Quantification of Optical Clarity of Transparent Soil Using the Modulation Transfer Function

Transparent synthetic soils have been developed as a soil surrogate to enable internal visualization of geotechnical processes in physical models. Transparency of the soil dictates the overarching success of the technique; however, despite this fundamental requirement, no quantitative framework has yet been established to appraise the visual quality of transparent soil. Previous approaches to assess and optimize transparency quality included an eye chart assessment method, although this approach is highly subjective and operator-dependent. In this paper, an independent method for quantitatively assessing the optical quality of transparent soil is proposed based on the optical calibration method, Modulation Transfer Function (MTF). The work explores this hypothesis and assesses the potential for MTF to quantify the optical quality of transparent soils for a number of aspects including (i) optimum oil blend ratio, (ii) depth of viewing plane, and (iii) temperature. The results confirmed that MTF offers a robust and reliable method to provide an independent quantitative measure of the optical quality of transparent soil. The impact of reduced soil transparency and the ability to track speckle patterns—thus accuracy and precision of displacement measurement—was correlated with MTF to evaluate the permissible viewing depth of transparent soil

Transparent soil to model thermal processes: An energy pile example

Managing energy resources is fast becoming a crucial issue of the 21st century, with groundbased heat exchange energy structures targeted as a viable means of reducing carbon emissions associated with regulating building temperatures. Limited information exists about the thermo-dynamic interactions of geothermal structures and soil owing to the practical constraints of placing measurement sensors in proximity to foundations; hence, questions remain about their long-term performance and interaction mechanics. An alternative experimental method using transparent soil and digital image analysis was proposed to visualize heat flow in soil. Advocating the loss of optical clarity as a beneficial attribute of transparent soil, this paper explored the hypothesis that temperature change will alter its refractive index and therefore progressively reduce its transparency, becoming more opaque. The development of the experimental methodology was discussed and a relationship between pixel intensity and soil temperature was defined and verified. This relationship was applied to an energy pile example to demonstrate heat flow in soil. The heating zone of influence was observed to extend to a radial distance of 1.5 pile diameters and was differentiated by a visual thermal gradient propagating from the pile. The successful implementation of this technique provided a new paradigm for transparent soil to potentially contribute to the understanding of thermo-dynamic processes in soil

Influence of foundation compressibility on reinforcement loads in geosynthetic reinforced soil walls

A numerical FLAC model was used to investigate the influence of vertical stiffness of the foundation on the performance of an idealized 6-m high reinforced soil modular block retaining wall. Three different Winkler linear spring values were used to simulate a rigid foundation and two compliant foundation cases. For each foundation condition, the influence of reinforcement material stiffness was also investigated. One material matched the properties of a relatively extensible polymeric geogrid product and the other a relatively inextensible welded wire mesh material with much higher stiffness but the same strength. The results of simulations show that as foundation stiffness decreases, reinforcement loads increase. However, for the two reinforcement materials in this study, the influence of axial stiffness of the reinforcement had a greater effect on wall performance than the foundation stiffness for walls subjected to operational (working stress) conditions at end of construction.Postprint (published version

Influence of foundation compressibility on reinforcement loads in geosynthetic reinforced soil walls

A numerical FLAC model was used to investigate the influence of vertical stiffness of the foundation on the performance of an idealized 6-m high reinforced soil modular block retaining wall. Three different Winkler linear spring values were used to simulate a rigid foundation and two compliant foundation cases. For each foundation condition, the influence of reinforcement material stiffness was also investigated. One material matched the properties of a relatively extensible polymeric geogrid product and the other a relatively inextensible welded wire mesh material with much higher stiffness but the same strength. The results of simulations show that as foundation stiffness decreases, reinforcement loads increase. However, for the two reinforcement materials in this study, the influence of axial stiffness of the reinforcement had a greater effect on wall performance than the foundation stiffness for walls subjected to operational (working stress) conditions at end of construction