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MSE STRUCTURES

• Design Issues – creep, construction damage, environmental factors

• Case Studies• Partial Factors of Safety

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21 m high retaining structure in France (Foix, 1994)

Temporary reinforced embankment – “dual-function” geotextile provides reinforcement and drainage for acceleration of consolidation

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Soil reinforcement composite (geogrid)

Ancient Babylonian Zigurat, 60 m high, constructed of reinforced clay (photo Dr. S. Dikran)

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Sum of reinforcing tensile forces retains active wedge

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12 m high wrapped-face wall, constructed 1982 at Prapoutel, France (Gourc et al, 1994). Woven polyester with 200 kN/m tensile strength and reinforcement spacing = 1m.

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Bitumen coating for UV protection.

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Woven facing for wrapped-face wall, UV protection is green needle-punched nonwoven. Photo after construction, 1983 (Gourc,1996).

Woven/nonwoven composite after establishment of vegetation, 1998 (Gourc, 1996).

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Immediately after construction, 1983

After establishment of vegetation

Mechanically Stabilized Earth Retaining Structures

Reinforced Embankments

Reinforced Steep Slopes

Reinforced Soil Retaining Walls

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Use of bottom-ash as fill in a MSE structure (Bossoney et al, 1995)

Use of waste tires as lightweight fill in the same MSE structure(Bossoney et al, 1995)

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View of the same MSE structure during and after construction; Φ 'of the bottom ash was close to 40°, and likely gained strength over time. Note the growth of vegetation on the face was not inhibited. (Bossoney et al, 1995)

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Alkaline Environments are relatively rare in geotechnical engineering – one obvious case is lime-stabilized soils.

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For geogrids, the friction test should be replaced by a pullout test. Passive resistance is mobilized on the transverse elements of the geogrid

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Relationship between displacement and reinforcement tension (pull-out force) for 2 different anchorage lengths. The effect of increasing the anchorage length La is to increase the apparent stiffness of the reinforcement (Gotteland, 1985).

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Relationship between displacement and reinforcement tension (pull-out force) for two different reinforcement tensile moduli. The effect of increasing the tensile modulus J is to increase the apparent stiffness of the reinforcement (Gotteland, 1985).

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DESIGNING MSE

STRUCTURES

What is Ti ?

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Limit Equilibrium on a two-part wedge…

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OVERALL EQUILIBRIUM METHOD

Determine TMAX Value