ocpw wintersburg channel deep soil mixing
TRANSCRIPT
Sheet pile installation using silent piling
methods
Low-strength liquefiable soils
QA/QC procedures for deep soil mixing
Space & Environmental Restrictions
Topics:
What was The
Problem?
Crumbling levees incised in 1960s
High potential for major seismic event – Newport-Inglewood Fault Zone
Home-pads elevations several feet lower than monthly high tides
Liquefiable soil: >9-inches of settlement & > 3 feet of lateral spreading
How was it
Solved?
•“Selling” an innovative idea to Upper Management
•Permitting agencies approve construction method
•Conceptual adaptation by USACE in New Orleans
•Design endorsed by independent geotechnical firms
•Continued monitoring of the groundwater
Soil-Mix-Sandwich (SMS) Flood Control Levee
•Project acceptance by homeowners
Why did it consume a
decade to implement?
Several previous design concepts
confronted tough design issues
Who confirmed the SMS concpet?
By 2010, USACE began to
explore similar ideas and
then implemented them prior
to start of the C05 project.
When did Top
Management
adopt SMS?
Background to
East Garden Grove Wintersburg Channel Deep
Soil Mixing
Critical area subject to
flooding from a levee
failure with substantial
impact!!!
Why did it cost $42 Million?
Marine
Environment Tidal Influence Tectonic Fault
Environmental Sensitivity Contiguous Subdivisions
Liquefiable Soil
A Challenging Site Fit
for Ground
Improvement
How was the construction process accomplished?
Flood control channels are linearly horizontal projects
An “Assembly Line” process was implemented at the site
Atypical Site, Atypical Approach
How was the construction process accomplished?
Flood control channels are linearly horizontal projects
An “Assembly Line” process was implemented at the site
Atypical Site, Atypical Approach
Assembly Line Components: 1)Cistern below Trees and top soil
2)Dual Sheet Piles Deep Soil Cement Mixing (DSCM)
Components of Assembly Line:
1: Infiltration Cistern
Construction Sequence
Preparation for Cistern-Trench Excavation
Install Cistern
Dual Functions of Infiltration Cistern:
1. Groundwater fluctuation buffer during
construction and post construction
2. Surface drainage storage for
infiltration as a WQMP component
Infiltration cistern acted as a pseudo-surge tank
Cistern design was an elaboration on infiltration trenches.
Stacks of
Infiltration
cisterns
Section of Infiltration Cistern
Trench-Box and Compactor and Gravel Sub-base for Cistern
Multiple Surveys and Construction Monitoring
Components of Assembly Line:
2: Sheet Piles
Construction Sequence
Buffer Area between Residences and Levee was
Layout Area prior to Sheet Piles Duo Insertion
Sheet piles over covered cistern
Sheet pile rows inserted with Press-In method
Contractor employed up to
three Giken Press-In
(Reaction Base) Pile Drivers
during construction
Platform for Soil-Mixing within Sheet Piles Duo in-progress
Platform almost ready
for Soil-Mixing
Components of Assembly Line:
3: Deep Soil Cement Mixing
(DSCM)
Construction Sequence
Find a Staging Area for Cement Plant!
How to overcome High Mobilization Cost?
Large flood-control project → realizes economy of scale
How to
overcome
Difficult Access
Constraints?
Identify logistics,
acquire easements,
conduct
constructability
review to assess
viability of using a
“behemoth-
machine” in an
Assembly-Line
process for a linear
project
Typical access restriction on C05!
Traditional DSCM is below ground
C05 SMS DSCM was above and below ground!
Target Locations for C05 DSCM
Subterranean: traditional-beneath levees (as an example) beneath large storage tanks
Supra-terranean: within confinement above a channel invert horizon
Traditional DSCM literature was focused
on Subterranean applications
Benchmarks for
Sheet Piles & SMS
Lateral pressure mitigation
along the length of a levee
Seepage mitigation
Environmental
engineering:
contamination,
solid waste liner
DSCM Applications:
“Risk Analysis for Flood
Damage Reduction Studies”
• ER 1105-2-101 became effective 3
January 2006.
• It provided guidance on the
evaluation-framework for USACE
flood damage reduction studies.
