Page 200 - Urban Construction Project Management

Logistics 155
Exhibit 6-34
Grade A A
Soldier beams
details.
Soil
Wide flange beam

Bottom of
excavation
Soil
Soil

Rock
Rock

H pile Wood
lagging

Soil

PLAN VIEW
A - A

cables) into the soil or rock behind the H piles and lagging and then anchoring them in
place by grouting the rods or cables. If the soil is not capable of taking the load of the
anchors, then rackers are placed to brace the soldier beams and lagging from inside the
excavation. This method is problematic because it restricts working around the rackers
within the excavated area.

Steel sheeting—Four feet length (or longer) of steel sheeting is “piled” into place to the
depth of the excavation. The sheeting sections are attached to one another by interlock-
ing with the next section. As the earth is excavated, the sheeting is anchored back to the
soil or rock as described in the previous paragraph.

Slurry wall—A clam bucket excavates a trench around the site. As soon as the trench
reaches a depth where the earthen walls are no longer stable (and will collapse) a slurry
mixture (bentonite) is placed in the trench to stabilize the walls. Once the trench and
slurry reaches a depth below the excavation elevation, then a reinforcing steel cage is
placed in the trench. Once this process is completed, concrete is poured into the trench,
replacing the slurry mixture (which is reused). Once the concrete hardens, the concrete
wall is then anchored to the soil or rock as stated previously. In some cases, precast pre-
stressed concrete panels are used in lieu of pouring the concrete (with the reinforcing
steel cage). See Exhibit 6-35 for a slurry wall section and Exhibit 6-36 for a photograph
of a slurry wall with tiebacks.