07/1571 - Response to Information Request [As Published] · 142007.1571

Project 305-2325
February, 2006 Page 14

 

6&5 Retaining Walls

Retention systems should be designed in accordance with AS 4678-2002 ‘Earth- retaining
structures’. :

Basement walls should be designed using a pressure coefficient for the at rest case of Ko
= 0.5.

Unit wall force P is given by:-

Pp = 0.5 Ko y H:? (kKN/m cun of wall)
«where y = density of sand = 18kN/m?

Ko = 0.5

Hy = height of wall (m)

Until the base of the wall is prevented from inward movement by the strutting action of the
first floor, the resistance of movement is provided by the friction of the soil beneath the
base slab, and by the passive resistance of the soil against the vertical face of the toe of
the wall. The intensity of passive resistance can be calculated from:-

P = 0.5K, yH?
where K, = 3.25 (ignores wall friction effects)
He = front face of wall contributing to passive resistance (m)

For the calculation of sliding resistance, the angle of friction for sand (¢) compacted to not
less than 75% density index can be taken as 32° for walls with a key, For walls without a

key, the angle of friction for sliding resistance may be taken as 2/3 ¢ or 21°.

Note: The above expressions assume a horizontal plane ground surface and no
surcharge.

CONSTRUCTION INSPECTION

 

It is recommended that groundfloor foundation and footing excavations be inspected by
Soil Surveys Engineering Pty. Limited. or a duly qualified Geotechnical Engineer. Should
subsurface conditions other than those described in this report be encountered, Soil
Surveys Engineering Pty. Limited. should be consulted immediately and appropriate
modifications developed and implemented if necessary.

 

WB SOIL SURVEYS ENGINEERING