Getting the Low Down on Dirt in Wormtown: Hands On Soil - PowerPoint PPT Presentation

Getting the Low Down on Dirt in Wormtown: Hands ‐ On Soil Classification Workshop Zachary D. Baum, PE, Project Engineer November 19, 2019

Getting the Low Down on Dirt in Wormtown: Hands ‐ On Soil Classification Workshop Construction Specifications Institute, Worcester Chapter is an approved AIA CES provider. This program is eligible for one Continuing Education Unit, qualifying for Health, Safety, Welfare.

Getting the Low Down on Dirt in Wormtown: Hands ‐ On Soil Classification Workshop Program Description: This program will be a hands ‐ on educational experience and Q&A on the how ‐ tos of soil classification using the Modified Burmister Soil Classification System. Following this presentation, you can try your hand at soil classification at the Yankee Engineering & Testing lab. Attendees will also have the opportunity to view soil laboratory testing equipment, including soil sieves, hydrometer, and liquid limit test equipment.

Getting the Low Down on Dirt in Wormtown: Hands ‐ On Soil Classification Workshop Learning Objectives: 1. Distinguish between the different major soil types in accordance with the Modified Burmister Soil Classification System 2. Visually classify soils and understand soil descriptions frequently presented in subsurface exploration logs 3. Understand how soil laboratory test results are used to confirm visual classifications 4. Compare soils encountered during construction to conditions described in geotechnical reports

Agenda • Soil types • Major/minor constituents • Density/consistency • Color • Assembling the description • Hands ‐ on classification exercise

Why is this Important? • Accurate classification of soils serves as basis for geotechnical evaluation • Architects and contractors should be aware of impacts of subsurface conditions on design and performance of structure • Structural/foundation design should be consistent with geotechnical evaluation • Understanding soils on logs is needed when observing excavation and backfilling of foundations

Why is this Important? • Exploration logs should present a clear, concise, and accurate representation of subsurface conditions • Good information can: - Significantly reduce the risk of unanticipated conditions and contractor claims - Result in cost effective solutions

Pepco Waterfront Substation 223 / Washington, DC

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Cobbs Creek Reservoir Project / Columbia, VA

Why is this Important?

Modified Burmister Soil Classification System • Commonly used by consulting engineers and environmental scientists • Visual/manual classification system • Provides a clear, concise description of the soil materials • Can be confirmed with lab test results Donald M. Burmister 1895 ‐ 1981

Soil Types • Three main soil types - Granular (non ‐ plastic) - Fine grained (plastic or non ‐ plastic) - Organic • Each main soil type can be broken down to more specific groups • Soil types are defined by ranges of sieve sizes

Soil Types – Granular Soils (Non ‐ Plastic) Sieve Size = The number of openings per one linear inch The larger the sieve number, the smaller the particle size Gravel Sand • 3/4” to 3” ‐ Coarse Gravel • No. 10 to No. 4 ‐ Coarse Sand • No. 4 to 3/4” ‐ Fine Gravel • No. 40 to No. 10 ‐ Medium Sand • No. 200 to No. 40 ‐ Fine Sand

Soil Types – Granular Soils (Non ‐ Plastic) Sand Gradation Proportion of Designation Component Identify by Fine <10% coarse and weight medium (sand or Medium <10% coarse and fine gravel) Fine to Medium <10% coarse Medium to <10% fine Coarse Identify grain size range Fine to Coarse All greater than 10% for sand >10% ‐ include it <10% ‐ exclude it

Soil Types – Granular Soils (Non ‐ Plastic) Test Pit: Identify the grain size for gravel Boring: Can’t define size of gravel from split spoon sample since opening is <2 inches Gravel Gradation Designation Proportion of Component Fine <10% coarse Coarse <10% fine Fine to Coarse All greater than 10%

