By: Tia Maria Richardson, P.E. Principal Investigator
WV DOH
RP #121
Experimental and
Analytical Behavior of
Slide Suppressors Embedded in
Bedrock
“A design Model for Pile Walls Used to Stabilize Landslides”
Pile Walls*Are often used by the WV DOH as a soil reinforcement technique to remediate failed slopes
*They can be placed in lieu of traditional earth retaining structures
*The are particularly useful when space is limited
*Often referred to as “Slide Suppressors”
*Landslides are a common problem in WV
Usually consist of pre-cast concrete panels
supported by drilled or driven piers
Other lagging has also been
used
Greenbag Road Morgantown, WV
They transfer the loadfrom the weak upper
strata to the stable material below
Lagging (in this application)not structural
Purpose: *Aesthetics
Contain loose debris
Piles MUST Penetrate the Slip Surface
Must be embedded to fixity - into a stable material that is sufficiently strong to resist the landslide forces
Subsurface data is a MUST!
Top of Rock
Slip surface BELOW Top of Rock
Subsurface data is a MUST!
Driven to Refusal
Pile Wall Failure Rt. 857, Morgantown, WV (Cheat Lake Area)
Stable material below
Rock ?? Not always!
WV has a lot of Inter-bedded weak clay seams in shale
SITE specific!
In a landslide situationThe Design & Analysis Requires Defining Two Main Variables:
1) The driving forces from the landslide
2) The passive resistance provided by placing the piles
WILL COME BACK TO THIS!
RP #97 - Dr. M.A. Gabr•Graduate Student
DOH Installing piles into rock10 feet or L/3
Conservative Approach
Fu
Deformation
EI1, L1
EI2, L2
LTBASE Pile ProgramCurves
Allowable deformation
Thesis: Develop aSoil Curve
Developed by Dr. Gabr
TOR
Unbalanced Force, Fu
FuHyperbolic
Shear - Stress Shear - Strain Relationship
VERY Theoretical!
Test SiteBridgeport, WV
Rt. 73/73
Bridgeport, WV Rt. 73/73 Landslide
Road Closed!
Magnitude of Cracks
Dead Man
Custom built a frame to house the dial gauges
Also strained gauged along its length
•Validated LTBASE for a load at the top via strain gauges and dial gauges
Rt. 73/73 Test Site
•Demonstrated that after the point of fixity is reached - increased pile length does not reduce movements
*Phase II: Demonstrated it actually increases bending moment & movement at the top
Phase II Phase I
Inclinometer cut to size (or shorter)
LL
*Important !
What you are
measuring with the
instrument
Tygart Lake - Test Hole #2 - A-PlanePipe Bent 7-2-98
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
-1.0 0.0 1.0 2.0 3.0
Deflection (inches)
Dept
h (f
eet)
4/16/1998 2/19/1998 3/19/1998
5/19/1998 Cumulative
Cumulative deflection
Slip plane (soil movement)
*Keep in mind – the rigid piles will move different than flexible soil
Will see both soil movement data and pile movement data throughout this presentation
Incremental data
*Full Scale PerformancePerformance Monitoring2 Sites: Green Bag Road
And Forest Ave
Full Scale Test SiteTygart Lake
•109 Piles in the wall•Embedded in Lacustrine Clay on a 10 batter•Total Pile Lengths = 30 Feet•~7 ft. above centerline, ~2 ft. above G.S. in the back
•Monitoring 3 piles in the wall# 29, 49 and 73
•And 2 test piles on end 25 - 30 feet long
GBR
Old pipe piles
Piles at toe of slope
Generic Profile View
Installation of Pile #29Green Bag RoadMorgantown, WV
InclinometerPipe
*Position*
Plane ofmaximummovement
Pile #29Pile #49Pile #73Test Piles
Pile #49 and Test Pile #2 show the most movement
Pile Size
H 12x53ASTM A-36
Carbon Grade Steel
Plan View
Green Bag Road
Maximum Movement
~ 0.6 Inches
Pile #49
Near the center of the
wall
Test Pile #2
~ 0.3 Inches
Rest < 0.1”
Test Pile #2 Pile #49
Greenbag RoadTest Hole #4 - PILE #49 - A-Plane
Cumulative at Pile Top ~ 0.6 Inches
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
