case studies linking foundation performance and in-situ
TRANSCRIPT
Case Studies Linking Foundation Performance and In-Situ Tests in the Appalachian Piedmont
Paul W. Mayne, PhD, P.E. Georgia Institute of Technology
01 October 2013
Appalachian Piedmont Geologic Province
Surficial Extent of Appalachian Piedmont
VA-MD-DC
GA-AL-SC-NC
Piedmont Geologic Province
AL
GA SC
NC
VA
MD DE
PA NJ
"Georgia Red Clay"
Stone Mountain Red Top Mountain
North Lake Lanier
Primary Rock Types by Geologic Origin
Grain
Aspects
Clastic Carbonate Foliated Massive Intrusive Extrusive
Coarse Conglomerate
Breccia
Limestone
Conglomerate
Gneiss Marble Pegmatite
Granite
Volcanic Breccia
Medium Sandstone
Siltsone
Limestone
Chalk
Schist
Phyllite
Quartzite Diorite
Diabase
Tuff
Fine-
Grained
Shale
Mudstone
Calcareous Mudstone
Slate Amphi-bolite
Rhyotite Basalt
Obsidian
Sedimentary Types Metaphorphic Igneous Types
PIEDMONT
Geologic Time Scale
Geologic Time Scale Era Period Epoch Time Boundaries (Years Ago) Holocene - Recent Quaternary 10,000 Pleistocene 2 million Pliocene 5 million Cenozoic Miocene 26 million Tertiary Oligocene 38 million Eocene 54 million Paleocene 65 million Cretaceous 130 million Mesozoic Jurassic 185 million Triassic 230 million Permian 265 million Pennsylvanian Carboniferous 310 million Mississippian 355 million Paleozoic Devonian 413 million Silurian 425 million Ordovician 475 million Cambrian 570 million Precambrian 3.9 billion
Earth Beginning 4.7 billion
Piedmont Gneiss
and Schist
Piedmont Granite
Z-Age ≈ 1 billion years ago
Major Rock Formations in USA
Piedmont
Piedmont Subsurface Profile
"Georgia Red Clay" (CL - ML)
RESIDUUM (ML to SM)
SAPROLITE
Partially-Weathered Rock (PWR)
Intact Rock: Gneiss
Schist, Granite
GT Load Test Site, West Campus
0
10
20
30
40
50
60
70
80
0 10 20 30 40 50 60 70 80 90 100
SPT N-values (bpf)Dep
th (fe
et)
GRANITIC GNEISS
Piedmont Residuum:
Silty Fine Sand (SM)
PWR
0
10
20
30
40
50
60
0 10 20 30 40 50
In-Situ Testing in the Piedmont • SPT = standard penetration testing
• PMT = pressuremeter testing
• DP = dynamic penetrometers
• percussive soundings (air-track)
• VST = vane shear testing
• DMT = flat plate dilatometer
• CPT = cone penetration testing
• CPTu = piezocone testing
• Vs = shear wave velocity
• SCPTu = seismic piezocone
• SDMT = seismic dilatometer
Miller & Sowers (1967). Shear characteristics of
Piedmont soils using rotating vanes
SCPTU in Piedmont residual silts Winston-Salem, NC
0
2
4
6
8
10
12
14
16
18
0 500 1000
Modulus ED (atm)
0
2
4
6
8
10
12
14
16
18
0 1000 2000 3000 4000
Dep
th (
mete
rs)
Pressure (kPa)
Po
P1
0
2
4
6
8
10
12
14
16
18
0 1 10
Material Index ID
Clay Silt Sand0
2
4
6
8
10
12
14
16
18
0 5 10 15
Horiz. Index KD
Fairfax Hospital, Northern Virginia (1984) Case Study: Drilled shaft (L = 65' and d = 3') in Piedmont residuum
Axial Pile Influence Factors (Rigid Pile)
Randolph & Wroth (1979); Poulos & Davis (1980)
Rigid Pile in an Infinite Elastic Medium
0.01
0.10
1.00
0 10 20 30 40 50 60 70 80 90 100
