Title: New England Soils 101
1New EnglandSoils 101
2New England Soil
- Soil is not like concrete or steel
- Soil is not always homogenous
- Soil is generally reviewed at the surface
- Soil is one of the few construction materials
with variable design criteria - Need to involve a geotechnical engineer
3New England Geology - Soil
- Generally glacial soil underlain by shallow
bedrock with some marine and post glacial
deposits - Glacial Till
- Glacial Lake glaciolacustrine
- Glacial River glaciofluvial or outwash
- Marine Deposit sand, silt, clay
- Post Glacial River alluvial, fluvial, and
organics
4New England Geology - Bedrock
- Igneous
- Granite
- Schist
- Basalt
- Metamorphic
- Gneiss
- Phyllite
- Sedimentary
- Shale
- Sandstone
5Soil Design Criteria
- Depends on
- Density
- Grain size soil type
- Moisture content
- Maximum past pressure
6Soil Density Evaluation
- Test boring with Standard Penetration Test SPT
- Cone Penetrometer Test CPT
- Density Gauge
- Nuclear Densometer
- Balloon
- Sandcone
7Estimating Soil Density
Estimate Consistency By
Standard Penetration Test (blows/foot)
Soil Condition
Equipment/Visual
Cohesionless
Cohesive
Very Soft
Man standing sinks gt 3
lt2
Loose
Soft
Man walking sinks 2 - 3
2-4
Medium
Man walking sinks 1
4-8
Stiff
8-15
Pickup truck ruts ½ 1
Medium Dense
Very Stiff
15-30
Loaded dump truck ruts 1 3
Insignificant rutting by loaded dump truck
Dense to Very Dense
Hard
gt30
8Fundamentals of Compaction
- Soil compaction is the action of increasing the
density of the soil through manipulation, by
pressing, ramming or vibrating the soil particles
into a closer state of contact - Appropriate soil compaction requires
- Lift thickness
- Moisture content
- Equipment
- Proctor Value
9Fundamentals of Compaction Mechanics
- The mechanics of consolidating fine-grained soil
is very complex involving capillary action, pore
pressure, permeability, and other factors. - What are fine grained soils?
- Impacts of water
- Past pressure influence
10Standard Proctor ASTM D698
- Developed prior to World War II
- Utilizes a lower compactive effort than the
Modified Proctor - 5.5 lb Hammer, 12-inch drop, 25 Blows/lift
- Typically higher compaction requirements are
recommended (98 Building, 95 Pavement) - Stone correction
11Modified Proctor ASTM D1557
- Developed After World War II
- More energy onto the soil sample than the
Standard Proctor Test - 10 lb Hammer, 18-inch drop, 56 blows/lift
- Stone correction
12AASHTO T-180 Method D
- Recommended for reclaimed aggregates
- Similar to Modified Proctor ASTM D 1557
- ¾-inch plus material is removed and replaced with
¼-inch material - No stone correction is applied
13Moisture Density Relationship Proctor Test
14Moisture Density Relationship Proctor Test
15Moisture Density Relationship Proctor Test
RANGE
16Foundation Systems
- Shallow foundations
- Ground improvements
- Deep foundations
17Shallow Foundations
- Most common foundation type
- Minimal engineering low tech
- Generally have the most risk of settlement
18Spread Footings
- Design based on soil bearing pressure
- Typically constructed to frost depth
- Shape square, rectangular, strip
- Usually min 3,000 psi concrete
- Economical
19Reducing Risk
- To reduce risk you need to understand the geology
and implement recommendations of the geotechnical
report - Bearing capacity review
- Verify correct soil
- Evaluate proofrolling
- Evaluate compaction of fill
- Appropriate use of geotextiles
20Geotextiles
- Non-woven geotextile filter
- Woven geotextile filter and improves stability
- GeoGrid improves stability
21Shallow Foundation Pitfalls
- Frozen subgrades
- Existing fill conditions
- Use of crushed stone
22Ground Improvements
- Preload/surcharge
- Deep dynamic compaction
- Rammed aggregate piers
- Soil stabilization
23Preloading/Surcharge
- Can be used for shallow and deep cohesive or
organic soils - Requires placing fill to design loads before
construction - Pre-evaluation of settlement and time
- Used with or w/o wick drains to speed settlement
- Verify by monitoring settlement
24Preload/Surcharge
25Deep Dynamic Compaction
- High energy densification of soils up to 40 feet
deep - More suitable for granular deposits
- Systematic dropping weights from 40 to 80 feet.
Energy required is a function of depth of
improvement and soil conditions - Verify with borings or crater measurements
26Rammed Aggregate Piers
- Compacted aggregate shafts Patented 1990s
- Improved bearing capacity replace mass
excavation greater than 5 to 6 feet - Allows spread footings/soil supported slabs
- 24 to 30 inch diameter 10 to 30 feet deep,
spacing 8 to 12 feet - 20 to 40 ton capacity, verify w/ modulus test
27Soil Stabilization
- Soil mixed with cementitious materials at surface
or in columns - Grouting
- Compaction
- Jet
- Chemical
- GeoGrid
28Deep Foundations
- Driven Piles
- Steel HP Sections
- Steel Pipe or Shell
- Pre-cast Prestressed Concrete
- Timber
- Pressure-Injected Footing (PIF)
- Drilled Shafts
- Drilled Mini-Piles
29Steel H-Piles
- 60 to 120 tons
- End-bearing
- Full penetration welded splices
- Capacity gt 50 tons require load test
30Steel Pipe Piles
- 65 to 125 tons
- End-bearing typically
- Welded base plate w/ full penetration welded
splices - Capacity gt 50 tons require load test
- 3,000 to 4,000 psi concrete filled
31Pre-cast Pre-stressed Concrete Piles
- 70 to 135 tons
- End-bearing or friction
- Splicing possible but difficult
- 4,000 psi concrete
- 10x10 to 16x16, square or octagonal cross
section - Lengths w/o prestress 40 to 50 feet
- Lengths w/ prestress 130 feet max
32Treated Timber
- 15 to 25 tons
- End-bearing or friction
- Typical length 35 to 45 ft., max 50 to 55 feet,
non spliceable - CCA treated
33Pressure-Injected Footings
- Also known as Frankie Pile
- 50 to 150 tons
- Bottom driven thick walled drive tube
- High energy rammed concrete base
- 3,000 to 4,000 psi poured or rammed concrete
shaft - 10 to 35 feet deep
- Load test required
34Drilled Shafts
- 100 to 500 tons
- End-bearing and friction
- Often rock-socketed for high capacity
- 30 inch to 120 inch diameter
- 3,000 to 4,000 psi concrete
- Cost 350 to 450/cy
- Load test required
35Drilled Mini-Piles
- 20 to 150 tons
- Friction based, minor end-bearing
- Often rock-socketed for high capacity
- 4 to 8 inch diameter
- 4,000 to 5,000 psi grout w/steel center bar
- Installed w/ temp steel casing
36