-0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
Deflection (inches)
Dept
h (f
eet)
10/24/1997 7/31/1998 3/5/1999
2/13/2000 10/15/2000 5/10/2001
Cumulative 7/31/1998 6/10/1999
cum 9-7-02 cum 5-8-03 9/7/2002
5/8/2003
Greenbag Road - Test Hole #2 A-Plane
Cumulative at Pile Top 0.4 Inches
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
-0.2 0.0 0.2 0.4
Deflection (inches)
Dept
h (f
eet)
5/20/1998 9/12/1997 10/24/1997
7/31/1998 11/18/1998 6/10/1999
2/13/2000 10/15/2000 5/10/2001
Cumulative cum 9-6-02 cum 5-8-03
Section Cut Near Test Pile #49
A retrogressive slip was indicated
Slope Stability Analysis - Green Bag Road
Figure 3.3.4: Green Bag Road - Original Profile, Retrogressive Slide #1
0
20
40
60
80
100
120
0 50 100 150 200 250 300 350 400
X-Distance (Feet)
Y-El
evat
ion
(Fee
t)
Ground Surface Assumed Critical Slip #1, FS=1.01
Cohesion = 0Residual Friction Angle = 25 Degrees
Slope Stability Analysis - Green Bag Road
Figure 3.3.5: Green Bag Road - Profile #2, Retrogressive Slide #2
0
20
40
60
80
100
120
140
0 50 100 150 200 250 300 350 400
X Distance (feet)
Y El
evat
ion
(feet
)
Profile 2 Slip #1 Assumed Critical Slip #2, FS = 1.0
Slope Stability Analysis - Green Bag Road
Figure 3.3.6: Green Bag Road - Profile #3, Retrogressive Slide #3
0
20
40
60
80
100
120
140
0 50 100 150 200 250 300 350 400
X-Distance (Feet)
Y-El
evat
ion
(Fee
t)
Profile 3Slip 1Slip 2Assumed Critical Slip #3 FS 0 86
Figure 3.3.7: Green Bag Road - Original Profile, Pile Location and Summary of Slides
0
20
40
60
80
100
120
140
0 50 100 150 200 250 300 350 400
X-Distance (Feet)
Y-El
evat
ion
(Fee
t)
Surface 1, FS=1.01 Surface 2, FS = 1.0 Surface 3, FS=0.86 Pile Original Profile
Analyzed
Final Slope Stability Analysis on Green Bag Road
Model Developed does NOT work for this casei.e. When Piles are placed near the toe of the slope
Landslide force is grossly overestimated
Another procedure is needed
City of Morgantown Site16 piles in the wall - HP 12 x 74Design L = 25 feet (some 30)Design overkill - 40%L+ Embedded in bedrock
Monitoring 3 piles in the wall
#4, 8 (30 ft.) and 12
Bilco
Triad
City Engineer
Terry Huff
Two test piles on the end
- NOT connected, 20 feet Long
40%+ L
Profile View
Plan View Pile #4
25 feet7.1 ft.in rock
Pile #830 feet12.1 ftin rock
Pile #1225 feet7.1 ft.in rock
TestPiles4.6 ft. in Rock
Looking at Wall
2.5 ft. above GS15.4 feet to Top of rock
NotConnected
Very LITTLE Movement
Forest Avenue - Test Hole #3 - PILE #4A-Plane, L=25 Feet, 2.5 Feet Above GS
Cumulative at Top < 0.1 Inches
4
6
8
10
12
14
16
18
20
22
-0.2 -0.1 0.0 0.1 0.2
Deflection (inches)
Dept
h (f
eet)
5/20/1998 9/12/1997 10/24/1997
7/31/1998 11/23/1998 2/26/1999
6/10/1999 10/15/2000 5/10/20019/6/2002 5/8/2003 cum 5-8-03
Forest Avenue - Test Hole #4 - PILE #8-Plane, L = 30 Feet, 2.5 Feet Above GSCumulative at Pile Top < 0.1 Inches
.2 -0.1 0.0 0.1 0.2
Deflection (inches)
A
4
6
8
10
12
14
16
18
20
22
-0
Dept
h (f
eet)
5/20/1998 10/24/1997 7/31/1998
11/23/1998 2/26/1999 6/10/1999
11/3/1999 2/17/2000 5/10/20019/6/2002 5/8/2003 cum 5-8-03
Forest Avenue - Test Hole #5 - PILE #12A-Plane, L=25 Feet, 2.5 Feet Above GS
Cumulative at Top < 0.1 Inches
4
6
8
10
12
14
16
18
20
22
-0.2 -0.1 0.0 0.1 0.2
Deflection (inches)
Dept
h (f
eet)
5/20/1998 9/12/1997 10/24/1997
7/31/1998 11/23/1998 2/26/1999
6/10/1999 2/17/2000 10/15/2000
5/10/2001 Cumulative
Forest Avenue – Results of Inclinometer Readings, < 0.1”
TOR @ 15.4’
Note X - Scale
Forest Avenue – Results of Slope Stability Analysis
Figure 3.2.4: Forest Avenue - Profile and Critical Slip Surface
0
10
20
30
40
50
60
0 10 20 30 40 50 60 70 80 90 100
Horizontal Distance
Verti
cal D
ista
nce
Ground SurfaceWaterRock25 Foot PileCritical Circle
Model works beautifully for this case!
