J001701-006-R-Rev1_Medihub_Geo

Stockwell



Table 2: Retaining Structure Design Parameters.
                                                        Unit         Friction
                                                                                    Lateral Earth Pressure Coefficient
                                                       Weight         Angle
                   Retained Material                                                   Ka             Ko
                                                       (t/m3)      (Degrees)        (Cantilever   (Non yielding       Kp
                                                                                      Wall)          wall)

 Stiff Clay                                             1.8            27             0.41           0.58            2.46

 Very Stiff Clay                                        1.9            29             0.36           0.53            2.77

 Hard Clay                                              2.0            33              0.3           0.45             3.5
 Notes:
 Ka - active; Ko - at rest; Kp - passive

 For yielding walls active state develops when: Deflection > 0.001H to 0.004H (granular soil), or deflection > 0.01H to
 0.04H (cohesive soil).
 Positive permanent drainage must be installed behind all walls unless they are designed for development of full
 hydrostatic pressures (i.e. a ‘tanked’ basement).


     6.6 Design CBR
CBR testing on a sandy clay sample (fill/reworked natural soil) returned a CBR value of 5%, with a swell
value of 1%. Based on our experience with similar materials, and on consideration of the test results, a
design CBR of 5% is recommended for the residual sandy clay subgrade.
The recommended design CBR value is applicable for properly drained subgrades only that are compacted
to a minimum dry density of 98% (standard). Properly drained subgrades should allow for open graded
drains that shed water and prevent ponding.
If exposed clay subgrades are exposed to rainfall or stormwater, softening (and resulting subgrade strength
less than nominated above) can occur and the material will become difficult to handle or moisture condition.
This can cause significant delays during construction and must be considered in the design/planning and site
management (e.g. timing of work and temporary/long term site drainage design).
Construction validation testing is recommended on pavement subgrades to confirm design parameters prior
to pavement construction.

     6.7 Soil Aggressivity
The chemical composition of soil can provide an indication of the potential for long term damage to
foundations, buried pipelines, in-ground structures, services and other infrastructure. Soil texture is also
important in this regard, as granular soils allow oxygen exchange (oxidation) to occur more readily and are
also more permeable.
Australian Standard AS 2159-2009 Piling - Design and installation provides the range of exposure
classification of the surface of concrete piles based on the range of chemical conditions in soil and
groundwater.
Our previous experience indicates that the residual clays encountered can be classified as ‘Mild’ in
accordance with the definitions given in AS 2159-2009 Table 6.4.2(C) Exposure Classification for Concrete
Piles – Piles in Soil.




J001701-006-R-Rev1                                                                                                Page 9