Embankment Design Methods - Ground Improvement - Lecture Notes, Study notes of Geology

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Module 9:Design methods of Geotextiles and Geogrids

Lecture 25:Embankment design methods

The Lecture Contains:

Applications

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Module 9:Design methods of Geotextiles and Geogrids

Lecture 25:Embankment design methods

Application of Geotextiles

Design methods:

An embankment placed upon very soft foundation soil and supported by a Geotextile or geogrid, a number of design elements arises

● Bearing capacity – Overall embankment geometry. ● Global stability – Design strength in major principal stress direction

• Design strength in minor principal stress direction ● Elastic deformation Modulus and failure strain in major principal stress direction Minor principal direction ● Pullout or Anchorage Anchorage length behind slip planes. ● Lateral spreading Frictional properties of Geosythetic.

Figure 25.

Allowable bearing capacity

= Unit wt of embankment.

= Allowable ht of embankment.

undrained shear strength of foundation soil.

.

Module 9:Design methods of Geotextiles and Geogrids

Lecture 25:Embankment design methods

Application of Geotextiles

Global Stability

Figure 25.

Elastic deformation

Figure 25.

The amount of elastic deformation allowed by the geotextile will govern the deformation of embankment. Relatively high modulus values of geosynthetic are required.

According to Flower et al The desired value of maximum strain at the required stress is approximately 10% thus.

Module 9:Design methods of Geotextiles and Geogrids

Lecture 25:Embankment design methods

Application of Geotextiles

Pullout or Anchorage:

Figure 25.

Friction angle of soil.

Friction angle of the soil to the Geosynthetic.

average ht of embankment above Geosynthetic.

efficiency of Geosynthetic to soil.

For

Module 9:Design methods of Geotextiles and Geogrids

Lecture 25:Embankment design methods

Application of Geotextiles

Lateral spreading:

Figure 25.

Tension cracks have been obsereved on the surface of the embankments. It could be analysed by using equation for active earth pressure and considering granular fills to the above the geosynthetic

Module 9:Design methods of Geotextiles and Geogrids

Lecture 25:Embankment design methods

Application of Geotextiles

Percent open area

POA is a fabric property that has applicability only for woven fabrics.POA is a comparison of the total open area (the void spaces between adjacent fibers) to the total specimen area. This test is applicable to woven monofilament fabric not applicable to non woven’s, since the over lapping fibers tend to keep any light from passing directly through the fabric.

Apparent opening size: Developed by U.S. Army corpe of Engineers.

The AOS or EOS of the fabric specimen is the retained on U.S. standard sieve number of this size. It is

the equivalent sieve size opening in millimeters. Referred to as the opening size or.

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