Attachment 5 - Geotechnical Assessment · MCU18/0015

RTI 11/055 Folio B395

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November 2003 ~ll- 03632248-001

 

Selection of the temporary support system will need to consider the feasibility of using the
structure for long-term support and the associated cost benefits. For example, it may be
practical to incorporate some of these support systems into the permanent structure by
covering them with sprayed concrete and attaching facing panels. However, if the system
relies on temporary anchors or is prone to corrosion (eg. sheet piles), it will be necessary to
construct a permanent retaining system (e.g. a propped or cantilevered wall). Detailed advice
regarding design and installation of the support system should be obtained from a specialist
contractor.

7.2. _ Retaining Structure Design

Retaining wall design should be carried out using a triangular pressure distribution applicable to
the wall type (ie. active pressures for a cantilever wall or at rest pressures for a
propped/anchored wall) and based on the parameters in Table 5. The values in, Table 5 assume
that the walls are fully drained and no allowance is included for construction loading, up-
slope foundation loadings, the effect of sloping ground, or backfill compaction’stresses.

Table 5 — Retaining Structure Design Parameters

 

 

 

 

 

 

 

Unit Friction Lateral.Earth Pressure Coefficient
Weight Angle
(thm*) |\(Degrees)
Ky K, K,
1.7 30 0.3 0.5 3.0
Va 34 0.25 0.45 3.4
1.9 40 0.2 0.4 4.5
1.8 27 0.4 0.6 2.6
* * * * *

 

 

 

 

 

 

 

 

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

Positive permanent drainage must be installed behind retaining walls unless they are designed
for development of full hydrostatic pressures.

Golder Associates