Construction Inspection for FO Activities - Soils and Earthwork

Construction Inspection for FO Activities - Soils and Earthwork
NEDC Construction Inspection for Field Office Activities Get Earthfill QA problem ready from Class Problems Section Will be using Earthfill Problem as part of this presentation. Have the class remove it from the problems section at the start of the presentation. USDA is an equal opportunity provider and employer.

Soils and Earthwork - Objectives
Construction Inspection for FO Activities - Soils and Earthwork Soils and Earthwork - Objectives Describe and discuss the reasons for excavation and the equipment used Review of different soil types based on USCS and their correlation to USDA textural classes Describe compaction characteristics and correct construction equipment for different soils

Soils and Earthwork – Objectives (continued)
Construction Inspection for FO Activities - Soils and Earthwork Soils and Earthwork – Objectives (continued) Identify 3 major factors that affect compaction of soil Describe how compaction and water content affect the properties of soils Learn some field observations to assist with earthwork inspection

Earthwork includes: Excavation and Earthfill Excavation or “CUT”. Earthfill or “FILL”.

Excavation Equipment Typical Excavation equipment. From top left: Shovel, loader backhoe, hydraulic excavator, dozer or track type tractors. Explain difference between backhoe and excavator; backhoe mounted on a tractor with a limited swing, excavator mounted on tracks or wheels and normal have a full circle swing. Others may include loader, skid loader, clam shell or shovel.

Excavation Equipment Typical Excavation equipment. From top left: Wheel tractor scraper(pan), Ag tractors and scrapers (pans). Scrapers or pans can be elevating as shown or bowl type. Self propelled or pull type. Self propelled may be single or double engine and can be push-pull as well. Others may include loader, skid loader, clam shell or shovel.

Reasons for Excavation
Construction Inspection for FO Activities - Soils and Earthwork Reasons for Excavation Remove objectionable materials Provide a base for structures Provide required storage Provide required flow area and grade line Excavation is done to remove objectionable materials to provide a good foundation for earthfill. Examples would be cutoff trenches for embankments or stripping and foundation preparation for structures. Excavation is also done to provide the proper elevation for storage requirements in excavated ponds (fresh water or waste storage) or the proper grade line for channels. (waterways, open channels, and spillways)

Foundation Excavation
Construction Inspection for FO Activities - Soils and Earthwork Foundation Excavation Suitable Unsuitable Examples of suitable bottom of cutoff trench and unsuitable materials for bottom of cutoff trench. Materials are suitable if they have adequate strength to support equipment and additional fill. Similar to materials for earthfill are suitable if they have proper moisture to allow compaction. (Not too dry or too wet!) Cutoff trenches for embankments provide a base to work from and can also help reduce seepage losses from coarse materials in the foundation.

Excavation for Structures
Construction Inspection for FO Activities - Soils and Earthwork Excavation for Structures Concrete structures Pipes Examples of excavation for structures can be for concrete structures and pipes in dams. Discuss the importance of the elevation of the excavated bottom since pipes and structures are set to designed elevations to operate properly. Discuss why the material at the excavated elevation is important since the structures are very heavy and need to be on a solid base. This base can either be a compacted fill or natural ground that is adequately consolidated.

Excavation for Structures
Construction Inspection for FO Activities - Soils and Earthwork Excavation for Structures Water control structures Pipes and Drains Examples of excavation for structures include water control structures such as inline water control structures, spring boxes, underground outlets for terraces, or drains for embankments or foundations. Discuss the importance of the elevation of the bottom or the material encountered in the bottom as being suitable or not.

Excavation for Storage
Construction Inspection for FO Activities - Soils and Earthwork Excavation for Storage Waste storage ponds Excavated wetlands Examples of excavation for storage include waste storage ponds, freshwater ponds, and excavated wetlands. Discuss how the proposed bottom may or may not be suitable for each of the excavations shown.

Excavation for Flow Area and Grade Line
Construction Inspection for FO Activities - Soils and Earthwork Excavation for Flow Area and Grade Line Spillways and channels Waterways Examples of excavation for flow area and grade line. Discuss the importance of the elevation of the designed bottom and flow area to meet the designers intent. (waterway grade or channel elevation) Soils at the finished grade need to be suitable to be vegetated or withstand the velocities of the expected flows in the channels. (undercut and add topsoil to waterways to promote vegetation, stilling basins and outlet channels to be non-erosive during flow events)

Excavation Review Suitable Fill Material? Review the reasons for excavation: remove unsuitable materials, prepare foundation for structures or embankments, provide storage, and provide flow area and grade line. Discuss what may constitute suitable and unsuitable excavated conditions. Transition into earthfill as the next segment and why earthfill is an important of NRCS activity. In most cases the excavated material will be used as earthfill if it is suitable.

