15 AUGUST 2005
RETAINING WALLS AND CELLULAR COFFERDAMS
Purpose. The criteria presented in this UFC are to be used by the
engineer to develop the type, dimensions, and materials for building retaining walls
under waterfront conditions to mountainous terrain. The materials may be concrete,
reference and paragraphs are added here for cellular cofferdams. Cellular cofferdams
are very similar to retaining walls but require special design attention.
Scope. Apply the Geotechnical criteria to all projects for the military
services. The methods of determining settlement potential, bearing capacity, earth
pressures, and the size of the retaining walls is presented in detail. The criteria for
designing retaining structures or walls that include gravity, concrete, steel, tied and
braced bulkheads and cofferdams is presented in easily understood formats with real
life examples to guide the engineer.
Related Criteria. Chapters 7, Slope Stability Analysis, Chapter 8,
Excavation, Fill, Backfill, and Soil Stabilization for Structures, Chapter 9, De-watering
and Groundwater Control, Chapter 10, Foundation in Expansive Soils, Chapter 11,
Foundations in Areas of Significant Frost Penetration and Chapter 12, and Foundations
for Vibrating Equipment and seismic loadings should be consulted for conditions that
may effect the design of the retaining wall systems.
Cellular Cofferdams. Double-walled or cellular cofferdams consist of a
line of circular cells connected by smaller arcs, parallel semi-circular walls connected by
straight diaphragms or a succession of cloverleaf cells (see Figure 6-1). For analysis,
these configurations are transformed into equivalent parallel wall cofferdams of width B.
Analysis. Stability depends
on the ratio
to height, the resistance
of an inboard berm, if any, and type and drainage of cell fill materials.
Exterior Pressures. Usually active and passive pressures act on exterior
faces of the sheeting. However, there are exceptions. These are illustrated in Figure
Stability Requirements. A cell must be stable against sliding on its base,
shear failure between sheeting and cell fill, and shear failure on the centerline of the
cell. It must also resist bursting pressures through interlock tension. These failures are
influenced by foundation type. See Figure 6-1 for design criteria for cofferdams with,
and without, berms, on rock, and on fine-grained or coarse-grained soil.