- Title
- Engineering geology of the Richmond river estuary
- Creator
- Bishop, Daniel
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2010
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- The ongoing development on the coastal plains of eastern Australia represents a significant challenge to the engineering profession. The need to understand the distribution and behaviour of soft clays associated sediments in the coastal estuaries is critical to the planned and ongoing upgrade of the Pacific Highway between Sydney and Brisbane on the east coast of Australia. An extensive, cross-disciplinary literature review has been undertaken to develop depositional and geotechnical frameworks within which a detailed site investigation of the Richmond River has been undertaken. The relationship between the point data of a geotechnical investigation is not arbitrary and the systematic trends of sediments within deposits are described by three key boundary conditions (variables); the regional sea level curve, estuary geomorphology (including geology, catchment area, relief) and climate (including rainfall intensity/distribution, wind direction/intensity etc). The sediment found at a given location and depth within the deposit, is defined by the interaction of the boundary conditions that would have existed when sedimentation was active at that point. This can be understood using the principles of morphodynamics. The evolution of these conditions, over time, leads to characteristic transitions in the vertical succession of sediment layers, which is described by the concepts of sequence stratigraphy, and which can be recognized in CPTU data. The microstructure and geotechnical performance of sediment is a function of its deposition environment and in particular the biology, geochemistry and pore water chemistry of the environment at the time of deposition. As important to its subsequent behaviour as a foundation element is the evolution over time of its biogeochemical characteristics as defined within the evolutionary model. From a geotechnical perspective a better appreciation of the geological relationships of estuarine clays leads to the elucidation of significant observations of what and why particular behaviours are found in specific locations within the stratigraphy. The structured clay framework provides a convenient tool for this. These include the occurrence of highly sensitive clays in locations where central basin clays have remained saturated and normally consolidated but have been flushed by fresh water. Many soils that are considered to be “over consolidated” in the classical sense, are actually normally consolidated, but have had the stability of their fabric modified in the post-depositional environment, by changes to the bio/chemical characteristics at the particle and/or molecular scale, without ever being overloaded/unloaded. In particular, the presence of organic substances in estuarine sediments leads to the stabilization in “normally consolidated” clays at high void ratio resulting in slightly overconsolidated and anomalies in the correlation between excess pore pressure dissipation and rate of consolidation, sometimes observed beneath fills. The integration of the various frameworks means that the geotechnical data is being interpreted within a single coherent model. This in turn means that new point data either validates the model or the model must be adjusted to explain the new observations.
- Subject
- geotechnical; CPTu; barrier; geology; engineering geology; sea level; oedometer; organic matter; biology; microbiology; geochemistry; estuary
- Identifier
- http://hdl.handle.net/1959.13/1042457
- Identifier
- uon:14058
- Rights
- Copyright 2010 Daniel Bishop
- Language
- eng
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| Thumbnail | File | Description | Size | Format | |||
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| View Details Download | ATTACHMENT01 | Abstract | 200 KB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Thesis | 33 MB | Adobe Acrobat PDF | View Details Download |