Earthfill for conservation practices and compaction requirements
Construction Inspection for FO Activities - Soils and Earthwork Earthfill for conservation practices and compaction requirements Many of the engineering practices involve earthfill as part of the construction. Structures made from earthfill require some type of compaction to meet the requirements of the conservation practice or the drawings and specifications. Compaction requirements and techniques are based on soil types. A review of the USCS versus USDA textural follows.

Soils Review - What is USCS?
Construction Inspection for FO Activities - Soils and Earthwork Soils Review - What is USCS? The Unified Soil Classification System groups soils based on their predicted engineering behavioral characteristics. It uses laboratory tests for gradation and index tests to determine the classification. Soils are grouped based on gradation, how they react to forces such as vibration and pressure, and how much water they can retain.

What are the USCS Groups?
Construction Inspection for FO Activities - Soils and Earthwork What are the USCS Groups? Two main groups are Coarse grained and Fine grained. Coarse grained have more than 50% by weight greater than #200 sieve. Group names start with G or S. Fine grained have less than 50% by weight greater than #200 sieve. Group names start with M, C or O. Discuss this as a review of Soil Mechanics modules Coarse soils are Gravels and Sands, either clean or dirty. Fine grained are silty (M), Clayey, or Organic. Flow chart in back of section has entire list of USCS labels. Use easel charts as needed to show groups and labels.

USCS labels for coarse grain soils
Construction Inspection for FO Activities - Soils and Earthwork USCS labels for coarse grain soils Clean sand and gravel modifiers – W or P Example GW or SP Dirty sand and gravel modifiers – M or C Example GM or SC Clean gravels and sands are either Well graded or Poorly graded. Briefly explain well graded and poorly graded. Use easel charts as needed to show main group label and modifier, such as GW, GP and SW or SP. Silts and clays can modify coarse grained such as GC or SM and are based on plasticity or how well they hold their shape.

USCS labels for fine grain soils
Construction Inspection for FO Activities - Soils and Earthwork USCS labels for fine grain soils Fine grained modifiers – H or L based on Atterberg limits Example CH, ML, or OH Fine grained soils are modified by high or low liquid limit based on lab tests. It is a measure of how much moisture they can hold before behave more like a liquid than a solid. H has a liquid limit of more than 50.

Liquid Limit Test - Laboratory
Construction Inspection for FO Activities - Soils and Earthwork Liquid Limit Test - Laboratory Note that this is the method of determining the liquid limit in the lab. Discuss how the test is run and the results are recorded. Note: If the soil mechanics lab will be visited during the class, limit the discussion and just indicate the lab will talk more about this test.

Plastic Limit (PL) - Laboratory
Construction Inspection for FO Activities - Soils and Earthwork Plastic Limit (PL) - Laboratory The water content at which a 1/8” thread of soil can be rolled out before it begins to crack and cannot then be re-rolled. Note that this is the method of determining the liquid limit in the lab. Discuss how the test is run and the results are recorded. Note: If the soil mechanics lab will be visited during the class, limit the discussion and just indicate the lab will talk more about this test. Stop here and use soil samples and ceramic tiles to demonstrate this procedure. At least two soil samples at different moistures will be available. Let participants get their hands dirty at this point. May need a short break after this point or next slide to allow clean up.

Plot test results to determine USCS label Plasticity Index Discuss how test results determine label. Use next slide to illustrate Plasticity Index (PI) Liquid Limit

Atterberg Limits Soils containing clays and silts perform best when placed in a plastic state as opposed to a solid or a liquid state. The range of moisture in which these soils are plastic is represented by the Atterberg Limits. Liquid Limit (LL) Plastic Limit (PL) Solid Plastic Liquid Use yardstick and clips as demonstration of PI range. Show differences in PI between sandy soils and clay soils. Discuss issues with soils that have a low PI vs soils that have a higher PI. Include discussion that optimum is slightly higher than the Plastic Limit and soils must be in a plastic state to achieve good compaction for reduced permeability. Compaction for strength only can be achieved below the Plastic Limit. Inspector must understand why compaction is required to know whether soils must be above or below optimum moisture. The plasticity index (PI) = LL – PL

How do USCS labels compare to USDA textural labels?
Construction Inspection for FO Activities - Soils and Earthwork How do USCS labels compare to USDA textural labels? Clays and silty clays will typically be CH or sometimes MH Loams and silty clay loams will typically be CL Loams and silt loams will be ML Refer to Chart at end of section for guide. The USCS label will be used for soils for the remainder of the course. The chart in the back of the section was developed by a soil scientist as a comparison between the textural class and USCS label. It is good for fine grained soils and sands, not for gravels.

