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Pua Pita, Lina Maria
Macedo, Jorge
Mayne, Paul W.
Caicedo, Bernardo
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Multiple studies have recognized that spatial variability of soil deposits affects the performance and reliability of geotechnical structures. Even though the relevance of spatial variability has been acknowledged, it is not always explicitly included and quantified in practice, mainly because characterizing soil variability has multiple challenges. First, it is generated at multiple scales, and each scale impacts the geotechnical structures differently. Second, multiple uncertainty sources affect soil behavior, such as measurement error, inherent variability, and transformation uncertainty. This thesis evaluates tools to study soil variability at two different scales: laboratory and field scales. The laboratory scale is evaluated using physical models to assess the effect of spatial variability on the dynamic properties (i.e., the maximum shear modulus, Gmax, and shear modulus reduction curves G/Gmax) and wave propagation phenome. The spatially variable models are made of clay-like materials located in space using a 3D printer to represent a random field simulation. The results show that the internal specimen variability affects Gmax and the G/Gmax curves. Moreover, the results suggest that the theory of composite materials is suitable for estimating the response of specimens with low to medium variability. The wave propagation measurement on the spatially variable samples was measured using multiple accelerometer arrays. The data show that increasing soil variability increases the wave scattering process, filtering the high-frequency content, and reducing the coherency of the signals. The field scale was evaluated using the seismic piezocone (SCPTu) to assess spatial variability. Multiple studies have shown it is a useful in-situ test to assess spatial variability and characterize the in-situ soil response. This study presents an overview of the use of SCPTu to quantify stratigraphical and inherent variability from field measurements. For the stratigraphical variability, the SCPTu is a tool that defines the layering of a soil profile by using classification charts. On the other hand, the inherent variability quantifies how rapidly the properties change in space for a single layer. Since the SCPTu measures a continuous profile, it provides sufficient information to quantify the inherent variability by estimating the extent of the correlated domain. In order to facilitate the processing of SCPTu data and the analysis of soil variability, a Matlab-based computational tool was developed. The tool has six moduli to interpret the SCPTu data: (1) Basic soil parameters, (2) Shear wave velocity, (3) Dissipation tests, (4) Liquefaction assessment, (5) Foundation analysis, and (6) data analytics module. Finally, a sounding performed in southwestern Illinois is used to exemplify how the SCPTu can be used to assess stratigraphical and inherent variability and the capabilities of the computational tool. The results show that the SCPTu is a complete in-situ test that allows for the measurement of multiple soil responses and characteristics in a single profile, with the capability of quantifying stratigraphical and inherent variability.
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