Historically, the design of structures on
soft compressible soils (clays) has created problems for civil engineers.
Construction without some sort of soil treatment is usually impractical due to
unpredictable long-term settlement. Simple surcharging as a soil consolidation
method can take many years. Although surcharging increases water pore pressure,
settlement can take considerable time, as the water lacks easy path to leave
the soil.
The solution
Soil consolidation using prefabricated vertical drains (also commonly called
wick drains or band drains) can reduce settlement times from years to months.
Most settlement can occur during construction, thus keeping post-construction
settlements to a minimum.
Consolidation of water-saturated, fine-grained soil occurs very slowly because
the low permeability of these soils impedes the escape of pore water from the
soil voids. Even under large temporary surcharge loads, settlements can take
years because of this slow water movement and the great distance the water must
move to exit the soil. The installation of prefabricated vertical drains
greatly reduces the distance the water must move to reach a free drainage path,
and therefore greatly increases settlement rate. Drain spacing may be adjusted
to match the required settlement time.
|
|