What is Soil Compaction?
Construction Inspection for FO Activities - Soils and Earthwork What is Soil Compaction? Soil compaction is the removal of air from the soil Soil compaction increases the density of a given soil. It is not intended to remove water and usually the compacted soil moisture content is the same before and after compaction.

Smooth drum roller on a soil that is intended as a subgrade for a plastic liner, rolled left, dozer placed on right.

When do we use Soil Compaction?
Construction Inspection for FO Activities - Soils and Earthwork When do we use Soil Compaction? Soils are compacted to achieve engineering properties that are not in the soil when it is put in place Higher strength and reduced permeability are two results obtained by compacting the soils at a moisture content and with a given compactive effort that is most effective in removing the voids in the soil. This moisture content is called optimum moisture. Compacting the soil above optimum moisture content will allow the soil to achieve good compaction, retain some flexibility, and be more impermeable than a soil compacted at optimum moisture. Note “engineering properties” which is why we use the Unified System rather than textural system.

What engineering properties of soil change with compaction?
Construction Inspection for FO Activities - Soils and Earthwork What engineering properties of soil change with compaction? These engineering properties include: Increased strength Decreased permeability Reduced settlement over time Strength increase in bearing and shear. Bearing is the ability to support a direct load without penetration of structure into the soil, such as a foundation footing. Shear strength is the ability of soil to resist being broken apart and failing catastrophically, such as in a sloping backfill behind riprap, or a fill over a pipe that needs to resist traffic loads Decreased permeability means that the capacity for water to move through soil is reduced Reduced settlement means that a well compacted embankment fill will be less likely to slump or drop in elevation over time, and that fills over a pipe will not settle and leave ruts

What engineering property?
Leaning tower of Pisa caused by a lack of equal bearing strength in the entire foundation. Soft clays on one side. Some thinking that moisture content also was involved. Construction stopped for various reasons after 1st 3 stories. Later contractor made next three stories uneven to make it look straight, but this just added more weight to that side. Last fix was to install lead counterweights to stabilize structure, but maintain lean.

Where are soils compacted?
Construction Inspection for FO Activities - Soils and Earthwork Where are soils compacted? Soils are compacted when they are in their final location as part of an embankment or structure. So for fill material it is after it has been moved to where it is needed, it is compacted to meet the requirements of the design. In situ soil can be compacted in place to alter its properties to bring it in line with the design requirements.

How do we ‘do’ Soil Compaction?
Construction Inspection for FO Activities - Soils and Earthwork How do we ‘do’ Soil Compaction? Soils are usually compacted using mechanical methods: Pressure Vibration or both!

Describe each of the different types of compactive equipment. A dozer or track type tractor is used for compaction when the compactive effort required is low. Ground pressure of a lightweight sheepsfoot roller will usually exceed 100 psi and can reach 1250 psi. Dozers are designed to push soil along the ground in an excavated area without sinking in….and so will have a ground pressure of less than 20 psi.

The three major factors affecting compaction….
Construction Inspection for FO Activities - Soils and Earthwork The three major factors affecting compaction…. Soil type – CL(clay), SC(sand), etc. Compactive effort (how much force or vibration) Soil moisture (very wet to very dry) Refer soil type back to USCS soil types.

Soil type has an impact on compaction
Construction Inspection for FO Activities - Soils and Earthwork Soil type has an impact on compaction Different soil types require different compaction methods Fine grained soil >>> Pressure Coarse grained soil >>> Pressure and Vibration Fine grained soils are CL, CH, ML, and MH (silts and clays), coarse grained soils are SC, SM, GC, or GM (sands and gravels).