Slenderness Ratio, L/d
Infl
uen
ce F
acto
r, I
o
Boundary Elements
Closed Form v = 0.5
Closed Form v = 0.2
Closed Form v = 0s
pt
tEd
IPw
Poulos & Davis (1980) Solution vs. Randolph Solution
Pt = load at top = Ps + Pb
Homogeneous Soil: Es = Elastic modulus n' = Poisson's ratio
RIGID PILE RESPONSE Length L and diameter d
Side Load, Ps
= Pt - Pb
Top Displacement, wt
s
tt
Ed
IPw
Load Transfered to Base:
)]1)(/(5ln[
)/(
)1(1
1
1
2 vdL
dLI
21
I
P
P
t
bPb = Base load
Ground Surface
Randolph Solution
Fairfax Hospital, Northern Virginia
0
1
2
3
4
5
6
7
8
9
10
0 500 1000 1500 2000 2500 3000 3500 4000
Dis
pla
cem
en
t, w
t(m
m)
Axial Load, Q (kN)
Elastic Soln: Qtotal = Qs + Qb
Elastic: Pred. Qs
Elastic Pred. Qb
Measured Load Test
s
pt
tEd
IPw
E' ≈ ED (ave. 64 DMTs) = 35 MPa = 364 tsf L = 65 feet and d = 3 feet Ratio L/d = 21.7 gives Ip = 0.076
Buildings on Piedmont - Northern Virginia and Washington DC
0
100
200
300
400
500
600
700
800
0 10 20 30 40 50 60
Ela
sti
c M
od
ulu
s, E
' (b
ars
)
SPT N60 value (bpf)
DMT-SPT Relationship in Piedmont Residuum
TRR 1169 (1988)
ADSC/ASCE
Opelika NGES
NCSU Site
Olympic Stadium
Northern Piedmont
Building Foundations
ED = 22 ∙satm∙N60 0.82
DMT-SPT Correlation in Piedmont Residuum (Mayne & Frost, TRR 1988) Also EPRI Manual (1990)
Foundation Systems in the Piedmont Spread footings
Mat foundations
Augercast pilings
Drilled shafts
Micropiles
Driven pipe piles
H-pilings
Monotubes
Step-taper piles
Franki piles (PIFs)
First American Bank Mat
22-story Bank Building - Mat Foundation Tysons Corner, Virginia
0
50
100
150
200
0 50 100 150 200
West Side (feet)
No
rth
Sid
e (
feet)
Structural Reinforced
Concrete Mat
Foundation:
t = 4.5 feet
Foundation Perimeter
Bank Tower: Total Q = 73,400k
Bearing Elev = +495 feet msl Mat Thickness, t = 4.5 ft Applied Stress: q = 3.47 ksf
Georgia Tech
Wachovia/Wells Fargo Tysons Corner, VA
-4.0
-3.5
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
0 50 100 150 200 250 300 350
Dis
pla
ce
me
nts
(in
ch
es
)
Time (days)
FAB Measured Displacements
Corner (pt 13)
Edge (pt 4)
Edge (pt 14)
Center (pt 7)
Center (pt 9)
PREDICTED
Corner
Edge
Center
Georgia Tech
Settlements: GSU Dormitory, Atlanta
0
1
2
0 1 2 3 4 5 6
Finite Layer Thickness, h/d
Inf
luenc
e F
act
or, IH
d
c
c/d
10
5
3
2
1.5
1
Harr (1966)
Approximation
s
Hc
E
IdqDeflectionCenter
)1(:
2n
c
Dormitory B Settlement Contours
0
5
10
15
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105
Breadth Distance (m)
Width
Dista
nce (m)
100 mm 120 mm 140 mm 160 mm
180 mm 200 mm 220 mm 240 mm
North
Reinforced Concrete Mat Foundation: c = 105 m; d = 18.3 m, thickness t = 1.07 m
-0.64
-0.54
-0.44
0
50
100
150
200
250
300
0 10 20 30 40 50 60 70 80 90 100
Distance (meters)
Se
ttle
me
nt
(mm
)
SW-NE Diagonal
NW-SE Diagonal
DMT Calculated (h = 12 m)
DMT Calculated (h = 18 m)
DMT Calculated (h = 24 m)
10" mat settlements DMT ED = 85 tsf www.geoengineer.org
ADSC-ASCE-FHWA Load Test Program Georgia Tech, Atlanta
Load Tests