Will return to this site after the models are introduced
State ParkOffice
US Army Corps of
Engineers
District #4 DOH
Taylor County DOH
1. Subsurface InvestigationSoil and Rock samples - 10 holes5 Slope Indicators holes5 Monitoring Wells - in a triangular grid
3 deep, 2 shallow
Good indication of the slip PLANES2. Monitored slope for 1 year
PROFILE VIEW
5 Test Piles4 Slope Indicators
1 Slope Indicator
1 Wells
Lake
2 Wells
5 Wells placed in a triangular grid – shallow and deep
2 Wells
Monitoring wells - Deep and Shallow
Perched Water Table Detected
PROFILE VIEW
5 Test Piles4 Slope Indicators
1 Slope Indicator
1 Wells
Lake
*Should have put
an indicator
or two down slope2 Wells
Wells placed in a triangular grid – shallow and deep
2 Wells
LodgeDam
Slope Indicators
Wells
5
1120 ft
326240 ft 150 ft
PLAN VEIW
Profile
View
Lake
Toe?
Visual Observations
Near Test Hole # 1 and 5
Test Hole #5ToeTest Hole #1
Initial theory based on visual observations proven wrong
Tygart Lake - Test Hole #1 - A-PlaneNote: Pipe bend 3-3-00
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42
44
46
-1.5 -0.5 0.5 1.5 2.5
Deflection (inches)
Dept
h (f
eet)
1145
1147
1149
1151
1153
1155
1157
1159
1161
1163
1165
1167
1169
1171
1173
1175
1177
1179
1181
1183
1185
1187
1189
1191
Elev
atio
n
8-3-98 10-13-98 2-23-99
Cumulative 11-24-98
Tygart Lake - Test Hole #5 - A-Plane
0
2
4
6
8
10
12
14
16
18
20
22
24
-0.5 0.5 1.5 2.5 3.5
Deflection (inches)
Dept
h (f
eet)
8/3/1998 2/23/1999 6/2/1999
3/3/2000 5/10/2000 10/14/2000
5/10/2001 Cumulative cum 9-6-02
9/6/2002 cum 5-8-03 5/8/2003
Movement detected in
Test Hole #5 May 2003
5 years later
Movement detected in Test
Hole #1 August 1998
Plan
View
LodgeDam
Slope Indicators
Wells
5
13120 ft
26240 ft 150 ft
Down Slope
Test Hole #3 - Visual Observations
Test Hole #3 - Visual Observations
Assumed an deep angular slip
ONE deep slip initially detected
Profile
View
Lake
Complicated Slide S!Inclinometer Observations
Test Hole #31 deep slip within the first year.
Two more detected 2 years later
Test Hole #3
Threedistinct slip
planes detected!
Tygart Lake - Test Hole #3 - A-Plane
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
-0.5 0.5 1.5 2.5 3.5
Deflection (inches)
Dept
h (f
eet)
1148
1150
1152
1154
1156
1158
1160
1162
1164
1166
1168
1170
1172
1174
1176
Elev
atio
n
8-3-98 2/23/1999 6/2/1999
3/3/2000 5/10/2000 10/14/2000
5/10/2001 Cumulative cum 9-6-02
9/6/2002 cum 5-8-03 5/8/2003
11-24-98
Tygart Lake - Test Hole #3 - B-Plane
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
-3.0 -2.0 -1.0 0.0 1.0
Deflection (inches)
Dept
h (f
eet)
1148
1150
1152
1154
1156
1158
1160
1162
1164
1166
1168
1170
1172
1174
1176
Elev
atio
n
8-3-98 2/23/1999 3/3/2000
5/10/2000 10/14/2000 5/10/2001
Cumulative cum 9-6-02 9/6/2002
cum 5-8-03 5/8/2003 11-24-98
PLUS it was slipping on an angle as
evidenced by movement in
both the A and B
direction
Plan
View
LodgeDam
Slope Indicators
Wells
5
126120 ft
3240 ft 150 ft
Visible scarp, supports indicator data
TYGART LAKE
Test Holes #2 & 6 FIRST to move
Pipes Bent Last Full Reading
July1998
Assumed same slip given the locations
and time frames
Tygart Lake - Test Hole #2 - A-PlanePipe Bent 7-2-98
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
-1.0 0.0 1.0 2.0 3.0
Deflection (inches)
Dept
h (f
eet)
4/16/1998 2/19/1998 3/19/1998
5/19/1998 Cumulative
Tygart Lake - Test Hole #6 - A PlanePipe Bent 7-2-1998
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
-1.0 0.0 1.0 2.0 3.0Deflection (inches)
Dept
h (f
eet)
4/16/1998 2/19/1998 3/19/1998
5/19/1998 Cumulative
SummaryAfter One (1) year:
TB # 2 & 6 Moved the most(so much we couldn’t monitor them anymore)
TB #3 Indicated one deep angular slip
No other significant movement
Test Piles were installed based on the results after ONE year
After Six (6) years:
TB#3 Showed signs of 3 independent slip planes
TB#1 Showed yet another independent surface
5 INDEPENDENT SLIP PLANES – 3 Sections
Plan View
TEST PILES
LodgeDam
5 13 2
Test Piles
4
5 - TOR4 - L/63 - L/3
1 - L/62 - L/3
After 1 year
*Installed 5 SMALL piles at this site on purpose – we wanted them to move!
