- Title
- Optimal geotechnical site investigations for slope design
- Creator
- Yang, Rui
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2020
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Almost all natural soil and rock deposits are highly variable in their properties. Soil properties can vary by orders of magnitude from site to site, and even within a single site. As a result, the soil profiles cannot be identified with certainty, even if an extensive subsurface exploration program is executed. In most cases, measurements are only obtained from a limited number of site investigation tests at scattered locations over a construction site constrained by operational and economic considerations. Insufficient or inappropriate site investigation tests can lead to a range of undesirable consequences. Numerous geotechnical projects have experienced cost overruns, unexpected delays, and occasional failure due to unforeseen variability in the subsurface. It is of great significance to develop a design based on an effective site investigation that performs satisfactorily while providing an appropriate level of safety and minimizing the use of financial and human resources. This research proposed a framework which can quantify the benefits of undertaking site investigation of different sampling locations, increased scope and better testing methods. To assess the effectiveness of a site investigation, a simulated slope where the properties are known exactly at every location is used to act as a benchmark. The slope design based on the complete knowledge of the soil properties reflects the true state of the slope, which has only been possible due to the use of simulated soil properties. The site investigation is then carried out numerically at discrete locations from the simulated slope. The slope stability analysis based on the obtained measurements is performed by the finite element method. Such a design would be unreliable because the decision about the stability of slope is made on the basis of a set of samples. Comparisons between the designs based on complete and limited information indicate that two types of decision errors could be made due to inaccurately or inadequately site investigations. This comparison is repeated many times within a Monte Carlo framework to incorporate the uncertainties in the slope design process. Uncertainties due to inherent soil variability, measurement errors and limit measurements have been included. The Monte Carlo simulations have also provided the means to estimate the probabilities of decision errors by counting how many times the unreliable designs have been made based on limited site investigation measurements. Furthermore, the costs associated with the site investigations and making wrong decisions are assigned. It is then possible to assess the site investigation effectiveness through quantifying the relationship between various aspects of a site investigation and the corresponding cost and risk of slope design. The proposed framework enables the direct comparison of different sampling locations, numbers of the site investigation tests, and the testing methods. This allows the identification of optimal site investigation that provides a design with the lowest risk. Results indicated that there is an optimal sampling location that gives the most information while the probability of making the wrong decisions is a minimum. It also appears an optimal site investigation scope, beyond which the cost of additional samplings does not justify the cost savings due to reduced slope failure risk. However, if the cost of slope failure is high, increasing the scope of a site investigation will lead to a lower risk that is because the expected savings in terms of risk are significant when compared to the increased investigation cost. The proposed framework and those results would assist engineers in designing a more efficient and accurate, geotechnical site investigation.
- Subject
- site investigations; slope design; thesis by publication
- Identifier
- http://hdl.handle.net/1959.13/1427611
- Identifier
- uon:38554
- Rights
- Copyright 2020 Rui Yang
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 23 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 1 MB | Adobe Acrobat PDF | View Details Download |