REINFORCED EARTH WALLS

Dr. P. NANJUNDASWAMY

Dept. of Civil Engineering

S J C E, Mysore

Advantages

Flexible Poor foundation soils

Differential movements

Seismically active

Corrosion and Chemical resistant

Cost effective Quicker construction

Less weather dependent

Less earthwork

Component parts

Component parts

Other forms

Applications

Analysis Types

External Stability

Global Stability

Internal Stability

Tension Failure Pull Out Failure

Local Stability

Forces on a wall

L0

L

H

z

LELR

Sv`

45+f/2

P2(live loads)P1

DSurcharge

+shs

Soil pressure

+shq

Surcharge pressure

=sht

Live load pressure

sh

Total lateral pressure

Engineering ScienceReal Life Application

Sliding Failure

Resisting Force

= γf H L µ

Sliding Force

= ½ Kab γbH2

Factor of Safety - 2

Overturning Failure

Overturning moment

= 1/6 Kab γb H3

Resisting moment

= W L / 2

= γf H L2 / 2

Factor of Safety - 2

Bearing Failure

Bearing Pressure

• Uniform

• Trapezoidal

• Meyerhoff

Allowable bearing capacity

• Increase in base width

• Stone columns

• Foundation matresses

Trapezoidal distribution

��,���,��� =�

�� ±

�

� �⁄

� =��

�

Meyerhoff distribution

��,��� =���� +���

� − ��

� =��

�

Slip Failure

All possible potential slip surfaces

Factor of safety – 1.5

Slip Failure . . .

Slip Failure . . .

Internal Stability

Tension Failure Pull Out Failure

Internal Stability

Tie back-wedge analysisRankine’s equillibrium condition

Coherent gravity analysis

Ko to Ka upto 6m depth

Tie Back Wedge Analysis

Tie Back Wedge Analysis

H

Potential Failure Plane

Facing Assumed to rotate about toe of wall

β = 45 - Ø / 2

Li

Ka

Ka

Coherent Gravity Analysis

Coherent Gravity Analysis

Assumed line of max tension

Facing Assumed to rotate about top of wall

tan -1 0.6

Li

H2

H2

0.3H Ko

Ka

6m

Analysis

Tension Failure

The tensile force per meter width of geogrid or geofabric at depth hi is given by

�� = ������∆��

�� = ������∆��∆��

The maximum tensile force will be acting on the bottom most reinforcing element

Ti for a reinforcing strip is given by

Analysis

Pull-out Failure

The critical reinforcing element is the top most strip

Resisting force

�� = ����(�������)

Problems

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