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Jesse G
Rauser, PE
LADOTD DRIVEN PILE
DESIGN & VERIFICATION
USING LRFD
Not all of our policies, guidelines, and SOP’s are in the same location
Answer commonly asked questions about LADOTD pile design & verif ication procedures
Address misconceptions about pile design & verif ication processes used by LADOTD
Identify relevant research projects associated with driven piles
Highlight changes to Section 804 in the upcoming 2016 Standard Specif ications
Provide links to useful information and codes
OBJECTIVES
Geotechnical Investigations
In-House vs. Consulted
Site investigation guidelines
Lab testing requirements
Soil boring logs
Driven Pile Design Methods
Scour
Design procedures
Resistance Factor Selection
Research Projects
Constructability
Specification changes
Field Verification
Test Piles
Monitor Piles
Indicator Piles
Pile Setup
PRESENTATION OUTLINE
FHWA Geotechnical Library:
http://www.fhwa.dot.gov/engineering/geotech/library_listing.cfm
Louisiana Transportation Research Center (LTRC) Downloads:
http://www.ltrc.lsu.edu/downloads.html
LADOTD Bridge Design Section
http://wwwsp.dotd.la.gov/Inside_LaDOTD/Divisions/Engineering/Bridg
e_Design/Pages/default.aspx
LADOTD Pavement & Geotechnical Section
http://wwwsp.dotd.la.gov/Inside_LaDOTD/Divisions/Engineering/Pave
ment_Geotechnical/Pages/default.aspx
USEFUL LINKS
GEOTECHNICAL
INVESTIGATIONS
PROJECT ASSIGNMENT HIERARCHY
Project Management (or other)
Pavement/ Geotechnical Section
LADOTD In-House Crew
LADOTD Materials Lab
Geotechnical Retainer Contract
Bridge Design Section
Bridge Retainer Contract
Geotechnical Subconsultant
Geotechnical Consultant
“What are the LADOTD
boring and laboratory
testing requirements?”
GEC No. 5 – Evaluation of
Soil & Rock Properties
(FHWA-IF-02-034)
Table 3 provides guidelines
for minimum investigation
Also in LRFD Bridge Design
Specification Table 10.4.2-1
SITE INVESTIGATION GUIDELINES
GEC No. 5 Cover Page
http://isddc.dot.gov/OLPFiles/FHWA/010549.pdf
Number of Borings
When foundation layout is
known:
At least one boring at every
substructure (bent or pier)
Two borings per substructure,
for widths greater than 100’
When foundation layout is
unknown:
At least one boring every 100’
of alignment
Depth of Investigation
Use the greater of:
At least 20’ below anticipated tip
2x maximum pile group dimension
In general, we use 120’ for bridge foundations
Subgrade borings should terminate at least 8’ below f inished roadway elevation
SITE INVESTIGATION GUIDELINES
SITE INVESTIGATION GUIDELINES
For embankment/fill,
consider depth of influence
(based on width), not only
height of f i l l
It may be appropriate to drill
to depths over 2B
Penetrate through weak
strata into denser material
to terminate boring, when
possible
No SPT’s in clay! Stress Distribution Beneath
Continuous Strip (from Coduto)
Deep Borings
75% of all cohesive samples
tested with Atterberg Limits
and UU Triaxial tests
This easily covers costs of
testing sand instead of clay
Per form some consolidation
tests in f i l l areas
Data submitted electronically
in gINT format and printed in
the LADOTD log format
Subgrade Borings
Test enough samples to classify using AASHTO system
This should include hydrometer tests to identify silt content
pH & resistivity in culver t areas
Data submitted in gINT format, log format varies among consultants
LAB TESTING REQUIREMENTS
10-2GT – Geotechnical Database Phase 2 standardized the gINT database format
Soil boring log format was also standardized
We can now plot consultants’ data directly into charts, fences, etc.
This cuts down on errors introduced by retyping data & saves time
Double check -200 results before classifying (SP versus SP -SM, etc.)
Make sure SPT termination is repor ted properly ( Standard Penetration Test)
Stratify the soil borings:
Only group 2 adjacent consistencies (i.e., very soft to soft, med. to stiff)
Do not group different USCS types to avoid drawing additional layers
SOIL BORING LOGS
DRIVEN PILE DESIGN
METHODS
Certain constraints are set before pile design begins
Type & size of pile
Unsupported length & slenderness ratio
Type of field verification available due to budget or accessibility
Scour Considerations
Scour of ten has a major impact upon the pile design
BDTM 21 Describes DOTD Policy for Predicting Scour Elevation
DESIGN CONSTRAINTS
Bridge Profile with Scour Information
For permanent structures:
Subtract Contraction & Local Scour from the lowest point in channel
Apply this calculated elevation to all piers/bents and end bents
Abutment scour is not usually calculated – this does not mean to ignore scour at abutments!