Use several constitutive models for sheet pile design
1) Rankine Limit State Model
2) Sheet Pile “Fixity-Point”
with Euler Buckling Model
3)SESAME Axial-Flexural interaction Model
4) Winkler Springs, Beam-in-Elastic
Foundation Sheet Pile Model
Soil-Recession in the field necessitated→
Geo-Structural
Analysis to
Evaluate 2nd
Order P-Delta
Effect for
Construction
Phase
Pre-construction evaluation of soil-recession utilized→
the Single Element
Stiffness Analysis
Method -SESAME
See Section16-15 “Buckling of Fully and Partially Embedded
Piles and Poles” by J.E. Bowles in “Foundation Analysis &
Design”, 4th Ed.
What were
the Deep
Soil Cement
Mixing
(DSCM)
metrics for?
They enable
modeling
SMS as a
Simplified
Rigid Block
Pseudo-Static
Analysis of SMS
Benchmarked
by established
State-of-
Practice
methods to
reduce
uncertainty
Use several
constitutive
models for
SMS design
Combining DSCM and Sheet
Piles in a Hybrid Structure SMS created a
pattern of Single
overlapping DSCM
cells within the
confined space
between two sheet
pile rows
DSCM Columns Primary System, Soil-Mix-Sandwich (SMS) DSCM sub-
contractor initially
hired a
geotechnical
engineer to
provide an
alternate pattern
for DSCM
Sequestering and
Compartmentalizing
into a Wafer System
Project hexagonal-lattice
work plan appeared
complicated on paper
In reality, the whole plan
is summarized by two
dimensions any which
way one looks(5.5’ & 4.75’)
DSCM Metrics
Site: type of soil, access, staging
Water content: wet mixing, dry mixing, MDM,
water cement ratio, volume of spoils
Energy: torque, size of machine
Material testing: exhuming to inspect, coring, samples
Frequency of sampling: How often? From what depth?
Binder & Additives: cement, lime, Bentonite
DSCM Parameters →
Specifications →
Binder Content
Mixing Method
DSCM Pattern vs. Function
Depth of DSCM
Inspection
Record keeping
Frequency of Testing
Depth of soil-mixed columns based on CPT Logs Anchor into competent strata without impacting deep aquifer!
Hard Metrics Used in DSCM
• UCS: Unconfined Compressive Strength
• Permeability: the speed of water through
the DSCM media under ASTM test
Standards
Importance varies depending on the
primary utility of the DSCM product
Soft Metrics Used in DSCM
Reproducibility of pattern by drill-rig
Uniform densification
of work-space
Impact to confining
structure or sheet pile
Grab-sample effect on hard-metrics
Potential need for retrofit 28 days after demobilization
Benchmarks for Soil Mixing
Q: How can engineer predict the amount of cement needed to achieve minimum UCS?
A: Perform pre-tests to establish a baseline (per the C05 specs)!
C05 UCS Pre-Testing Sample-Sources
Textbook Recipe →FHWA, TX-DOT
FHWA, TX-DOT distinguishes between
Dosage & Content
QA/QC for Soil Mixing
C05 UCS Pre-Testing Samples
C05 Project @56 Days
UCS Sample Results
@28 Days C05 UCS Sample Results Post
Cement-Reduction in HBI Recipe Results of jet-grouting were excluded from analysis
Probabilistic UCS test values set an “average-value” for
results to be acceptable for a given level of risk
Deterministic UCS test values set a “floor-value” below which
results are deemed unacceptable for a given level of risk
Approach selection depends on whether there is a “multitude of
columns” vs. a “single cell” resisting the lateral forces or seepage
Soil-Mix-Sandwich (SMS) Flood Control Levee
Geosyntec,
SCM
Construction
QA,
1322 page
Report,
documenting
verification of
intent of Plans
&
Specifications
• Densification is
far more affected
by pattern in
Confined-Work-
Space than Free-
Field-Work-
Space
• Sheet-Pile Duos
are further
confined with
ends-embedded
braces←
Confined DSCM vs. Free-Field DSCM
SMS, Embedded End-Brace
Use Accordion Sheet Pile where
SMS was not used
Issues, Challenges, & Mitigation
Several Fault-Zones identified in geotechnical reports traversing project.
Accommodation of surfacing tectonic fault with Accordion Sheet Pile confirmed by →
Accordion Sheet Pile was achieved via in-line introduction of redundant joint-T-piles
“Accordion” was designed to mitigate tectonic slip over life cycle of project
