Attachment 5 - Geotechnical Assessment · MCU18/0015

RTI 11/055 Folio B394

 

{ ) fb ce to

November 2003 -10- 03632248-001

 

repeated rolling to achieve a dry density ratio of at least 98% of the Maximum Standard Dry
Density for cohesive soils, or 75% Dry Density Index for cohesionless soils.

In accordance with good construction practice, fill embankments should be ‘benched’ into
slopes following stripping and ‘over built’ then trimmed back to the well compacted material.

7.1.4 Batter Slopes

As a general guideline, temporary unsurcharged cut batters in sand and clay should not be
formed steeper than 1V:2H. Flatter batters may be required if groundwater is encountered
during construction.

Cut batters should be assessed by a geotechnical engineer from Golder Associates during
excavation. Such assessments should be undertaken progressively, with excavated face
heights prior to inspection being limited to 2 m.

7.1.5 Temporary Excavation Support

For proposed excavations up to about 6 m deep within the yery loose grading to dense sands
on the western side of the creek, some form of'temporary support will be required to enable
construction to proceed safely. Options-for temporary support include:

e ‘Soldier’ piles comprising ‘H’ sections or CFA,piles with timber lagging;

e Sheet piles;

e Contiguous CFA piles with infiil grouting of voids;

e Secant piles; and

e Micro-fine grouting.

One or two rows of anchors will probably be required to provide sufficient lateral restraint for
the temporary support system depending on the height of the cut. Design of the support
system must be conducted with due consideration of embedded depth below the excavation
level, variability in stratigraphy over the anchor embedment length, dewatering requirements,
and anticipated ground conditions. Temporary support design must also take into account the
impact on nearby structures and ground vibrations from driving ‘H’ section or sheet piles
should be avoided.

Heavy duty drilling equipment is likely to be impractical for this site, as there are restrictions

to access due to the presence of trees and loose sandy slopes. Small tripod type auger rigs (for
CFA pile construction) or small skid rigs are available and would be well suited to the site.

Golder Associates