MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity...

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MSE Wall Design

Transcript of MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity...

Page 1: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

MSE Wall Design

Page 2: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

MSE Wall as a Gravity Wall

• An MSE wall is a gravity wall.

Heavy walls are good

Page 3: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

External Stability• Bearing resistance• Settlement• Sliding• Overturning• Overall Stability

Page 4: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

External Stability

Bearing

Page 5: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

Bearing Failure

Page 6: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

External Stability

Settlement

Page 7: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

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Flexibility of Wall Systems

TYPE OF FACING LIMIT OF DIFFERENTIAL SETTLEMENT

CIP Gravity Wall 1/500 2 In. in 100 Ft.

Welded Wire Facing 1/50 2 Ft. in 100 Ft.5’ x 5’ Panels with ¾” Joints 1/100 1 Ft. in 100 Ft.5’ x 10’ Panels with ¾” Joints 1/200 6 In. in 100 Ft.Modular Block Walls 1/200 6 In. in 100 Ft.Full Height Facing Panels 1/500 2 In. in 100 Ft.

Page 8: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

External Stability

Sliding

Page 9: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

Sliding Failure

Page 10: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

External Stability

Overturning

Page 11: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

External Stability

Overall Stability

Page 12: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

Forces

Water Pressure

Earth Pressure

Surcharge

Earthquake

Page 13: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

ForcesBack Slope Surcharge

Page 14: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

ForcesSurcharge

Page 15: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

Drainage

• If the wall backfill “fills” with water ….• Weight of soil increases• Shear strength of backfill decreases• Pressures on the wall increase• Greater tendency for fill to settle• Potential for movement of soils as water exits

wall or slope.• Buoyancy needs to be considered

• Appropriate drainage systems are critical !!

Page 16: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

Drainage System Installation

Page 17: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

Why Care about Drainage?

An example…

Page 18: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

20’

5’

20’

Page 19: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

20’

5’

Hw=

20’

LATERAL EARTH PRESSURES

H=25’

Page 20: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

Design Concepts

Topic 2

Internal Stability Design of MSE Walls

Page 21: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

What is a Failure Surface ??

Geosynthetic Reinforced Wall

H

L

Active

Zone

Resistant

Zone

Potential

Failure

Surface

Soil ReinforcementReinforced

Soil Mass

Metal Reinforced Wall

Page 22: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

How do Reinforcements Hold Up the Wall ?

L

Soil

Reinforcement

“Active” Force

Resistant Length, LeActive

Length, La

Page 23: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

Internal Stability Reinforcement Failure

Modes

• Pull out• Reinforcement tensile strength• Connection

Page 24: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

Internal Stability Reinforcement Failure Modes – CORROSION/DEGRADATION

• STEEL REINFORCEMENT• Area of steel is increased to account for the

anticipated corrosion loss over the design life• GEOSYNTHETIC REINFORCEMENT

• Ultimate tensile strength increased to account for strength loss due to installation damage, creep, and durability

Page 25: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

The internal stability of this wall seems OK!

• Compare the internal stability of the Design MSE wall and the As-Built MSE Wall

Design Checks

Page 26: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

Continuous Geogrid Reinforcement

H =

20

ft

L = 20 ft

2

1

Section

Backfill

Medium sand with 15% (max) non-plastic fines at

95% compaction

Spacing

18”

Chimney Drain

4 ft

3 ft

31

Turf reinforcement mat, topsoil, and seed

Design

Page 27: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

H =

25

ft

L = 20 ft

1.5

1

Plan Section

L = 15 ft

Backfill

Medium sand with 35% plastic fines at 95% compaction

Spacing 36”

Geogrid

Reinforcement

Note: Geogrid Coverage = 50%

2 ft

2 ft

21

As-Built

Page 28: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

Durability

• MSE Walls• Corrosion of steel reinforcement• Degradation of geosynthetic

reinforcement• Durability of the facing

Page 29: MSE Wall Design. MSE Wall as a Gravity Wall An MSE wall is a gravity wall.An MSE wall is a gravity wall. Heavy walls are good.

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MSE Facing Durability