Compaction Characteristics of Soils
Construction Inspection for FO Activities - Soils and Earthwork Compaction Characteristics of Soils Engineers use the Unified Classification System of classifying soils to describe soils and their engineering properties as discussed in the previous presentation. When compacting soils it is helpful to know the compaction characteristics of various classes of soils. As an example, consider two soils: a GC and a CH. Reference handout material in workbook. A GC is a clayey gravel that may also contain sand. It is relatively easy to compact. Since it has some clay in it, the water content is very important with a typical water content ranging from 9 to 14%. It can be best compacted with a tamping roller.

Compaction Characteristics of Soils
Construction Inspection for FO Activities - Soils and Earthwork Compaction Characteristics of Soils Now look at a CH soil. A CH is a high plastic clay that is very difficult to compact. Since it is all clay, the water content is critical to attaining compaction. It is a soil with very small particles which means it has significantly more voids to fill than does the GC. The typical water content of a CH soil ranges from 20 to 40%. A tamping roller is needed for compacting a CH.

Compactive Effort The amount of effort is affected by: Weight of equipment Type of roller Vibration or static Roller or hammer Lift thickness Weight of equipment varies depending on type and class of machine (size of machine) from light to heavy. Type of roller can be sheepsfoot (wide or narrow, shallow or deep) or smooth drum or rubber tire. Roller may have vibration or be static, some can switch vibration on or off. Small manually directed tampers may use a hammering effect instead of roller or plate. Thicker lifts require more weight and maybe a different foot type

Compactors Selection of Compactor Type
Construction Inspection for FO Activities - Soils and Earthwork Compactors Selection of Compactor Type Each type of soil has a unique type of equipment that is best suited for compacting the soil most efficiently. No single piece of equipment is best for all soils. Sheepsfoot rollers work best for compacting clays and clayey sands and gravels. They provide a kneading action that is best for compacting clays. Vibratory rollers are used for sandy and gravelly soils. Pneumatic rollers are best for silts and silty sands and gravels. The specifications or drawings will normally indicated the type of compaction equipment to use. If the contractor wants to use something different, the designer should evaluate and determine suitability.

Compactors Smooth-wheeled steel rollers
Construction Inspection for FO Activities - Soils and Earthwork Compactors Smooth-wheeled steel rollers Best for compacting sands and gravels with few fines when operating in the vibratory mode. Vibration under load is the key to rearranging soil particles and reducing voids. The frequency and amplitude of vibration of this equipment can be adjusted on most vibratory rollers. As the frequency goes up the amplitude goes down and visa versa. An operator may experiment with various settings to find the optimum frequency and amplitude setting for the soil being compacted. Generally speaking, clean sands may compact better at a higher frequency whereas sands that contain some cohesive material may compact better at a higher amplitude.

Compactors Pneumatic rollers
Construction Inspection for FO Activities - Soils and Earthwork Compactors Pneumatic rollers Best for compacting silts and silty sands and gravels. These may also be used to provide a smooth surface for geotextile placement.

Compactors Sheepsfoot rollers
Construction Inspection for FO Activities - Soils and Earthwork Compactors Sheepsfoot rollers Best for silts and clays Many types and sizes of rollers are available Kneading action is required to compact soils that have some plasticity.

Compactors Selecting a sheepsfoot roller
Construction Inspection for FO Activities - Soils and Earthwork Compactors Selecting a sheepsfoot roller Discuss smaller vs. larger: -Smaller, lighter rollers will perform best for moist soils that do not require heavy compaction -Larger, heavier rollers will be needed for drier soils that must be heavily compacted Why would you use a smaller one vs. a larger one?

Compactors Pad foot rollers
Construction Inspection for FO Activities - Soils and Earthwork Compactors Pad foot rollers Versatile compactor that works well in silts and clays as well as sands and gravels. Vibration may be added. Pad foot, also called a sheepsfoot but with wide pads, sometimes called an elephant foot roller….

Compactors Manually Directed Power Tamper
Construction Inspection for FO Activities - Soils and Earthwork Compactors Manually Directed Power Tamper For compaction in areas that are inaccessible to larger equipment Thin lifts required Often used around pipes or small precast structures

Compactors Manually Directed Power Tamper
Construction Inspection for FO Activities - Soils and Earthwork Compactors Manually Directed Power Tamper For compaction in areas that are inaccessible to larger equipment Thin lifts required This type used for subgrades of small slab areas or pipe trench backfills. This is a vibrating tamper useful with sands and gravels, not as good for clays since it does not apply much force.

