Appendix D Geotechnical report · MCU18/0013

Project No. 304-2014
November, 2004 Page 9

6.3.2 High Level Footings

Table 4 outlines allowable bearing capacities for high level footings on the site.

TABLE 4 ALLOWABLE BEARING CAPACITIES FOR HIGH LEVEL FOOTINGS

 

 

 

 

 

Material Allowable Bearing Capacity (kPa)
Strip Footing Pad Footing
Sand - Loose NR NR
- compacted to 70% Density Index 125 150
- Medium Dense 125 150
- Dense 200 250
- Very Dense 350 500

 

 

 

 

The base of all pad and strip footings should be individually recompacted using a
vibrating plate compactor prior to placement of reinforcing steel and concrete as soils

may be loosened during the excavation process by machinery action.

If the sand is dry, it should be saturated and left for a short period prior to vibration.
Should any loose areas be encountered in the footing excavations the density of these
areas must be improved. If any doubt exists as to whether ground improvement has
achieved the required density of 70% density index for support of the proposed building
loads, further testing in the way of dynamic cone penetrometer tests should be carried

out to confirm the adequacy of the founding soils.
6.3.3 Raft Foundation

Where sensitive and heavy masonry construction is proposed, consideration may be
given to the use of a raft foundation to reduce the effects of the differential settlements.

Compaction of the sand foundation as per high level footings is recommended.

Due to the raft size, bearing capacity failure is unlikely, however to limit local
overstressing a maximum design allowable bearing pressure of 125kPa should be
adopted based on 70% density index being achieved for a minimum distance of 1.0m

below foundation level.

Rafts have an advantage over individual strip and pad footings in that the effect of an

isolated loose area is much less under a raft than under an individual strip or pad footing.

 

# SOIL SURVEYS ENGINEERING