Minimum tip elevation for scour:
20’ below scour elevation for piles less than 24” in diameter
25’ below scour elevation for piles 24” in diameter or greater
From “old” Bridge Design Manual, not in new Bridge Design Manual
For detour bridges, apply local scour from the design ground surface at each bent location
SCOUR CONSIDERATIONS
#1 Question: “What is the status of DRIVEN?”
FHWA does not want to be in the software development business
Other software exists, including DrivenPiles (successor to DRIVEN)
You could run DRIVEN in a Virtual Machine running an older Win OS
Create your own spreadsheet/software
LADOTD has no current plans to vet/endorse any specif ic sof tware package
A future research proposal may address this later – no timeline
Ultimately, we will accept methods providing results consistent with the DRIVEN methods
Cohesionless soil – Nordlund Method
Cohesive soil – Tomlinson/α Method
AXIAL PILE DESIGN
“Does guidance exist for designing driven piles?”
DOTD generally tr ies to adopt methods described in the NHI course manuals
An older (1998) version of the manual is available on the FHWA website
Newer versions (2006) are available to those who take the associated NHI course
AXIAL PILE DESIGN
FHWA HI 97-013 Cover Page
http://isddc.dot.gov/OLPFiles/FHWA/009746.pdf
We have had success designing piles with CPT on recent projects
LTRC developed the PILE-CPT software to design piles
A new research proposal aims to evaluate newer CPT methods & update software
To develop experience, we recommend evaluating CPT & borings side by side for any projects with both
AXIAL PILE DESIGN BY CPT
Louisiana Pile Design by CPT Software
http://www.ltrc.lsu.edu/zip/pile_cpt_windows_7.zip
RESISTANCE FACTORS
Selection of φ must consider tradeoff between pile length & cost of f ield verification
Table 10.5.5.2.3-1 is a star ting point for φ
Region-specific research is also used to refine our selection of φ values
Site-specific φ calibration may be warranted on large projects
RESISTANCE FACTOR SELECTION
LRFD Bridge Design Specifications 2012
http://isddc.dot.gov/OLPFiles/FHWA/009746.pdf
Resistance Factor Determination Method Resistance
Factor (φ)
Static Load Testing of at least 1 pile per site condition, plus Dynamic
Testing on at least 2% of production piles (minimum 2/site) 0.80
Static Load Testing of at least 1 pile per site condition, no Dynamic
Testing 0.75
Dynamic Testing conducted on 100% of production piles 0.75
Driving criteria established by Dynamic Testing, plus Dynamic Testing
of at least 2% of production piles (minimum 2/site) 0.65
Wave Equation Analysis, no Dynamic Monitoring or Load Testing 0.50
FHWA-modified Gates dynamic formula at end-of-drive only 0.40
Static Methods (α-method/Nordlund method) 0.35/0.45
RESISTANCE FACTOR SELECTION
From Table 10.5.5.2.3-1 (LRFD Bridge Design Spec - 6th Edition w/2013 Revisions)
Note: Dynamic Testing includes restrike testing and signal matching analyses
07-2GT – Calibration of Resistance Factors Needed in the LRFD Design of Driven Piles
Completed May 2009
14-1GT – Calibration of Region-Specific Gates Equation for LRFD
Draft report reviewed, implementation is imminent
11-2GT – Field Instrumentation and Testing to Study Set -up Phenomenon of Piles Driven into Louisiana Clayey Soils
Draft report reviewed, implementation plan in progress
03-1GT, 10-2GT, 15-1GT – Geotechnical Database Projects
Phases 1 & 2 complete, Phase 3 underway
RESISTANCE FACTOR CALIBRATION
Resistance Factor Determination Method LRFD LADOTD
Static: ≥ 1 pile/site
Dynamic: ≥ 2% production piles (≥ 2/site) 0.80
0.70-
0.75
Static: ≥ 1 pile/site
Dynamic: None 0.75 -
Static: None
Dynamic: 100% production piles 0.75 0.75
Dynamic: Used to establish driving criteria
Dynamic: ≥ 2% production piles (≥ 2/site) 0.65 0.65
Wave Equation Analysis only, no Dynamic/Static 0.50 -
FHWA-modified Gates dynamic formula at end-of-drive only 0.40 0.40 *
Static Methods (α-method/Nordlund method) 0.35/0.45 0.50
RESISTANCE FACTOR SELECTION
AASHTO LRFD Bridge Design Manual vs. Typical LADOTD Practice
* Implementation of new research should increase to 0.55
CONSTRUCTABILITY
Remember, conservative
strength parameters in
design become the opposite
when considering drivability
Designs must be
constructible and capacity
must be verif iable
We need to f ind a better way
for consultants to maintain
oversight during
construction phase testing
For 200-ton Strength Load
Static Test:
200t / 0.75 = 267 tons
Indicator Pile:
200t / 0.65 = 308 tons
Gates Method:
200t / 0.40 = 500 tons
Can the same hammer be
used to verify 267 tons and
500 tons?
