Soil Structure Interaction Construction Dynamics of Transportation Earthworks and Structures
computational modeling tools and associated visualizations allow for a more
comprehensive understanding of soil mechanics problems than the simplified
analytical solutions of the past. Yet many relatively common geotechnical
situations have not been re-explored in either parametric studies or investigated
using step-wise construction sequences. An improved understanding of the
behavior of embankments, slopes, and foundations when modeled through various construction
and life-cycle events can be gained if relatively simple foundation elements
and geotechnical features are more fully explored using current powerful computational
modeling tools. Exploring the influence of geometry, material properties,
reinforcing elements, construction events, or life cycle changes and the
subsequent impact on geotechnical and geo-structural performance, can lead to
new insight and reveal areas for additional research and practice improvement.
Research is needed to examine, and in some
cases re-explore, “real world” geotechnical situations, assessed analytically
in the past, using modern computational modeling methods. This will allow new insight
on deformable-body behavior especially when changes in geometry, material
properties, structural components, extent of excavations and fills, and effects
of the actual construction loading sequence can be included allowing the subsequent
impacts on performance, risk, reliability, and safety to be examined in more
comprehensive detail and in the current LRFD framework, rather than a single
“safety factor” which may not appropriately capture service limit state or
other performance considerations. Improved
understanding of stress/force and strain/displacement characteristics will help
improve geotechnical practice by relating performance to LRFD strength and
proposed project has the following significant objectives:
computational modeling tools to several basic transportation construction
features, examining how the soils and structures interact and react to
construction and life-cycle events with time, with an emphasis on stress and
deformation characteristics relating to LRFD strength and service
the impact of construction sequence and methods on geotechnical behavior,
comparing results with traditional analytical methods, where they exist.
Through investigation of basic problems of bearing
capacity, soil-structure interaction, and slope stability, use computational
modeling to reveal the impact of changes in geometry, material properties, time,
deformation, reinforcing and structural elements, and sensitivity to site changes
over time (such as from erosion, scour, man-made excavations, soil stockpiles
and surcharges, and similar external effects).
Provide modeling to use as a comparison
to real world case histories and project observations from State DOT and other
Make the models available to
educators and professional groups to aid in teaching and continuing education.
improved understanding of the impacts of superposition of effects and construction
sequencing, through computational models, will aid in the effective
establishment of appropriate service limit state and strength limit state
performance criteria in the LRFD framework (e.g. use of spread footings based
on construction point methodologies; improved understanding of dragload; and
performance of embankments with various side slopes and/or reinforcing).
Results for various cases could be compared against guidance
in manuals (NAVAC, state DOT) for established geometric cases (such as loading
and situations with slopes or live vehicle load).
The visualizations of construction
sequencing and the mechanics of how foundations and geotechnical works perform
while being constructed has not been well investigated generally- although it
certainly has been for complex project specific cases- these cases however
seldom are referenced or provided for use in general geotechnical training and
Computer modeling output and visualizations of stress and
strain (load and deformation) can be very effective teaching and educational
aids for use in college curriculums and for continuing education FHWA/NHI etc.
A literature review
would need to be conducted, but to the best of our knowledge a general analysis of several
types of transportation foundations during the construction and service life
has not been conducted.
research tasks to include the following:
examination using computational modeling tools to investigate stress/strain
and load/deformation of the following six areas:
assessment of soil stresses/deflections on a ‘typical’ dimension of a bridge
spread footing as seen from a construction sequence standpoint (e.g.
foundation, stem, backfill, beams, deck, rail, service etc.) [6+
construction stages and both soft and stiffer foundation soils]. Continue
the model to simulate at least 2 possible modes of failure (e.g. due to soil
loss or erosion of the foundation or overstressing).
assessment of soil stresses/deflections on a foundation on piles or shafts
of a bridge as seen from a construction sequence standpoint (e.g.
foundation, stem, backfill, beams, deck, rail, etc.) to investigate positive
and negative side friction distribution and end-bearing under different
conditions of soil strength and pile toe stiffness. [several construction
stages and several soil types for side resistance and base resistance;
potentially also multi-layered systems or external effects, such as liquefaction].
