next fillsmust be well graded,particle size well distributed through the range of the material. Not single sized appropriate specification to choose Compaction plant and numbers of passes / correct Compaction plant is on compacting bituminous materials ensure they are above minimum rolling thickness of 40mm nominal size bituminous roadbase is 150mm, (with a BIG roller).