HP 10 x 42
A-36 Carbon Grade Steel
Test Pile Installation at the Full Scale
Tygart Lake Test Site
Tygart Lake - Test PILE #1 - A-PlanePile Top 2' Above GS
Near TB #3, L/3 ~9 Feet, L = 33 Feet
2
4
6
8
10
12
14
16
18
20
22
24
26
28
-0.2 0.8 1.8 2.8 3.8
Deflection (inches)
Dept
h (f
eet)
1148
1150
1152
1154
1156
1158
1160
1162
1164
1166
1168
1170
1172
1174
1176
1178
Elev
atio
n2/23/1999 3/3/2000 5/10/2000
10/14/2000 5/10/2001 Cumulative
Cum 10-14-00 cum 5-10-00 cum 9-6-02
9/6/2002 cum 5-8-03 5/8/2003
6/2/1999
TOR
Tygart Lake - Test PILE #2 - A PlaneCumulative at Pile Top = 0.3 InchesNear TB #3, L/6 ~ 5 Feet, L = 27 Feet
0
2
4
6
8
10
12
14
16
18
20
22
24
26
-0.4 0.1 0.6 1.1
Deflection (inches)
Dept
h (f
eet)
1150
1152
1154
1156
1158
1160
1162
1164
1166
1168
1170
1172
1174
1176
Elev
atio
n
11/24/1998 2/23/1999 3/3/2000
5/10/2000 10/14/2000 5/10/2001
Cumulative cum 9-6-02 9/6/2002
cum 5-8-03 5/8/2003 6/2/1999
Tygart Lake TEST PILERESULTS
Near Test Hole #3 (3 slips)
Test Pile #2NOT fixed at its base
**Very important
*Important !
Tygart Lake - Test PILE #1 - A-PlanePile Top 2' Above GS
Near TB #3, L/3 ~9 Feet, L = 33 Feet
2
4
6
8
10
12
14
16
18
20
22
24
26
28
-0.2 0.8 1.8 2.8 3.8
Deflection (inches)
Dept
h (f
eet)
1148
1150
1152
1154
1156
1158
1160
1162
1164
1166
1168
1170
1172
1174
1176
1178
Elev
atio
n2/23/1999 3/3/2000 5/10/2000
10/14/2000 5/10/2001 Cumulative
Cum 10-14-00 cum 5-10-00 cum 9-6-02
9/6/2002 cum 5-8-03 5/8/2003
6/2/1999
TOR
Tygart Lake - Test PILE #2 - A PlaneCumulative at Pile Top = 0.3 InchesNear TB #3, L/6 ~ 5 Feet, L = 27 Feet
0
2
4
6
8
10
12
14
16
18
20
22
24
26
-0.4 0.1 0.6 1.1
Deflection (inches)
Dept
h (f
eet)
1150
1152
1154
1156
1158
1160
1162
1164
1166
1168
1170
1172
1174
1176
Elev
atio
n
11/24/1998 2/23/1999 3/3/2000
5/10/2000 10/14/2000 5/10/2001
Cumulative cum 9-6-02 9/6/2002
cum 5-8-03 5/8/2003 6/2/1999
Tygart Lake TEST PILERESULTS
Near Test Hole #3 (3 slips)
Test Pile #2NOT fixed at its base
*Very Important*
Test Pile #1Behaved as
expected
Tygart Lake - Test PILE #5 - A-PlanePile Top 2' above GS
Near TB #2/6, L=24 Feet
2
4
6
8
10
12
14
16
18
-0.4 0.6 1.6 2.6 3.6
Deflection (inches)
Dept
h (f
eet)
1153
1155
1157
1159
1161
1163
1165
1167
1169
1171
1173
Elev
atio
n
11/24/1998 2/23/1999 5/10/200010/14/2000 5/10/2001 cum 9-6-029/6/2002 cum 5-8-03 5/8/20036/2/1999
Tygart Lake - Test PILE #4 - A-PlaneCumulative at Pile Top 1.3 Inches
Near TB #2/6, L/6 ~ 5 Feet, L = 30 Feet
2
4
6
8
10
12
14
16
18
20
22
24
26
28
-0.2 0.8 1.8 2.8 3.8
Deflection (inches)
Dept
h (f
eet)
1143
1145
1147
1149
1151
1153
1155
1157
1159
1161
1163
1165
1167
1169
1171
Elev
atio
n
11/24/1998 2/23/1999 3/3/20005/10/2000 10/14/2000 5/10/2001cum 9-6-02 9/6/2002 cum 5-8-035/8/2003 6/2/1999
Tygart Lake - Test PILE #3 - A-PlanePile Top 2' above GS
Near TB #2/6, L/3 ~ 13 Feet, L = 40 Feet
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
-0.2 0.8 1.8 2.8 3.8
Deflection (inches)
Dept
h (f
eet)
1137
1139
1141
1143
1145
1147
1149
1151
1153
1155
1157
1159
1161
1163
1165
1167
1169
1171
1173
Elev
atio
n
11/24/1998 2/23/1999 3/3/20005/10/2000 10/14/2000 5/10/2001cum 9-6-02 9/6/2002 cum 5-8-035/8/2003 6/2/1999
TEST PILE RESULTS
Near Test Holes 2 & 6
Longest Pile
Ground Surface
ROCK dip NOT to same vertical scale
Some embedment
After initial data collection
Considers a Landslide Based on an Impending Failure
Factor of Safety = 1.0
Requires defining two main factors
1. The force the piles must resist
Based on a landslide
2. The passive resistance provided by the piles
Based on the location of the slip
A slope stability analysis is first conducted to define the shape of the slip surface
A limit equilibrium analysis of a circular failure surface determined via the method of ordinary slices was selected
The program STABL was usedKnowledge
of slope stability analysis required!