CONSTRUCTABILITY
“Why do you overdesign your
piles?”
The Required Pile Resistance
is almost 5x greater than the
Factored Load!
Common with high scour &
sandy soils
Feasibility of design must
consider overburden effect
In some cases, drilled shafts
may be a better choice
OVERBURDEN EFFECT
Pile Data Table with Significant Overburden Effect
OVERBURDEN EFFECT
Sand
Clay
Clay (Scour Zone)
0’
-10’
-20’
-30’
20’
Design Case: • Pile 1 = 122 tons
• Pile 2 = 122 tons
No Predrill Case: • Pile 1 = 187 tons
• Pile 2 = 320 tons
Predrill Case: • Pile 1 = 150 tons
• Pile 2 = 206 tons
Pile
1: 2
4”
Sq
ua
re P
PC
Pile
Pile
2: 2
4”
Sq
ua
re P
PC
Pile
20’ of Overburden:
• 56 tons • 46% of nominal
resistance
Alternate hammer approval
method has been removed
from Specs
Contractor’s Pile Driving Plan
must include WEAP analysis
Many were already doing so
DOTD will continue to look at
a basic drivabil ity analysis
during design process
Contractor is responsible for
the specifics of his proposed
driving system
PILE DRIVING – SPEC CHANGES
GRLWEAP Software
Contractor is responsible for Pile Construction Log
Documents all pile installation activities including predrilling
Provides a record of driving resistance for every foot of drive
Practical refusal broadly defined as 20 blows/inch at maximum stroke, for 3 consecutive inches
Hammer must be in working order
Dynamic monitoring may be needed to verify hammer efficiency
We will not accept a refusal condition on a hammer that is malfunctioning
Dynamic Load Test item renamed to “Dynamic Monitoring Assistance”
Dynamic Monitoring Instrumentation moved from nonstandard item into the Specif ication
PILE DRIVING – SPEC CHANGES
FIELD VERIFICATION
Test Pile (φ=0.70-0.75)
Driven in advance of the permanent piles
Load tested
Dynamic testing is typically done as well
Indicator Pile (φ=0.65)
Same as test pile, dynamic testing only
Monitor Pile
Permanent pile with dynamic monitoring
PILE CATEGORIES
Preparing to Drive a Test Pile
How many test p i les are needed?
1 per “site condition”
1 per pile size (unless similar enough to back out unit resistances)
Consider additional piles if end bearing conditions differ
Consider additional piles if additional information is needed for design
What is the maximum pi le test load under LRFD?
“Old” way was to use 300% of the design load
Now, use 150% of the Required Nominal Resistance (with predrilling) in plans
Spec Change: Spec now references ASTM D -1143, Procedure A , with minor modif ications:
Load is applied in 20 equal increments, or as directed by engineer
Load is removed in 5 equal increments, based on max test load
Deflection is measured with 3 independent gauges accurate to +/ - 0.001”
TEST PILES
TEST PILES
Load Test Reaction System
Testing schedule should be
f lexible
Some static tests done as
early as 7 days
Restrike tests do not have to
be exactly at 24 hours
Load test plus dynamic
testing allows us to verify
design methodology,
calibrate PDA, establish
setup criteria, and verify
hammer performance
Indicator Piles
How many Indicator Piles
are needed?
Same criteria as Test Piles
Can be used to establish
setup criteria but not
calibrate PDA to a load test
Permanent Piles
Spec Change – Modified
Gates to be used only when
specified in the plans
Based on research, we hope
to change φ from 0.40 to
0.50 or 0.55
INDICATOR & PERMANENT PILES
We use test piles and indicator piles to
Confirm static calculations
Reduce uncertainty
Assess pile setup behavior
Establishing setup rates may allow for accelerated f ield verif ication
In some cases, we can provide acceptance before reaching the nominal resistance
20-hr restrikes on LA-1 project (65% to 75% of capacity)
PILE SETUP
Pile Setup Curve Compared to Static Test Results
MACARTHUR BLVD. PROJECT
Pile Setup Curves
No room to do static testing
Used restrikes on monitor piles to establish setup behavior
Late restrikes had to be eliminated due to vibrations
In some piers, early restrikes saved the contractor t ime and allowed pile acceptance prior to 24 hours
Setup curves were used to estimate pile capacity deficiency and determine pile extension lengths
FHWA Geotechnical Library:
http://www.fhwa.dot.gov/engineering/geotech/library_listing.cfm
Louisiana Transportation Research Center (LTRC) Downloads:
http://www.ltrc.lsu.edu/downloads.html
LADOTD Bridge Design Section
http://wwwsp.dotd.la.gov/Inside_LaDOTD/Divisions/Engineering/Bridg
e_Design/Pages/default.aspx
LADOTD Pavement & Geotechnical Section
http://wwwsp.dotd.la.gov/Inside_LaDOTD/Divisions/Engineering/Pave
ment_Geotechnical/Pages/default.aspx
QUESTIONS?