# Presentation: 562921

## Unified Soil Classification System Training

- Part C - USCS using Field Tools

## Flow Chart for Coarse-Grained

## Flow Chart for Fine-Grained

## USCS Flow Chart - Activity 3

## Flow Chart Overview

- Two Broad Categories
- Fine-Grained - 50% or more finer than the # 200 sieve
- Coarse-Grained - Less than 50% finer than the # 200 sieve

## Remember system uses minus 3”

## Visual Determination

## Visual Determination

## Visual Determination

- Remember that percent is by dry weight.  Gravel Particles overpower gradation

## Visual Determination

- A sand size particle is the smallest that can be seen without magnifier

## Textural Determination

- When wetted thoroughly, coarse-grained soils have a distinct grittiness.  Practice on known samples

## Tests to Characterize Fines

- Liquid Limit Evaluation
- High - Greater than 50
- Low - Less than 50
- Begin with standard amount of minus # 40 soil - begin adding water with wash bottle

## Activity 4 - Liquid Limit Evaluation

## Activity 4 - Liquid Limit Evaluation

- Low LL soils
- water penetrates quickly

*Activity 4 -** Liquid Limit Evaluation*

## Activity 4 - Liquid Limit Evaluation

*Activity 4 -** Liquid Limit Evaluation*

- High LL soils
- water penetrates slowly - check for heat of hydration in CH soils

## Activity 4 - Liquid Limit Evaluation

- High LL soils -
- requires more than 50 drops per tablespoon of soil - calibrate with known samples data

## Activity 5 - Dilatency Evaluation

- When shocked, dilatent soil releases free water and becomes “livery”in appearance

*Activity 5 -** Dilatency Evaluation*

## Activity 5 - Dilatency Evaluation

- When squeezed, dilatent soil becomes dull

*Activity 5 -** Dilatency Evaluation*

## Activity 6 - Toughness Evaluation

*Activity 6 -** Toughness Evaluation*

- Reaching plastic limit requires adding considerable dry soil.
- Thread can be re-rolled several times after reaching plastic limit.
- Thread requires pressure to form.
-   Thread can be rolled out to lengths > 2”

## Activity 7 - Ribbon Evaluation

*Activity 7 -** Ribbon Evaluation*

- Length of Ribbon
- Strength
- Related to Clay Content
- See Module 3
- Ribbon more than 2 inches long indicates clay content is >  40 %

## Activity 8 - Shine Evaluation

## Activity 8 - Dry Strength Evaluation

- Very High - cube cannot be crushed even on hard surface
- High - Can be crushed only against hard surface
- Medium - Can be crushed with considerable pressure
- Low - crumbles with some pressure

## Typical Behavior CH soil

- High Liquid Limit

- High toughness - easily roll out thread to 1/8 inch diameter to length of several inches
- Zero dilatency
- Ribbons to more than 1-1/2 inch
- High dry strength
- High Shine

## Typical CH soil

- Slickensides

## Typical CH soil

## Typical Behavior ML soil

- Low Liquid Limit

- Slight to no toughness - If a thread can be formed to 1/8 inch diameter it can’t be reformed
- Medium to high dilatency
- Ribbons only slightly if any
- Low to very low dry strength
- No Shine (watch out for mica)

## Typical Behavior MH soil

- High Liquid Limit

- Medium toughness - If a thread can be formed to 1/8 inch diameter it has low strength
- Low dilatency
- Ribbons slightly to moderately
- Low to Medium dry strength
- Low Shine (watch out for mica)

## Typical Behavior CL soil

- Low Liquid Limit

- Medium to high toughness - A thread can be formed to 1/8 inch diameter with medium toughness
- Low to none dilatency
- Ribbons slightly to moderately
- Medium dry strength
- Low to Medium Shine (watch out for mica)

## Distinguishing between CL and MH difficult

- MH

- CH

- CL

- ML

- PI is the same -
- Only difference is in LL

- 50

- A-Line

## Coarse-Grained Classes

- Visual Examination
- Determine whether G or S is predominant
- Determine if Clean or Dirty
- If Clean
- Determine if Poorly or Well Graded
- If Dirty
- Determine if Fines are Plastic or Not

## Clean or Dirty ?

*Clean or Dirty ?*

- When wetted a clean coarse-grained soil will not leave a stain on your palm.  A dirty soil will leave a stain

## Clean or Dirty ?

- If a soil sample is dropped in a beaker of water, a cloud remaining after about 30 seconds indicates more than 12 % fines

## Visual Determination Well or Poorly Graded

- A well graded sample has a wide range of particle sizes that are about equally distributed by weight

## Visual Determination Well or Poorly Graded

- A gap-graded sample has a range of particle sizes missing.  This sample has coarse and fine but no medium size particles

## Visual Determination Well or Poorly Graded

*Visual Determination **Well or Poorly Graded*

- A well-graded sample has a wide range of particle sizes that are about equally distributed.

## Visual Determination Well or Poorly Graded

- A poorly graded sample is predominately one size of particle

## Poorly Graded Sand

## Well Graded Sand

## Evaluation of Plasticity of Fines

- The Most Useful Field Tests are Toughness and Dilatency

## Typical GC soil - glacial till

- Gravel with matrix of clay

## Typical GM soil - Alluvium

- Gravel with matrix of silt