0
20
40
60
80
100
120
140
-20 0 20 40 60 80 100 120
Horizontal Distance
Verti
cal D
ista
nce R
X, Y Circle Center
BASIC PREMIS
The surface of failure is
represented by the arc of a
circle
The soil within the circle
rotates about the center of
the circle
Depends on the distribution of Normal Stress, N,along a failure surface
Is analyzed by discretizing the mass of the failed slope into n smaller slices
Each slice is treated as a unique sliding blockand is affected by a general system of forces
N = Wi * sin (alphai)
Blown up Pictorial
Wi
Ni
Resisting Force
Inter-slice forces
Driving Forces
Wi
The tangential vector (driving force) represents the slide-inducing forces
The resisting forces consist of the soil cohesion, c, along the arc length, l, and the angle of internal friction, phi
S = cl + sum ( Ni * tan (phi) )
T = Wi sin (alphai)
Pore water pressures are considered by reducing N
Resisting Force: Shear Strength of Soil
Wi
S = cl + sum ( Ni * tan (phi) )
Factor of
SafetyResisting
to Sliding
Figure 4.2.3: Pictorial of the Development of the Model ForceForest Avenue - Profile and Critical Slip Surface
0
20
40
60
80
100
120
140
-20 0 20 40 60 80 100 120
Horizontal Distance
Verti
cal D
ista
nce R
X/3
Y
XP
(sum T - sum (N-U) * tan phi ) * R = P * Y
X, Y Circle Center
(Driving – Resisting) * Radius = What the
pile must provide
Statics problem!Inter slice forces are
neglected
Basic geometry of analyzing a landslide with a circular failure surface
Figure 4.2.3: Pictorial of the Development of the Model ForceForest Avenue - Profile and Critical Slip Surface
0
20
40
60
80
100
120
140
-20 0 20 40 60 80 100 120
Horizontal Distance
Verti
cal D
ista
nce R
X/3
Y
XP
X, Y Circle Center
Solving for PRest is based on
geometry
Variables from slope stability analysis
DEFINE XDistance from ground surface
to bottom of slip
Y = f (X)
Spreadsheet designed to calculate total force on the piles – based on the contributing slices
Note:
It was determined in Phase I (RP #97) that the vertical
component did not
contribute
Resisting passive support is only included below the slip plane
Inclined ground surface
Requires defining two main factors
1. The force the piles must resist
Based on a landslide
2. The passive resistance provided by the piles
Based on the location of the slip
Laterally loaded Pile Programs – Consider a
lateral force at the PILE TOP
Can modify GS
Pile Programs
Model Lateral force at the pile TOP
Variable ground surface and/or batter
As given in LPILE by
Reese et al. 1999
Resulting driving force from a landslide
Does NOT act at the pile TOP
Passive Supportf (slip plane) and location of pile
Critical Case Based on how the
pile programs operate
L’Pile analysis length
Considers a load at the top
L’Pile analysis length
Analysis ground surface on passive side
Analysis Ground Surface
Actual ground surface geometry and pile length
1. Excessive deflection at the pile top greater than 2”
2. Movement at the bottom indicating that fixity was notobtained:
> 0.0004b
3. Moment developed > Moment allowable for pile size
Pile Analysis
Excessive deflection at the pile top > ~2 inches
A. No movement at base – Implies excessive bending. Pile section is not BIG enough
B. Movement detected in the base – Implies fixity was not obtained. Increase the pile length and reexamine the results.
Failure 3
Failure 2
IF deflection is STILL excessive after you increase the length and obtain fixity – increase section
2. Movement at the bottom indicating that fixity was notobtained:
> 0.0004b
Pile Analysis
i.e. Not socketed into a firm enough material
Fixity NOT obtained!