End-bearing drilled shaft: d = 0.76 m L = 19.2 m
Friction-type drilled shaft: d = 0.76 m L = 16.9 m
Deep plate load test: d = 0.61 m z = 16.9 m
GT End-Bearing Shaft C1: d = 2.5' by L = 70'
Axial Load Transfer Distribution
0
10
20
30
40
50
60
70
80
0 200 400 600 800 1000
Axial Load, Q (tons)
Dep
th (
feet)
50 tons
100 tons
200 tons
300 tons
400 tons
500 tons
600 tons
700 tons
800 tons
900 tons
1000 tonsBas
LOAD Q
Base
Vibrating Wire Strain Gages
Elastic Continuum Response - GT Shaft C1
0
10
20
30
0 2000 4000 6000 8000 10000
Axial Load, Q (kN)Top D
eflection,
wt (m
m)
Qtotal = Qs + Qb Pred. Qs Pred. Qb
Meas. Total Meas. Shaft Meas. Base
Using DMT ED Modulus in Elastic Solution
Elastic Continuum Response - Shaft C2
0
50
100
150
200
0 1000 2000 3000 4000 5000 6000
Axial Load, Q (kN)Top D
eflection,
wt (m
m)
Qtotal = Qs + Qb Pred. Qs Pred. Qb
Meas. Total Meas. Shaft Meas. Base
Using DMT ED Modulus
in Elastic Solution
Cone Penetration Tests (CPT) at GT West Campus
0
2
4
6
8
10
12
14
16
18
20
0 2 4 6 8 10
Dep
th (
m)
qt (MPa)
0
2
4
6
8
10
12
14
16
18
20
0 100 200 300
fs (kPa)
0
2
4
6
8
10
12
14
16
18
20
0 1 2 3 4 5 6
FR = fs/qt (%)
qt
fs
Continuous Readings at 20 mm/s
CPT • Current Phase Tranformer
• Cross Product Team
• Cellular Paging Teleservice
• Chest Percussion Therapy
• Crisis Planning Team
• Consumer Protection Trends
• Computer Placement Test
• Current Procedural Terminolgy
• Cost Per Treatment
• Choroid Plexus Tumor
• Cardiopulmonary Physical Therapy
• Corrugated Plastic Tubing
• Cumulative Price Threshold
• Cell Prepartion Tube
• Central Payment Tool
• Certified Proctology Technologist
• Cockpit Procedures Trainer
• Cone Penetration Test
• Color Picture Tube
• Critical Pitting Temperature
• Certified Phelbotomy Technician
• Control Power Transformer
• Cost Production Team
• Channel Product Table
• Conditional Probability Table
• Command Post Terminal
Piezocone Response in the Piedmont
0
0
0
1
2
3
4
5
6
7
8
9
10
0 2 4 6 8 10
De
pth
(m
ete
rs)
Cone Tip Resistanceqt (MPa)
0
1
2
3
4
5
6
7
8
9
10
0 100 200 300 400
Sleeve Frictionfs (kPa)
0
1
2
3
4
5
6
7
8
9
10
-100 0 100 200
Porewater Pressureu2 (kPa)
0
1
2
3
4
5
6
7
8
9
10
0 500 1000 1500
Porewater Pressureu1 (kPa)
qt
u1
u2
fs
Height of Capillarity
CPTu in Piedmont PWR- Atlanta, GA
SPT
N60
23
34
71
34
56
67
50/6"
50/6"
50/2"
50/3"
0
2
4
6
8
10
12
14
0 10 20 30 40 50 60
qT (MPa)
Dep
th (
m)
0 0.2 0.4 0.6 0.8 1
fs (MPa)
-0.1 -0.05 0 0.05 0.1
u2 (MPa)
Partially-
Weathered
Rock
(gneiss)
Saprolite
(hard fine
sandy silt)
Residuum:
silty fine
sand
SCPTU in Piedmont residual silts Winston-Salem, NC
Geotechnics 2013 in the Piedmont
More Measurements
is
More Better
Mas Mejor
Seismic Piezocone (SCPTu) Piedmont silts in Marietta, GA
Tip Resistance
0
2
4
6
8
10
12
14
16
18
20
22
24
0 10 20 30
qT (MPa)
Dep
th (
m)
Sleeve Friction
0 200 400 600
fs (kPa)
Porewater Pressure
-100 0 100 200
u2 (kPa)
0
5
1
0
1
5
2
0
Shear Wave Velocity
0 100 200 300 400 500
Vs (m/s)
Vs
fs
u2
qt
u0
Piezo-Dissipation in Piedmont Residuum
