005 Lesson Soil Properties
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Transcript of 005 Lesson Soil Properties
8/9/2015
1
SOIL REINFORCEMENT PRINCIPLES AND SYSTEM
DESIGN PROPERTIES
Lessons PW 5, 6 and 7
RM Chapter 3
Lesson Plan PW Lesson 5 (RM Section 3.2)
– Properties of Reinforced and Retained Fill Soils
PW Lesson 6 (RM Section 3.3 – 3.4)– Soil-reinforcement interaction
PW Lesson 7 (RM Section 3.5)– Reinforcement structural design properties
– Steel corrosion, geosynthetic degradation, andlong-term design strength
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Properties of Reinforced and Retained Fill Soils
PW Lesson 5
RM Chapter 3.2
Lesson 5 – Learning Outcome
The participants will be able to:
Define the reinforced fill and retained backfill soil parameters required for design
Identify issues/concerns with marginal fills
Soil Properties
Foundation soil
, wc, Φ´, c´, cu , Cc, Cv
Reinforced fill
, Φ´, c´, k, D50, Dmax, electrochemical
Retained fill
, Φ´, c´, k, electrochemical
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Reinforced Fill Materials
Select backfill / AASHTO
Urban stone
Marginal materials
Select Granular Fill for MSEW
U.S. Sieve Size Percent Passing
4-inch (102 mm)* 100
No. 40 (0.425 mm) 0 – 60
No. 200 (0.075 mm) 0 - 15Plasticity Index (PI) shall not exceed 6
Soundness tests required
* ¾ in. for geosynthetics & epoxy or PVC coated steel unless construction installation damage tests performed
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GRADATION AND SHEAR STRENGTH
(From research on sand ; after Schlosser and Long, 1972)
Gradation & Drainage After J. P. Powers (1992)
“Construction Dewatering”
% Fines and Permeability
(from NAVFAC DM-7.1)
Free Draining
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5
MSEW Fill Gradation Max 15% fines for gravity drainage
and shear strength
Some fines needed to aid compaction
Limit top size to prevent reinforcement damage & for compaction
Beware of problem soils!
– Gap graded soils
– Soils with Cu < 4 or >20
– High strain soils (i.e., with mica, gypsum, smectite, montmorilinite)
– Recycled concrete or asphalt
Fine Grained Soil
MarginalReinforced Fill?
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Marginal Reinforced Fill Issues
Property Result
PI
Fines
Fines/PI
Marginal Reinforced Fill Issues
Property Result
Horizontal Stress
Load Transfer
PI Construction Deformations
Creep Deformations
Fines Drainage &
Water Pressure Problems
Fines/PI Corrosion
Reinforced Fill for RSS
U.S. Sieve Size Percent Passing
4-inch (100 mm)* 100No. 4 (4.76 mm) 100 - 20
No. 40 (0.425 mm) 0 – 60
No. 200 (0.075 mm) 0 - 50Plasticity Index (PI) < 20
* ¾ in. for geosynthetics & epoxy or PVC coated steel unless construction installation damage tests performed
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Reinforced fill
Contracting Agency should develop detailed backfill specifications that uniformly apply to all MSE wall systems
Backfill properties and specs do not replace QC/QA inspection
Reinforced Fill
For MSE wall
- use 34° friction angle
For RSS systems
- allow > % fines
- 28° reasonable, but run test
Retained Backfill
Run tests to obtain backfill properties or use conservative values (e.g., 28°)
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Reinforced Fill Electrochemical Properties
Steel Reinforcements
Resistivity > 3000 ohm-cm AASHTO T-288
pH > 5 and < 10 AASHTO T-289
Chlorides 100 ppm ASTM D4327
Sulfates 200 ppm ASTM D4327
Organic Content 1% maximum AASHTO T-267
Reinforced Fill Electrochemical Properties
pH Limits for
Geosynthetic ReinforcementsPET > 3 and < 9 AASHTO T-289
PP & HDPE > 3 AASHTO T-289
Lesson 5 – Learning Outcome
The participants will be able to:
Define the reinforced fill and retained backfill soil parameters required for design
Identify issues/concerns with marginal fills