1. GLE/CEE 330: Soil Mechanics Earth Retaining Structures
Geological Engineering
University of Wisconsin-Madison
(Select Images from Coduto)

2. Learning Objectives Discuss different types of retaining structures
Describe simplified design procedures

3. Slopes and Retaining Structures
Options for grade changes….
Failure surface
Slopes
Retaining Structures
Earth
Pressure
Is there enough room (right of way)?
How steep can we make the slope?
Effects of…
water, vegetation, surface loads..
What is lateral pressure distribution?
How much will the wall move?
How do I design the wall structure?

4. Types of Retaining Structures

5. Massive Gravity Wall
Mechanically Stabilized Earth (MSE) Wall
Geosynthetic
reinforcement
Cantilevered Gravity Wall

6. Sheet Pile Walls

7. Soldier Pile Wall
Timber lagging
Driven soldier piles
Soil Nail – Shotcrete Wall

8. What is the earth pressure distribution???

9. Role of the geotechnical engineer…
What is the earth pressure distribution?
What are resultant forces on wall?
Static equilibrium (overturning analysis, sliding analysis)
Bearing capacity analysis
Settlement analysis
Special loading (e.g., earthquakes)
“active” earth
pressure
“passive” earth
pressure
friction
Bearing pressure

10. Example – Cantilevered wall with flat sand backfill, check for overturning and sliding
Direct Shear Results on Sand
Sand
g = 100 pcf
Test
sf (psf)
tf (psf) 1
500
320 2
1000
639 3
2000
1278
20’
Active
Failure
wedge 2’
g c= 150 pcf
45+f/2 3’ 2’
10’
f = 32.6 deg.
c = 0
15’

11. Sand
g = 100 pcf
20’
P = force per unit width 2’
g c= 150 pcf 3’ 2’
10’
15’

12. 20’
Check Factor of Safety for Overturning
Moment equilibrium about Point A Wf P Ws 2’ A Wb
Resisting moments
FS = 3’ 2’
10’
Driving moments
15’
Plenty safe!

13. Check Factor of Safety for SlidingP Wt
F = Wttand
Resisting forces
Let d=15
FS =
Driving forces
A bit low!! What could we do??