Soil Types – Fine Grained (Silt and Clay) • Can be plastic or non ‐ plastic Determine the identity • Fraction passing the No. 200 • Roll a thread of the fine ‐ grained soil in your hands sieve • May need to adjust the moisture content by wetting or drying • Leaves the fingers dirty. Fills • The smallest diameter rolled determines the identity in fingerprints. Cannot be seen with the naked eye. Identity Smallest Diameter Plasticity Index SILT (non ‐ plastic) None 0 Clayey SILT 1/4" 1 ‐ 5 SILT & CLAY 1/8” 5 ‐ 10 CLAY & SILT 1/16” 10 ‐ 20 Silty CLAY 1/32” 20 ‐ 40 CLAY 1/64” >40

Organic Soil Types – Peat and Organic Silt Organic Silt Peat • Typically gray to dark gray • Typically black or dark brown • Can have strong H 2 S odor • Fibrous ‐ Light weight, spongy, intact organic matter, typically near top of • Often found near coastal regions deposit • May contains sea shells or shell • Fine Grained ‐ Light weight, spongy, less fragments intact organic matter, more homogeneous, may contain roots, found below fibrous peat

Soil Classification – Assembling the Description Density/Consistency (if SPTs are performed) Modified Burmister Soil Classification System Color Major Constituent Minor Constituents Other Comments

Soil Classification – Density/Consistency • Based on “N” Value - Only applies if Standard Penetration Tests (SPTs) are performed - The sum of the middle foot of blow counts from the SPT - Example: Blows per 6 inches are 6 ‐ 5 ‐ 4 ‐ 7. N ‐ value is 9. Plastic Soils (Fine Grained) Granular Soils N ‐ Value Density N ‐ Value Consistency 0 ‐ 4 Very Loose <2 Very Soft 2 ‐ 4 Soft 4 ‐ 10 Loose 10 ‐ 30 Medium Dense 4 ‐ 8 Medium 30 ‐ 50 Dense 8 ‐ 15 Stiff >50 Very Dense 15 ‐ 30 Very Stiff >30 Hard

Soil Classification – Color (Keep it Simple!) • “Black” • “Brown” Use only one ordinary color • “Gray” • “Orange” • “Tan” • “Light Brown” Max limit to 2 ‐ word description • “Olive ‐ Brown” • “Dark Gray” • “Reddish dark brown/gray” Avoid lengthy combinations • “Light green/yellowish brown”

Soil Classification – Major Constituent Entirely CAPITALIZED • Example: medium to coarse SAND • Example: SILTY CLAY • Example: FIBROUS PEAT For granular soils grain sizes from smallest to largest • Example: fine SAND • Example: fine to medium SAND • Example: fine to coarse GRAVEL

Soil Classification – Minor Constituents Follow the major constituent in the description Listed in order of decreasing percentage Only the first letter of the minor constituent is capitalized • Example: some fine to medium Sand, little Silt • Example: little fine to coarse Gravel, trace Silt • Example: some Silt & Clay, trace Gravel Always at least trace Silt! Percentage Label 0 ‐ 10 trace 10 ‐ 20 little 20 ‐ 35 some 35 ‐ 50 and

Soil Classification – Assembling Proper Order At end of description add any additional details: •Moisture (dry, moist, wet) Medium dense, Density / •% Cobbles/boulders •Anthropogenic fill materials: brick, glass, Consistency ash/cinders, wood, etc. •Odors, contaminants (petroleum, solvents, etc.) Fill: Any material placed by humans tan, •Could be natural material that is not native Color fine to medium SAND, Major Constituent some Silt, trace fine Gravel, Minor Constituents dry

Soil Classification – Assembling Proper Order • Examples - Stiff, gray, Clayey SILT, little Gravel, trace fine Sand, moist - Medium, dark brown, FIBROUS PEAT, trace fine to medium Sand, trace roots, wet - Very dense, brown, fine to coarse SAND, some fine to coarse Gravel, little Silt, trace brick, trace ash/cinders, petroleum odor, moist (FILL) - Document and note everything you observe

QUESTIONS?

HANDS ‐ ON EXERCISE Try your hand at classifying soil samples

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