Moment developed > Moment allowable for pile size
Pile Analysis
Select a larger Pile SECTION
Figure 3.2.4: Forest Avenue - Profile and Critical Slip Surface
0
10
20
30
40
50
60
0 10 20 30 40 50 60 70 80 90 100
Horizontal Distance
Verti
cal D
ista
nce
Ground SurfaceWaterRock25 Foot PileCritical Circle
Figure 4.5.1: Example Problem #1 - Forest AvenueBlown Up View of Contributing Slices and Input Information
20
25
30
35
40
45
50
55
60
48 50 52 54 56 58 60 62 64 66
Horizontal Distance
Verti
cal D
ista
nce
Ground Surface
Water
Rock
Pile
slip circle
Slice 3Slice 2Modified Slice 1
3 Contributing Slices/ 4 PointsEach slice contains two corresponding X, Y coordinates from Slope Stability Analysis. One must manually calculate the corresponding Y of the ground surface for each point. Slice 1 stops at the pile intersection and must be adjusted accordingly.
*Important Point - Point #1 Locates the pile and includes a portion of a slice. One must manually calculate the X and Y coordinates of this point and the corresponding Y of the ground surface.
Alpha 1Point 2
Alpha 2
Points labeled Alpha 1 and 2: Are used to calculate the slope of the ground surface at the top of the passive soil resistance. Soils above the slip surface do not contribute to the passive resistance.
Point 3
Point 4
Y surf 1Y surf 2 Y surf 3
From stability analysis
ManualGS corresponding to each X, Y on circle (manual)
Passive GS
Data Input
GENERAL INFORMATION FORCE DEVELOPMENT - Automatically Calculates
Project Name: Forest Avenue Distance from Ground Surface to Slipat intersection of pile and slip
Section: Critical (Variable X) 8.44
Operator: Tia Richardson X/3 2.81
Date: 6/16/2003 Y Coordinate of X/3 43.78
Distance from X/3 to RadiusSOIL INPUT REQUIRED (Variable Y) 85.72
Unit Weight of Soil (pcf): 130 Force P = R/Y ( (Sum T) - ( Sum (N - U)*Tan (Phi) )
Cohesion (psf): 0 Force P 2,152.95
Residual Phi (degrees): 28
Phi (radians) - no input req'd 0.4887Center to Center Spacing of Piles - INPUT REQUIRED 4
CRITICAL FAILURE SURFACE - INPUT REQUIRED TOTAL FORCE P (lbs/ft) 8,612 (From Slope Stability Analysis)
X Coordinate - (Center of circle): -11.9
Y Coordinate - (Center of Circle): 129.5
Radius of Circle: 110.5 INPUT REQUIRED FOR PLOTTING, Pile Length 25
Pile Location (assumes 2 ft. above GS) Force P
GWT Information - INPUT REQUIRED X Y X YRequired to calculate U = Pore Water PressureDepth of GWT from Ground Surface, hw 5 54.25 51.41 54.25 43.78 *See Note 3 on Page 2 54.25 26.41 64.25 43.78
Note: For plotting purposes,ALPHA Information to determine slope of passive resistance adjust cell L39 as needed toX and Y coordinates of 2 points, one on each side of the pile show horizontal line of force P
X1 49.38 Y1 37.51 ALPHA (Radians) 0.63X2 57.45 Y2 43.42 ALPHA (Degrees) 36.2
Example #1 - SOIL MODEL SPREADSHEET - Page 1 of 3
Input
Data Input
INPUT REQ'DSlice Test
Point X-Coordinate Y-Coordinate Slice Alpha Alpha Y-Coordinate Weight Driving Normal Y-top Y-bot H Ave for UCircle Circle Width of Slice of Slice of Ground of Force Force ave ave Pore N-U
Contibuting Contibuting B (Radians) (Degrees) Surface Slice (Tangential) Pressure tan PhiSlices Slices Hw
1 54.25 40.97 49.412 57.45 43.42 3.2 0.653 37.439 49.81 3,084.64 1,875.19 2,449.22 49.61 42.20 2.42 607.33 9793 61.27 46.65 3.82 0.702 40.216 49.89 2,391.13 1,543.89 1,825.90 49.85 45.04 -0.18 9714 64.60 49.72 3.33 0.745 42.674 49.72 701.30 475.35 515.61 49.81 48.19 -3.38 274
SUMMATIONS 3,894.43 4,790.73 607.33
Note 3: Adjust H of GWT in each cell if GWT is NOT equal distance from SurfaceNote 1: Delete rows below that which are not needed! Formulas will adjust accordingly (as input on page #1 - Cell E38) First entry point must be on line corresponding to to Point 1 Note 4: If H (Col M) is Negative, U is zeroNote 2: Can copy cells down if more rows are needed Note 5: Check Slice test in Col O and P, if negative, U is zero
Rock Line for Plotting purposes - Optional Sub routine for Interpolation Only Water Line for Plotting purposes - Optional(Input Required) (Input Required)
X Y X YX Y
54.25 34.0159 34.6 51 33.669 34.6 54.25 Y