Compaction and Lift Thickness
Construction Inspection for FO Activities - Soils and Earthwork Compaction and Lift Thickness Typical statement from a construction specification. “The maximum thickness of a layer (lift) of fill before compaction shall be 9 inches.” Why? Explain why earthfill is placed in lifts and why the thickness is limited. Next slide will help explain.

Lift Thickness Compaction energy is diluted with depth. COMPACTOR Higher density The reason for restricting the lift thickness is illustrated here. If the uncompacted lift is too thick, the compaction equipment may not be capable of supplying enough compaction energy so that the lower limits of the uncompacted lift can be compacted to the specified density. This sketch also illustrates the reason for checking density at different depths to verify that the density requirement is met throughout the lift. Why is compaction energy diluted with depth? There is friction between soil particles. Soil that is immediately below and in intimate contact with the base of the compactor receives the highest compactive force per area. As the compaction energy travels down through the soil, some of the energy is transferred to adjacent soil because of the friction between the particles. The force per unit area is diluted with depth because the area being compacted increases with depth but the compactive energy stays the same. Lower density

Soil Moisture and Compaction
Construction Inspection for FO Activities - Soils and Earthwork Soil Moisture and Compaction “The effect of the moisture content of a soil upon the density to which it may be compacted is the most important principle of soil compaction.” - R.R. Proctor, Field Engineer, Bureau of Waterworks and Supply, Los Angeles, California. August 31, 1933

The dry density changes as the result of increasing compactive effort at the same moisture content. 10 passes of equipment Dry Density, pcf 4 passes of equipment 3 passes of equipment 2 passes of equipment Look at increasing compactive effort graphically. Explain portions of graph. Click to show different densities at more compactive effort. 1 pass of equipment Water content, %

At this point, the sample has had most of its air driven out by the compaction 10 passes of equipment Dry Density, pcf 100 % saturation line 100% saturation line is reality check. Water content, %

Effect of Water Content @ constant energy
Construction Inspection for FO Activities - Soils and Earthwork Effect of Water constant energy Dry density, pcf Maximum dry density, pcf Click to show different water contents and results. Define maximum dry density and optimum water content. Discuss this is the basis of a Proctor Curve. Note: if a trip to the Soil Mechanics lab is schedules, limit the amount of discussion about Proctor testing. Use yardstick demonstration again to show how the PI and steepness of proctor curve relate. Steep curves equate to low PI’s and small range of working moistures. Optimum water content, % Water content, %

NRCS Philosophy on Water Content
Construction Inspection for FO Activities - Soils and Earthwork NRCS Philosophy on Water Content NRCS engineers generally favor compaction of embankment soils at water contents at or above optimum water content for two reasons: Gain flexibility Reduce permeability Generally speaking it is best, for most NRCS applications, to compact soils at a water content above the optimum water content. In very high dams or for installations where high soil strength is needed, compaction at a water content that is at optimum to approximately 2% below optimum would be desirable. The gain in flexibility is a primary benefit of compacting soils at above optimum moisture content. Flexibility is reduced by over compaction, but it is difficult to over-compact soils that have a water content at or above optimum. Permeability is reduced by compaction at higher water contents because the soil particles are effectively lubricated allowing them to reorient to form a less permeable soil matrix

Soil Moisture Vs. Soil Density (Proctor Curve)
Construction Inspection for FO Activities - Soils and Earthwork Soil Moisture Vs. Soil Density (Proctor Curve) Maximum 100% Saturation Density (lb/ft3) Optimum Discuss and explain the curve, maximum dry density, and optimum water content. Compacting soils at moisture contents below optimum moisture improves the strength of the soil but creates a more brittle and permeable soil structure. Conversely, compacting soils at moisture contents above optimum (commonly referred to as wet of optimum) results in a more flexible and less permeable soil structure. So which one do you want: strength and permeability or flexibility and impermeability? It depends on the application. For very tall dams you need strength so you sacrifice some water tightness for increased strength and design a filter and drainage system that will allow the dam to leak without failing. For lower dams, dikes, terraces, pond liners, etc., flexibility and impermeability are the most desirable physical characteristics. And you can have both by compacting the soil above the optimum water content. Water Content (%)

Soil Moisture Content % Moisture = (Wwater ÷ Wsoil dry) x 100% Example: 120 grams of soil is dried completely in an oven and now weighs 105 grams. Wwater = 120 g – 105 g = 15 g % Moisture = (15 g ÷ 105 g) x 100% = 14.3% % Moisture is also shown as W Soil moisture is defined as the weight of the water in the soil divided by the weight of the oven-dried soil expressed as a percentage. In critical fills like a manure pit embankment or WRP pond we will know what the optimum moisture is…

Class Problem Time Earthwork Problem – Friendly Farmer Grade Stabilization Question 1 w = (Wwater ÷ Wdry soil) x 100% Earthwork problem in Class Problems tab of workbook. Give participants 2 minutes to answer question 1 at this point. Next slide shows the answer. This problem will be used again later so they can keep it handy.

