1. New England Soils 101
October 8, 2009

2. New 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

3. New 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]

4. New England Geology - Bedrock
Igneous
Granite
Schist
Basalt
Metamorphic
Gneiss
Phyllite
Sedimentary
Shale
Sandstone

5. Soil Design Criteria Depends on: Density Grain size [soil type]
Moisture content
Maximum past pressure

6. Soil Density Evaluation
Test boring with Standard Penetration Test [SPT]
Cone Penetrometer Test [CPT]
Density Gauge
Nuclear Densometer
Balloon
Sandcone

7. Estimating Soil Density
Estimate Consistency By:
Standard Penetration Test (blows/foot)
Soil Condition
Equipment/Visual
Cohesionless
Cohesive
Very Soft
Man standing sinks > 3”
<2
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
>30

8. Fundamentals 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

9. Fundamentals 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

10. Standard 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

11. Modified 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

12. AASHTO 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

13. Moisture Density Relationship [Proctor Test]

14. Moisture Density Relationship [Proctor Test]

15. Moisture Density Relationship [Proctor Test]
RANGE

16. Foundation Systems Shallow foundations Ground improvements
Deep foundations

17. Shallow Foundations Most common foundation type
Minimal engineering [low tech]
Generally have the most risk of settlement

18. Spread Footings Design based on soil bearing pressure
Typically constructed to frost depth
Shape – square, rectangular, strip
Usually min 3,000 psi concrete
Economical

19. Reducing 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

20. Geotextiles Non-woven geotextile [filter]
Woven geotextile [filter and improves stability]
GeoGrid [improves stability]

21. Shallow Foundation Pitfalls
Frozen subgrades
Existing fill conditions
Use of crushed stone

22. Ground Improvements Preload/surcharge Deep dynamic compaction
Rammed aggregate piers
Soil stabilization

23. Preloading/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

24. Preload/Surcharge

25. Deep 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

26. Rammed Aggregate Piers
Compacted aggregate shafts– Patented 1990’s
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

27. Soil Stabilization
Soil mixed with cementitious materials at surface or in columns
Grouting
Compaction
Jet
Chemical
GeoGrid

28. Deep Foundations Driven Piles Pressure-Injected Footing (PIF)
Steel HP Sections
Steel Pipe or Shell
Pre-cast Prestressed Concrete
Timber
Pressure-Injected Footing (PIF)
Drilled Shafts
Drilled Mini-Piles

29. Steel H-Piles 60 to 120 tons End-bearing
Full penetration welded splices
Capacity > 50 tons require load test

30. Steel Pipe Piles 65 to 125 tons End-bearing typically
Welded base plate w/ full penetration welded splices
Capacity > 50 tons require load test
3,000 to 4,000 psi concrete filled

31. Pre-cast Pre-stressed Concrete Piles
70 to 135 tons
End-bearing or friction
Splicing possible but difficult
4,000 psi concrete
10”x10” to 16”x16”, square or octagonal cross section
Lengths w/o prestress – 40 to 50 feet
Lengths w/ prestress – 130 feet max

32. Treated Timber 15 to 25 tons End-bearing or friction
Typical length: 35 to 45 ft., max 50 to 55 feet, non spliceable
CCA treated

33. Pressure-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

34. Drilled 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

35. Drilled 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. Questions?