Table 10. Summary of key observations...

Table 10.

Summary of key observations from design, installation, and test of test piles and associated test results

Item	Observations
1	The results from Test Pile #2A, along with those from Test Piles #1 and #3, have validated the appropriateness of the design approaches, assumptions, and processes adopted for this project.
2	Polymer fluid proved effective in stabilising drilling hole in challenging ground conditions, including in completely weathered residual soils, extremely low strength sedimentary breccia, and very low strength sedimentary sandstone. The test results demonstrated no adverse impact on shaft friction due to polymer use, supporting the advice provided by the designer.
3	The testing successfully met the design intent, and the requirements outlined in the PSTR.
4	The base cleaning methodologies and procedures adopted were proven effective, that is, achieving over 80% of base cleanliness.
5	Creep requirements under SLS loading condition and loading increments were met as per AS2159-2009.
6	Base cleaning process as described in the Construction Execution Procedure* should be followed to achieve at least 50% base cleanliness as per design intent for production piles.
7	To mitigate potential collapse and swelling/softening along the shaft and at the toe due to stress relaxation, avoid leaving hole from being left open over an extended period and pour concrete as quickly as possible This risk is particularly high for residual soils and ‘very low to low strength’ breccia and sandstone/siltstone.
8	The successful completion of 3 test piles demonstrated that a geotechnical strength reduction, ϕ_g as high as 0.81 is acceptable for production pile design. However, considering the project’s importance and high-risk characteristics, a more conservative value of 0.7 was adopted.
9	The strategy of adopting conservative shaft friction resistance coefficient values for rock socket pile design proved successful. This approach allowed the contractor to proceed without the need to validate shaft roughness during drilling operations.

Item	Observations
1	The results from Test Pile #2A, along with those from Test Piles #1 and #3, have validated the appropriateness of the design approaches, assumptions, and processes adopted for this project.
2	Polymer fluid proved effective in stabilising drilling hole in challenging ground conditions, including in completely weathered residual soils, extremely low strength sedimentary breccia, and very low strength sedimentary sandstone. The test results demonstrated no adverse impact on shaft friction due to polymer use, supporting the advice provided by the designer.
3	The testing successfully met the design intent, and the requirements outlined in the PSTR.
4	The base cleaning methodologies and procedures adopted were proven effective, that is, achieving over 80% of base cleanliness.
5	Creep requirements under SLS loading condition and loading increments were met as per AS2159-2009.
6	Base cleaning process as described in the Construction Execution Procedure* should be followed to achieve at least 50% base cleanliness as per design intent for production piles.
7	To mitigate potential collapse and swelling/softening along the shaft and at the toe due to stress relaxation, avoid leaving hole from being left open over an extended period and pour concrete as quickly as possible This risk is particularly high for residual soils and ‘very low to low strength’ breccia and sandstone/siltstone.
8	The successful completion of 3 test piles demonstrated that a geotechnical strength reduction, ϕ_g as high as 0.81 is acceptable for production pile design. However, considering the project’s importance and high-risk characteristics, a more conservative value of 0.7 was adopted.
9	The strategy of adopting conservative shaft friction resistance coefficient values for rock socket pile design proved successful. This approach allowed the contractor to proceed without the need to validate shaft roughness during drilling operations.

Notes:

*The Construction Execution Procedure is a document prepared by the contractor with specific procedures to be followed and technical requirements to be achieved during the construction which were pre-discussed, reviewed and agreed by the designer and the independent verifier, and so on

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