Civil Engineering Reference
In-Depth Information
Method
Technique
Principles
Suitable soils
Remarks
Soil replacement methods
Remove and replace
Excavate weak or undesirable material
Any
Limited depth and area where
and replace with better soils
cost-effective; generally
30 ft
Displacement
Overload weak soils so that they shear
Very soft
Problems with mud waves
and are displaced by stronger fill
and trapped compressible soil
under the embankment; highly
dependent on specific site
Water removal methods
Trenching
Allows water drainage
Soft, fine-grained
Effective depth up to 10 ft;
soils and hydraulic fills
speed dependent on soil and
trench spacing; resulting desic-
cated crust can improve site
mobility
Precompression
Loads applied prior to construction to
Normally consolidated
Generally economical; long
allow soil consolidation
fine-grained soil,
time may be needed to obtain
organic soil, fills
consolidation; effective depth
only limited by ability to
achieve needed stresses
Precompression
Shortens drainage path to speed
Same as above
More costly; effective depth
with vertical drains
consolidation
usually limited to
100 ft
Electroosmosis
Electric current causes water to flow
Normally consolidated
Expensive; relatively fast;
to cathode
silts and silty clays
usable in confined area; not
usable in conductive soils; best
for small areas
Site strengthening methods
Dynamic compaction
Large impact loads applied by repeated
Cohesionless best;
Simple and rapid; usable above
dropping of a 5- to 35-ton weight;
possible use for soils
and below the groundwater
larger weights have been used
with fines; cohesive
table; effective depths up to 60
soils below ground-
ft; moderate cost; potential
water table give
vibration damage to adjacent
poorest results
structures
