Reference Documents - MCU23 0070

Cambooya Pty Ltd




6.2.2       Site Classification
The site classification derived in accordance with Australian Standard AS 2870-2011 Residential slabs and
footings is not directly applicable to developments of this type but can provide an indication of the likely
magnitude of reactive (shrink and swell) movements associated with normal seasonal soil moisture
variations; and be used for plumbing design.
The site, in its state at the time of our investigation, would be classified as ‘Class ‘S’ in accordance with AS
2870-2011. The estimated characteristic ground surface movement due to seasonal moisture variation (‘ys’
value) is less than 20 mm.
It should be noted that the predicted order of movement is based on the existing soil profile (i.e., no cutting or
filling), and moisture content changes within soils due to normal seasonal moisture variations only (i.e., does
not consider soil settlement).


6.3     Retaining Wall Design
It is anticipated that the use of a contiguous piled system will be required to support cut excavations, and to
transfer proposed structure loads beneath the zone of influence of footings of the adjacent structures (on the
eastern and western site boundaries).
The design of flexible retaining walls (either fully cantilevered, or single propped) may be undertaken using a
triangular pressure distribution and the earth pressure coefficients provided in Table 1.
Flexible walls are those which are free to rotate or tilt (i.e., cantilevered walls or single anchored or propped
walls) and should be designed using an ‘active’ earth pressure coefficient (Ka). Where the walls are rigid and
cannot rotate or tilt, then an ‘at-rest’ earth pressure coefficient (K0) should be used.
Passive pressure (Kp) should be ignored where there is potential for in-ground services trenches (or similar)
in front of the wall.

Table 1: Lateral Earth Pressure Coefficients.

                                                   Lateral Earth Pressure Coefficients

                          Bulk        Friction
 Retained Material      Density        Angle
                        (kN/m3)      (degrees)        Kp           Ko            Ka



      Loose sand           17           27           2.66          0.55         0.37
Medium dense Sand          18           32           3.26          0.47          0.3
      Dense sand           19           37           4.02          0.4          0.25
  Very dense sand          21           42           5.05          0.33          0.2

If appropriate, an allowance of 10 kPa should be made for lateral stress induced by compaction plant
operating behind the walls. The effects of surcharge should be included by multiplying the vertical pressure
developed by the surcharge by the appropriate lateral earth pressure coefficient from Table 1.


J001873-001-R-Rev1                                                                                    Page 7