Case History (Continued)
Geotechnical offshore site investigation and reclamation design at Port Kembla
The depth below existing seabed level of the residual soils is noted to increase in a southerly direction. Towards the central and southern part of the Stage 1A area the residual soils were encountered at increasingly greater depths as the thickness of the overlying alluvial and dredged fill increases.
4.3 Geotechnical unitisation
Soil and rock units encountered concur well with published geological data, with six separate units being encountered during the investigation. The units encountered are presented in Table 1.
Table1: Geotechnical unit descriptions
|
Unit |
Description | Thickness(m) |
Typical composition |
| 1a1b | Fill (cohesive) Fill (granular) | 0.0to8.2 | Poorly consolidated clay and sand fill mixed with variable minor fractions. Clay fill is very soft to firm, plasticity is variable. Sandfillis very loose to medium dense. Man made artifacts include charcoal,ash,slag gravels,possible coal-wash and metal wire. |
| 2 | Marine and estuarinesediment | 0.0to1.0 | Very soft to soft silty clay of variable plasticity. Only encountered as thin layers in BHS102, BHS106 and BHS111. |
| 3a | Quaternary alluvium(cohesive) | 0.0to3.4 | Soft to firm clays were encountered within this unit. Shell fragments noted throughout. |
| 3b | Quaternary alluvium(granular) | 0.0to2.6 | Typically very loose to medium dense sand with variable minor fractions. Shell fragments noted throughout. |
| 4 | ResidualSoil | 0.4to3.7 | Typically very stiff to hard clays of low plasticity,with gravels of latite, sandstone and siltstone noted throughout. Sand and gravel units also encountered. |
| 5 | DaptoLatiteMember | 0.0to>1.0 | Extremely weathered to highly weathered fine to coarse grained latite with medium to coarse gravels. |
| 6 | Budgong SandstoneFormation | >12.6 | Extremely weathered becoming fresh sand stone and siltstone. Defect spacing and rock strength noted to increase markedly with depth. |
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