59 34.6
8 14.75 Y2 - Y
4.75 276.8 -8 Y
8 272.05
34.01 = Y
INPUT REQUIREDPore Water Calculations
*See Notes 3, 4 and 5
Example #1 - SOIL MODEL SPREADSHEET - Page 2 of 3
Data Input
INPUT REQ'DSlice Test
Point X-Coordinate Y-Coordinate Slice Alpha Alpha Y-Coordinate Weight Driving Normal Y-top Y-bot H Ave for UCircle Circle Width of Slice of Slice of Ground of Force Force ave ave Pore N-U
Contibuting Contibuting B (Radians) (Degrees) Surface Slice (Tangential) Pressure tan PhiSlices Slices Hw
1 54.25 40.97 49.412 57.45 43.42 3.2 0.653 37.439 49.81 3,084.64 1,875.19 2,449.22 49.61 42.20 2.42 607.33 9793 61.27 46.65 3.82 0.702 40.216 49.89 2,391.13 1,543.89 1,825.90 49.85 45.04 -0.18 9714 64.60 49.72 3.33 0.745 42.674 49.72 701.30 475.35 515.61 49.81 48.19 -3.38 274
SUMMATIONS 3,894.43 4,790.73 607.33
Note 3: Adjust H of GWT in each cell if GWT is NOT equal distance from SurfaceNote 1: Delete rows below that which are not needed! Formulas will adjust accordingly (as input on page #1 - Cell E38) First entry point must be on line corresponding to to Point 1 Note 4: If H (Col M) is Negative, U is zeroNote 2: Can copy cells down if more rows are needed Note 5: Check Slice test in Col O and P, if negative, U is zero
Rock Line for Plotting purposes - Optional Sub routine for Interpolation Only Water Line for Plotting purposes - Optional(Input Required) (Input Required)
X Y X YX Y
54.25 34.0159 34.6 51 33.669 34.6 54.25 Y
59 34.6
8 14.75 Y2 - Y
4.75 276.8 -8 Y
8 272.05
34.01 = Y
INPUT REQUIREDPore Water Calculations
*See Notes 3, 4 and 5
Example #1 - SOIL MODEL SPREADSHEET - Page 2 of 3
No Reduction
Figure 4.5.2: Example #1 - Soil Model Spreadsheet - Page 3 of 3OUTPUT for Forest Avenue, 25 Foot Pile
20.00
25.00
30.00
35.00
40.00
45.00
50.00
55.00
50.00 55.00 60.00 65.00
X - Distance
Dep
th
Ground Surface Contributing Slices Pile Force P Rock Line Alpha
Some knowledge of Excel required for range adjustments on output plot
Figure 5.2.1: Example #1 - Forest Avenue - Pile ProblemPiles 4, 8 and 12
20.00
25.00
30.00
35.00
40.00
45.00
50.00
55.00
50.00 55.00 60.00 65.00
X - Distance
Dep
th
Ground Surface Contributing Slices Pile Force P Rock Line Alpha
L' - Pile Analysis LengthL' = L - 2/3X - H above actual GS
202" or 262"
Resultant Force Location P = 8,612 lbs per footAlpha = 36 degrees
Top of Rock
Actual Ground Surface
Passive Soil Resistance84"
Passive Rock Resistance84" or 144"
Distance aboveAnalysis Ground Surface, X/3 = 34"
2/3X = 68"
Note: Actual Pile LenghtsPile #4 & 12 = 300"Pile #8 = 360"
30"
Analysis GroundSurface
Additional information added manually to better describe pile problem
Figure 5.3.1.3: Comparison of Predicted Deflection Versus Measured DeflectionForest Avenue
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
20.00
22.00
24.00
-0.100 -0.050 0.000 0.050 0.100 0.150 0.200
Inches
Feet
from
GS
Predicted DeflectionPile #4 InclinometerPile # 8 Inclinometer
Pile 4 and Pile 8Deflection ~ 0.06 inches
Predicted Deflections via LPILE ~ 0.12 inches
It is well documented that
the programs are conservative
and predict more movement
Figure 3.4.4: Tygart Lake, Section B-B (Near TB # 2 & 6)Profile and Critical Slip
40
50
60
70
80
90
100
110
120
60 70 80 90 100 110 120 130 140 150 160
Horizontal Distance (feet)
Verti
cal D
ista
nce
(feet
)
Ground Surface GWT TOR Critical Circle 40 Foot Pile
Figure 4.5.4: Example Problem #2 - Tygart Lake, Section B-B (Near TB # 2 & 6)Blown up View of Contributing Slices
40
50
60
70
80
90
100
110
120
120 125 130 135 140 145
Horizontal Distance (feet)
Verti
cal D
ista
nce
(feet
)
Ground Surface GWT TOR Critical Circle Pile
Alpha 2Alpha 1Point 2
Point 1125, 90.91
Point 3Point 4
Point 5Point 6
See Figure 4.5.1 for additional information
Contributing Slices
Figure 4.5.5: Example #2 - Soil Model Spreadsheet - Page 3 of 3Output for Tygart Lake - Section B-B, 30 Foot Pile
70.00
75.00
80.00
85.00
90.00
95.00
100.00
105.00
110.00
100.00 110.00 120.00 130.00 140.00 150.00 160.00
X - Distance
Dep
th
Ground Surface Contributing Slices Pile Force P Rock Line GWT Alpha
