Abstract
This paper presents a philosophy – defined, in this context, as an attitude for guiding actions – for developing reliable offshore geotechnical engineering models that are fit for the proposed engineering applications. A key concept of the philosophy is “integrated thinking”; which is thinking in a manner that recognises that a Geotechnical Engineering Model (GEM) can only be developed by consistently integrating the complementary geomorphological, geological and geophysical data-sets, and taking account of proposed engineering applications. The philosophy is illustrated using a series of simple examples.
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Abbreviations
- BPT:
-
Ball Probe Test
- d:
-
Diameter of object
- c:
-
Coefficient of consolidation (cv) of the soil
- CPT:
-
Cone Penetration Test
- DSS:
-
Direct Simple Shear test
- e:
-
Voids ratio
- LV:
-
Laboratory Vane test
- TBT:
-
T-bar Test
- v:
-
Velocity of penetration
- V:
-
Normalised velocity (v.d/cv)
- σ’v:
-
Effective vertical stress
- σ’vc:
-
Effective vertical stress after consolidation
- σ’vmax:
-
Maximum previous effective vertical stress
References
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Appendix 1: Geotechnical Engineering Model (GEM) Check-List
Appendix 1: Geotechnical Engineering Model (GEM) Check-List
Item | Issue | Notes |
|---|---|---|
1 | Is the scope of work consistent with the proposed engineering applications? | The scope of work must enable the project objectives to be achieved - so proposed foundation types, geometries and loadings should be defined |
2 | Are the geomorphology and geology understood? | It is essential vital to understand the geomorphology and geology of the site, as these provide essential frameworks for GEM development |
3 | Have all potential geohazards been identified? | Consider geology; near-field topography; far-field topography; mineralogy; project-induced changes |
4 | Is there sufficient information to develop a reliable GEM? | A reliable GEM needs adequate geological; geophysical, geomorphological and geotechnical information |
5 | Is the soil investigation coverage adequate? | Ensure there is sufficient investigation for the project requirements – noting that geohazards may be located outside the project area |
6 | Is the quality of data adequate for purpose? | High quality numerical analyses need high quality input data |
7 | Have all anomalous data been reviewed and discussed in the report text? | Consider the possibility of aleatory, epistemic, transformational and measurement errors, and whether the GEM needs to be amended |
8 | Is the acquired geotechnical information fit for purpose? | Consider geology; magnitude, direction and rate of loading; temperature and salinity; and drainage conditions under loading |
9 | Has sufficient information been gathered in all significant geotechnical units? | Consider vertical and lateral variability; possible weak zones; possible strong zones, peak strength and post-peak behaviour; stiffness degradation; cyclic/dynamic behaviour; and potential change in material properties with loading and/or time |
10 | Is the GEM consistent with the geological, geophysical and geomorphological data-sets? | If, for engineering reasons, the GEM is inconsistent with the geomorphological or geological or geophysical data-sets, then the reason for each inconsistency should be clearly highlighted in the report |
11 | Have the ranges of applicability of all characteristic values been clearly defined? | Consider the consolidation behaviour of the soil, drainage length, intended design purpose, design life of the structure, magnitudes and durations of static and dynamic loadings, rates and directions of loading and time-dependent changes (e.g. scour) |
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Ramsey, N. (2019). A Philosophy for Developing Offshore Geotechnical Engineering Models. In: Randolph, M., Doan, D., Tang, A., Bui, M., Dinh, V. (eds) Proceedings of the 1st Vietnam Symposium on Advances in Offshore Engineering. VSOE 2018. Lecture Notes in Civil Engineering , vol 18. Springer, Singapore. https://doi.org/10.1007/978-981-13-2306-5_2
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