-100
0
100
200
300
400
500
600
1 10 100 1000
Pore
wate
r P
ressu
re (
kP
a)
Time (seconds)
5.59 m
6.57 m
7.47 m
8.38 m
10.45 m
13.53 m
u1 dissipations
u2 dissipationsu0
u1
u2
SCPTù at Atlanta Airport Runway 5
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
0 5 10 15 20
qT (MPa)
De
pth
(m
)
0 200 400 600
fs (kPa)
-100 0 100 200 300
ub (kPa)
0
5
10
15
20
0 100 200 300 400
Vs (m/s)t50 (seconds)
1 10 100 1000
Five Independent Readings of Soil Behavior: qt, fs, ub, t50, Vs
Equivalent Elastic Modulus for Static Loading
Gmax = t Vs2
t = gt/g
Emax = 2Gmax(1+n)
Modulus Reduction Scheme (Fahey & Carter 1993)
0.15
0.17
0.19
0.21
0.23
0.25
0.27
0.29
0.31
0.33
0.35
0.37
0.39
0.41
0.43
0.45
0.47
0.49
0.51
0.53
0.55
0.57
0.59
0.61
0.63
0.65
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Mo
du
lus R
ed
uctio
n, G
/G0
Mobilized Strength, q/qmax = 1/FS
Resonant Column, Torsional Shear,and Triaxial Data
g = 0.2 0.3 0.4 0.5 = exponent
Algorithm: G/G0 = 1 - (q/qmax)g
Randolph Compressible Pile
sL
pt
tEd
IPw
:]1[
d
L
L
Lx
nn
)tanh(
)1(
811)1(41
d
L
L
Lx E
n
)tanh(4
)1(
43
[2] Ip = x1/x3
The proportion of load transferred from the top to base:
[3] Pb/Pt = x2/x3
The proportion of load carried in side shear is:
[4] Ps/Pt = 1 - Pb/Pt
The displacement at the pile toe/base is given by:
[5] wb = wt/cosh(L)
[6] = db/d = eta factor (Note: db = base diameter, so that = 1 for straight shaft piles)
[7] = EsL/Eb = xi factor (Note: = 1 for floating pile; < 1 for end-bearing pile)
[8] E = Esm/EsL = rho term. The parameter can be evaluated from: E = ½(1+Es0/EsL).
[9] = 2(1+n)Ep/EsL = lambda factor
[10] = ln{[0.25 + (2.5 E(1- n) - 0.25)] (2L/d)} = zeta factor
[11] L = 2(2/)0.5 (L/d) = mu factor
)cosh(
1
)1(
42
Lx
n
Es = Equivalent Elastic
Soil Modulus
AXIAL PILEDISPLACEMENTS
LengthL
Diameter d
Eso(surface)
EsM (mid-length)
EsL (along side at tip/toe/base)
Eb (base geomaterial
Modulus of layer 2)
sL
t
tEd
IPw
Pt Where Ip = displacement
Influence factor from
elastic continuum theory
z = Depth
Soil Layer 1
Soil or Rock Layer 2
National Geotechnical Experimentation Site Opelika, Alabama
LAB TESTING
Grain size
Hydrometer
Plasticity indices Unit weights
Triaxial shear (CIUC, CIDC)
Direct shear, UU, and UC
Fixed wall permeameter Flex-wall permeability Resonant column tests One-dim consolidation
IN-SITU TESTING and GEOPHYSICS
Standard penetration tests (SPT)
Full-displacement pressuremeter (FDPMT)
Menard pre-bored pressuremeter (PMT)
Flat plate dilatometer tests (DMT)
Cone penetration tests (CPT)
Piezocone tests with dissipations (CPTù)
Seismic dilatometer tests (SDMT)
Dual element piezocones (CPTu1u2)
Resistivity cones (RCPTu)
Seismic piezocones (SCPTu)
Dielectric cones (DCPTu)
Borehole shear tests (IBST)
Geophysical crosshole tests (CHT)
Spectral analysis of surface waves (SASW)
Torque measurements following SPT
Penetration rate effects studies
Frequent interval Vs profiling
Surface resistivity surveys
FULL-SCALE LOAD TESTS Drilled shaft foundations
