04 - Soil Stiffness and Problem Soils - University of Memphis - Measuring Soil...CBR 40 900 30% 3000...
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Soils
Transcript of 04 - Soil Stiffness and Problem Soils - University of Memphis - Measuring Soil...CBR 40 900 30% 3000...
Soils
Pavement Design Factors
Changes over Time
Subgrade Support ProvidedSeasonal Changes in Subgrade Support
Magnitude of Wheel Loads
Wheel Loads Applied to Pavement
Type of Wheel Loads (Single or Tandem Axles)
Number of Wheel Load Applications
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California Bearing Ratio (CBR)
CBR Inventor
Source: http://gsl.erdc.usace.army.mil/gl-history/images/gl_img_25r.jpg
O. James Porter
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Soaking CBR Sample
Source: http://www.archive.official-documents.co.uk/document/ha/dmrb/index.htm
AnnularWeights
Sample4 days
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CBR Test Setup
Source: http://www.archive.official-documents.co.uk/document/ha/dmrb/index.htm 8
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California Bearing Ratio
Penetration (inches)
0.0 0.2 0.3 0.4 0.5
9000
0
100
90
80
70
60
50
40
30
20
10
6000
Load
(pou
nds)
0.1
3000
100
4500
0.2
0
500
1000
1500
2000
2500
3000
0 0.1 0.2 0.3 0.4 0.5 0.6
Penetration (in)
Pist
on L
oad
(lb)
10
0
500
1000
1500
2000
2500
3000
0 0.1 0.2 0.3 0.4 0.5 0.6
Penetration (in)
Pist
on L
oad
(lb)
Identify straight-line portionof stress-deflection curve
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0
500
1000
1500
2000
2500
3000
0 0.1 0.2 0.3 0.4 0.5 0.6
Penetration (in)
Pist
on L
oad
(lb)
Shift stress-deflection curveuntil it intersects the origin
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0
500
1000
1500
2000
2500
3000
0 0.1 0.2 0.3 0.4 0.5 0.6
Penetration (in)
Pist
on L
oad
(lb)
1800 40%4500
CBR 40900 30%
3000
Compare to the ideal curve
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Typical Values of CBR
Material CBR Elastic Modulus(psi)
Crushed Stone(GW, GP, GM) 20 - 100 20,000 - 40,000
Sandy Soils(SW, SP, SM, SC) 5 - 40 7,000 - 30,000
Silty Soils(ML, MH) 3 - 15 5,000 - 20,000
Clayey Soils(CL, CH) 3 - 10 5,000 - 15,000
Organic Soils(OH, OL, PT) 1 - 5 < 5,000
Source: WSDOT Pavement Guide Interactive CD-ROM 16
Typical Values of CBRGeneral Soil Type USC Soil Type CBR Range
Coarse-grained soils
GW 40 - 80
GP 30 - 60
GM 20 - 60
GC 20 - 40
SW 20 - 40
SP 10 - 40
SM 10 - 40
SC 5 - 20
Fine-grained soils
ML ≤ 15
CL ≤ 15
OL ≤ 5
MH ≤ 10
CH ≤ 15
OH ≤ 5
Source: WSDOT Pavement Guide Interactive CD-ROM 17
Field CBR Test
Source: ASTM Standards on Disc, Vol. 04.03, Designation D 4429 - 04, June 2007 18
Field CBR
Source: http://www.ele.com/geot/cali.htm 19
Resilient Modulus(MR)
Resilient Modulus
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Resilient Modulus
Axial strain
Dev
iato
r stre
ss
MR
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Haversine Load Pulse
2max sin
cyclic
tP PT
- T
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Granular Soils
Source: WSDOT Pavement Guide Interactive CD-ROM
21 K
RM K
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Cohesive Soils
43 K
R dM K
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Estimating Subgrade MR
1500 RM CBRWARNING: Only for fine-grained soils with soaked CBR < 10.
1993 AASHTO Guide
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Estimating Subgrade MR
0.642555 RM CBRGood for a wide range of soil types
AASHTO MEPDG
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MR vs. CBR
0
3000
6000
9000
12000
15000
0 1 2 3 4 5 6 7 8 9 10
CBR
MR (p
si)
MR = 1500 CBR
MR = 2555 CBR0.64
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MR vs. CBR
0
10000
20000
30000
40000
50000
60000
70000
80000
0 5 10 15 20 25 30 35 40 45 50
CBR
MR (p
si)
MR = 1500 CBR
MR = 2555 CBR0.64
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Plate Load Test(k)
Plate Load Test
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Plate Load Test
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Plate Load Test
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Plate Load Test
0
5000
10000
15000
0 0.01 0.02 0.03 0.04 0.05 0.06Deflection (in)
Load
(lb)
ResidualDeflection
StraightPortion
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Plate Load Test
12"18"
24"30"
22 2A r 15 in 707 in
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Plate Load Test
k = 378 psi/inResidualDeflection 1
378
0
4
8
12
16
20
0 0.01 0.02 0.03 0.04 0.05 0.06Deflection (in)
Stre
ss (p
si)
StraightPortion
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