Soil improvement and construction methods in peat - Geotechnics of Organic Soils and Peat - page 153

Figure 6.30 AuGeo pile.
The pile consists of the base, cement mortar-filled plastic casing, sand blanket, pile
cap granular mattress and geogrids layer (Figure 6.30).
A typical embankment treatment with the AuGeo pile system for a 2 metre high
embankment is presented schematically in Figure 6.31.
6.5.6 Friction/floating piles
Orr andMcEnaney (1994) describe the use of timber friction poles for the construction
of a walkway across the Clara bog in Ireland.
Mortar-sand-rammed-column (MSRC) is a variant of the floating pile foundation
that combines the concept of a vertical drain (Figure 6.32).The vertical drain com-
ponent is the sand surrounding the mortar, and the whole system is a floating pile
foundation. Theoretically the ramming process increases the matrix soil lateral earth
pressure in the vicinity of the columns and between the columns, thus making the soil
stiffer. In time, as excess pore water pressure dissipates to the nearest column, the
compressibility as well as shear strength of the underlying soil will improve.
These columns can be constructed in a five-step process shown in Figure 6.33.
Holes of 0.5m to 1.0m diameter are drilled to a depth that typically varies from
approximately 2m to 10m below the ground surface. A temporary casing should be
employed to separate the mortar and compacted sand. Ramming the sand layer with a
high-energy tamper to form undulating very dense sand stabilizes the bottom layer of
sand. The process should be carried out layer by layer to avoid difficulties in withdraw-
ing the casing. The subsequent step is preloading, and the duration of the waiting period