Appendix 5. Geotechnical Engineering Report [As Published] · 132007.2399

October 2007                                           - 15 -                               077682076(AB)


Permanent batters should be formed no steeper than 1V:2.5H in sandy materials and 1V:2H in
clay (or engineered fill batters). Steeper cuts or fill batters should be retained.

6.1.2     Retaining Structures

Design for retaining structures could be carried out using a triangular pressure distribution
applicable to the wall type and based on the parameters listed in the table below. The values in
Table 3 assume that the walls are fully drained and no allowance is included for construction
loading, up-slope footing loadings, the effects of sloping ground, and backfill compaction
stresses.

                        Table 3 – Retaining Structure Design Parameters

Retained Material             Unit         Friction             Lateral Earth Pressure Coefficient
                             Weight         Angle
                             (t/m3)       (Degrees)
                                                                Ka                   Ko            Kp

    Loose to Medium            1.9            30                0.33                 0.5           3.0
      Dense Sand

      Dense Sand               1.9            35                0.27                 0.4           3.6

        Stiff Clay             1.8            27                0.4                  0.6           2.6

    Compacted Fill              *              *                 *                    *              *

Note:
•    Variable dependent upon the type of material used and the degree of compaction achieved.




6.1.3     Preliminary Pavement Design

The design of pavements (flexible and rigid) is based upon the CBR value of the subgrade
material. The subgrade CBR may be obtained by i) laboratory soaked CBR tests, ii)
correlations with DCP tests, and iii) the Queensland Transport Pavement Design Manual –
1990 which provides presumptive insitu CBR values based on soil type and site conditions.

At this site, the subgrade material is expected to comprise mostly loose to medium dense and
dense silty sands and sands. Section 5.3.3, Table 5.5 of the Queensland Transport Pavement
Design Manual, suggests the CBR values in Table 4 below for various subgrade soil types and
site conditions.




                                            Golder Associates