Figure 4.5.6: Example #2 - Soil Model Spreadsheet on Tygart Lake - Section B-BAdded Information to clarify model output to help define the pile problem - 30 Foot Pile
70.00
75.00
80.00
85.00
90.00
95.00
100.00
105.00
110.00
100.00 110.00 120.00 130.00 140.00 150.00 160.00
X - Distance
Dep
th
Ground Surface Contributing Slices Pile Force P Rock Line Alpha
Top of Rock
Actual GS
X = 9.09
Distance above Analysis Ground Surface, X/3 = 3.03
Force P = 17,178 lbs/ft
L' - Pile Analysis LengthL' = L - 2/3 X - H above GS
Analysis GSSlope of PassiveResistance, 23.8 degrees
Passive Soil Zone
Passive Rock
ActualL
Figure 5.3.2.4: Tygart Lake, Section B-B, Measured Deflections
0
5
10
15
20
25
30
35
40
-1.0000 0.0000 1.0000 2.0000 3.0000 4.0000 5.0000
Deflection (Inches)
Dep
th B
enea
th G
S (F
eet)
Pile 3 ~ L/3
Pile 4 ~ L/5
Pile 5 - 1' into Rock
NOTE: Longest pile showed most movement
Figure 5.3.2.5: Tygart Lake Section B-B, Movement Compairsons, Pile #3
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
-1.00 0.00 1.00 2.00 3.00 4.00 5.00 6.00
Deflection (Inches)
Dep
th B
enea
th G
S (F
eet)
Pile 3 - PredictedPile 3 - Measured
Predicted
Measured
Figure 5.3.2.6: Tygart Lake Section B-B, Movement Compairsons, Pile 4 & 5
0.00
5.00
10.00
15.00
20.00
25.00
30.00
-1.00 0.00 1.00 2.00 3.00 4.00 5.00 6.00
Deflection (Inches)
Dep
th B
enea
th G
S (F
eet)
Pile 4 - Predicted
Pile 5 - Predicted
Pile 4 - Measured
Pile 5 - Measured
Predicted
Measured
Figure 5.3.2.7: Tygart Lake, Section B-B, Moment Compairsons - Pile 3
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
-500,000 0 500,000 1,000,000 1,500,000 2,000,000 2,500,000
Deflection (Inches)
Dep
th B
enea
th G
S (F
eet)
Pile 3 - PredictedPile 3 - Measured
PredictedMeasured
Figure 5.3.2.8: Tygart Lake, Section B-B, Moment Compairsons - Pile 4
0.00
5.00
10.00
15.00
20.00
25.00
30.00
-500,000 0 500,000 1,000,000 1,500,000 2,000,000
Deflection (Inches)
Dep
th B
enea
th G
S (F
eet)
Pile 4 - PredictedPile 4 - Measured
MeasuredPredicted
Figure 5.3.2.9: Tygart Lake, Section B-B, Moment Compairsons - Pile #5
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
20.00
-500,000 0 500,000 1,000,000 1,500,000 2,000,000
Deflection (Inches)
Dep
th B
enea
th G
S (F
eet)
Pile 5 - PredictedPile 5 - Measured
MeasuredPredicted
Run stability with the pile in place
FS > 1.25 - 1.5
Some programs can do this (Gregory – GSTABL7)Otherwise, model pile as a strong a rock layer
Very common
1. Move the pile: Find the optimal location in the slope
2. Add another row of piles
Most WV DOH Applications Want to save the road and the down slope materials are not a concern
*Site Specific*
Proposed Model is suitable for predicting landslide forces acting on piles when:
The piles are placed near the top of the slope
Only one slip is occurring
Demonstrated close agreement at two full scale sites:
Forest Avenue – One Section
Tygart Lake - Two Sections
Same general trends observed as those found by other researchers:
Pile programs predict more movement than that which actually occurs in the field
The two pile programs used (LTBASE and LPILE) produced similar results.
LPILE has graphing advantages and rock options that LPILE does not
Model overestimates the landslide forces when the piles are placed near the toe of the slope - Green Bag Road
Use indicators on large projects!
At least drill test holesTake samples and run lab tests
Another method needed
Subsurface Data is paramount to the success
Ones ability to define the critical slip surface is important.
*It predicts the force on the piles and the amount of passive resistance to include in the pile analysis
Ones ability to use a slope stability program, run a laterally loaded pile program and function in Excel or other spreadsheet is important.
*Using a deeper seated slip is more conservative
The behavior of rock at a particular site can be dictated by cracks, fissures, etc.
There exists a limited amount of experimental data on rock in the literature
And, only for loads applied at the top to failure
Not full-scale working conditions
Tia Maria Richardson, P.E.
Associate Professor
Fairmont State University
