Estabilizacion de solidos

SOIL STABILIZATION―
A Historical Perspective and Growth of Geosynthetics as a Construction Material BRAJA M. DAS

For construction of civil engineering structures, in many cases it becomes necessary to stabilize soil to improve its properties, such as  Strength  Compressibility  Workability

Two major types of stabilization:
 Chemical Stabilization  Mechanical StabilizationCommon Chemical Agents
  

Lime Cement Fly Ash

CHEMICAL STABILIZATION
Involves mechanical reworking of the soil and addition of chemical agent  To modify and improve the physico–chemical environment in and around clay particles

 To stabilize, i.e., best strength gain/void filling

Chemical Stabilizers


Silicate  Lignin  Epoxy  Ester
 Amine

 Aliphatic

compound Plasticizer  Ether  Alcohol


Surfactant



Formaldehyde  Acetate  Sulfonate  Emulsifier



Chloride (K, Na, Ca)  Hydroxide (K, Na, Ca)  Biological

MECHANICAL STABILIZATION

   

Dynamic compaction Vibroflotation Precompression Sand drains / wick drains or prefabricated vertical drains

MECHANICAL STABILIZATION— Vibroflotation

MECHANICAL STABILIZATION—Vibroflotation

MECHANICAL STABILIZATION—
Dynamic Compaction

MECHANICAL STABILIZATION—
Reinforced Earth

 Use of galvanized metal strips  Use of geosynthetics (geotextiles, geogrids)

MECHANICAL STABILIZATION—
Reinforced Earth

Generally referred to as mechanically stabilized earth (MSE).
MSE—construction material strengthened by:  Metal rods and/or strips  Non-biodegradable fabricsMetallic Strip Reinforcement

 Vidal (1966)—provided modern concept of designing MSE with metal strips  French Road Research Laboratory provided extensive research results • Darbin (1970) • Schlosser and Long (1974) • Schlosser and Vidal (1969)

Retaining Walls with Metallic Strip Reinforcement
Reinforced-earth walls are flexible walls. Main components:  Backfill — granular soil Reinforcing strips — thin, wide strips placed at regular intervals  A skin or cover on the front of the wall

Retaining Walls with Metallic Strip Reinforcement
 With a conservative design, a 5-mm-thick (0.2 in.) galvanized steel skin would be enough to hold a wall about 14-15 m (45–50 ft) high. In most cases, precast concrete slabs can also be used as skin. The slabs are grooved to fit into eachother so that the soil cannot flow out between the joints. When metal skins are used, they are bolted together and reinforcing strips placed between the skins.

 

DEVELOPMENT OF GEOSYNTHETICS
 1930’s — In U.S., use of fabric to reinforce soil was attempted by South Carolina State Highway Department. • Heavy cotton fabric was used to reinforce subgrade. • Road functioned well untilfabric deteriorated.  1940’s — Production of non-biodegradable material began. Made from polymeric materials such as: • Polyester  Nylon • Polyethylene  Polystyrene • Polypropylene

DEVELOPMENT OF GEOSYNTHETICS
PVC HDPE EPS Polyvinyl chloride High-density polyethylene Expanded polystyrene 1927 1941 1950 1950 1956 1957 1960 1965

PET Polyester LLDPE Linear low-density polyethylene PP EPDM CSPEPolypropylene Thermoset polymers such as ethylene propylene diene terpolymer Chlorosulphonated polyethylene

Specific Gravity
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        

Steel = 7.87 Soil/rock = 2.9 to 2.4 Glass = 2.54 Polyvinyl chloride = 1.69 Cotton = 1.55 Polyester = 1.38 to 1.22 Nylon = 1.14 to 1.06 Polyethylene = 0.96 to 0.90 Polypropylene = 0.91 Polymer industry enormous; worldwide sales – over $50 billion/yr  Distribution reflects strength and diversity of consumption  Consumption of thermo-plastic polymers (of type used in geosynthetics) in 2000 was:
United States Western Europe Eastern Europe Canada Mexico Central/South America Japan Other Asia Africa/Middle East 26,797,000 27,071,000 4,111,000 2,525,000 2,224,000 6,201,000...