Continue the model to simulate at least 2 possible modes of failure (e.g.
due to soil loss or erosion of the foundation or overstressing).
assessment of soil stresses/deflections on a shallow foundation placed over
a column supported embankment using auger-cast or controlled modulus columns
or similar foundation elements for a bridge as seen from a construction
sequence standpoint (e.g. foundation, stem, backfill, beams, deck, rail,
do stress and displacement profiles look like below cantilever walls, MSE
walls, GRS-IBS walls, and other types of complex soil reinforced structures
or those supported on deep foundations?
are the impacts of drainage clogging [failure] on cantilever walls (if
hydrostatic pressure builds)? Continue the model to simulate at least 2
possible modes of failure (e.g. due to soil loss or erosion of the
foundation or overstressing).
the deflection below a new 30ft. embankment over soft ground as it is
constructed in stages. Include an examination of reinforced 1H:1V side
slopes; unreinforced 2H:1V side slopes, with internal reinforcing;
unreinforced 2H:1V side slopes without internal reinforcing; and
unreinforced 3H:1V side slopes without internal reinforcing. Continue the
model to simulate at least 2 possible modes of failure (e.g. due to soil
loss or erosion of the foundation or overstressing).
research tasks may also include:
examination of the following additional subject areas:
movements- construction of a bridge abutment in two stages, or construction
of a new embankment adjacent to an existing embankment [modeling performance
of new construction’s impacts on original construction].
are the impacts of excavation in front of a retaining wall supported on
piling. How do displacements differ depending on the slope of the
are stresses distributed in column-supported-embankments with different
amounts of soil cover above the columns?
does settlement below a foundation react to use of prefabricated vertical
drains [triangular and square spacing]?
Passive, At-rest pressure on earth walls. What if a cantilever wall is
constructed on compressible fill and the system rotates backward? What are
the global impacts?
are the impacts of changing the friction angle of soils in the backfill of
do retaining walls behave when either the slope above or below the wall
changes from flat to various inclinations?
do retaining walls on piling react to different degrees of slope in front of
does settlement occur below a foundation above variable soils (different
loads from impacts to traffic barriers on tall walls (MSE or cantilever)
transmitted to foundation elements?
do traditional and integral abutments comparatively behave due to thermal
Departments of Transportation and other infrastructure
owners (such as FHWA Federal Lands) can immediately benefit from the work,
improving training guides and educational materials.
Any insights from the work can also be immediately used to
improve policy and procedures and/or focus new and additional research
The most significant benefit is through an improved
understanding of service limit and strength limit performance
considerations. Computational modeling can aid in providing visualizations
which show how performance is impacted at service limit and strength limit
thresholds, which could be used to adapt the code to better reflect
construction sequence and the impacts of other external life-cycle events.
Geotechnical engineering is complicated and frequently there can be a superposition of measured effects such that unexpected results are observed from expected events. The geotechnical and geo-structural engineering communities will benefit from this research, in addition to teachers and educational institutions. The improved understanding through the thoughtful examination of ‘common’ transportation soil mechanics “problems” in a computational modeling setting will provide a valuable basis for geotechnical education- whether for undergraduate students first learning or practicing engineers in a continuing education setting. Force, deflection, settlement, creep, pore-water-pressure dissipation and structural elements of various strengths and stiffnesses interacting- considering changes in geometry, construction staging, and construction practice- will be examined to show the impact of various influences.
|Sponsoring Committee:||AKG60, Geotechnical Instrumentation and Modeling
|Research Period:||12 - 24 months|
|RNS Developer:||Derrick Dasenbrock, PE, D.GE, F.ASCE Geotechncial Engineer Federal Highway Admiration, Resource Center 12300 W. Dakota Ave, Lakewood, CO, 80228 202.923.0972 firstname.lastname@example.org|
|Source Info:||Committee members and friends.|
|Index Terms:||Soil structure interaction, Earthwork, Computer models, Geotechnical engineering, Load and resistance factor design, |
Bridges and other structures