## Cantilever retaining Wall Drawings

July 14, 2012

In the pictures below you can see 2D representations of a cantilever retaining wall in cross section and in elevation:

Note that these drawings are to be used only for presentation purposes and that if you choose to use the drawins you must consult a structural engineer for different heights depending on the soil types found in site and the structural calculations.

## Basic steps for calculating a cantilever retaining wall

July 14, 2012

In terms of basic calculations needed to design a retaining wall the following checks are needed:

-local stability calculations(checks of overturning,sliding,and pressure s);

-structural calculations (area of rebars needed to reinforce the cantilever retaining wall);

-global stability calculations  needed to ensure the entire slope’s stability .

For local stability calculations the drawing below illustrates the forces and diagrams needed to perform the static  calculations:

That generate

Pa= Kayh2/2+qhKa-total active earth pressure where using Rankine’s theory:

Py-active pressure load generated by the retained earth;

Pq-active pressure generated by the surcharge(q);

Ka-active earth pressure coeficient{Ka=tan2(45deg-Ø/2)};

Ø-angle of friction of the retained earth .

Checking the wall for sliding

VL=(fN)/Pa=(fΣGi)/Pa =…>1.3 in static conditions  where

Gi-the weight of the wall sections;

f-friction coeficient .

Checking the wall for overturning

vR=Ms/Mr=(ΣGixbi)/(Paxba) =…>1.5 in static conditions  where:

Ms-the stability moment(the moment that oposes the overturning  tendency of the wall);

Mr-the overturning moment(the moment that generates the overturning);

bi-the level arm of  the forces that opose the overturning

ba-the level arm of the active pressure

Checking the pressures on the field:

pmax/min=N/A+/-M/W [kN/m2]

pmax<=1.2pconv

pmin>=0    where:

pconv-the conventional pressure of the soil where the wall is to be build;

N-the resultant of vertical forces;

M-the moment of all forces along point O ;

A-area of the surface of the retaining wall in direct  contact with the field(A=Bx1)[m2];

W-the resisting modulus(W=B2x1/6)[m3];

## Cantilever retaining wall design principles

July 5, 2012

The cantilever retaining wall is a wall that is usually used to take over lateral considerable lateral  pressures or surcharges but with limiting geometric conditions.

The usual material used for building a retaining wall is reinforced concrete but in special conditions,can be used other materials as well depending on the loads that is designed for such as :wood,masonry reinforced with rebars or even steel for high loads.

The geometric shape of a custom cantilever wall design is an L but can be also an inverted T or even an V shape.

If it is out of concrete it can be poured on  site or if it is a prefabricated it can be placed using a crane .

For heights above 2m the excavation needs to have suports and needs to be made in plots of 3 to 5 m to ensure overall stability.

In terms of geometric  restrictions the picture below will ensure the basic needed geometric design restrictions for a cantilever retaining wall:

Cantilever retaining wall design scheme

where :

Df-foundation depth(m)

B-base length(m)

h-overall height of the cantilever retaining wall .

In the picture below we can study different cross sections that are used  depending on the soil types in terms of :

-Ø =angle of friction(deg);

-c=cohesion(kPa);

-y =unit weight(kN/m3);

-q=surcharge(kN/m2) .

Note that the pictures are shown from left to right from more stable ground conditions to less stable ground conditions as follows:

a-cantilever retaining wall

b-cantilever retaining wall with small buttress;

c-cantilever retaining wall with buttress on entire height of the wall;

d-cantilever retaining wall with discharge plaque and buttress on entire height of the wall .

Cantilever retaining wall designs