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Description
Underground construction and rehabilitation projects are prevalent in many urban areas across the
country. Space for construction activities is usually limited at these project sites because of the close
proximity of adjacent infrastructure. A major concem for projects involving deep excavations is the
impact of excavation-related ground movements on adjacent buildings and utilities. Excessive lateral
movements at the edge of the excavated area can lead to significant displacements and rotations in
adjacent structures. Consequently, control oflateral displacements is a major design consideration for
excavation support systems. In many urban areas, the project sites are underlain by soft clays. This
requires additional considerations because of the contributions fTomconsolidation and creep of the
soil. Strict defonnation control is often required to minimize damage to adjacent structures far many
urban projects. Control of defonnations is typically achieved with stifT excavation support systems.
Traditionally, excavation support systems are designed using apparent earth pressure diagrams. Using
this approach, the support system design becomes a function of the maximum anticipated earth
pressure and is govern by overall structural stability as opposed to maximum allowable horizontal or
vertical defonnation. This approach produces a support system that is adequate with regards to
preventing structural failure, but may result in excessive wall defonnations and ground movements.
Existing methods that do considered defonnations relate lateral wall movements to excavation support
system stiffness and basal stability. However, these were developed using a limited number of wall
types and configurations, and do not include considerations for differing materials of an excavation
support system; the three-dimensional effects of the wall construction; the effects of different support
types; the influences of the excavation geometry and sequencing; or complex site geology. Due to the
complexity of the excavation support system and the excavation process, it is easily concluded that for
a realistic analysis of the interaction between the soil and the excavation support system, a threedimensional
finite element model is rcquired.
The intellectual merit of this research is that the most recent studies have shown that cxcavationinduced
ground movements and the complicated soil-structure interactions of the excavation support
system are three-dimensional in nature. However, to date limited data has been reported in the
literature that presents a fully three-dimensional finite element analysis of a deep excavation. In
addition, no one has presented a design methodology for excavation support systems that incorporate
the three-dimensional influences of constructing the support wall and installing the support system; the
three-dimcnsional influences of excavating and backfilling the site (including time delays for
infrastructure construction); and the influences of three-dimensional ground defannations. This
research will provide the three-dimensional finite element analysis of three case historics and will
develop a defannation-based design methodology
The broader impact of this research is that a defannation-based designed methodology will potentially
save millions of dollars typically expended for repairs and mitigation of excavation-induced damage to
adjacent infrastructure. In addition, the results of this research will directly and indirectly be applicable
to tunnel design, design of earth rctaining walls, cofTerdam design, and deep foundations design (eg.
drilled shafts, auger-cast piles, cassions, etc.). It is also envisioned that these research results will be
extended to evaluating structure response to ground movements resulting from construction activities
such pipe jacking and construction dewatering. Another logical extension of this research is evaluating
the building and utility response to dynamic loading-induced ground movements such as blast loads,
construction vibrations, and earthquake loading. This research will also facilitate participation of
undergraduate researchcrs, with special emphasis on participation of underrepresented groups.
Status | Finished |
---|---|
Effective start/end date | 10/1/06 → 8/31/09 |
Funding
- National Science Foundation: $91,000.00
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Projects
- 1 Finished
-
Deformation Based Design Methodology for Excavation Support Systems
Bryson, L. (PI)
5/2/07 → 8/31/09
Project: Research project