Earthwork Problem – Friendly Farmer Grade Stabilization Question 1 w = (Wwater ÷ Wdry soil) x 100% Wwater = (210 – 169.3) = 40.7 g w = (Wwater ÷ Wdry soil) x 100% = (40.7 ÷ 169.3) x 100% = 24.04% or 24% Click to show answer and then discuss the answer. This problem will be used again later so they can keep it handy.

In many cases for field office activities, the technician (inspector) will not be required to test for moisture. One good visual indicator is soil color. The darker the soil, the wetter it is.

What to do if soil is too dry
Construction Inspection for FO Activities - Soils and Earthwork What to do if soil is too dry Add Water! Water can be added by use of a watering truck, or even a manure spreader

How much Water to Add? Discuss the use of water requirements handout found in the back of this section. Example: Soil has a dry density of 96.0 lb/cu ft From graph, it takes 3.1 gallons/cu yd to raise moisture 1% Have the class look at the handout and explain how it can be used.

Earthwork Problem – Friendly Farmer Grade Stabilization Question 2 Using the same problem, answer question #2 Use water requirements handout Demonstrate where to get soil properties From Web Soil Survey Give the participants 5 minutes to answer this question and they can work on it in groups of 2-3, depending on table size. Answer on next slide.

Class Exercise Earthwork Problem – Question 2 Answer #2 Bulk dry density is 84.2 pcf from WSS. Using water requirements handout, 2.7 gal/cu yd are needed to raise the moisture 1% Target moisture is 28% and the current moisture is 24% so enough water needs to be added to raise the moisture 4% (28%-24%) Water needed = (2.7 x 5000) x 4 = 54,000 gal. Discuss the answer. Keep the problem handy for later.

Fill is probably too dry, clay soil sheepsfoot roller (dust is an indicator)

Fill probably too dry but compactor feet riding on top of soil indicates either good compaction or equipment cannot break up clods

Fill being moved into place is probably close to good moisture, by color, machines working in tandem helps to assure proper lift thicknesses

Good job being done, soil is probably close to correct moisture and feet are starting to ride up out of soil to indicate compaction is being done

Too much water is bad for compaction, here cannot finish bottom for concrete work

Trying to dry out soil

Getting rid of excess water

Another shot of good compaction level, surface appears dense, feet riding up out of soil

Operator driven compactor with switchable vibration control

Drag behind equipment and remote operated trench compactor

Remote in action

Typical drag behind with large narrow feet for breaking up clods, note cap on drum in left, for filling with liquid usually water or oil for additional ground pressure

Typical drag behind with slightly wider and shorter feet

Older drag behind style, this one is not filled at this time and still punches into the soil a good amount

Manually driven power tamper (plate tamper) for backfill over pipes

Manually driven vibrating plate tamper, good for coarse soils but not clays.

Good compaction of granular fill material but on top of steel, not ideal…

Smooth drum roller used for finish grade in this subgrade for a plastic lined manure storage

Ideal job, good compaction working with other equipment for lift thickness control (appears to be less than 9 inches), moisture content appears good, color of soil, shine to soil (we know this is a clayey soil) Note NRCS inspectors trucks in center of view!!!!

Soils and Earthwork Review
Construction Inspection for FO Activities - Soils and Earthwork Soils and Earthwork Review True or False: The three major factors affecting compaction are soil type, compactive effort, and soil moisture. Soils compacted above optimum moisture will be flexible. Soils usually become a lighter color when they are wet. A CL soil has a liquid limit below 50. Have class vote with show of hands or colored sheets of paper then discuss each item in detail. True. These are the three major factors in compaction. True. Soils compacted above optimum will be flexible and usually less permeable. False. A dark color usually indicates more soil moisture. True. Fine grained soils with an L as the modifier have a liquid limit below 50. H modifiers have a liquid limit of 50 or above. 80

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