Axial tests on drilled shafts Lateral tests on drilled shafts Time and construction effects studies Driven pipe piles at varied rates
De Waal piles Lateral loading testing of pile groups Shafts with self-compacting concrete
Opelika NGES, Alabama - Piedmont Residuum
Mean SCPTu Profiles Opelika NGES, Alabama
Opelika NGES in the Piedmont
Drilled Shaft Load Tests: Opelika, Alabama (Brown 2002)
4 Drilled Shafts d = 0.91 m L = 11.0 m
Q (total)
Q shaft
Q base
0
20
40
60
80
100
120
0 1000 2000 3000 4000
Dis
pla
ce
me
nt,
s (
mm
)
Applied Load, Q (kN)
Opelika NGES
Shaft S02
Shaft S04
Shaft S07
Shaft S09
Load Test at I-85 Bridge, Coweta County, GA
GDOT Drilled Shaft Load Test: D = 0.91 m L = 20.1 m Load Test Directed by Mike O'Neill
SCPTu at I-85 Bridge, Newnan, GA
0
2
4
6
8
10
12
14
16
18
0 2 4 6 8
qT (MPa)
De
pth
(m
)
0
2
4
6
8
10
12
14
16
18
0 100 200 300
fs (kPa) Ub (kPa)
0
2
4
6
8
10
12
14
16
18
-100 0 100 200
0
2
4
6
8
10
12
14
16
18
0 100 200 300 400
Vs (m/s)
Drilled Shaft Response, Coweta County, GA
0
10
20
30
40
50
0 2000 4000 6000 8000
Dis
pla
cem
ent,
wt(m
m)
Axial Load, Q (kN)
Qtotal = Qs + Qb
Pred. Qs
Pred. Qb
Meas. Total
Meas. Shaft
Meas. Base
RHYMES WITH ORANGE by Hilary Price
Rock → Stone → Sand = Formation of Residuum
Saprolitic
Class “A” Prediction of Axial Pile Response Jackson County, Georgia
Gmax from SCPTu for dynamically-loaded block foundations
Switched to driven 273 mm diameter closed-ended steel pipe piles: 8 < L < 18 m.
CPT qt, fs and u2 used for axial capacity and Vs for initial stiffness.
Turbine Foundations,
Plant Dahlberg Power Station
Southern Companies
Courtesy Marty Meeks
Seismic Piezocone Sounding, Jackson County, GA
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
0 2 4 6 8 10
De
pth
(m
)
qt (MPa)
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
0 100 200 300 400
fs (kPa)
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
-100 0 100 200
u2 (kPa)
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
0 100 200 300 400 500
Vs (m/sec)
fs
qt
Vs
u2
Axial Pile Response from SCPTu, Jackson County, GA
Driven Steel Pipe Pile No. P22 (L = 9.45 m)
0
2
4
6
8
10
12
14
0 200 400 600 800 1000 1200
Axial Load, Q (kN)
Deflect
ion,
w t
(m
m)
Predicted by SCPTu
in Advance
Measured
Axial Pile Response from SCPTu, Jackson County, GA
Driven Steel Pipe Pile No. P33 (L = 17.8 m)
0
2
4
6
8
10
12
14
0 200 400 600 800 1000 1200
Axial Load, Q (kN)
Deflect
ion,
w t
(m
m)
Predicted in advance
from SCPTU data
Measured from Load Test
51
www.hindu.com www2.dot.ca.gov
www.statnamiceurope.com
Reaction Frame Dead Weight
Osterberg Cell Statnamic Load Test www.fhwa.dot.gov
Pile Load Tests
GDOT O-Cell Load Test for Viaduct at CNN
2.9 m
11.8 m
6.2 m
d = 1.68 m
d = 1.59 m
d = 1.44 m
Residual Soils
(ML/SM)
Partially-Weathered
Rock (PWR)
Stage 1 O-cell
Stage 2 O-cell
Constructed Dimensions
of Drilled Shaft
GT Seismic Piezocone Sounding (SCPTu) GDOT - International Blvd.
Notes: Electronic data lost from 15.70 m to 16.70 m due to computer malfunction.
