Reference Document - MCU26 0012 & OPW26 0034 (As Published)

Table 3: Retaining Wall Design Parameters
                                                                               Lateral earth pressure coefficients
                          Unit weight                                                         K0
 Retained material                           Friction angle (°)          Ka
                           (kN/m3)                                                       (Non-yielding               Kp
                                                                  (Cantilever wall)
                                                                                             wall)


 Natural Stiff to
                              19                    27                  0.38                  0.55                   2.66
 Very Stiff Residual
 Soils


 Future/Existing Fill          *                     *                    *                     *                     *


* Depends on type of fill material used and compaction achieved

These parameters do not include allowance for surcharge above the wall, or additional loads imposed by
sloping ground.
Retaining structures should be engineer designed in accordance with AS4678-2002 Earth-retaining
structures. Retaining wall footings are to be founded as required in Section 4.4 (at a minimum). Internal
stability of any proposed retaining walls, including confirmation of sufficient resistance to sliding, over-
turning and bearing capacity failure, as well as global stability (if required), shall be assessed by the wall
designers.

4.4        Footing Design
It is recommended that all footings are taken to found a minimum of 1 m below ground level and a
minimum of 0.3 m into stiff (or stiffer) natural residual soils (whichever is greatest). Footings so founded
could be designed using a maximum allowable bearing pressure of 100 kPa (high level footings) or
150 kPa maximum allowable end bearing pressure for piles. Soils greater than 1 m depth below the
existing surface were noted by ASI to be very stiff, and therefore allowable bearing pressures of up to
200 kPa could be tolerated where this material is verified in the foundation subgrade. It is expected that
high-level footings could be utilised following site stripping in areas of earthworks cut. A transition
through mass poured concrete pads (‘bucket piers’) and piles would be required in deeper areas of
proposed filling.
Footing design should also account for the characteristic surface movement (ys), including allowance for
the proposed earthworks.
All footings should found such that they are not adversely affected by (or affect) any adjacent
excavations, trenches, or retaining walls that are not designed to support building loads. Footings
should found at least below a plane extending 1 m horizontally from the base of trenches/excavations/
retaining walls, then rising up at 1V:1H, as illustrated in Text Figure 9 on the following page.
Additionally, footings should not be founded closer than 1.5H from the crest of the batter slopes
(H being the maximum height of fill).




13 February 2026
26020-001-Rev0                                                                                                        11 of 13