Engineering Geology Soils Quiz

Soils (Civil Engineering)

Material that can be disaggregated in water by gentle aggregation

Soils (Construction)

Material removed by conventional means without blasting

Soils (Geology)

Thing layer of material that covers earth’s surface formed by gradual weathering

Soils

Able to support plant life; formed by surface weathering

Soil Horizons - Zone of leaching

O (organic) horizons, A (top soil), E

Soil Horizons - Zone of accumulation

B

Soil Horizons - Weathered Bedrock

C

Soil Horizons - Bedrock

D

Soil Horizons

Zone of leaching, Zone of accumulation, Weathered Bedrock, Bedrock

Soil Taxonomy

How soils are named; 12 types; based on less developed (recently formed, slightly weathered) to highly developed (heavily weathered, old)

Index Properties

Observable physical characteristics that significantly influence soil behaviorT

Types of Index Properties

Soil Particles, Soil Density, Moisture Content, Soil Consistency, Phase Relationships

Grain Size Distribution - Gravel

> 2mm

Grain Size Distribution - Sand

2mm - 0.1mm

Grain Size Distribution - Silt

0.1mm - 0.01mm

Grain Size Distribution - Clay

< 0.01mm

Well Graded, Poorly Sorted

Particles are all different sizes

Poorly Graded, Well Sorted

Particles are all same size

Uniformity Coefficinet

A measure of how poorly or well sorted a sediment is

CU < 4

Well sorted, poorly graded

CU > 6

Poorly sorted, well graded

CU = 1

Uniform

USCS

Unified Soil Classification System

Soil Densification

Make soil more dense, achieved by compaction and consolidation

Compaction

The rearrangement of soil particles to remove air space, application of mechanical energy, does not involve fluid flow, instantaneous process

Consolidation

Water is squeezed out from its pores under load, fluid flow away, takes place over long periods of time

Engineering focus for compaction

Increasing soil density

Factors of Compaction

Compaction effort, soil type and gradation, moisture content, and dry density

Which compacts better, well graded or poorly graded?

Well graded

Ramming

Low frequency (800 blows/min)

Vibration

High frequency (2000-6000 blows/min), compacts granular soils

Smooth wheel rollers

Thin Layer

Sheepsfoot rollers

Clayey soils

Compaction equipment

Ramming, vibration, static roller, and lifts

Proctor Testing

To find out optimal moisture content and maximum dry density

Standard Proctor Test

Hold volume, compacted in 3 layers, apply 25 blows per layer

Field Compaction Testing

Determine density and water content; sand cone test and nuclear density meters

Soil Consistency

Ease with which soil can be deformed, depends on mineral and water content

Cohesive Soil

Contains clay minerals and posses plasticity, sticks to itself

Non-Cohesive Soils

Soil has no shear strength if no confinement, cannot hold shape

Atterberg Limits

Limits of water content used to define soil behavior, distinguish between silt and clay types

Types of Atterberg Limits

Shrinkage, plastic limit, and liquid limit

Plastic Index

The range between liquid limit and plastic limit

Plastic Limit Test

Roll soi/clay between hand and table then measure the length until it breaks

Liquid Limit Test

Separate soil/clay down the middle and perform drops to see how it comes back togetherA

A - line

Separates Silts vs Clays

U - line

Upper bound for common soils

Soil Hazards - Compressible Soil

Occurs in high organic soils like glacial deposits and flood plains, excessive settlement with low bearing capacity and low shear strength

Soil Hazards - Collapsing Soil

Occurs in sandy coastal plains, sandy glacial deposits, and alluvial deposits of intermountain regions; settlement within loose sands and silts

Soil Hazards - Expansive Soil

Occurs in swelling clays, primarily smectite; expands when absorbing water and shrink when losing it; the most costly natural hazard

Soil Hazards - Corrosive Soils

High acidity (if resistivity p < 700 Om); Low acidity (if resistivity p > 1750 Om)

Soil Hazards - Fine textured Soil

Dominated by tiny clay particles

Soil Hazards - Saturated Fine Sands and Silts

Liquefactions failures, alluvial soils in particular

Soil Hazards - Permeability of soils

Coarse gravel (high K) to clays (low K)