Tip Resistance
0
2
4
6
8
10
12
14
16
18
20
22
0 10 20 30
qT (MPa)
De
pth
(m
)
Sleeve Friction
0 200 400 600 800
fs (kPa)
Porewater Pressure
-100 0 100 200
u2 (kPa)
0
5
1
0
1
5
2
0
Shear Wave velocity
0 100 200 300 400 500 600
Vs (m/s)
Class A Prediction - GDOT Bridge at CNN
GDOT International Blvd. at CNN
0
10
20
30
40
50
0 1 2 3 4 5 6 7 8 9 10 11 12
Axial Load, Q (kN)
Top
Deflect
ion,
wt (m
m)
Qt Predicted
O-cell top down
O-cell Creep Limit
(MN)
Elastic Continuum Solution with SCPTu data input
LoadTest
O-cell load tests in Piedmont rocks Drilled shafts - Lawrenceville, GA (2011)
O-Cell Elastic Solution
01
1
111o1s
1
r
L2
wrG
P
P = applied force
L = pile length
ro = pile radius
Ep = pile modulus
Gs = soil side shear modulus
n = Poisson's ratio of soil
2o
2
222o2s
2
r
L2
)1(
4
wrG
P
Rigid pile or plate under compression loading
Rigid pile shaft under upward loading upper
segment
lower segment
O-Cell
w = pile displacement
l = Ep/GsL = soil-pile stiffness ratio
= Gs2/Gsb (Note: floating pile: = 1)
Gsb = soil modulus below pile base/toe
= ln(rm/ro) = soil zone of influence
rm = L{0.25 + [2.5 (1-n) – 0.25]} = magic radius
P1 = P2
Diameter d1 = 2r1
Length L1
Diameter d2 = 2r2
Length L2
O-cell tests - ADSC/ASCE Lawrenceville, GA
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
0 1000 2000 3000 4000 5000 6000
Dis
pla
cem
en
t, w
(in
che
s)
Applied Load, Q (tons)
Upper Segment Base Response
Elastic Pred Upward Elastic Down Pred
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
0 200 400 600 800 1000 1200
Dis
pla
cem
ent,
w (
inch
es)
Applied Load, Q (tons)
Upper Segment Base Response
Elastic Pred Upward Elastic Down Pred
E' = 3500 tsf E' = 1050 tsf
Test Shaft 1 in Rock Test Shaft 2 in PWR
Application of Randolph Elastic Solution
Recommendations to Geotechnical Practice
Site Characterization
in the Piedmont
FIRM CLAY
DIRECT-PUSH TECHNOLOGY
SDMTà Vp
Vs
tflex
p1
p0
NON-INVASIVE GEOPHYSICS
(Resistivity, Radar, Conductivity)
SCPTù Vs
fs
t50
u2
qt
DENSE SAND
loose sand
soft clay
Direct Push Borehole Methods Continuous Push Sampling Steel mandrel with inner plastic lining (d = 35 to 70 mm) Hydraulic and/or percussive push in 3-m strokes
www.geoprobe.com www.ams-samplers. com boartlongyear.com
Sonic Drilling
Vibrations at resonant frequency of drill pipe Fast and continuous sampling of soil and rock
Calibration of SPT Energy - Auto Hammers
Manufacturer Type ID No. Mean Energy Ratio (%) Reference
Diedrich D-120 ID 26 46 UDOT Diedrich D-50 321870551 56 GRL CME 850 ID 21 62.7 UDOT BK-81 w/ AW-J rods B2 68.6 ASCE Mobile B-80 ID 18 70.4 UDOT SK w/ CME hammer B6 72.9 ASCE Diedrich D50 UF5 76 UF CME 55 UF2 78.4 FDOT CME 850 296002 79 GRL CME 45 UF1 80.7 UF CME 85 UF4 81.2 UF CME 75 w/ AW-J rods A3 81.4 ASCE CME 75 UF3 83.1 UF CME 750 ID 4 86.6 UDOT Mobile B-57 DR-35 93 GRL CME 75 rig ID 10 94.6 UDOT
Factor of 2.1
O-cell load tests in Piedmont rocks Drilled shafts - Lawrenceville, GA (2011)
Methods for Rating Rock Masses
Core Recovery (CR) Rock Quality Designation (RQD); Deere et al. (1966) Rock Mass Rating (RMR); Bieniawski (1976, 1989) Q-System by NGI; Barton et al. (1976, 1991) Geological Strength Index (GSI); Hoek (1995, 2009)
Uniaxial Compressive Strength, qu
Rock Quality Designation (RQD) Spacing of Joints Condition of joints and/or infilling Groundwater conditions
Rock Mass Rating (RMR)
Shear Wave Velocity Profile in Piedmont VC Summer Power Station, South Carolina
Intact Rock
CR = 98 - 100%
RQD = 97 - 100%
Vs = 10,100 fps = 3078 m/s
qu = 25 ksi = 170 MPa
gt = 180 pcf = 28 kN/m3
Shear Wave, Vs (fps) Shear Wave, Vs (fps)
Elev
atio
n (
feet
msl
)
Vs from suspension logging in boreholes
Geotechnics 2013 in the Piedmont
• Beyond conventional SPT and PMT, showed advent and value of DMT, CPT, + SCPTu, SDMT
• Elastic continuum solution for pile foundations
Static top down loading
Bi-directional O-cell load tests
• Fundamental soil stiffness: Gmax = Vs2
• Presented case studies in Piedmont
• Use of Rock Mass Rating (RMR)
• Recommended more use of geophysics for site characterization, particularly Vs profiling
thanks